Archive for September 2018

Without treatment, why does African sleeping sickness invariably lead to death?

07:13

Without treatment, why does African sleeping sickness invariably lead to death?



The trypanosomes that cause this disease are capable of expressing a glycoprotein coat with a different molecular structure with each generation. Because the immune system must respond to specific antigens to raise a meaningful defense, the changing nature of trypanosome antigens prevents the immune system from ever clearing this infection. Massive trypanosome infection eventually leads to host organ failure and death.

How does killing Anopheles mosquitoes affect the Plasmodium protists?

07:13

How does killing Anopheles mosquitoes affect the Plasmodium protists?



Plasmodium parasites infect humans and cause malaria. However, they must complete part of their life cycle within Anopheles mosquitoes, and they can only infect humans via the bite wound of a mosquito. If the mosquito population is decreased, then fewer Plasmodium would be able to develop and infect humans, thereby reducing the incidence of human infections with this parasite.

Why might a light-sensing eyespot be ineffective for an obligate saprobe? Suggest an alternative organ for a saprobic protist.

07:12

Why might a light-sensing eyespot be ineffective for an obligate saprobe? Suggest an alternative organ for a saprobic protist.



By definition, an obligate saprobe lacks the ability to perform photosynthesis, so it cannot directly obtain nutrition by searching for light. Instead, a chemotactic mechanism that senses the odors released during decay might be a more effective sensing organ for a saprobe.

The chlorophyte (green algae) genera Ulva and Caulerpa both have macroscopic leaf-like and stem-like structures, but only Ulva species are considered truly multicellular. Explain why.

07:10

The chlorophyte (green algae) genera Ulva and Caulerpa both have macroscopic leaf-like and stem-like structures, but only Ulva species are considered truly multicellular. Explain why.



Unlike Ulva, protists in the genus Caulerpa actually are large, multinucleate, single cells. Because these organisms undergo mitosis without cytokinesis and lack cytoplasmic divisions, they cannot be considered truly multicellular.

Which of the following statements about the Laminaria life cycle is false?

07:09

Which of the following statements about the Laminaria life cycle is false?




a. 1n zoospores form in the sporangia.
b. The sporophyte is the 2n plant.
c. The gametophyte is diploid.
d. Both the gametophyte and sporophyte stages are multicellular.



Answer: c. The gametophyte is diploid.

Which of the following statements about Paramecium sexual reproduction is false?

07:08

Which of the following statements about Paramecium sexual reproduction is false?




a. The macronuclei are derived from micronuclei.
b. Both mitosis and meiosis occur during sexual reproduction.
c. The conjugate pair swaps macronuclei.
d. Each parent produces four daughter cells.


Answer: c. The conjugate pair swaps macronuclei.

Alternation of generations describes which of the following?

07:08

Alternation of generations describes which of the following?




a. The haploid form can be multicellular; the diploid form is unicellular.
b. The haploid form is unicellular; the diploid form can be multicellular.
c. Both the haploid and diploid forms can be multicellular.
d. Neither the haploid nor the diploid forms can be multicellular.


Answer: c. Both the haploid and diploid forms can be multicellular.

Mitochondria most likely evolved by _____________.

07:07

Mitochondria most likely evolved by _____________.




a. a photosynthetic cyanobacterium
b. cytoskeletal elements
c. endosymbiosis
d. membrane proliferation


Answer: c. endosymbiosis

Bioremediation includes _____.

07:06

Bioremediation includes _____.




a. the use of prokaryotes that can fix nitrogen
b. the use of prokaryotes to clean up pollutants
c. the use of prokaryotes as natural fertilizers
d. All of the above


Answer: b. the use of prokaryotes to clean up pollutants

Which of these occurs through symbiotic nitrogen fixation?

07:06

Which of these occurs through symbiotic nitrogen fixation?




a. The plant benefits from using an endless source of nitrogen.
b. The soil benefits from being naturally fertilized.
c. Bacteria benefit from using photosynthates from the plant.
d. All of the above occur.


Answer: d. All of the above occur.

Researchers have discovered that washing spinach with water several times does not prevent foodborne diseases due to E. coli. How can you explain this fact?

07:06

Researchers have discovered that washing spinach with water several times does not prevent foodborne diseases due to E. coli. How can you explain this fact?



E. coli colonizes the surface of the leaf, forming a biofilm that is more difficult to remove than free (planktonic) cells. Additionally, bacteria can be taken up in the water that plants are grown in, thereby entering the plant tissues rather than simply residing on the leaf surface.

Which of these statements is true?

07:05

Which of these statements is true?




a. An antibiotic is any substance produced by a organism that is antagonistic to the growth of prokaryotes.
b. An antibiotic is any substance produced by a prokaryote that is antagonistic to the growth of other viruses.
c. An antibiotic is any substance produced by a prokaryote that is antagonistic to the growth of eukaryotic cells.
d. An antibiotic is any substance produced by a prokaryote that prevents growth of the same prokaryote.


Answer: a. An antibiotic is any substance produced by a organism that is antagonistic to the growth of prokaryotes.

Which of the statements about biofilms is incorrect?

07:05

Which of the statements about biofilms is incorrect?




a. Biofilms are considered responsible for diseases such as cystic fibrosis.
b. Biofilms produce dental plaque, and colonize catheters and prostheses.
c. Biofilms colonize open wounds and burned tissue.
d. All statements are incorrect.


Answer: d. All statements are incorrect.

Think about the conditions (temperature, light, pressure, and organic and inorganic materials) that you may find in a deep-sea hydrothermal vent. What type of prokaryotes, in terms of their metabolic needs (autotrophs, phototrophs, chemotrophs, etc.), would you expect to find there?

07:05

Think about the conditions (temperature, light, pressure, and organic and inorganic materials) that you may find in a deep-sea hydrothermal vent. What type of prokaryotes, in terms of their metabolic needs (autotrophs, phototrophs, chemotrophs, etc.), would you expect to find there?



In a deep-sea hydrothermal vent, there is no light, so prokaryotes would be chemotrophs instead of phototrophs. The source of carbon would be carbon dioxide dissolved in the ocean, so they would be autotrophs. There is not a lot of organic material in the ocean, so prokaryotes would probably use inorganic sources, thus they would be chemolitotrophs. The temperatures are very high in the hydrothermal vent, so the prokaryotes would be thermophilic.

Ammonification is the process by which _____.

07:04

Ammonification is the process by which _____.




a. ammonia is released during the decomposition of nitrogen-containing organic compounds
b. ammonium is converted to nitrite and nitrate in soils
c. nitrate from soil is transformed to gaseous nitrogen compounds such as NO, N2O, and N2
d. gaseous nitrogen is fixed to yield ammonia


Answer: a. ammonia is released during the decomposition of nitrogen-containing organic compounds

Which of the following statements about the nitrogen cycle is false?

07:04

Which of the following statements about the nitrogen cycle is false?




a. Nitrogen fixing bacteria exist on the root nodules of legumes and in the soil.
b. Denitrifying bacteria convert nitrates (NO3-) into nitrogen gas (N2).
c. Ammonification is the process by which ammonium ion (NH4+) is released from decomposing organic compounds.
d. Nitrification is the process by which nitrites (NO2-) are converted to ammonium ion (NH4+).


