PCB 3023C / PCB3023C Exam 2: (Latest Update 2026 / 2027) Cell Biology | Questions & Answers | Exam study material | 100% Correct - FGCU

PCB 3023C / PCB3023C Exam 2: (Latest Update 2026 / 2027) Cell Biology | Questions & Answers | Exam study material | 100% Correct - FGCU PCB 3023 Exam 2026 / 2027 Academic Year Q: Which of the following changes is least likely to arise from a point mutation in a regulatory region of a gene? A) A mutation that changes the time on an organism's life during which a protein is expressed B) A mutation that eliminates the production of a protein in a specific cell type C) A mutation that changes the subcellular localization of a protein D) A mutation that increases the level of protein production in a cell C) A mutation that changes the subcellular localization of a protein Q: Which one statement below is true? A. To develop a new function, evolution essentially builds from first principles, designing from scratch, to find the best possible solution. B. Nearly every instance of DNA duplication leads to a new functional gene. C. A pseudogene is very similar to a functional gene but cannot be expressed because of mutations. D. Most genes in vertebrates are unique, and only a few genes are members of multigene families. E. Horizontal transfer is very rare and thus has had little influence on the genomes of bacteria. C. A pseudogene is very similar to a functional gene but cannot be expressed because of mutations. Q: Which of the following is not a mechanism of genetic variation? A. purifying selection B. mutation within the regulatory DNA of a gene C. gene duplication and divergence D. exon shuffling E. mutation within the coding sequence of a gene A. purifying selection Q: What is the most general term for a change in a single nucleotide pair? A. point mutation B. frameshift mutation C. missense mutation D. nonsense mutation E. neutral mutation A. point mutation Q: Determine whether the following statement is true or false: In sexually reproducing organisms, only mutations that occur in the germ line are passed along to progeny. True Q: Which of these statements is consistent with the information presented in the figure? A. Mutation A is heritable to offspring because the mutation took place in the germ line. B. Mutation A is heritable to offspring because the mutation took place in a somatic cell. C. Mutation B is heritable to offspring because the mutation took place in the germ line. D. All of the above are correct. E. None of the above are correct. A. Mutation A is heritable to offspring because the mutation took place in the germ line. Q: It is thought that gene duplications are generated primarily by which process? A. sexual reproduction B. replication of chromosome ends C. DNA replication and repair D. homologous recombination E. transcription D. homologous recombination Q: In eukaryotes, what separate component generally encodes individual protein domains? A. genes B. introns C. codons D. mRNAs E. exons E. exons Q: Although vertebrate genomes all contain roughly the same number of genes, they vary greatly in size; for example, humans, mice, and dogs have genomes that are three times the size of the chicken genome. Which of the following could account for the increased size of mammalian genomes? A. chromosome breakage B. the movement of mobile genetic elements C. chromosomal translocations D. the accumulation of point mutations E. purifying selection B. the movement of mobile genetic elements Q: Determine whether the following statement is true or false: Once a gene has been duplicated, only one of the copies is free to accumulate mutations that might allow it to perform a slightly different function; the other will remain unchanged. False Q: In humans, the globin gene family evolved through which process? A. exon shuffling B. repeated rounds of duplication and mutation C. whole-genome duplication D. horizontal gene transfer B. repeated rounds of duplication and mutation Q: Determine whether the following statement is true or false: DNA duplication events always lead to the evolution of genes with new functions. False Q: Determine whether the following statement is true or false: Most genes in the genomes of vertebrates exist in multiple versions. True Q: The exons that encode protein domains can be moved without becoming damaged. Why is this? A. because exons are so similar in size B. because recombination enzymes recognize special sequences that mark the beginnings and ends of exons C. because recombination tends to occur in introns, not exons D. because the recombination process that moves exons is precise and carefully regulated E. because exons are so plentiful C. because recombination tends to occur in introns, not exons Q: Which of the following statements about exon shuffling is not true? A. Exon shuffling allows the generation of hybrid proteins with new functions. B. Exon shuffling allows bacteria to become antibiotic resistant. C. All human proteins are thought to have arisen from the duplication and shuffling of a few thousand exons. D. Exon shuffling requires the presence of introns. B. Exon shuffling allows bacteria to become antibiotic resistant. Q: Which is not true of mobile genetic elements? A. Mobile genetic elements can serve as targets of homologous recombination, resulting in DNA duplication and deletion. B. Mobile genetic elements can destroy a gene’s capacity to encode a useful protein but cannot alter a gene’s expression pattern. C. Mobile genetic elements can alter the course of an organism’s development and may have played a role in the evolution of the body plans of multicellular organisms. D. Mobile genetic elements can rearrange neighboring DNA sequences in the host genome, generating novel genes. E. Mobile genetic elements have shaped the evolution of modern genomes, including our own. B. Mobile genetic elements can destroy a gene’s capacity to encode a useful protein but cannot alter a gene’s expression pattern. Q: Antibiotic resistance is a serious problem. The U.S. Centers for Disease Control and Prevention estimates that each year 2 million Americans are infected with antibiotic-resistant bacteria and 23,000 people die from their infection. Scientists are searching for new antibiotic drugs that would target the process of conjugation to lessen the spread of antibiotic resistance.Why might a new antibiotic that blocks conjugation be a potentially effective drug? A. Blocking conjugation would lead to the removal of antibiotic-resistance genes from drug resistant bacteria. B. Blocking conjugation would block genetic transfer between two cells, potentially blocking the transfer of antibiotic-resistance genes between bacteria. C. Blocking conjugation would kill bacteria that already have the antibiotic-resistance genes. D. Blocking conjugation would only be effective against harmful bacteria with antibiotic-resistance genes. B. Blocking conjugation would block genetic transfer between two cells, potentially blocking the transfer of antibiotic-resistance genes between bacteria. Q: Conjugation occurs through a series of steps. Scientists are searching for new antibiotic drugs that could block different parts of the conjugation pathway. Predict the molecular pathways that could be targeted by a new drug to block conjugation and reduce the sharing of antibiotic resistance genes.Choose one or more: A.block formation of