AP Biology Unit Two

What is the net gain of ATP at the end of glycolysis? a. 1 b. 2 c. 4 d. 8 e. 12

2

The overall efficiency of respiration (the percentage of the energy released that is saved in ATP) is approximately __________. a. 0.5% b. 2% c. 35% d. 94% e. 100%

35% The efficiency of respiration is 7.3 kcal per mole times 32 moles (maximum ATP yield per mole of glucose) divided by 686 kcal (the amount of energy contained in one mole of glucose), or about 35%.

How many molecules of ATP are gained by substrate-level phosphorylation from the complete breakdown of a single molecule of glucose in the presence of oxygen? a. 2 b. 3 c. 4 d. about 16 ATP e. about 32 ATP

4 There is a net gain of two ATP from glycolysis and one from each molecule of acetyl CoA oxidized in the citric acid cycle for a total of four per glucose.

How many reduced dinucleotides would be produced with four turns of the citric acid cycle? a. 1 FADH2 and 4 NADH b. 2 FADH2 and 8 NADH c. 4 FADH2 and 12 NADH d. 1 FAD and 4 NAD+ e. 4 FAD+ and 12 NAD+

4 FADH2 and 12 NADH

Approximately what percentage of the energy of glucose (C6H12O6) is transferred to storage in ATP as a result of the complete oxidation of glucose to CO2 and water in cellular respiration? a. 2% b. 4% c. 10% d. 25% e. 40%

40%

Approximately how many molecules of ATP are produced from the complete oxidation of two molecules of glucose (C6H12O6) in cellular respiration? a. 2 b. 4 c. 15 d. 38 e. 76

76

In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of a. ATP, CO2, and ethanol (ethyl alcohol). b. ATP, CO2, and lactate. c. ATP, NADH, and pyruvate. d. ATP, pyruvate, and oxygen. e. ATP, pyruvate, and acetyl CoA.

ATP, CO2, and ethanol (ethyl alcohol)

Which of the following metabolic processes can occur without a net influx of energy from some other process? a. C6H12O6 + 6 O2 → 6 CO2 + 6 H2O b. 6 CO2 + 6 H2O → C6H12O6 + 6 O2 c. amino acids → protein d. ADP + i → ATP + H2O e. glucose + fructose → sucrose

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O

All of the NADH's and FADH2's transport their electrons to the... a. cytosol b. matrix of mitochondria c. intermembrane space of the mitochondria d. protiens of the electron transport chain e. Choices 1 and 3 are correct f. Choices 2 and 3 and correct g. Choices 2 and 4 are correct

Choices 2 and 4 are correct

Which of the following best describes the electron transport chain? a. Acetyl CoA is fully oxidized to CO2. b. Electrons are pumped across a membrane by active transport. c. Glucose is broken down to a three-carbon compound in preparation for the citric acid cycle. d. Electrons are passed from one carrier to another, releasing a little energy at each step. e. Hydrogen atoms are added to CO2 to make an energy-rich compound.

Electrons are passed from one carrier to another, releasing a little energy at each step. NADH and FADH2 deliver electrons from the breakdown products of glycolysis and the citric acid cycle to the electron transport chain, which passes these electrons from one molecule to another, releasing a small amount of energy at each step.

Living organisms would be examples of isolated systems. a. True b. False

False

Oxygen is a requirement for anaerobic respiration. a. True b. False

False

If something is being reduced than it is giving up its electrons. a. True b. False

False Reduction means a substance gains electrons while oxidation is the loss of electrons.

In order to produce ATP (ATP synthesis) the members of the electron transport chain are oxidized. a. True b. False

False The reduction reactions of the electron transport chain is what powers the oxidative phosphorylation of ATP synthesis.

A gram of fat oxidized by respiration produces approximately twice as much ATP as a gram of carbohydrate. Which of the following best explains this observation? a. Fats do not form true macromolecules as sugars do. b. Fats are better electron donors to oxygen than are sugars. c. Fats are closely related to lipid molecules, which are the basic building blocks of cellular membranes. d. Fats are produced when cells take in more food than they need. e. Fats are less soluble in water than sugars.