Answer: d. Nitrification is the process by which nitrites (NO2-) are converted to ammonium ion (NH4+).

Explain the statement that both types, bacteria and archaea, have the same basic structures, but built from different chemical components.

07:03

Explain the statement that both types, bacteria and archaea, have the same basic structures, but built from different chemical components.



Both bacteria and archaea have cell membranes and they both contain a hydrophobic portion. In the case of bacteria, it is a fatty acid; in the case of archaea, it is a hydrocarbon (phytanyl). Both bacteria and archaea have a cell wall that protects them. In the case of bacteria, it is composed of peptidoglycan, whereas in the case of archaea, it is pseudopeptidoglycan, polysaccharides, glycoproteins, or pure protein. Bacterial and archaeal flagella also differ in their chemical structure.

Mention three differences between bacteria and archaea.

07:03

Mention three differences between bacteria and archaea.



A possible answer is: Bacteria contain peptidoglycan in the cell wall; archaea do not. The cell membrane in bacteria is a lipid bilayer; in archaea, it can be a lipid bilayer or a monolayer. Bacteria contain fatty acids on the cell membrane, whereas archaea contain phytanyl.

The cell wall is ________.

07:02

The cell wall is ________.




a. interior to the cell membrane
b. exterior to the cell membrane
c. a part of the cell membrane
d. interior or exterior, depending on the particular cell


Answer: b. exterior to the cell membrane

Which of the following statements is true?

07:01

Which of the following statements is true?




a. Gram-positive bacteria have a single cell wall anchored to the cell membrane by lipoteichoic acid.
b. Porins allow entry of substances into both Gram-positive and Gram-negative bacteria.
c. The cell wall of Gram-negative bacteria is thick, and the cell wall of Gram-positive bacteria is thin.
d. Gram-negative bacteria have a cell wall made of peptidoglycan, whereas Gram-positive bacteria have a cell wall made of lipoteichoic acid.


Answer: a. Gram-positive bacteria have a single cell wall anchored to the cell membrane by lipoteichoic acid.

Halophiles are organisms that require________.

07:01

Halophiles are organisms that require________.




a. a salt concentration of at least 0.2 M
b. high sugar concentration
c. the addition of halogens
d. all of the above


Answer: a. a salt concentration of at least 0.2 M

Microbial mats __________.

07:00

Microbial mats __________.




a. are the earliest forms of life on Earth
b. obtained their energy and food from hydrothermal vents
c. are multi-layered sheet of prokaryotes including mostly bacteria but also archaea
d. all of the above


Answer: d. all of the above

Compared to free-floating bacteria, bacteria in biofilms often show increased resistance to antibiotics and detergents. Why do you think this might be the case?

07:00

Compared to free-floating bacteria, bacteria in biofilms often show increased resistance to antibiotics and detergents. Why do you think this might be the case?




The extracellular matrix and outer layer of cells protects the inner bacteria. The close proximity of cells also facilitates lateral gene transfer, a process by which genes such as antibiotic resistance genes are transferred from one bacterium to another. And even if lateral gene transfer does not occur, one bacterium that produces an exo-enzyme that destroys antibiotic may save neighboring bacteria.

Influenza virus is packaged in a viral envelope that fuses with the plasma membrane. This way, the virus can exit the host cell without killing it. What advantage does the virus gain by keeping the host cell alive?

07:00

Influenza virus is packaged in a viral envelope that fuses with the plasma membrane. This way, the virus can exit the host cell without killing it. What advantage does the virus gain by keeping the host cell alive?




The host cell can continue to make new virus particles

How are viroids like viruses?

06:59

How are viroids like viruses?



They both replicate in a cell, and they both contain nucleic acid.

Prions are responsible for variant Creutzfeldt- Jakob Disease, which has resulted in over 100 human deaths in Great Britain during the last 10 years. How do humans obtain this disease?

06:59

Prions are responsible for variant Creutzfeldt- Jakob Disease, which has resulted in over 100 human deaths in Great Britain during the last 10 years. How do humans obtain this disease?



This prion-based disease is transmitted through human consumption of infected meat.

Why is immunization after being bitten by a rabid animal so effective and why aren't people vaccinated for rabies like dogs and cats are?

06:59

Why is immunization after being bitten by a rabid animal so effective and why aren't people vaccinated for rabies like dogs and cats are?



Rabies vaccine works after a bite because it takes week for the virus to travel from the site of the bite to the central nervous system, where the most severe symptoms of the disease occur. Adults are not routinely vaccinated for rabies for two reasons: first, because the routine vaccination of domestic animals makes it unlikely that humans will contract rabies from an animal bite; second, if one is bitten by a wild animal or a domestic animal that one cannot confirm has been immunized, there is still time to give the vaccine and avoid the often fatal consequences of the disease.

One of the first and most important targets for drugs to fight infection with HIV (a retrovirus) is the reverse transcriptase enzyme. Why?

06:58

One of the first and most important targets for drugs to fight infection with HIV (a retrovirus) is the reverse transcriptase enzyme. Why?



Reverse Transcriptases Needed To make more HIV-1 viruses, so targeting the reverse transcriptase enzyme may be a way to inhibit the replication of the virus. Importantly, by targeting reverse transcriptase, we do little harm to the host cell, since host cells do not make reverse transcriptase. Thus, we can specifically attack the virus and not the host cell when we use reverse transcriptase inhibitors.

Why can't dogs catch the measles?

06:58

Why can't dogs catch the measles?



The virus can't attach to dog cells, because dog cells do not express the receptors for the virus and/or there is no cell within the dog that is permissive for viral replication.

The first electron micrograph of a virus (tobacco mosaic virus) was produced in 1939. Before that time, how did scientists know that viruses existed if they could not see them?

06:58

The first electron micrograph of a virus (tobacco mosaic virus) was produced in 1939. Before that time, how did scientists know that viruses existed if they could not see them? (Hint: Early scientists called viruses "filterable agents.")



Viruses pass through filters that eliminated all bacteria that were visible in the light microscopes at the time. As the bacteria-free filtrate could still cause infections when given to a healthy organism, this observation demonstrated the existence of very small infectious agents. These agents were later shown to be unrelated to bacteria and were classified as viruses.


Which statement is true of viroids?

06:57

Which statement is true of viroids?



a. They are single-stranded RNA particles.
b. They reproduce only outside of the cell.
c. They produce proteins.
d. They affect both plants and animals.


Answer: a. They are single-stranded RNA particles.

Which is true of DNA viruses?

06:56

Which is true of DNA viruses?



a. They use the host cell's machinery to produce new copies of their genome.
b. They all have envelopes.
c. They are the only kind of viruses that can cause cancer.
d. They are not important plant pathogens.


Answer: a. They use the host cell's machinery to produce new copies of their genome.

Oncogenic virus cores can be_______.

06:56

Oncogenic virus cores can be_______.



a. RNA
b. DNA
c. neither RNA nor DNA
d. either RNA or DNA


Answer: d. either RNA or DNA

Which transcriptase statement is true of reverse?

06:56

Which transcriptase statement is true of reverse?



a. It is a nucleic acid.
b. It infects cells.
c. It transcribes RNA to make DNA.
d. It is a lipid.