the cytoplasmic bridge between the two cells B.block the DNA polymerase that replicates the plasmid DNA C.block nicking of the DNA plasmid D.block formation of the sex pilus E. All of the above E. All of the above Q: Determine whether the following statement is true or false: Horizontal gene transfer from one organism to another is common in both eukaryotes and prokaryotes. False In present-day organisms, which trait or gene is commonly acquired by horizontal gene transfer? A. antibiotic resistance B. lactose tolerance C. β globin D. sickle-cell anemia E. antibodies A. antibiotic resistance Q: You are studying the mechanisms of genome evolution in the fruit fly Drosophila melanogaster and have found a mutant strain that seems to have an unusually high rate of gene duplication and exon shuffling. Which of the following mutations would be MOST likely to cause the effects that you have observed? A. Mutation in uracil DNA glycosylase, which is involved in repair of mutations caused by deamination of cytosine (which results in formation of uracil) B. Mutation in the Piwi gene, which controls the activity of P-elements, a kind of DNA-only transposon C. Mutation in the Mlh1 gene, which is important for the detection and correction of nucleotide mismatches during DNA replication D. Mutation in the 3'-to-5' exonuclease domain of DNA polymerase B. Mutation in the Piwi gene, which controls the activity of P-elements, a kind of DNA-only transposon Which of the following would be most likely to accumulate changes to its sequence? A. a gene that is highly conserved among a wide diversity of organisms B. a gene that has recently been duplicated in the genome C. a regulatory DNA sequence D. a gene that codes for a highly optimized essential protein or RNA molecule E. a gene encoding DNA polymerase B. a gene that has recently been duplicated in the genome Which of the following mechanisms for genetic change involves the acquisition of genetic material from another organism? A. gene duplication B. transposition C. horizontal transfer D. mutation C. horizontal transfer Mutations that occur in germ-line cells are the only ones that lead to evolutionary change because: A. germ cell mutations can lead to cancer. B. germ cells are the only ones that express their DNA. C. germ cells form progeny. D. germ cells undergo meiosis. C. germ cells form progeny. Shown here are regions of two homologous chromosomes. If homologous recombination occurred between the short repetitive sequence after the gene in Chromosome 1 and the short repetitive sequence before the gene in Chromosome 2, what would be the result? A. Chromosome 1: deletion of the gene; Chromosome 2: deletion of the gene B. Chromosome 1: inversion of the gene; Chromosome 2: duplication of the gene C. Chromosome 1: duplication of the gene; Chromosome 2: deletion of the gene D. Chromosome 1: duplication of the gene; Chromosome 2: duplication of the gene C. Chromosome 1: duplication of the gene; Chromosome 2: deletion of the gene Mobile genetic elements can promote gene duplication and exon shuffling by A. replicating genes during the mobilization process. B. excising themselves from a gene. C. serving as targets for homologous recombination. D. inserting into an exon and destroying its function. C. serving as targets for homologous recombination. Germ-line mutations that are deleterious are likely to A. be lost from a population. B. be preserved or lost depending on chance. C. expand and be duplicated in a population. D. be preserved in a population. A. be lost from a population. Which of the following DNA sequences is the LEAST likely to accommodate mutations? A. DNA sequences found between genes B. regulatory DNA sequences C. the coding sequence of a duplicated gene D. ribosomal RNA sequence D. ribosomal RNA sequence Which of the following statements is true? A) Transmembrane proteins are classified as peripheral membrane proteins because the polypeptide chain does not pass through the bilayer B) A protein that relies on protein-protein interactions for its membrane association is classified as a peripheral membrane protein C) A peripheral protein binds covalently to the cytosolic side of the membrane via its attached carbohydrates D) Membrane proteins that move ions in and out of the cell are classified as enzymes B) A protein that relies on protein-protein interactions for its membrane association is classified as a peripheral membrane protein Which of the following molecules is most likely to diffuse across a synthetic lipid bilayer that does not contain any protein components? A) Glucose B) Water C) Glycerol D) K+ E) CO2 E) CO2 Which of the following best describes the behavior of a gated channel? A) It stays open continuously when stimulated B) It closes in response to a given stimulus C) It opens more widely as the stimulus becomes stronger D) It remains closed if un-stimulated D) It remains closed if un-stimulated If Na+ channels are opened in a cell that was previously at rest, how will the membrane potential be affected? A) It becomes more positive B) It becomes more negative C) It is permanently reset D) The membrane potential is not affected by Na+ A) It becomes more positive The Na+/K+ pump is responsible for maintaining the high extracellular sodium ion concentration and the high intracellular potassium ion concentration. What happens immediately after the pump hydrolyzes ATP? A) Na+ is bound B) ADP is bound C) The pump is dephosphorylated D) The pump changes conformation D) The pump changes conformation Which of the following locations are the correct places where LDL would be found during internalization? Choose one or more: A.Bound to the receptor inside the transport vesicle B.Bound to the receptor outside the transport vesicle C.Bound to the receptor inside the endosome D.Bound to the receptor outside the endosome A.Bound to the receptor inside the transport vesicle C.Bound to the receptor inside the endosome Which portion of a membrane phospholipid faces the outside of the membrane?Choose one: A) amphipathic portion B) fatty acids C) tail D) none, because phospholipids are confined to the interior of the membrane E) head E) head Why do phospholipids form bilayers in water?Choose one: A) The hydrophobic tail is attracted to water, while the hydrophilic head shuns water. B) The hydrophilic head is insoluble in water. C) The hydrophilic head is attracted to water, while the hydrophobic tail shuns water. D) The hydrophobic head is attracted to water, while the hydrophilic tail shuns water. E) The hydrophobic head shuns water, while the hydrophilic tail is attracted to water. C) The hydrophilic head is attracted to water, while the hydrophobic tail shuns water. In a lipid bilayer, where do lipids rapidly diffuse?Choose one: A) within the plane of one monolayer and back and forth between the monolayers B) in and out of the bilayer C) back and forth from one monolayer to the other in the bilayer D) not at all, because they remain in place within the bilayer E) within the plane of their own monolayer E) within the plane of their own monolayer In eukaryotic cells, phospholipids are synthesized by enzymes bound to which of the following?Choose one: A) both monolayers of the endoplasmic reticulum B) the cytosolic face of the endoplasmic reticulum C) the inside of the endoplasmic reticulum D) the cytosolic face of the plasma membrane E) the