Fats are better electron donors to oxygen than are sugars. Fats contain more hydrogen and less oxygen than sugars—it is the transfer of electrons from good donors such as hydrogen atoms to good acceptors such as oxygen that provides the energy in respiration.

With regards to the chemical equation for cellular respiration and redox reactions...what reactant is reduced and what reactant is oxidized. a. Oxygen is oxidized and glucose is reduced b. Glucose is oxidized and CO2 is reduced c. Glucose is oxidized and Oxygen is reduced d. Water is reduced and oxygen is oxidize

Glucose is oxidized and Oxygen is reduced

The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the a. affinity of oxygen for electrons. b. H+ concentration across the membrane holding ATP synthase. c. flow of electrons down the electron transport chain. d. transfer of phosphate to ADP. e. oxidation of glucose and other organic compounds.

H+ concentration across the membrane holding ATP synthase.

In liver cells, the inner mitochondrial membranes are about 5 X the area of the outer mitochondrial membranes, and about 17 X that of the cell's plasma membrane. What purpose must this serve? a. It allows for increased rate of glycolysis. b. It allows for increased rate of the citric acid cycle. c. It increases the surface for oxidative phosphoryation. d. It increases the surface for substrate-level phosphorylation. e. It allows the liver cell to have fewer mitochondria.

It increases the surface for oxidative phosphoryation.

Phosphofructokinase is an important control enzyme in the regulation of cellular respiration. Which of the following statements describes a function of phosphofructokinase? a. It is activated by AMP (derived from ADP) b. It is activated by ATP. c. It is inhibited by citrate, an intermediate of the citric acid cycle. d. It catalyzes the conversion of fructose-1,6-bisphosphate to fructose-6-phosphate, an early step of glycolysis. e. It is an allosteric enzyme.

It is an allosteric enzyme

Each ATP molecule contains about 1% of the amount of chemical energy available from the complete oxidation of a single glucose molecule. Cellular respiration produces about 32 ATP from one glucose molecule. What happens to the rest of the energy in glucose? a. It is used to make water from hydrogen ions and oxygen. b. It is converted to heat. c. It is released as carbon dioxide and water d. It is stored as fat. e. It is converted to starch.

It is converted to heat. The process is only about 38% efficient, with the rest of the energy lost as heat.

When solid tumors of animals reach a certain size, the center of the tumor begins to die. To prevent this, the tumor can recruit new blood vessels. What purpose does the recruitment of blood vessels to growing tumors serve? a. It supplies glucose to the rapidly dividing cells of the tumor. b. It supplies oxygen so that aerobic cellular respiration can occur instead of fermentation. c. It supplies a non-oxygen electron acceptor to cells so that the cells can respire anaerobically. d. It supplies a non-oxygen electron acceptor to cells so that the cells can respire anaerobically, and it supplies oxygen so that aerobic cellular respiration can occur instead of fermentation. e. It supplies oxygen so that aerobic cellular respiration can occur instead of fermentation, and it supplies glucose to the rapidly dividing cells of the tumor.

It supplies oxygen so that aerobic cellular respiration can occur instead of fermentation, and it supplies glucose to the rapidly dividing cells of the tumor. The new blood vessels provide the fuel for cellular respiration: oxygen and glucose. The new blood vessels also eliminate wastes such as carbon dioxide from the tumor. Some anti-cancer drugs attempt to block the process of recruitment of new blood vessels to tumors.

In glycolysis in the absence of oxygen, cells need a way to regenerate which compound? a. carbon dioxide b. ethanol c. glucose d. NAD+ e. lactate

NAD+ The NAD+ needs to be regenerated, which is why ethanol or lactate is formed.