Answer: c. It transcribes RNA to make DNA.

Which statement is true of viral replication?

06:55

Which statement is true of viral replication?



a. In the process of apoptosis, the cell survives.
b. During attachment, the virus attaches at specific sites on the cell surface.
c. The viral capsid helps the host cell produce more copies of the viral genome.
d. mRNA works outside of the host cell to produce enzymes and proteins.


Answer: b. During attachment, the virus attaches at specific sites on the cell surface.

Which statement is not true of viral replication?

06:55

Which statement is not true of viral replication? 



a. lysogenic cycle kills the host cell.
b.There are six basic steps in the viral replication cycle.
c. Viral replication does not affect host cell function.
d. Newly released virions can infect adjacent cells.


Answer: d. Newly released virions can infect adjacent cells.

Viruses_______.

06:55

Viruses_______.



a. all have a round shape
b. cannot have a long shape
c. do not maintain any shape
d. vary in shape


Answer: d. vary in shape

Which statement is true?

06:54

Which statement is true?



a. A virion contains DNA and RNA.
b. Viruses are acellular.
c. Viruses replicate outside of the cell.
d. Most viruses are easily visualized with a light microscope.


Answer: b. Viruses are acellular.

Which of the following statements is false?

06:54

Which of the following statements is false?



a. In the lytic cycle, new phage are produced and released into the environment.
b. In the lysogenic cycle, phage DNA is incorporated into the host genome.
c. An environmental stressor can cause the phage to initiate the lysogenic cycle.
d. Cell lysis only occurs in the lytic cycle.


Answer: c. An environmental stressor can cause the phage to initiate the lysogenic cycle.

Which of the following statements about virus structure is true?

06:54

Which of the following statements about virus structure is true?



a. All viruses are encased in a viral membrane.
b. The capsomere is made up of small protein subunits called capsids.
c. DNA is the genetic material in all viruses.
d. Glycoproteins help the virus attach to the host cell.


Answer: d. Glycoproteins help the virus attach to the host cell.

Enzymes are

15:12

Enzymes are



A) carbohydrates.
B) lipids.
C) proteins.
D) nucleic acids.


Answer: C) proteins.

Which of the following is an example of hydrolysis?

15:11

Which of the following is an example of hydrolysis?



A) the reaction of two monosaccharides, forming a disaccharide with the release of water
B) the synthesis of two amino acids, forming a peptide with the release of water
C) the reaction of a fat, forming glycerol and fatty acids with the release of water
D) the reaction of a fat, forming glycerol and fatty acids with the utilization of water
E) the synthesis of a nucleotide from a phosphate, a pentose sugar, and a nitrogenous base with the production of a molecule of water


Answer: D) the reaction of a fat, forming glycerol and fatty acids with the utilization of water

A new organism is discovered in the forests of Costa Rica. Scientists there determine that the polypeptide sequence of hemoglobin from the new organism has 72 amino acid differences from humans, 65 differences from a gibbon, 49 differences from a rat, and 5 differences from a frog. These data suggest that the new organism

15:11

A new organism is discovered in the forests of Costa Rica. Scientists there determine that the polypeptide sequence of hemoglobin from the new organism has 72 amino acid differences from humans, 65 differences from a gibbon, 49 differences from a rat, and 5 differences from a frog. These data suggest that the new organism



A) is more closely related to humans than to frogs.
B) is more closely related to frogs than to humans.
C) may have evolved from gibbons but not rats.
D) is more closely related to humans than to rats.
E) may have evolved from rats but not from humans and gibbons.


Answer: B) is more closely related to frogs than to humans.

What is the structural feature that allows DNA to replicate?

15:11

What is the structural feature that allows DNA to replicate?



A) sugar-phosphate backbone
B) complementary pairing of the nitrogenous bases
C) disulfide bonding (bridging) of the two helixes
D) twisting of the molecule to form an α helix
E) three-component structure of the nucleotides


Answer: B) complementary pairing of the nitrogenous bases

Which of the following statements best summarizes the structural differences between DNA and RNA?

15:10

Which of the following statements best summarizes the structural differences between DNA and RNA?



A) RNA is a protein, whereas DNA is a nucleic acid.
B) DNA is a protein, whereas RNA is a nucleic acid.
C) DNA nucleotides contain a different sugar than RNA nucleotides.
D) RNA is a double helix, but DNA is single-stranded.
E) A and D are correct.


Answer: C) DNA nucleotides contain a different sugar than RNA nucleotides.

The difference between the sugar in DNA and the sugar in RNA is that the sugar in DNA

15:10

The difference between the sugar in DNA and the sugar in RNA is that the sugar in DNA



A) is a six-carbon sugar and the sugar in RNA is a five-carbon sugar.
B) can form a double-stranded molecule.
C) has a six-membered ring of carbon and nitrogen atoms.
D) can attach to a phosphate.
E) contains one less oxygen atom.


Answer: E) contains one less oxygen atom.

A double-stranded DNA molecule contains a total of 120 purines and 120 pyrimidines. This DNA molecule could be composed of

15:09

A double-stranded DNA molecule contains a total of 120 purines and 120 pyrimidines. This DNA molecule could be composed of



A) 120 adenine and 120 uracil molecules.
B) 120 thymine and 120 adenine molecules.
C) 120 cytosine and 120 thymine molecules.
D) 240 adenine and 240 cytosine molecules.
E) 240 guanine and 240 thymine molecules.


Answer: B) 120 thymine and 120 adenine molecules.

Which of the following descriptions best fits the class of molecules known as nucleotides?

15:09

Which of the following descriptions best fits the class of molecules known as nucleotides?



A) a nitrogenous base and a phosphate group
B) a nitrogenous base and a pentose sugar
C) a nitrogenous base, a phosphate group, and a pentose sugar
D) a phosphate group and an adenine or uracil
E) a pentose sugar and a purine or pyrimidine


Answer: C) a nitrogenous base, a phosphate group, and a pentose sugar

Of the following functions, the major purpose of RNA is to

15:08

Of the following functions, the major purpose of RNA is to



A) transmit genetic information to offspring.
B) function in the synthesis of protein.
C) make a copy of itself, thus ensuring genetic continuity.
D) act as a pattern or blueprint to form DNA.
E) form the genes of higher organisms.


Answer: B) function in the synthesis of protein.

Which of the following statements about the 5ʹ end of a polynucleotide strand of DNA is correct?

15:08

Which of the following statements about the 5ʹ end of a polynucleotide strand of DNA is correct?



A) The 5ʹ end has a hydroxyl group attached to the number 5 carbon of ribose.
B) The 5ʹ end has a phosphate group attached to the number 5 carbon of ribose.
C) The 5ʹ end has thymine attached to the number 5 carbon of ribose.
D) The 5ʹ end has a carboxyl group attached to the number 5 carbon of ribose.
E) The 5ʹ end is the fifth position on one of the nitrogenous bases.


Answer: B) The 5ʹ end has a phosphate group attached to the number 5 carbon of ribose.

DNAase is an enzyme that catalyzes the hydrolysis of the covalent bonds that join nucleotides together. What would first happen to DNA molecules treated with DNAase?

15:08

DNAase is an enzyme that catalyzes the hydrolysis of the covalent bonds that join nucleotides together. What would first happen to DNA molecules treated with DNAase?