cytosolic face of the Golgi apparatus B) the cytosolic face of the endoplasmic reticulum Why are the oils found in plant seeds and the fat droplets found in the fat (or adipose) cells of animals similar?Choose one: A) Both form a lipid bilayer in water. B) Both are unsaturated. C) Both are saturated. D) Both are amphipathic. E) Both are hydrophobic. E) Both are hydrophobic. Which is the most abundant phospholipid in animal cell membranes?Choose one: A) phosphatidylinositol B) triacylglycerol C) phosphatidylcholine D) cholesterol E) glycolipid C) phosphatidylcholine When the transport vesicle shown below fuses with the plasma membrane, which monolayer will face the cell cytosol?Choose one: A) It depends on whether the vesicle is coming from the endoplasmic reticulum or the Golgi apparatus. B) The orange monolayer will face the cytosol. C) The blue monolayer will face the cytosol. D) It depends on the cargo the vesicle is carrying. E) Half the time the orange monolayer will face the cytosol, and half the time the blue monolayer will face the cytosol. B) The orange monolayer will face the cytosol. All of the carbohydrates in the plasma membrane face the cell exterior. Which direction do the carbohydrates on internal cell membranes face?Choose one: A) the cell exterior B) the glycocalyx C) the plasma membrane D) the lumen of the vesicle or organelle E) the cytosol D) the lumen of the vesicle or organelle Shown is a schematic diagram of a membrane phospholipid. Which segment could carry a positive charge? Choose one: ABCDE A Which is true of the molecule shown below?Choose one or more: A) It is found in the membranes of virtually all living cells. B) It is amphipathic. C) It makes the bilayer more permeable. D) It is a phospholipid. E) It makes the bilayer less fluid. F) It is a lipid. B) It is amphipathic. E) It makes the bilayer less fluid. F) It is a lipid. Naïve B cells found in our immune system each contain a specific cell-surface receptor capable of binding to a specific foreign antigen such as a protein from a pathogen like a bacterium or virus. Binding to an antigen triggers a process whereby the naïve B cell can differentiate into a plasma cell that secretes large quantities of an antibody that specifically binds to an antigen from the pathogen. Because plasma cells are long-lived cells, the immune system is then primed to rapidly respond to that antigen in the future if the person is again exposed to the pathogen. During differentiation, the cell rapidly expands the amount of endoplasmic reticulum and Golgi membranes needed for secreting the antibodies. Which organelle(s) will become particularly active in synthesizing new membrane lipids? Choose one or more: A.Endoplasmic reticulum B.Golgi apparatus C.Transport vesicle D.Plasma membrane A.Endoplasmic reticulum Which of the following is a function of proteins in the plasma membrane?Choose one or more: A) allow specific ions to cross the plasma membrane, thereby controlling its electrical properties B) transport molecules across the membrane C) generate the energy required for lipids to diffuse within the membrane D) serve as anchors to attach the cell to the extracellular matrix E) transmit extracellular signals to the cell interior A) allow specific ions to cross the plasma membrane, thereby controlling its electrical properties B) transport molecules across the membraneD) serve as anchors to attach the cell to the extracellular matrix E) transmit extracellular signals to the cell interior Where are new phospholipids made?Choose one: A. Golgi apparatus B. mitochondria C. endoplasmic reticulum D. nucleus C. endoplasmic reticulum If a phospholipid is located in the outer layer of the bilayer in a vesicle, where will it end up when the vesicle fuses with the plasma membrane?Choose one: A. Vesicles cannot fuse with the plasma membrane. B. the cytosolic face of the bilayer C. randomly on one side or another D. the extracellular face the bilayer B. the cytosolic face of the bilayer How does the inclusion of cholesterol affect animal cell membranes?Choose one: A) It tends to make the lipid bilayer more fluid. B) It tends to make the lipid bilayer less fluid. C) It makes the lipid bilayer wider. D) It has little effect on the properties of the lipid bilayer. E) It makes the lipid bilayer more permeable. B) It tends to make the lipid bilayer less fluid. Proteins that are associated with the membrane by noncovalent interactions with other membrane proteins are called ___________ proteins.Choose one: A) lipid-linked B) monolayer-associated C) integral membrane D) peripheral membrane D) peripheral membrane If the backbone of a polypeptide is hydrophilic, how can a transmembrane alpha helix span the hydrophobic portion of the lipid bilayer?Choose one: A. because the membrane bends in such a way that the polar heads of the lipids contact the transmembrane helix B. because amino acid side chains in a transmembrane helix are hydrophobic and interact with the hydrophobic interior of the bilayer C. because many transmembrane alpha helices must come together in a way that neutralizes the hydrophilic backbone D. because the hydrophilic backbone makes a hole in the membrane B. because amino acid side chains in a transmembrane helix are hydrophobic and interact with the hydrophobic interior of the bilayer Which of the following form tiny hydrophilic pores in the membrane through which solutes can pass by diffusion?Choose one: A. anions B. liposomes C. pumps D. transporters E. channels E. channels Lipid bilayers are highly impermeable to which molecule(s)?Choose one: A) steroid hormones B) Na+ and Cl– C) carbon dioxide D) oxygen E) water B) Na+ and Cl– Which of the following inhibits inorganic ions, such as Na+ and Cl–, from passing through a lipid bilayer?Choose one: A. the ions’ large size B. the hydrophilic exterior of the lipid bilayer C. the carbohydrate layer on the surface of the lipid bilayer D. the hydrophobic interior of the lipid bilayer E. the watery environment on either side of the lipid bilayer D. the hydrophobic interior of the lipid bilayer Sodium ions, oxygen (O2), and glucose pass directly through lipid bilayers at dramatically different rates. Which of the following choices presents the correct order, from fastest to slowest?Choose one: In general, which of the following will diffuse across a lipid bilayer most rapidly?Choose one: A. a small hydrophobic molecule B. water C. a small hydrophilic molecule D. a large hydrophilic molecule E. a large hydrophobic molecule A. a small hydrophobic molecule A. sodium ions, oxygen, glucose B. oxygen, glucose, sodium ions C. oxygen, sodium ions, glucose D. glucose, oxygen, sodium ions E. glucose, sodium ions, oxygen B. oxygen, glucose, sodium ions Which of the following statements is true?Choose one: A) K+ and Na+ are present in the same concentration on both sides of the plasma membrane. B) K+ and Na+ are both excluded from cells. C) K+ is the most plentiful positively charged ion outside the cell, while Na+ is the most plentiful inside. D) K+ and Na+ are both maintained at high concentrations inside the cell compared to out. How do transporters and channels select which solutes they help move across the membrane?Choose one: E) Na+ is the most plentiful positively charged ion outside the cell, while K+ is the most plentiful inside. E) Na+ is the most plentiful positively charged ion