When a poison such as cyanide blocks the electron transport chain, glycolysis and the citric acid cycle also eventually stop working. Which of the following is the best explanation for this? a. Electrons are no longer available from the electron transport chain to power glycolysis and the citric acid cycle. b. A high level of NADH is present in the cell. c. NAD+ and FAD are not available for glycolysis and the citric acid cycle to continue. d. They run out of ADP. e. The uptake of oxygen stops because electron transport was inhibited.

NAD+ and FAD are not available for glycolysis and the citric acid cycle to continue. Unless the electron transport molecules (NADH and FADH2) can recycle back to their oxidized states (NAD+ and FAD), they will be unable to receive electrons in the other steps of cellular respiration.

After completion of the citric acid cycle, most of the usable energy from the original glucose molecule is in the form of __________. a. CO2 b. ATP c. acetyl CoA d. FADH2 e. NADH

NADH The citric acid cycle produces three NADH per turn of the cycle.

Which of the following vitamins is the coenzyme NAD derived from? a. Riboflavin b. Niacin c. Sulfer d. Vitamin C e. Vitamin B12

Niacin

f a compound that allows protons to freely diffuse across membranes is added to cells that are actively metabolizing glucose via cellular respiration, which of the following processes would stop? a. ATP synthesis b. glycolysis c. electron transport d. All of the listed responses are correct. e. None of the listed responses is correct.

None of the listed responses is correct. The chemiosmotic synthesis of ATP would stop in the mitochondria, but substrate-level phosphorylation could continue.

Which of the following is the process in which glucose is oxidized to generate two molecules of pyruvate, and in which ATP and NADH are produced? a. the citric acid cycle b. chemiosmosis c. the oxidation of pyruvate d. fermentation e. None of the listed responses is correct.

None of the listed responses is correct. The name of the process that oxidizes glucose to pyruvate and produces ATP and NADH is glycolysis.

If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur? a. Additional product will be formed b. Additional substrate will be formed c. The free energy of the system will change d. Nothing; the reaction will stay at equilibrium e. The reaction will change from endergonic to exergonic

Nothing; the reaction will stay at equilibrium

If an enzyme is added to a solution where its substrate and product are in equilibrium, what would occur? a. Additional product would be formed b. Additional substrate would be formed c. The reaction would change from endergonic to exergonic d. The free energy of the system would change e. Nothing; the reaction would stay at equilibrium

Nothing; the reaction would stay at equilibrium

Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description?( a. The metabolism of an organism is isolated from its surroundings b. Because energy must be conserved, organisms constantly recycle energy and thus need no input of energy c. Organisms acquire energy from their surroundings d. Heat produced by the organism is conserved in the organism and not lost to the environment e. all of the above

Organisms acquire energy from their surroundings.

In preparing pyruvate to enter the citric acid cycle, which of the following steps occurs? a. Pyruvate is oxidized and a molecule of carbon dioxide is removed. The electrons removed in this process are used to reduce NAD+ to NADH. b. Pyruvate is oxidized and a molecule of carbon dioxide is removed. The electrons removed in this process are donated to NADH to produce NAD+. c. Pyruvate is reduced to acetyl-coA, which involves the reduction of pyruvate, the addition of a carbon dioxide from the environment, and its reduction by NADH. d. Pyruvate is reduced and a molecule of carbon dioxide is removed. The electrons removed in this process are used to oxidize NAD+ to NADH. e. Pyruvate is ionized directly to acetyl-coA.

Pyruvate is oxidized and a molecule of carbon dioxide is removed. The electrons removed in this process are used to reduce NAD+ to NADH. In addition to these events, a molecule of coenzyme A is attached to the resulting acetyl group.

Succinylcholine is structurally almost identical to acetylcholine. If succinylcholine is added to a mixture that contains acetylcholine and the enzyme that hydrolyzes acetylcholine (but not succinylcholine), the rate of acetylcholine hydrolysis is decreased. Subsequent addition of more acetylcholine restores the original rate of acetylcholine hydrolysis. Which of the following correctly explains this observation? a. The active site must have the wrong configuration to permit succinylcholine binding b. The presence of succinylcholine changes the conditions in the solution, resulting in a denaturation of the enzyme c. Succinylcholine must be an allosteric regulator for this enzyme d. Succinylcholine must be a noncompetitive inhibitor e. Succinylcholine must be a competitive inhibitor with acetylcholine

Succinylcholine must be a competitive inhibitor with acetylcholine Competitive inhibition occurs when a molecule mimics the substrate by competing with it at the active site.