A) The two strands of the double helix would separate.
B) The phosphodiester bonds between deoxyribose sugars would be broken.
C) The purines would be separated from the deoxyribose sugars.
D) The pyrimidines would be separated from the deoxyribose sugars.
E) All bases would be separated from the deoxyribose sugars.


Answer: B) The phosphodiester bonds between deoxyribose sugars would be broken.

The function of each protein is a consequence of its specific shape. What is the term used for a change in a proteinʹs three-dimensional shape or conformation due to disruption of hydrogen bonds, disulfide bridges, or ionic bonds?

15:07

The function of each protein is a consequence of its specific shape. What is the term used for a change in a proteinʹs three-dimensional shape or conformation due to disruption of hydrogen bonds, disulfide bridges, or ionic bonds?



A) hydrolysis
B) stabilization
C) destabilization
D) renaturation
E) denaturation


Answer: E) denaturation

What method did Frederick Sanger use to elucidate the structure of insulin?

15:07

What method did Frederick Sanger use to elucidate the structure of insulin?



A) X-ray crystallography
B) bioinformatics
C) analysis of amino acid sequence of small fragments
D) NMR spectroscopy
E) high-speed centrifugation


Answer: C) analysis of amino acid sequence of small fragments

What would be an unexpected consequence of changing one amino acid in a protein consisting of 325 amino acids?

15:06

What would be an unexpected consequence of changing one amino acid in a protein consisting of 325 amino acids?



A) The primary structure of the protein would be changed.
B) The tertiary structure of the protein might be changed.
C) The biological activity or function of the protein might be altered.
D) Only A and C are correct.
E) A, B, and C are correct.


Answer: E) A, B, and C are correct.

The R group or side chain of the amino acid serine is —CH2OH. The R group or side chain of the amino acid alanine is —CH3. Where would you expect to find these amino acids in a globular protein in aqueous solution?

15:06

The R group or side chain of the amino acid serine is —CH2OH. The R group or side chain of the amino acid alanine is —CH3. Where would you expect to find these amino acids in a globular protein in aqueous solution?



A) Serine would be in the interior, and alanine would be on the exterior of the globular protein.
B) Alanine would be in the interior, and serine would be on the exterior of the globular protein.
C) Both serine and alanine would be in the interior of the globular protein.
D) Both serine and alanine would be on the exterior of the globular protein.
E) Both serine and alanine would be in the interior and on the exterior of the globular protein.


Answer: B) Alanine would be in the interior, and serine would be on the exterior of the globular protein.


The tertiary structure of a protein is the

15:05

The tertiary structure of a protein is the



A) bonding together of several polypeptide chains by weak bonds.
B) order in which amino acids are joined in a polypeptide chain.
C) unique three-dimensional shape of the fully folded polypeptide.
D) organization of a polypeptide chain into an α helix or β pleated sheet.
E) overall protein structure resulting from the aggregation of two or more polypeptide subunits.


Answer: C) unique three-dimensional shape of the fully folded polypeptide.

Polysaccharides, lipids, and proteins are similar in that they

15:04

Polysaccharides, lipids, and proteins are similar in that they



A) are synthesized from monomers by the process of hydrolysis.
B) are synthesized from monomers by dehydration reactions.
C) are synthesized as a result of peptide bond formation between monomers.
D) are decomposed into their subunits by dehydration reactions.
E) all contain nitrogen in their monomer building blocks.


Answer: B) are synthesized from monomers by dehydration reactions.

There are 20 different amino acids. What makes one amino acid different from another?

15:03

There are 20 different amino acids. What makes one amino acid different from another?



A) different carboxyl groups attached to an alpha (α) carbon
B) different amino groups attached to an alpha (α) carbon
C) different side chains (R groups) attached to an alpha (α) carbon
D) different alpha (α) carbons
E) different asymmetric carbons


Answer: C) different side chains (R groups) attached to an alpha (α) carbon

The bonding of two amino acid molecules to form a larger molecule requires

15:03

The bonding of two amino acid molecules to form a larger molecule requires



A) the release of a water molecule.
B) the release of a carbon dioxide molecule.
C) the addition of a nitrogen atom.
D) the addition of a water molecule.
E) both B and C


Answer: A) the release of a water molecule.

Why are human sex hormones considered to be lipids?

15:03

Why are human sex hormones considered to be lipids?



A) They are essential components of cell membranes.
B) They are steroids, which are not soluble in water.
C) They are made of fatty acids.
D) They are hydrophilic compounds.
E) They contribute to atherosclerosis.


Answer: B) They are steroids, which are not soluble in water.

The hydrogenation of vegetable oil results in which of the following?

15:02

The hydrogenation of vegetable oil results in which of the following?



A) saturated fats and unsaturated fats with trans double bonds
B) an increased contribution to artherosclerosis
C) the oil (fat) being a solid at room temperature
D) A and C only
E) A, B, and C


Answer: E) A, B, and C

Which of the following is true regarding saturated fatty acids?

15:02

Which of the following is true regarding saturated fatty acids?



A) They are the predominant fatty acid in corn oil.
B) They have double bonds between carbon atoms of the fatty acids.
C) They are the principal molecules in lard and butter.
D) They are usually liquid at room temperature.
E) They are usually produced by plants.


Answer: C) They are the principal molecules in lard and butter.

What is a triacylglycerol?

15:02

What is a triacylglycerol?



A) a protein with tertiary structure
B) a lipid made with three fatty acids and glycerol
C) a lipid that makes up much of the plasma membrane
D) a molecule formed from three alcohols by dehydration reactions
E) a carbohydrate with three sugars joined together by glycosidic linkages


Answer: B) a lipid made with three fatty acids and glycerol

Which of the following statements is false for the class of biological molecules known as lipids?

15:01

Which of the following statements is false for the class of biological molecules known as lipids?



A) They are soluble in water.
B) They are an important constituent of cell membranes.
C) They contain more energy than proteins and carbohydrates.
D) They are not true polymers.
E) They contain waxes and steroids.


Answer: A) They are soluble in water.

All of the following statements concerning saturated fats are true except

15:01

All of the following statements concerning saturated fats are true except



A) They are more common in animals than in plants.
B) They have multiple double bonds in the carbon chains of their fatty acids.
C) They generally solidify at room temperature.
D) They contain more hydrogen than saturated fats having the same number of carbon atoms.
E) They are one of several factors that contribute to atherosclerosis.


Answer: B) They have multiple double bonds in the carbon chains of their fatty acids.

Humans can digest starch but not cellulose because

15:01

Humans can digest starch but not cellulose because



A) the monomer of starch is glucose, while the monomer of cellulose is galactose.
B) humans have enzymes that can hydrolyze the beta (β) glycosidic linkages of starch but not the alpha (α) glycosidic linkages of cellulose.
C) humans have enzymes that can hydrolyze the alpha (α) glycosidic linkages of starch but not the beta (β) glycosidic linkages of cellulose.
D) humans harbor starch-digesting bacteria in the digestive tract.
E) the monomer of starch is glucose, while the monomer of cellulose is maltose.


Answer: C) humans have enzymes that can hydrolyze the alpha (α) glycosidic linkages of starch

Which of the following is true of cellulose?