outside the cell, while K+ is the most plentiful inside. What is the voltage difference across a membrane of a cell called?Choose one: A) potential balance B) electrical current C) membrane potential D) gradient establishment C) membrane potential A. Channels allow the passage of solutes that are electrically charged; transporters facilitate the passage of molecules that are uncharged. B. Channels discriminate between solutes mainly on the basis of size and electric charge; transporters bind their solutes with great specificity in the same way an enzyme binds its substrate. C. Channels will allow the passage of any solute as long as it has an electrical charge; transporters bind their solutes with great specificity in the same way an enzyme binds its substrate. D. Transporters discriminate between solutes mainly on the basis of size and electric charge; channels bind their solutes with great specificity in the same way an enzyme binds its substrate. E. Both channels and transporters discriminate between solutes mainly on the basis of size and electric charge. B. Channels discriminate between solutes mainly on the basis of size and electric charge; transporters bind their solutes with great specificity in the same way an enzyme binds its substrate. The movement of an ion down its concentration gradient is called what?Choose one: A) pumping B) active transport C) osmosis D) passive transport D) passive transport The movement of an ion against its concentration gradient is called what?Choose one: A) facilitated diffusion B) passive transport C) active transport D) osmosis C) active transport Which of the following requires an input of energy to occur?Choose one: A. the movement of a solute from a region of higher concentration on one side of a membrane to a region of lower concentration on the other side B. The movement of a solute from a region of lower concentration on one side of a membrane to a region of higher concentration on the other side C. Both of these options require energy investment because diffusion is a change in a system, and any change requires energy. B. The movement of a solute from a region of lower concentration on one side of a membrane to a region of higher concentration on the other side All other factors (concentration, solute size, etc.) being equal, which type of solute does a cell tend to pull inside?Choose one: A. negatively charged solutes B. uncharged solutes C. positively charged solutes C. positively charged solutes A. the movement of water from an area of high solute concentration to an area of low solute concentration In passive transport, the net movement of a charged solute across the membrane is determined by which of the following?Choose one: A) its electrochemical gradient B) its osmotic gradient alone C) the membrane potential D) its concentration gradient A) its electrochemical gradient Which of the following correctly describes osmosis?Choose one: B. the movement of water from an area of low solute concentration to an area of high solute concentration C. the movement of water from an area of low solvent concentration to an area of high solvent concentration D. the movement of water from an area of low water concentration to an area of high water concentration B. the movement of water from an area of low solute concentration to an area of high solute concentration A group of researchers wanted to sort different white blood cell types (monocytes, lymphocytes, and granulocytes) apart from each other based on size differences and to remove unwanted contaminating red blood cells. After a particular manipulation, the red blood cells lysed. The remaining white blood cells increased in size and, more importantly, the size differences among cells increased, allowing for size-based sorting (which requires minimum size differences among cells). What manipulation did the researchers use to increase cell size?Choose one: A. placing cells in an environment with a lower solute concentration than that in the cells B. placing cells in an environment with lower temperatures than the cells were previously exposed to C. placing cells in an environment with a higher solute concentration than that in the cells D. patch-clamp recording to monitor ion channel activity A. placing cells in an environment with a lower solute concentration than that in the cells The Na+ pump in the plasma membrane of animal cells uses energy from ATP hydrolysis to pump sodium and potassium ions against their electrochemical gradients. In which direction are the ions pumped across the membrane?Choose one: A) Na+ and K+ both out B) Na+ out and K+ in C) Na+ and K+ both in D) Na+ in and K+ out B) Na+ out and K+ in Each of these mechanisms of transport, as illustrated above, is best categorized by which term?Choose one: A. active transport B. facilitated diffusion C. osmosis D. simple diffusion A. active transport In most animal cells, which ion can move through “leak” channels?Choose one: A) K+ B) H+ C) Na+ D) Ca2+ E) Cl– A) K+ Auditory hair cells in the ear depend on what type of ion channel to detect sound vibrations?Choose one: A. ligand-gated B. mechanically-gated C. voltage-gated B. mechanically-gated For voltage-gated channels, a change in the membrane potential has what effect on the channel?Choose one: A. It alters the probability that the channel will be found in its open conformation. B. It makes the channel more sensitive to the binding of neurotransmitters. C. It either opens the channel or closes it, depending on the voltage. D. It changes which ions can pass through the channel. E. It changes the width of the channel opening. A. It alters the probability that the channel will be found in its open conformation. To pass through the pore of an ion channel, what must be true of an ion?Choose one: A) It must surround itself with water molecules. B) It must interact with polar groups in the narrowest part of the channel. C) It must interact with nonpolar groups in the selectivity filter. D) It must avoid contact with the channel wall. E) It must be positively charged. B) It must interact with polar groups in the narrowest part of the channel. During an action potential, which of the following actions does not help return the membrane to its resting potential?Choose one: A. the inactivation of voltage-gated Na+ channels B. the flow of K+ through K+ leak channels C. the opening of voltage-gated K+ channels D. the opening of voltage-gated Na+ channels D. the opening of voltage-gated Na+ channels Which of the following activities helps restore the ion gradients across the plasma membrane of an axon after an action potential has occurred?Choose one: A. the opening of voltage-gated Na+ channels B. the closing of voltage-gated K+ channels C. the action of Na+ pumps D. the activity of K+ leak channels C. the action of Na+ pumps Following an action potential, a nerve cell goes through a brief refractory period during which it cannot be stimulated. What is true during this refractory period?Choose one: A) The membrane potential remains unchanged. B) Voltage-gated Na+ channels in the nerve cell membrane are inactivated. C) Voltage-gated K+ channels in the nerve cell membrane are inactivated. D) Voltage-gated Ca2+ channels are open. E) Voltage-gated Na+ channels in the nerve cell membrane are open. B) Voltage-gated Na+ channels in the nerve cell membrane are inactivated. Which of the