Which of the following statements is the best explanation of what happens to the temperature and carbon dioxide concentration during a 1-hour class period in a classroom of 300 students if the heating and air conditioning is turned off and all doors are kept closed? a. Temperature goes up and the level of carbon dioxide goes down. This is because cellular respiration is an exergonic process that is only about 38% efficient; the remaining energy is lost to the environment as heat. Also, carbon dioxide is being converted to organic molecules such as fats and sugars during cellular respiration. b. Temperature goes down and carbon dioxide levels remain constant. This is because cellular respiration, being an endergonic reaction, requires an input of heat energy from the environment to occur and because carbon dioxide is neither produced nor consumed by cellular respiration. c. Neither temperature nor carbon dioxide levels change because cellular respiration is 100% efficient and because carbon dioxide produced by cellular respiration is just as rapidly consumed by cellular respiration. d. Temperature goes up but carbon dioxide levels remain constant because heat is a by-product of cellular respiration but carbon dioxide is converted to sugar during cellular respiration. e. Temperature and the level of carbon dioxide rise as heat and carbon dioxide are by-products of cellular respiration.

Temperature and the level of carbon dioxide rise as heat and carbon dioxide are by-products of cellular respiration. The oxidation of organic molecules produces carbon dioxide, and as the exergonic process of cellular respiration is not 100% efficient, some energy is lost to the environment as heat.

Which of these statements about enzyme inhibitors is true? a. When the product of an enzyme or an enzyme sequence acts as its inhibitor, this is known as positive feedback b. A competitive inhibitor binds to the enzyme at a place that is separate from the active site c. The action of competitive inhibitors may be reversible or irreversible d. Inhibition of enzyme function by compounds that are not substrates is something that only occurs under controlled conditions in the laboratory e. A noncompetitive inhibitor does not change the shape of the active site

The action of competitive inhibitors may be reversible or irreversible Competitive inhibitors that bind covalently to the enzyme would be irreversible, and those that bind weakly would be reversible.

Which of the following statements about the active site of an enzyme is correct? a. The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits b. The active site allows the reaction to occur under the same environmental conditions as the reaction without the enzyme c. The active site has a fixed structure (shape) d. The structure of the active site is not affected by changes in temperature e. Coenzymes are rarely found in the active site of an enzyme

The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits Only a restricted region of an enzyme molecule (the active site) binds to the substrate. Usually, the active site is formed by only a few of the amino acids, with the rest of the protein molecule providing a framework that reinforces the configuration of the active site.

If significant amounts of materials are removed from the citric acid cycle to produce amino acids for protein synthesis, which of the following will result? a. Less ATP will be produced by the cell. b. Less CO2 will be produced by the cell. c. The four-carbon compound that combines with acetyl CoA will have to be made by some other process. d. The first two answers are correct. e. The first three answers are correct.

The first three answers are correct.

If muscle cells in the human body consume O2 faster than it can be supplied, which of the following is likely to result? a. The muscle cells will have more trouble making enough ATP to meet their energy requirements. b. The cells will not be able to carry out oxidative phosphorylation. c. The cells will consume glucose at an increased rate. d. Only the first two answers are correct. e. The first three answers are correct.

The first three answers are correct. Muscle cells would not be able to produce enough ATP to meet demands, oxidative phosphorylation would stop, and muscle cells would consume glucose at an increased rate.

Which of the following substances is/are involved in oxidative phosphorylation? a. ATP b. oxygen c. ADP d. None of the listed responses is correct. e. The first three listed substances are involved in oxidative phosphorylation.