15:01

Which of the following is true of cellulose?



A) It is a polymer composed of sucrose monomers.
B) It is a storage polysaccharide for energy in plant cells.
C) It is a storage polysaccharide for energy in animal cells.
D) It is a major structural component of plant cell walls.
E) It is a major structural component of animal cell plasma membranes.


Answer: D) It is a major structural component of plant cell walls.

Which of the following is true of both starch and cellulose?

15:00

Which of the following is true of both starch and cellulose?



A) They are both polymers of glucose.
B) They are geometric isomers of each other.
C) They can both be digested by humans.
D) They are both used for energy storage in plants.
E) They are both structural components of the plant cell wall.


Answer: A) They are both polymers of glucose.


Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?

14:58

Which of the following best summarizes the relationship between dehydration reactions and hydrolysis?



A) Dehydration reactions assemble polymers, and hydrolysis reactions break down polymers.
B) Macromolecular synthesis occurs through the removal of water and digestion occurs through the addition of water.
C) Dehydration reactions can occur only after hydrolysis.
D) Hydrolysis creates monomers, and dehydration reactions break down polymers.
E) A and B are correct.


Answer: E) A and B are correct.

For this pair of items, choose the option that best describes their relationship.

14:49

For this pair of items, choose the option that best describes their relationship.

(A) The number of purines in the DNA strand 5ʹ-AAGAGGAGAAA-3ʹ
(B) The number of pyrimidines in the DNA strand 5ʹ-AAGAGGAGAAA-3ʹ


A) Item (A) is greater than item (B).
B) Item (A) is less than item (B).
C) Item (A) is exactly or very approximately equal to item (B).
D) Item (A) may stand in more than one of the above relations to item (B).


Answer: A) Item (A) is greater than item (B).

For this pair of items, choose the option that best describes their relationship.

14:49

For this pair of items, choose the option that best describes their relationship.


(A) The probability that amino acids with nonpolar side chains are hydrophobic.
(B) The probability that amino acids with side chains containing a carboxyl group are hydrophobic.


A) Item (A) is greater than item (B).
B) Item (A) is less than item (B).
C) Item (A) is exactly or very approximately equal to item (B).
D) Item (A) may stand in more than one of the above relations to item (B).


Answer: A) Item (A) is greater than item (B).

For this pair of items, choose the option that best describes their relationship.

14:49

For this pair of items, choose the option that best describes their relationship.

(A) The number of cis double bonds in saturated fatty acids
(B) The number of cis double bonds in unsaturated fatty acids



A) Item (A) is greater than item (B).
B) Item (A) is less than item (B).
C) Item (A) is exactly or very approximately equal to item (B).
D) Item (A) may stand in more than one of the above relations to item (B).


Answer: B) Item (A) is less than item (B).

For this pair of items, choose the option that best describes their relationship.

14:48

For this pair of items, choose the option that best describes their relationship.

(A) The probability of finding chitin in fungal cell walls
(B) The probability of finding chitin in arthropod exoskeletons


A) Item (A) is greater than item (B).
B) Item (A) is less than item (B).
C) Item (A) is exactly or very approximately equal to item (B).
D) Item (A) may stand in more than one of the above relations to item (B).


Answer: C) Item (A) is exactly or very approximately equal to item (B).

For this pair of items, choose the option that best describes their relationship.

14:48

For this pair of items, choose the option that best describes their relationship.

(A) The number of alpha glucose 1-4 linkages in cellulose
(B) The number of alpha glucose 1-4 linkages in starch


A) Item (A) is greater than item (B).
B) Item (A) is less than item (B).
C) Item (A) is exactly or very approximately equal to item (B).
D) Item (A) may stand in more than one of the above relations to item (B).


Answer: B) Item (A) is less than item (B).

You have two beakers. One contains a solution of HCl at pH = 1.0. The other contains a solution of NaOH at pH = 13. Into a third beaker, you slowly and cautiously pour 20 mL of the HCL and 20 mL of the NaOH. After complete stirring, the pH of the mixture will be

14:43

You have two beakers. One contains a solution of HCl at pH = 1.0. The other contains a solution of NaOH at pH = 13. Into a third beaker, you slowly and cautiously pour 20 mL of the HCL and 20 mL of the NaOH. After complete stirring, the pH of the mixture will be



A) 2.0.
B) 12.0.
C) 7.0.
D) 5.0.
E) 9.0


Answer: C) 7.0.

You have two beakers; one contains pure water, the other contains pure methanol (wood alcohol). The covalent bonds of methanol molecules are nonpolar, so there are no hydrogen bonds among methanol molecules. You pour crystals of table salt (NaCl) into each beaker. Predict what will happen.

14:42

You have two beakers; one contains pure water, the other contains pure methanol (wood alcohol). The covalent bonds of methanol molecules are nonpolar, so there are no hydrogen bonds among methanol molecules. You pour crystals of table salt (NaCl) into each beaker. Predict what will happen.



A) Equal amounts of NaCl crystals will dissolve in both water and methanol.
B) NaCl crystals will NOT dissolve in either water or methanol.
C) NaCl crystals will dissolve readily in water but will not dissolve in methanol.
D) NaCl crystals will dissolve readily in methanol but will not dissolve in water.
E) When the first crystals of NaCl are added to water or to methanol, they will not dissolve; but as more crystals are added, the crystals will begin to dissolve faster and faster.


Answer: C) NaCl crystals will dissolve readily in water but will not dissolve in methanol.

Equal volumes of vinegar from a freshly-opened bottle are added to each of the following solutions. After complete mixing, which of the mixtures will have the highest pH?

14:42

Equal volumes of vinegar from a freshly-opened bottle are added to each of the following solutions. After complete mixing, which of the mixtures will have the highest pH?



A) 100 mL of pure water
B) 100 mL of freshly-brewed coffee
C) 100 mL of household cleanser containing 0.5M ammonia
D) 100 mL of freshly-squeezed orange juice
E) 100 mL of tomato juice


Answer: C) 100 mL of household cleanser containing 0.5M ammonia

A 100 mL beaker contains 10 mL of NaOH solution at pH = 13. A technician carefully pours into the beaker, 10 mL of HCl at pH = 1. Which of the following statements correctly describes the results of this mixing?

14:42

A 100 mL beaker contains 10 mL of NaOH solution at pH = 13. A technician carefully pours into the beaker, 10 mL of HCl at pH = 1. Which of the following statements correctly describes the results of this mixing?



A) The concentration of Na+ ion rises.
B) The concentration of Cl- ion falls.
C) The concentration of undissociated H2O molecules remains unchanged.
D) The pH of the beakerʹs contents rises.
E) The pH of the beakerʹs contents falls.


Answer: E) The pH of the beakerʹs contents falls.

Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2 + H2O → H2CO3. Carbonic acid (H2CO3) is a weak acid. Respiring cells release CO2. What prediction can we make about the pH of blood as that blood first comes in contact with respiring cells?

14:42

Carbon dioxide (CO2) is readily soluble in water, according to the equation CO2 + H2O → H2CO3. Carbonic acid (H2CO3) is a weak acid. Respiring cells release CO2. What prediction can we make about the pH of blood as that blood first comes in contact with respiring cells?