following is a difference between transporters and channels?Choose one: A. Channels do not discriminate between ions, whereas transporters bind their solute with extreme specificity. B. Transporters can facilitate both active or passive transport of solutes; channels facilitate only passive transport. C. Transporters move solutes against their concentration gradient, whereas channels can move solutes with or against their concentration gradient. D. Channels are single-pass transmembrane proteins, whereas transporters are multipass transmembrane proteins. B. Transporters can facilitate both active or passive transport of solutes; channels facilitate only passive transport. Cells, compared with the extracellular fluid areChoose one: A) slightly negatively charged. B) extremely positively charged. C) electrically neutral. D) slightly positively charged. A) slightly negatively charged. An extracellular molecule binds to a channel and triggers it to move more often to the open conformation than the closed conformation, as shown in the figure. This is referred to as a ___________ channel.Choose one: A) voltage-gated B) ligand-gated C) mechanically gated D) light-gated B) ligand-gated What is the measure of disorder in a system called?Choose one: A. second law of thermodynamics B. entropy C. enthalpy D. free energy E. catabolism B. entropy Reactions that use energy to drive the synthesis of molecules inside the cell are most specifically considered: anabolic Carbon atoms cycle continuously through the biosphere. What is a by-product of cell respiration, and what does this by-product represent?Choose one: A) CO2; a reduced version of carbon B) C6H12O6; completely oxidized carbon C) CO2; completely oxidized carbon D) C6H12O6; a reduced version of carbon C) CO2; completely oxidized carbon What is the origin of the energy that animals acquire by eating plants or other animals?Choose one: A. fats B. heat C. sunlight D. carbohydrates E. sugars C. sunlight Which energy conversion characterizes photosynthesis?Choose one: A. electromagnetic (light) energy → chemical bond energy B. electromagnetic (light) energy → heat energy C. electromagnetic (light) energy → oxidation energy D. electromagnetic (light) energy → CO2 E. electromagnetic (light) energy → kinetic energy A. electromagnetic (light) energy → chemical bond energy Which of the following does not describe an oxidation reaction?Choose one: A. the conversion of a chlorine atom to Cl– B. the addition of oxygen atoms to a molecule C. the removal of electrons from a molecule D. the conversion of Fe2+ to Fe3+ A. the conversion of a chlorine atom to Cl– Which of the following statements is not true?Choose one: A. When a sugar molecule is oxidized to CO2 and H2O, the O2 molecules involved in forming the H2O are reduced. B. When a carbon atom in a C–H bond has somewhat more than its share of electrons, it is said to be reduced. C. Hydrogenation reactions are oxidations, and dehydrogenation reactions are reductions. D. Oxidation and reduction reactions always occur simultaneously. The cell regulates its metabolism through a vast interconnected web of anabolic and catabolic chemical pathways. Which of the following would be expected to release energy and generate activated carriers to drive energetically unfavorable reactions? Choose one: A. Glycolysis, where each glucose molecule is broken down into two molecules of pyruvate. B. Gluconeogenesis, a pathway where one molecule of glucose is generated from two molecules of pyruvate. C. Translation, where proteins are assembled from amino acid building blocks. D. Photosynthesis, where sugars are produced from atmospheric carbon dioxide molecules. A. Glycolysis, where each glucose molecule is broken down into two molecules of pyruvate. Your company has developed an organic molecule with commercial potential and you know how to produce it in the lab. You want to increase production and make as much of the molecule as possible, but the reaction has a positive ΔG°. What can you do to try to drive the reaction toward your desired product?Choose one or more: A.increase the concentration of reactants B.continually remove products C.add some products initially to get the reaction primed D.add an enzyme that does not couple to another reaction A.increase the concentration of reactants B.continually remove products Compared to adding heat to the system, what is the advantage of using an enzyme to overcome an energy barrier?Choose one: A. An enzyme is specific for one desired pathway and end product. B. An enzyme generates multiple different products using multiple pathways. C. An enzyme can catalyze a reaction in many different ways. D. An enzyme speeds up a reaction more than heat does. A. An enzyme is specific for one desired pathway and end product. All four possible reactions in the animation are energetically favorable; the energy of the four products is lower than the energy of the original starting molecule. Why does the starting molecule not completely and quickly convert to its possible products before the addition of heat or an enzyme?Choose one: A. The starting molecule can only form some of the products quickly. B. An activation energy barrier exists that must be overcome for conversion to products. C. The starting substrate does quickly convert to the four products. D. When heat was added to the reaction, only some of the products were produced. B. An activation energy barrier exists that must be overcome for conversion to products. In thermodynamics, what does the term “free energy” refer to?Choose one: A. energy that cannot be harnessed to do work or drive chemical reactions B. energy that can be harnessed to do work or drive chemical reactions C. excess energy from a reaction that a cell does not use D. energy that cells borrow from the environment E. energy required to initiate a chemical reaction B. energy that can be harnessed to do work or drive chemical reactions Which statement about enzymes is not true?Choose one: A. Enzymes can help build large polymers. B. Enzymes can speed up energetically favorable reactions. C. An enzyme can force an energetically unfavorable reaction to take place inside the cell. D. Enzymes reduce the activation energy required to initiate a spontaneous reaction. C. An enzyme can force an energetically unfavorable reaction to take place inside the cell. Is the following statement true, false, or either depending on the situation?After an enzyme catalyzes a reaction, the enzyme has been altered and cannot perform additional reactions. Choose one: A. always true B. always false C. true or false, depending on the enzyme B. always false Determine whether the following statement is true or false: Energetically unfavorable reactions can occur if they are coupled to a second reaction with a negative ΔG so large that the net ΔG of the entire process is negative. False Which is not true of a chemical reaction at equilibrium?Choose one: A) The net concentrations of substrate and product do not change. B) Both the forward and reverse reactions have stopped. C) The rates of the forward and reverse reactions are equal. D) ΔG is equal to zero. B) Both the forward and reverse reactions have stopped. A reaction A → B has a negative ΔG under experimental conditions. Which statement is true about this reaction?Choose one: A. Increasing the concentration of B will increase the ΔG, making