The first three listed substances are involved in oxidative phosphorylation. ADP is converted to ATP during oxidative phosphorylation, and oxygen functions as the terminal electron acceptor in oxidative phosphorylation.

Most of the electrons removed from glucose by cellular respiration are used for which of the following processes? a. reducing NAD+ to NADH in glycolysis and the citric acid cycle b. producing a proton gradient for ATP synthesis in the mitochondria c. driving substrate-level phosphorylation in glycolysis d. The first two choices are correct. e. The second and third answers are correct.

The first two choices are correct. Electrons from oxidation of glucose are used to reduce NAD+ and produce a proton gradient for ATP synthesis in the mitochondria.

Why is the citric acid cycle called a "cycle"? a. NADH is cycled down the electron transport chain. b. The acetyl CoA that enters the cycle is regenerated in the last step of the pathway. c. All of the carbon from glucose is cycled back into the atmosphere as carbon dioxide. d. NAD+ and FAD are recycled. e. The four-carbon acid that accepts the acetyl CoA in the first step of the cycle is regenerated by the last step of the cycle.

The four-carbon acid that accepts the acetyl CoA in the first step of the cycle is regenerated by the last step of the cycle. The cycling referred to is that of the resynthesis of the four-carbon compound.

When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs? a. The electrons gain free energy. b. The cytochromes phosphorylate ADP to form ATP. c. NAD+ is oxidized. d. The pH of the matrix increases. e. ATP synthase pumps protons by active transport.

The pH of the matrix increases.

Consider the growth of a farmer's crop over a season. Which of the following correctly states a limitation imposed by the first or second law of thermodynamics? a. The process of photosynthesis produces energy that the plant uses to grow b. Growth of the crops must occur spontaneously c. The entropy of the universe must decrease to account for the increased entropy associated with plant growth d. To obey the first law, the crops must represent an open system e. All of the listed responses are correct

To obey the first law, the crops must represent an open system The first law states that energy cannot be created. The growth of plants stores much energy in the body of the plant. That energy must have been obtained from the plant's environment; thus, the plant must be an open system.

A gram of fat oxidized by respiration produces more than twice as much ATP as a gram of carbohydrate. a. True b. False

True

It is possible to transform kinetic energy into potential energy and visa versa. a. True b. False

True

Fermentation

a catabolic process that makes a limited amount of ATP from glucose (or other organic molecules) without an electron transport chain and that produces a characteristic end product, such as ethyl alcohol or lactic acid

Catalyst

a chemical agent that selectively increases the rate of a reaction without being consumed by the reaction

Citric Acid Cycle

a chemical cycle involving eight steps that completes the metabolic breakdown of glucose molecules begun in glycolysis by oxidizing acetyl CoA (derived from pyruvate) to carbon dioxide; occurs within the mitochondrion in eukaryotic cells and in the cytosol of prokaryotes; together with pyruvate oxidation, the second major stage in cellular respiration

Redox Reaction

a chemical reaction involving the complete or partial transfer of one or more electrons from one reactant to another; short for reduction-oxidation reaction

ATP Synthase

a complex of several membrane proteins that functions in chemiosmosis with adjacent electron transport chains, using the energy of a hydrogen ion (proton) concentration gradient to make ATP; ATP synthases are found in the inner mitochondrial membranes of eukaryotic cells and in the plasma membranes of prokaryotes

Which of the following is an example of potential rather than kinetic energy? a. a boy mowing grass b. water rushing over Niagara Falls c. a firefly using light flashes to attract a mate d. a food molecule made up of energy-rich macromolecules e. an insect foraging for food

a food molecule made up of energy-rich macromolecules

Bar Graph

a graph in which the independent variable represents groups or nonnumerical categories and the values of the dependent variable(s) are shown by bars

Anabolic Pathway

a metabolic pathway that consumes energy to synthesize a complex molecule from simpler molecules

Catabolic Pathway

a metabolic pathway that releases energy by breaking down complex molecules to simpler molecules

Beta Oxidation

a metabolic sequence that breaks fatty acids down to two-carbon fragments that enter the citric acid cycle as acetyl CoA