A) Blood pH will decrease slightly.
B) Blood pH will increase slightly.
C) Blood pH will remain unchanged.
D) Blood pH will first increase, then decrease as CO2 combines with hemoglobin.
E) Blood pH will first decrease, then increase sharply as CO2 combines with hemoglobin.


Answer: A) Blood pH will decrease slightly.

Pure, freshly-distilled water has a pH of 7. This means that

14:42

Pure, freshly-distilled water has a pH of 7. This means that



A) there are no H+ ions in the water.
B) there are no OH- ions in the water.
C) the concentration of H+ ions in the water equals the concentration of OH- ions in the water.
D) the concentration of H+ ions in the water is 7 times the concentration of OH- ions in the water.
E) The concentration of OH- ions in the water is 7 times the concentration of H+ ions in the water.


Answer: C) the concentration of H+ ions in the water equals the concentration of OH- ions in the water.

Consider two solutions: solution X has a pH of 4; solution Y has a pH of 7. From this information, we can reasonably conclude that

14:41

Consider two solutions: solution X has a pH of 4; solution Y has a pH of 7. From this information, we can reasonably conclude that



A) solution Y has no free hydrogen ions (H+).
B) the concentration of hydrogen ions in solution X is 30 times as great as the concentration of hydrogen ions in solution Y.
C) the concentration of hydrogen ions in solution Y is 1,000 times as great as the concentration of hydrogen ions in solution X.
D) the concentration of hydrogen ions in solution X is 3 times as great as the concentration of hydrogen ions in solution Y.
E) None of the other answer choices correctly describes these solutions.


Answer: E) None of the other answer choices correctly describes these solutions.

Research indicates that acid precipitation can damage living organisms by

14:41

Research indicates that acid precipitation can damage living organisms by



A) buffering aquatic systems such as lakes and streams.
B) decreasing the H+ concentration of lakes and streams.
C) increasing the OH- concentration of lakes and streams.
D) washing away certain mineral ions that help buffer soil solution and are essential nutrients for plant growth.
E) both B and C


Answer: D) washing away certain mineral ions that help buffer soil solution and are essential nutrients for plant growth.

Assume that acid rain has lowered the pH of a particular lake to pH 4.0. What is the hydroxyl ion concentration of this lake?

14:41

Assume that acid rain has lowered the pH of a particular lake to pH 4.0. What is the hydroxyl ion concentration of this lake?



A) 1 × 10-10 mol of hydroxyl ion per liter of lake water
B) 1 × 10-4 mol of hydroxyl ion per liter of lake water
C) 10.0 M with regard to hydroxyl ion concentration
D) 4.0 M with regard to hydroxyl ion concentration
E) both B and D


Answer: A) 1 × 10-10 mol of hydroxyl ion per liter of lake water

Buffers are substances that help resist shifts in pH by

14:41

Buffers are substances that help resist shifts in pH by



A) releasing H+ in acidic solutions.
B) donating H+ to a solution when they have been depleted.
C) releasing OH- in basic solutions.
D) accepting H+ when the are in excess.
E) Both B and D are correct.


Answer: E) Both B and D are correct.

Which of the following statements is true about buffer solutions?

14:40

Which of the following statements is true about buffer solutions?



A) They maintain a constant pH when bases are added to them but not when acids are added to them.
B) They maintain a constant pH when acids are added to them but not when bases are added to them.
C) They maintain a constant pH of exactly 7 in all living cells and biological fluids.
D) They maintain a relatively constant pH when either acids or bases are added to them.
E) They are found only in living systems and biological fluids.


Answer: D) They maintain a relatively constant pH when either acids or bases are added to them.

If the pH of a solution is increased from pH 5 to pH 7, it means that the

14:40

If the pH of a solution is increased from pH 5 to pH 7, it means that the



A) concentration of H+ is twice (2X) what it was at pH 5.
B) concentration of H+ is half (1/2) what it was at pH 5.
C) concentration of OH- is 100 times greater than what it was at pH 5.
D) concentration of OH- is one-hundredth (0.01X) what it was at pH 5.
E) concentration of H+ is 100 times greater and the concentration of OH- is one-hundredth what they were at pH 5.


Answer: C) concentration of OH- is 100 times greater than what it was at pH 5.

If the pH of a solution is decreased from 9 to 8, it means that the

14:39

If the pH of a solution is decreased from 9 to 8, it means that the



A) concentration of H+ has decreased to one-tenth (1/10) what it was at pH 9.
B) concentration of H+ has increased 10-fold (10X) compared to what it was at pH 9.
C) concentration of OH- has increased 10-fold (10X) compared to what it was at pH 9.
D) concentration of OH- has decreased to one-tenth (1/10) what it was at pH 9.
E) Both B and D are correct.


Answer: E) Both B and D are correct.

Which of the following statements is completely correct?

14:38

Which of the following statements is completely correct?



A) H2CO3 is a weak acid, and NaOH is a weak base (alkali).
B) H2CO3 is a strong acid, and NaOH is a strong base (alkali).
C) NH3 is a weak base (alkali), and H2CO3 is a strong acid.
D) NH3 is a weak base (alkali), and HCl is a strong acid.
E) NH3 is a strong base (alkali), and HCl is a weak acid.


Answer: D) NH3 is a weak base (alkali), and HCl is a strong acid.

You have a freshly-prepared 1M solution of glucose in water. You carefully pour out a 100 mL sample of that solution. How many glucose molecules are included in that 100 mL sample?

14:37

You have a freshly-prepared 1M solution of glucose in water. You carefully pour out a 100 mL sample of that solution. How many glucose molecules are included in that 100 mL sample?



A) 6.02 × 1023
B) 3.01 × 1023
C) 6.02 × 1024
D) 12.04 × 1023
E) 6.02 × 1022


Answer: C) 6.02 × 1024

The molecular mass of glucose (C6H12O6) is 180 g. Which of the following procedures should you carry out to make a 0.5 M solution of glucose?

14:36

The molecular mass of glucose (C6H12O6) is 180 g. Which of the following procedures should you carry out to make a 0.5 M solution of glucose?



A) Dissolve 0.5 g of glucose in a small volume of water, and then add more water until the total volume of solution is 1 L.
B) Dissolve 90 g of glucose in a small volume of water, and then add more water until the total volume of the solution is 1 L.
C) Dissolve 180 g of glucose in a small volume of water, and then add more water until the total volume of the solution is 1 L.
D) Dissolve 0.5 g of glucose in 1 L of water.
E) Dissolve 180 g of glucose in 1 L of water.


Answer: B) Dissolve 90 g of glucose in a small volume of water, and then add more water until the total volume of the solution is 1 L.

The molecular mass of glucose is 180 g. Which of the following procedures should you carry out to make a 1 M solution of glucose?

14:36

The molecular mass of glucose is 180 g. Which of the following procedures should you carry out to make a 1 M solution of glucose?



A) Dissolve 1 g of glucose in 1 L of water.
B) Dissolve 180 g of glucose in 1 L of water.
C) Dissolve 180 g of glucose in 100 g of water.
D) Dissolve 180 mg (milligrams) of glucose in 1 L of water.
E) Dissolve 180 g of glucose in water, and then add more water until the total volume of the solution is 1 L.