it less negative. B. The reaction cannot proceed until it is coupled to a reaction with a positive ΔG. C. The formation of product B will decrease the entropy of the universe. D. The reaction will proceed spontaneously and rapidly. E. The reaction is energetically unfavorable. A. Increasing the concentration of B will increase the ΔG, making it less negative. Two molecules will bind to each other by means of noncovalent bonds if the ΔG° of the interaction is which of the following?Choose one: A. positive (the free energy of the product is greater than the sum of the free energies of the unbound partners) B. zero (the free energy of the product is the same as the sum of the free energies of the unbound partners) C. negative (the free energy of the product is less than the sum of the free energies of the unbound partners) C. negative (the free energy of the product is less than the sum of the free energies of the unbound partners) Throughout the 1920s, Otto Meyerhof, A. V. Hill, and colleagues investigated how cells use energy to power muscle contraction. They determined that during muscle contraction, glycogen is broken down into lactic acid, a product of fermentation. Originally Meyerhof thought that the conversion of glycogen into lactic acid directly powered muscle contraction. This idea was overturned by experiments performed by Einar Lundsgaard. What evidence did Lundsgaard provide to suggest that glycogen breakdown and lactic acid production did not directly power muscle contraction?Choose one: A. Creatine phosphate infusions into muscle cells inhibited muscle cell contraction. B. A pulse of electricity caused muscle contraction in isolated frog muscle tissue. C. Inhibition of fermentation immediately halted muscle contraction. D. Muscle contraction could continue for some time after inhibition of fermentation. D. Muscle contraction could continue for some time after inhibition of fermentation. Determine whether the following statement is true or false: In isolation, the formation of an activated carrier, such as ATP, NADH, or NADPH, is an energetically unfavorable reaction. True What is the difference between NAD+ and NADH?Choose one: A) NADH carries an extra phosphate group. B) NADH is the oxidized form, while NAD+ is the reduced form. C) NADH is involved in biosynthetic reactions. D) NADH is an electron acceptor, whereas NAD+ is an electron donor. E) NADH carries an extra proton and two high-energy electrons. E) NADH carries an extra proton and two high-energy electrons. What is true of the breakdown of polymers inside living cells?Choose one: A. It is associated with a negative change in free energy. B. It is energetically unfavorable .C. It occurs without the need for enzymes. A. It is associated with a negative change in free energy. Which statement about polymers is true?Choose one: A. Polymer breakdown requires an input of free energy and involves the release of water. B. Polymer breakdown requires an input of free energy and involves the consumption of water. C. Polymer synthesis requires an input of free energy and involves the release of water. D. Polymer synthesis requires an input of free energy and involves the consumption of water. C. Polymer synthesis requires an input of free energy and involves the release of water. Which carrier is in its activated state as used in the cell?Choose one: A) ADP B) NADP+ C) NADH D) FAD E) CoA C) NADH Which of the following best describes this reaction?Choose one A. redox B. condensation C. hydrolysis B. condensation Reactions that build larger molecules in the cell are called ___________; reactions that break down molecules into smaller ones are called ___________.Choose one: A) catabolic; anabolic B) anabolic; catabolic C) anabolic; metabolic D) metabolic; anabolic B) anabolic; catabolic Living systems can generate and maintain order without violating the second law of thermodynamics because they generateChoose one: A) heat. B) macromolecules. C) decreased entropy. D) order. A) heat In an enzymatic reaction, a molecule gains an electron. This is known as a(n) ___________ reaction.Choose one: A) hydrogenation B) oxidation C) electronegative D) reduction D) reduction Why is CO2 an end product of cellular respiration?Choose one: A. because plants can use it for respiration B. because it captures light energy for photosynthesis C. because it is the most stable form of carbon in our atmosphere D. because it can accept electrons and produce a reduced form of carbon C. because it is the most stable form of carbon in our atmosphere Enzymes increase the speed of a chemical reaction because theyChoose one: A) increase the temperature to provide the necessary boost of energy. B) make the reaction more energetically favorable. C) make the reaction spontaneous. D) lower the activation energy needed to start the reaction. D) lower the activation energy needed to start the reaction. What is the role of activated carriers in cells?Choose one: A. They are enzymes that catalyze the reactions that break down foodstuffs for energy generation in the cell. B. They capture energy from energy releasing reactions and transfer it to other reactions. C. They carry energy from anabolic reactions for use in catabolic reactions. D. They are enzymes that catalyze biosynthetic reactions and make them feasible at the temperature of a cell. B. They capture energy from energy releasing reactions and transfer it to other reactions. Which of the following has a higher concentration in the cell to allow it to be available to accept electrons from oxidation of food molecules?Choose one: A) NADPH B) NADH C) NAD+ D) NADP+ C) NAD+ Most of the energy released by oxidizing glucose is saved in the high-energy bonds of what molecules?Choose one: A) GDP and other activated carriers B) O2 C) ADP and other activated carriers D) H2O and CO2 E) ATP and other activated carriers E) ATP and other activated carriers Useful energy is obtained by cells when sugars derived from food are broken down by which processes?Choose one: A) gluconeogenesis, fermentation, and oxidative phosphorylation B) glycolysis, the citric acid cycle, and gluconeogenesis C) gluconeogenesis, the citric acid cycle, and oxidative phosphorylation D) glycolysis, the citric acid cycle, and oxidative phosphorylation E) glycolysis, the Calvin cycle, and oxidative phosphorylation D) glycolysis, the citric acid cycle, and oxidative phosphorylation Which of the following describes a breakdown process in which enzymes degrade complex molecules into simpler ones?Choose one: A) anabolism B) metabolism C) catabolism D) Enzymes are not needed to break down complex molecules into simpler ones. C) catabolism Where does the oxidative (oxygen-dependent) stage of the breakdown of food molecules occur in a eukaryotic cell?Choose one: A) mitochondrion B) cytosol C) Golgi apparatus D) endoplasmic reticulum A) mitochondrion Which of the following processes generates the largest number of ATP molecules?Choose one: A) citric acid cycle B) electron transport chain C) glycolysis D) fermentation E) gluconeogenesis B) electron transport chain What are the end products of glycolysis?Choose one or more: A) NADH B) pyruvate C) ADP D) H2O + CO2 E) NADPH F) ATP G) acetyl CoA A) NADH B) pyruvate F) ATP Which of the following are required for glycolysis to take place?Choose one or more: A) ADP B) NADH C) NAD+ D) O2 E) ATP F) Pi A) ADP