Feedback Inhibition

a method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway

Endergonic Reaction

a nonspontaneous chemical reaction in which free energy is absorbed from the surroundings

Electron Transport Chain

a sequence of electron carrier molecules (membrane proteins) that shuttle electrons down a series of redox reactions that release energy used to make ATP

Glycolysis

a series of reactions that ultimately splits glucose into pyruvate; glycolysis occurs in almost all living cells, serving as the starting point for fermentation or cellular respiration

Exergonic Reaction

a spontaneous chemical reaction in which there is a net release of free energy

Which of the following has the most free energy per molecule? a. a cholesterol molecule b. a fatty acid molecule c. a sugar molecule d. an amino acid molecule e. a starch molecule

a starch molecule Starch is a large polymer of sugar and thus contains many covalent bonds.

Noncompetitive Inhibitor

a substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing the enzyme's shape so that the active site no longer effectively catalyzes the conversion of substrate to product

Where do the catabolic products of fatty acid breakdown enter into the citric acid cycle? a. pyruvate b. malate or fumarate c. acetyl CoA d. -ketoglutarate e. succinyl CoA

acetyl CoA

Which of the following environments or actions affect(s) the rate of an enzyme reaction? a. heating the enzyme b. cooling the enzyme c. substrate concentration d. pH e. all of the above

all of the above

Which of the following is an example of the cellular work accomplished with the free energy derived from the hydrolysis of ATP? a. mechanical work, such as the beating of cilia b. transport work, such as the active transport of an ion into a cell c. chemical work, such as the synthesis of new protein d. all of the above e. none of the above

all of the above

Which of the following statements about enzymes is correct? a. Most enzymes are proteins b. An enzyme is not consumed by the catalytic process c. An enzyme is very specific in terms of which substrate it binds to d. An enzyme lowers the activation energy of a chemical reaction e. all of the above

all of the above

The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule is an example of ___. a. feedback inhibition b. competitive inhibition c. allosteric regulation d. non-competitive inhibition e. cooperativity

allosteric regulation

When protein molecules are used as fuel for cellular respiration, __________ are produced as waste. a. amino groups b. sugar molecules c. molecules of lactate d. ethanol and CO2 e. fatty acids

amino groups The amino group is a residual product of amino acid catabolism.

Chemiosmosis

an energy-coupling mechanism that uses energy stored in the form of a hydrogen ion gradient across a membrane to drive cellular work, such as the synthesis of ATP; under aerobic conditions, most ATP synthesis in cells occurs by chemiosmosis

Cytochrome

an iron-containing protein that is a component of electron transport chains in the mitochondria and chloroplasts of eukaryotic cells and the plasma membranes of prokaryotic cells

Coenzyme

an organic molecule serving as a cofactor; most vitamins function as coenzymes in metabolic reactions

Obligate Anaerobe

an organism that carries out only fermentation or anaerobic respiration; such organisms cannot use oxygen and in fact may be poisoned by it

Facultative Anaerobe

an organism that makes ATP by aerobic respiration if oxygen is present but that switches to anaerobic respiration or fermentation if oxygen is not present

During aerobic respiration, molecular oxygen (O2) is used for which of the following purposes? a. at the end of the citric acid cycle to regenerate citric acid b. at the end of glycolysis to oxidize pyruvate c. as a source of O2 in every reaction that produces CO2 d. at the end of the electron transport chain to accept electrons and form H2O e. between glycolysis and the citric acid cycle to split a carbon from pyruvate, producing CO2

at the end of the electron transport chain to accept electrons and form H2O O2 is the final electron acceptor.

In an experiment, mice were fed glucose (C6H12O6) containing a small amount of radioactive oxygen. The mice were closely monitored, and after a few minutes radioactive oxygen atoms showed up in __________. a. ATP b. water c. NADH d. carbon dioxide e. oxygen gas

carbon dioxide One molecule of CO2 is formed when pyruvate is converted to acetyl CoA, and two molecules of CO2 are produced in the citric acid cycle.