Answer: E) Dissolve 180 g of glucose in water, and then add more water until the total volume of the solution is 1 L.

When an ionic compound such as sodium chloride (NaCl) is placed in water the component atoms of the NaCl crystal dissociate into individual sodium ions (Na+) and chloride ions (Cl-). In contrast, the atoms of covalently bonded molecules (e.g., glucose, sucrose, glycerol) do not generally dissociate when placed in aqueous solution. Which of the following solutions would be expected to contain the greatest number of particles (molecules or ions)?

14:36

When an ionic compound such as sodium chloride (NaCl) is placed in water the component atoms of the NaCl crystal dissociate into individual sodium ions (Na+) and chloride ions (Cl-). In contrast, the atoms of covalently bonded molecules (e.g., glucose, sucrose, glycerol) do not generally dissociate when placed in aqueous solution. Which of the following solutions would be expected to contain the greatest number of particles (molecules or ions)?



A) 1 L of 0.5 M NaCl
B) 1 L of 0.5 M glucose
C) 1 L of 1.0 M NaCl
D) 1 L of 1.0 M glucose
E) C and D will contain equal numbers of particles.


Answer: C) 1 L of 1.0 M NaCl

One mole (mol) of a substance is

14:33

One mole (mol) of a substance is



A) 6.02 × 1023 molecules of the substance.
B) 1 g of the substance dissolved in 1 L of solution.
C) the largest amount of the substance that can be dissolved in 1 L of solution.
D) the molecular mass of the substance expressed in grams.
E) A and D only


Answer: E) A and D only

Hydrophobic substances such as vegetable oil are

14:33

Hydrophobic substances such as vegetable oil are



A) nonpolar substances that repel water molecules.
B) nonpolar substances that have an attraction for water molecules.
C) polar substances that repel water molecules.
D) polar substances that have an affinity for water.
E) charged molecules that hydrogen-bond with water molecules.


Answer: A) nonpolar substances that repel water molecules.

Why does ice float in liquid water?

14:32

Why does ice float in liquid water?



A) The liquid water molecules have more kinetic energy and thus support the ice.
B) The ionic bonds between the molecules in ice prevent the ice from sinking.
C) Ice always has air bubbles that keep it afloat.
D) Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water.
E) The crystalline lattice of ice causes it to be denser than liquid water


Answer: D) Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water.

Temperature usually increases when water condenses. Which behavior of water is most directly responsible for this phenomenon?

14:32

Temperature usually increases when water condenses. Which behavior of water is most directly responsible for this phenomenon?



A) the change in density when it condenses to form a liquid or solid
B) reactions with other atmospheric compounds
C) the release of heat by the formation of hydrogen bonds
D) the release of heat by the breaking of hydrogen bonds
E) the high surface tension of water


Answer: C) the release of heat by the formation of hydrogen bonds

Waterʹs high specific heat is mainly a consequence of the

14:31

Waterʹs high specific heat is mainly a consequence of the



A) small size of the water molecules.
B) high specific heat of oxygen and hydrogen atoms.
C) absorption and release of heat when hydrogen bonds break and form.
D) fact that water is a poor heat conductor.
E) inability of water to dissipate heat into dry air.


Answer: C) absorption and release of heat when hydrogen bonds break and form.

The nutritional information on a cereal box shows that one serving of a dry cereal has 200 kilocalories. If one were to burn one serving of the cereal, the amount of heat given off would be sufficient to raise the temperature of 20 kg of water how many degrees Celsius?

14:31

The nutritional information on a cereal box shows that one serving of a dry cereal has 200 kilocalories. If one were to burn one serving of the cereal, the amount of heat given off would be sufficient to raise the temperature of 20 kg of water how many degrees Celsius?



A) 0.2°C
B) 1.0°C
C) 2.0°C
D) 10.0°C
E) 20.0°C


Answer: D) 10.0°C

Which of the following statements correctly defines a kilocalorie?

14:31

Which of the following statements correctly defines a kilocalorie?



A) the amount of heat required to raise the temperature of 1 g of water by 1°F
B) the amount of heat required to raise the temperature of 1 g of water by 1°C
C) the amount of heat required to raise the temperature of 1 kg of water by 1°F
D) the amount of heat required to raise the temperature of 1 kg of water by 1°C
E) the amount of heat required to raise the temperature of 1,000 g of water by 1°F


Answer: D) the amount of heat required to raise the temperature of 1 kg of water by 1°C

Which of the following takes place as an ice cube cools a drink?

14:31

Which of the following takes place as an ice cube cools a drink?



A) Molecular collisions in the drink increase.
B) Kinetic energy in the drink decreases.
C) A calorie of heat energy is transferred from the ice to the water of the drink.
D) The specific heat of the water in the drink decreases.
E) Evaporation of the water in the drink increases.


Answer: B) Kinetic energy in the drink decreases.

Which of the following effects is produced by the high surface tension of water?

14:30

Which of the following effects is produced by the high surface tension of water?



A) Lakes donʹt freeze solid in winter, despite low temperatures.
B) A water strider can walk across the surface of a small pond.
C) Organisms resist temperature changes, although they give off heat due to chemical reactions.
D) Water can act as a solvent.
E) The pH of water remains exactly neutral.


Answer: B) A water strider can walk across the surface of a small pond.

Water is able to form hydrogen bonds because

14:29

Water is able to form hydrogen bonds because



A) oxygen has a valence of 2.
B) the water molecule is shaped like a tetrahedron.
C) the bonds that hold together the atoms in a water molecule are polar covalent bonds.
D) the oxygen atom in a water molecule has a weak positive charge.
E) each of the hydrogen atoms in a water molecule is weakly negative in charge.


Answer: C) the bonds that hold together the atoms in a water molecule are polar covalent bonds.

An example of a hydrogen bond is the bond between

14:29

An example of a hydrogen bond is the bond between



A) C and H in methane (CH4).
B) the H of one water molecule and the O of another water molecule.
C) Na+and Cl- in salt.
D) the two hydrogen atoms in a molecule of hydrogen gas (H2).
E) Mg+and Cl- in MgCl2.


Answer: B) the H of one water molecule and the O of another water molecule.

The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called?

14:29

The slight negative charge at one end of one water molecule is attracted to the slight positive charge of another water molecule. What is this attraction called?



A) a covalent bond
B) a hydrogen bond
C) an ionic bond
D) a hydrophilic bond
E) a hydrophobic bond


Answer: B) a hydrogen bond

Based on Figure 7.19 in your textbook, which of these experimental treatments would increase the rate of sucrose transport into the cell?

10:40

Based on Figure 7.19 in your textbook, which of these experimental treatments would increase the rate of sucrose transport into the cell?




A)
decreasing extracellular sucrose concentration
B)
decreasing extracellular pH
C)
decreasing cytoplasmic pH
D)
adding an inhibitor that blocks the regeneration of ATP
E)
adding a substance that makes the membrane more permeable to hydrogen ions


Answer: B

Which of the following processes includes all others?

10:40

Which of the following processes includes all others?



A)
osmosis
B)
diffusion of a solute across a membrane
C)
facilitated diffusion
D)
passive transport
E)
transport of an ion down its electrochemical gradient


Answer: D

Which of the following factors would tend to increase membrane fluidity?