C) NAD+ E) ATP F) Pi How many ATP molecules must be invested during the first part of glycolysis for each molecule of glucose broken down?Choose one: A) none B) two C) It depends on whether oxygen is present. D) 30 E) four F) one B) two The synthesis of ATP in glycolysis occurs by which process?Choose one: A) a transfer of electrons from NADH B) a transfer of phosphate from AMP C) oxidative phosphorylation D) substrate-level dephosphorylation E) substrate-level phosphorylation E) substrate-level phosphorylation For many anaerobic microorganisms, which metabolic pathway is the principal source of ATP?Choose one: A) glycolysis B) citric acid cycle C) gluconeogenesis D) oxidative phosphorylation E) Calvin cycle A) glycolysis Under anaerobic conditions, which metabolic pathway regenerates the supply of NAD+ needed for glycolysis?Choose one: A) breakdown of fats B) fermentation C) formation of acetyl CoA D) breakdown of amino acids E) citric acid cycle B) fermentation You have joined a lab that studies the metabolic pathway shown below. Just recently, an inhibitor for one of the enzymes, enzyme 3, has become available and the head of the lab wants you to use this inhibitor to determine whether the pathway is linear (as shown) or circular, with another enzyme (not shown) converting F back to A. You have access to all the molecules. What result suggests that the pathway may be circular rather than linear?Choose one: A. Inhibition of enzyme 3 and addition of extra metabolite A leads to buildup of C. B. Inhibition of enzyme 3 and addition of extra metabolite D leads to buildup of C. C. Inhibition of enzyme 3 and addition of extra metabolite D leads to buildup of F. D. Inhibition of enzyme 3 and addition of extra metabolite A leads to buildup of F. B. Inhibition of enzyme 3 and addition of extra metabolite D leads to buildup of C. What type of enzyme catalyzes the rearrangement of chemical bonds within a single molecule?Choose one: A) isomerase B) kinase C) dehydrogenase D) scramblase A) isomerase Although the citric acid cycle itself does not use O2, it requires a functioning electron transport chain (which uses O2) in order to regenerate which molecule for further use in the citric acid cycle?Choose one: A) ATP B) FADH2 C) NADH D) NAD+ E) ADP D) NAD+ The citric acid cycle converts the carbon atoms in acetyl CoA to which of the following?Choose one: A) citrate B) oxaloacetate C) glucose D) pyruvate E) CO2 E) CO2 The NADH generated during glycolysis and the citric acid cycle feeds its high-energy electrons to which of the following?Choose one: A) ADP B) the citric acid cycle C) the electron transport chain D) H2O E) FAD C) the electron transport chain In eukaryotic cells, what is the final electron acceptor in the electron transport chain?Choose one: A) NAD+ B) ATP C) FADH2 D) O2 E) CO2 D) O2 In plant cells, where does the citric acid cycle take place?Choose one: A) chloroplasts and mitochondria B) The citric acid cycle does not occur in plant cells. C) cytosol D) mitochondria E) chloroplasts D) mitochondria During the citric acid cycle, what happens to the acetyl group in acetyl CoA?Choose one: A) It is eliminated to produce CO2. B) It is vaporized to produce CO2. C) It is oxidized to produce CO2. D) It is hydrolyzed to produce CO2. E)It is reduced to produce CO2. C) It is oxidized to produce CO2. Which two-carbon molecule enters the citric acid cycle?Choose one: A) citrate B) acetyl CoA C) pyruvate D) carbon dioxide E0 oxaloacetate B) acetyl CoA What occurs in the first step of the citric acid cycle?Choose one: A) CO2 is released. B) Two molecules of acetyl CoA combine to form oxaloacetate. C) ATP is consumed. D) NADH is produced. E) A two-carbon molecule is combined with a four-carbon molecule to form citrate. E) A two-carbon molecule is combined with a four-carbon molecule to form citrate. CO2 is released in which steps of the citric acid cycle, as shown below?Choose one: A) Steps 2 and 4 B) Steps 1 and 8 C) Steps 3 and 4 D) Steps 1 and 5 E) Steps 2, 3, and 4 C) Steps 3 and 4 How do fermentation reactions in oxygen-starved muscle cells and anaerobically grown yeast cells differ?Choose one: A) Fermentation in yeast cells includes glycolysis, whereas in muscle cells it bypasses glycolysis. B) Fermentation in muscle cells produces ethanol plus CO2 and in yeast produces lactate. C) Fermentation in muscle cells generates NAD+ and in yeast generates NADH. D) Fermentation in muscle cells produces lactate and in yeast produces ethanol plus CO2. E) Fermentation in muscle cells regenerates NAD+ and in yeast regenerates glucose. D) Fermentation in muscle cells produces lactate and in yeast produces ethanol plus CO2. What happens to the energy captured during glycolysis and the citric acid cycle by the activated carriers NADH and FADH2.Choose one: A) It is used to drive biosynthetic reactions. B) It is passed to an electron transport chain that uses it to oxidize food molecules. C) It is passed to an electron transport chain that uses it to produce oxygen. D) It is passed to an electron transport chain that uses it to generate a proton gradient across the inner mitochondrial membrane. E) It is passed to ADP to form ATP. D) It is passed to an electron transport chain that uses it to generate a proton gradient across the inner mitochondrial membrane. The ethanol in wine and beer is produced from metabolic reactions carried out by the yeast Saccharomyces cerevisiae. Since it is of great commercial value, researchers have studied factors that influence ethanol production. To maximize ethanol yield, which environmental factor should be limiting?Choose one: A. glucose B. oxygen C. carbon dioxide D. sunlight B. oxygen Your friends are on a low-fat, high-carbohydrate diet, which they claim will prevent fat accumulation within their bodies. They eat tons of pasta and bread without worrying about calorie count. What can you correctly say to your friends about their potential to accumulate lipids on their low-fat diet?Choose one: A. They will not accumulate fats because cells have no way of storing fats. B. They will accumulate fats because cells have no way of storing carbohydrates. C. They will accumulate fats because cells can convert glycolytic metabolites into lipids. D. They will not accumulate fats because carbohydrates have less energy per gram than fats. C. They will accumulate fats because cells can convert glycolytic metabolites into lipids. The main regulatory step of glycolysis occurs in step 3. Choose all of the following that correctly describe some aspect of step 3 in glycolysis. Choose one or more: A.The reaction is an irreversible reaction. B.The enzyme that catalyzes step 3 is phosphofructokinase. C.The reaction generates the product fructose 1,6-bisphosphate. D.The enzyme uses an ATP. A.The reaction is an irreversible reaction. B.The enzyme that catalyzes step 3 is phosphofructokinase. C.The reaction generates the product fructose 1,6-bisphosphate. D.The enzyme uses an ATP. In substrate-level phosphorylation, a phosphate is transferred from an organic compound (the "substrate") to ADP to form ATP. Cells contain many phospho-compounds, some of which could potentially be used for substrate-level phosphorylation. Given the standard free energy of hydrolysis of ATP (–30.6 kJ/mol), which of the following molecules could serve as a phosphate donor for substrate-level phosphorylation? The standard