What is the term for metabolic pathways that release stored energy by breaking down complex molecules? a. anabolic pathways b. catabolic pathways c. fermentation pathways d. thermodynamic pathways e. bioenergetic pathways

catabolic pathways

Which is the most abundant form of energy in a cell? a. chemical and electrical gradients b. mechanical energy c. heat d. kinetic energy e. chemical energy

chemical energy

Glucose molecules provide energy to power the swimming motion of sperm. In this example, the sperm are changing... a. chemical energy into kinetic energy b. chemical energy into potential energy c. kinetic energy into potential energy d. kinetic energy into chemical energy e. None of the choices are correct

chemical energy into kinetic energy

Increasing the substrate concentration in an enzymatic reaction could overcome which of the following? a. denaturization of the enzyme b. allosteric inhibition c. competitive inhibition d. saturation of the enzyme activity e. insufficient cofactors

competitive inhibition

When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the a. formation of ATP b. reduction of NAD+ c. restoration of the Na+/K+ balance across the membrane d. creation of a proton gradient e. lowering of pH in the mitochondrial matrix

creation of a proton gradient

Which curve represents the behavior of an enzyme taken from a bacterium that lives in hot springs at temperatures of 70°C or higher? a. curve 1 b. curve 2 c. curve 3 d. curve 4 e. curve 5

curve 3

Which curve was most likely generated from analysis of an enzyme from a human stomach where conditions are strongly acid? a. curve 1 b. curve 2 c. curve 3 d. curve 4 e. curve 5

curve 4

Where in the cell does glycolysis take place? a. chloroplast b. mitochondrial matrix c. Mitochondrial cristae (inner membrane) d. cytosol (cytoplasm) e. lumen of the golgi

cytosol (cytoplasm)

Fermentation is essentially glycolysis plus an extra step in which pyruvate is reduced to form lactate or alcohol and carbon dioxide. This last step __________. a. prevents pyruvate from accumulating b. enables the cell to recycle the reduced NADH to oxidized NAD+ c. extracts a bit more energy from glucose d. enables the cell to make pyruvate into substances it can use e. removes poisonous oxygen from the environment

enables the cell to recycle the reduced NADH to oxidized NAD+ Normally, the reduced NADH delivers its electrons to the electron transport chain, enabling NAD+ to be recycled to glycolysis.

Chemical Energy

energy available in molecules for release in a chemical reaction; a form of potential energy

In chemiosmotic phosphorylation, what is the most direct source of energy that is used to convert ADP + Pi to ATP? a. energy released as electrons flow through the electron transport system b. energy released from substrate-level phosphorylation c. energy released from ATP synthase pumping hydrogen ions from the mitochondrial matrix d. energy released from movement of protons through ATP synthase e. No external source of energy is required because the reaction is exergonic.

energy released from movement of protons through ATP synthase

Choose the pair of terms that correctly completes this sentence. Catabolism is to anabolism as _____ is to _____. a. exergonic; endergonic b. work; energy c. exergonic; spontaneous d. entropy; enthalpy e. free energy; entropy

exergonic; endergonic

The function of cellular respiration is to __________. a. reduce CO2 b. extract CO2 from the atmosphere c. produce carbohydrates d. extract usable energy from glucose e. synthesize macromolecules from monomers

extract usable energy from glucose The most efficient pathway for ATP generation is cellular respiration, in which oxygen is consumed as a reactant, along with the organic fuel (frequently glucose).

Which of the following represents the major (but not the only) energy accomplishment of the citric acid cycle? a. utilization of O2 b. completion of substrate-level phosphorylation c. formation of ATP d. formation of CO2 e. formation of NADH and FADH2

formation of NADH and FADH2 Each turn of the citric acid cycle releases carbon dioxide, forms one ATP by oxidative phosphorylation, and passes electrons to three NAD+ and one FAD.