10:40

Which of the following factors would tend to increase membrane fluidity?



A)
a greater proportion of unsaturated phospholipids
B)
a greater proportion of saturated phospholipids
C)
a lower temperature
D)
a relatively high protein content in the membrane
E)
a greater proportion of relatively large glycolipids compared with lipids having smaller molecular masses


Answer: A

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly

10:40

According to the fluid mosaic model of membrane structure, proteins of the membrane are mostly



A)
spread in a continuous layer over the inner and outer surfaces of the membrane.
B)
confined to the hydrophobic core of the membrane.
C)
embedded in a lipid bilayer.
D)
randomly oriented in the membrane, with no fixed inside-outside polarity.
E)
free to depart from the fluid membrane and dissolve in the surrounding solution.


Answer: C

In what way do the membranes of a eukaryotic cell vary?

10:39

In what way do the membranes of a eukaryotic cell vary?



A)
Phospholipids are found only in certain membranes.
B)
Certain proteins are unique to each membrane.
C)
Only certain membranes of the cell are selectively permeable.
D)
Only certain membranes are constructed from amphipathic molecules.
E)
Some membranes have hydrophobic surfaces exposed to the cytoplasm, while
others have hydrophilic surfaces facing the cytoplasm.


Answer: B

In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis?

10:39

In receptor-mediated endocytosis, receptor molecules initially project to the outside of the cell. Where do they end up after endocytosis?



A)
on the outside of vesicles
B)
on the inside surface of the cell membrane
C)
on the inside surface of the vesicle
D)
on the outer surface of the nucleus
E)
on the ER


Answer: C

The difference between pinocytosis and receptor-mediated endocytosis is that

10:12

The difference between pinocytosis and receptor-mediated endocytosis is that



A)
pinocytosis brings only water into the cell, but receptor-mediated endocytosis brings in other molecules as well.
B)
pinocytosis increases the surface area of the plasma membrane whereas receptor-mediated endocytosis decreases the plasma membrane surface area.
C)
pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity.
D)
pinocytosis requires cellular energy, but receptor-mediated endocytosis does not.
E)
pinocytosis can concentrate substances from the extracellular fluid, but receptor-mediated endocytosis cannot.


Answer: A

Familial hypercholesterolemia is characterized by which of the following?

10:11

Familial hypercholesterolemia is characterized by which of the following?




A)
defective LDL receptors on the cell membranes
B)
poor attachment of the cholesterol to the extracellular matrix of cells
C)
a poorly formed lipid bilayer that cannot incorporate cholesterol into cell membranes
D)
inhibition of the cholesterol active transport system in red blood cells
E)
a general lack of glycolipids in the blood cell membranes


Answer: A

Several seriously epidemic viral diseases of earlier centuries were then incurable because they resulted in severe dehydration due to vomiting and diarrhea. Today they are usually not fatal because we have developed which of the following?

10:10

Several seriously epidemic viral diseases of earlier centuries were then incurable because they resulted in severe dehydration due to vomiting and diarrhea. Today they are usually not fatal because we have developed which of the following?




A)
antiviral medications that are efficient and work well with all viruses
B)
antibiotics against the viruses in question
C)
intravenous feeding techniques
D)
medication to prevent blood loss
E)
hydrating drinks that include high concentrations of salts and glucose


Answer: E

Proton pumps are used in various ways by members of every kingdom of organisms. What does this most probably mean?

10:10

Proton pumps are used in various ways by members of every kingdom of organisms. What does this most probably mean?



A)
Proton pumps must have evolved before any living organisms were present on the earth.
B)
Proton pumps are fundamental to all cell types.
C)
The high concentration of protons in the ancient atmosphere must have necessitated a pump mechanism.
D)
Cells with proton pumps were maintained in each Kingdom by natural selection.
E)
Proton pumps are necessary to all cell membranes.


Answer: D

The sodium-potassium pump in animal cells requires cytoplasmic ATP to pump ions across the plasma membrane. When the proteins of the pump are first synthesized in the rough ER, what side of the ER membrane will the ATP binding site be on?

10:09

The sodium-potassium pump in animal cells requires cytoplasmic ATP to pump ions across the plasma membrane. When the proteins of the pump are first synthesized in the rough ER, what side of the ER membrane will the ATP binding site be on?



A)
It will be on the cytoplasmic side of the ER.
B)
It will be on the side facing the interior of the ER.
C)
It could be facing in either direction because the orientation of proteins is scrambled in the Golgi apparatus.
D)
It doesn't matter, because the pump is not active in the ER.


Answer: A

Ions diffuse across membranes down their

10:09

Ions diffuse across membranes down their



A)
chemical gradients.
B)
concentration gradients.
C)
electrical gradients.
D)
electrochemical gradients.
E)
A and B are correct.


Answer: D

The movement of potassium into an animal cell requires

10:06

The movement of potassium into an animal cell requires



A)
low cellular concentrations of sodium.
B)
high cellular concentrations of potassium.
C)
an energy source such as ATP or a proton gradient.
D)
a cotransport protein.
E)
a gradient of protons across the plasma membrane.


Answer: C

If a membrane protein in an animal cell is involved in the cotransport of glucose and sodium ions into the cell, which of the following is most likely true?

10:06

If a membrane protein in an animal cell is involved in the cotransport of glucose and sodium ions into the cell, which of the following is most likely true?



A)
The sodium ions are moving down their electrochemical gradient while glucose is moving up.
B)
Glucose is entering the cell along its concentration gradient.
C)
Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell.
D)
Potassium ions move across the same gradient as sodium ions.
E)
A substance that blocked sodium ions from binding to the cotransport protein would also block the transport of glucose.


Answer: E

The sodium-potassium pump is called an electrogenic pump because it

10:06

The sodium-potassium pump is called an electrogenic pump because it




A)
pumps equal quantities of Na+ and K+ across the membrane.
B)
pumps hydrogen ions out of the cell.
C)
contributes to the membrane potential.
D)
ionizes sodium and potassium atoms.
E)
is used to drive the transport of other molecules against a concentration gradient.


Answer: C

In most cells, there are electrochemical gradients of many ions across the plasma membrane even though there are usually only one or two electrogenic pumps present in the membrane. The gradients of the other ions are most likely accounted for by

10:05

In most cells, there are electrochemical gradients of many ions across the plasma membrane even though there are usually only one or two electrogenic pumps present in the membrane. The gradients of the other ions are most likely accounted for by




A)
cotransport proteins.
B)
ion channels.
C)
carrier proteins.
D)
B and C only
E)
A, B, and C


Answer: A

What is the voltage across a membrane called?

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What is the voltage across a membrane called?



A)
water potential
B)
chemical gradient
C)
membrane potential
D)
osmotic potential
E)
electrochemical gradient


Answer: C

Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?

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Glucose diffuses slowly through artificial phospholipid bilayers. The cells lining the small intestine, however, rapidly move large quantities of glucose from the glucose-rich food into their glucose-poor cytoplasm. Using this information, which transport mechanism is most probably functioning in the intestinal cells?



A)
simple diffusion
B)
phagocytosis
C)
active transport pumps
D)
exocytosis
E)
facilitated diffusion


Answer: E
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