free energy of hydrolysis for each compound is indicated in parentheses. Choose all that apply—there may be more than one correct answer. Choose one or more: A.1,3-Bisphosphoglycerate (–49.0 kJ/mol) B.Fructose-6-phosphate (–15.9 kJ/mol) C.Creatine phosphate (–43.0 kJ/mol) D.3-Phosphoglycerate (–12.5 kJ/mol) A.1,3-Bisphosphoglycerate (–49.0 kJ/mol) C.Creatine phosphate (–43.0 kJ/mol) The first step of glycolysis uses one ATP molecule in order toChoose one: A) breakdown sucrose. B) store glucose. C) phosphorylate glucose. D) transport glucose. C) phosphorylate glucose. Which of these processes require a membrane?Choose one or more: A) generation of energy by mitochondria B) generation of ATP by glycolysis C) generation of ATP by photosynthesis in bacteria D) generation of ATP by oxidative phosphorylation E) generation of ATP by photosynthesis in plants A) generation of energy by mitochondria C) generation of ATP by photosynthesis in bacteria D) generation of ATP by oxidative phosphorylation E) generation of ATP by photosynthesis in plants Which of the following drives the production of ATP from ADP and Pi by ATP synthase?Choose one: A) a sodium (Na+) gradient B) a proton (H+) gradient C) hydrolysis D) sunlight E) phosphorylation B) a proton (H+) gradient In the electron-transport chain, as electrons move along a series of carriers, they release energy that is used to do what?Choose one: A) oxidize food molecules B) phosphorylate ADP to form ATP C) hydrolyze ATP D) split water into protons and oxygen E) pump protons across a membrane E) pump protons across a membrane What is true of the organelles that produce ATP in eukaryotic animal cells?Choose one: A) They reproduce sexually. B) They evolved from bacteria engulfed by ancestral cells billions of years ago. C) They harbor eukaryotic-like biosynthetic machinery for making RNA and protein. D) They have a separate set of DNA that contains many of the same genes found in the nucleus. E) They contain the same genes as the chloroplasts of plant cells. B) They evolved from bacteria engulfed by ancestral cells billions of years ago. ATP synthase is a large molecular machine that converts the energy in an electrochemical gradient into the bond energy stored in ATP. Which of the following events are required for the synthesis of ATP?Choose one or more: A.conformational changes of the F1 ATPase B.movement of protons down their gradient through ATP synthase C.binding of ATP to an empty F1 ATPase subunit D.rotation of the rotor in the membrane A.conformational changes of the F1 ATPase B.movement of protons down their gradient through ATP synthase D.rotation of the rotor in the membrane Suppose the shaft of ATP synthase that is attached to the rotor were truncated (shortened) such that it no longer extended into the F1 ATPase head. What would be the consequence of this mutation? Choose one: A. ATP would not be produced because the conformation of the F1 ATPase head would not be changed. B. ATP synthase would work in reverse, breaking down ATP and pumping protons against their gradient. C. The rotor in the membrane would no longer turn. D. Protons would not cross the membrane using the rotor. A. ATP would not be produced because the conformation of the F1 ATPase head would not be changed. Which of the following organisms have mitochondria in their cells?Choose one or more: A) animals B) plants C) yeasts D) bacteria E) protozoa A) animals B) plants C) yeasts E) protozoa In what ways can mitochondria adapt to the changing needs of a cell?Choose one or more: A) They can change their location. B) They can carry out glycolysis. C) They can change their shape. D) They can change their internal structure. E) They can change their number. A) They can change their location. C) They can change their shape. E) They can change their number. Which part of the mitochondrion contains the proteins that carry out oxidative phosphorylation?Choose one: A B C D B Which of the following are consumed as fuel within mitochondria?Choose one or more: A.pyruvate B.acetyl CoA C.glucose D.fatty acids E.amino acids A.pyruvate B.acetyl CoA D.fatty acids E.amino acids The electron-transport chain in mitochondria accepts high-energy electrons directly from which molecule?Choose one: A) H2O B) NADH C) acetyl CoA D) pyruvate E) ATP B) NADH Which is true about electrons as they move through the electron-transport chain?Choose one: A. Electrons start out at very low energy and gain energy at each transfer step. B. Electrons start out at very high energy and lose energy at each transfer step along the electron transport chain. C. Electrons are pumped across the mitochondrial membrane as they move along the electron transport chain. D. Electrons neither gain nor lose energy as they move along the electron-transport chain. E. Electrons can gain or lose energy, depending on where they enter along the electron-transport chain. B. Electrons start out at very high energy and lose energy at each transfer step along the electron transport chain. In mitochondria, what is the final electron acceptor in the electron-transport chain?Choose one: A) water (H2O) B) oxygen (O2) C) carbon dioxide (CO2) D) NADH and FADH2 E) ADP B) oxygen (O2) What is true of mobile electron carriers?Choose one: A) They transfer electrons to oxygen to produce water. B) They pump protons across a membrane. C) They ferry electrons between one respiratory complex and the next. D) They accept electrons from NADH. E) They feed electrons into the electron-transport chain. C) They ferry electrons between one respiratory complex and the next. The electron-transport chain pumps protons in which direction?Choose one: A) from the matrix to the intermembrane space B) from the cytosol to the intermembrane space C) from the matrix to the cytosol D) from the intermembrane space to the cytosol E) from the intermembrane space to the matrix A) from the matrix to the intermembrane space Which is true of ATP synthase?Choose one: A) It can break down ATP but not generate it. B) It can generate ATP but not break it down. C) It is not present in plants or bacteria. D) It cannot serve as a proton pump. E) It can either produce or break down ATP depending on the magnitude of the electrochemical proton gradient. E) It can either produce or break down ATP depending on the magnitude of the electrochemical proton gradient. In this illustration of the structure of ATP synthase, which of the components catalyzes the synthesis of ATP?Choose one: 1 2 3 4 5 4 During oxidative phosphorylation, why does a single molecule of NADH result in the production of more ATP molecules than a single molecule of FADH2?Choose one: A) FADH2 is less likely than NADH to participate in the electron-transport chain. B) FADH2 promotes the pumping of more protons than does NADH. C) FADH2 and NADH feed their electrons to different carriers in the electron-transport chain. D) NADH donates more electrons to the electron-transport chain than does FADH2. E) FADH2 has a lower electron affinity than does NADH. C) FADH2 and NADH feed their electrons to different carriers in the electron-transport chain. Which metal ion is found in all three respiratory enzyme complexes?Choose one: A) copper B) iron C) manganese D) sulfur E) heme During electron transport, which serves as a ready source for protons that can be pumped across the membrane?Choose one: A) glucose B) NADH C) H2O