Which of the following molecules in the process of glycolysis possesses the most chemical energy? a. fructose-6-phosphate b. glyceraldehyde-3-phosphate c. glucose d. pyruvate e. fructose-1,6-bisphosphate

fructose-1,6-bisphosphate Fructose-1,6-bisphosphate has received two phosphate groups from ATP, conserving some of the energy derived from the hydrolysis of ATP in the fructose-1,6-bisphosphate molecule.

Which of the following reactions would be endergonic? a. HCl » H+ + Cl- b. C6H12O6 + 6 O2 » 6 CO2 + 6 H2O c. ATP » ADP + Pi d. glucose + fructose » sucrose e. all of the above

glucose + fructose » sucrose

In the overall process of glycolysis and cellular respiration, __________ is oxidized and __________ is reduced. a. glucose ... ATP b. oxygen ... ATP c. glucose ... oxygen d. carbon dioxide ... water e. ATP ... oxygen

glucose ... oxygen In cellular respiration, electrons and hydrogen are removed from glucose and added to oxygen.

Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule? a. glycolysis b. the citric acid cycle c. the electron transport chain d. reduction of pyruvate to lactate e. synthesis of acetyl CoA from pyruvate

glycolysis

Which of the following normally occurs whether or not oxygen (O2) is present? a. glycolysis b. fermentation c. oxidation of pyruvate to acetyl CoA d. citric acid cycle e. oxidative phosphorylation (chemiosmosis)

glycolysis

Of the metabolic pathways listed below, which is the only pathway found in all organisms? a. fermentation b. the citric acid cycle c. cellular respiration d. glycolysis e. the electron transport chain

glycolysis Ancient prokaryotes probably used glycolysis to make ATP long before oxygen was present in Earth's atmosphere. Glycolysis is the most widespread metabolic pathway.

Alcohol Fermentation

glycolysis followed by the reduction of pyruvate to ethyl alcohol, regenerating NAD+ and releasing carbon dioxide

Lactic Acid Fermentation

glycolysis followed by the reduction of pyruvate to lactate, regenerating NAD+ with no release of carbon dioxide

A molecule that is phosphorylated a. has been reduced as a result of a redox reaction involving the loss of an inorganic phosphate. b. has a decreased chemical reactivity; it is less likely to provide energy for cellular work. c. has been oxidized as a result of a redox reaction involving the gain of an inorganic phosphate. d. has an increased chemical reactivity; it is primed to do cellular work. e. has less energy than before its phosphorylation and therefore less energy for cellular work.

has an increased chemical reactivity; it is primed to do cellular work.

There is no production of carbon dioxide in glycolysis. Which of the following is the best explanation for this fact? a. There is very little ATP produced in glycolysis. b. The products of glycolysis contain the same total number of carbon atoms as in the starting material. c. Glucose contains more carbons than the number of carbons found in the pyruvate products that are produced by glycolysis. d. There are no oxidation or reduction reactions in glycolysis to produce CO2. e. The initial steps of glycolysis require an input of energy in the form of ATP (two per glucose).

he products of glycolysis contain the same total number of carbon atoms as in the starting material. All of the carbon in one glucose molecule is accounted for in the two molecules of pyruvate produced by glycolysis.

Enzyme activity is affected by pH because ___. a. most substrates don't function well at high or low pH b. high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site c. low pH will denature all enzymes d. changes in pH can cause loss of cofactors from the enzyme e. the binding of hydrogen ions to the enzyme absorbs energy and thus there may not be enough energy to overcome the activation energy barrier

high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site

A chemist has discovered a drug that blocks phosphoglucoisomerase, an enzyme that catalyzes the second reaction in glycolysis. He wants to use the drug to kill bacteria in people with infections. However, he cannot do this because __________. a. human cells must also perform glycolysis; the drug might also poison them b. glycolysis produces so little ATP that the drug will have little effect c. this step in the pathway of glycolysis can be skipped in bacteria, but not in humans d. glycolysis can occur without the action of enzymes e. bacteria are prokaryotes; they usually do not need to perform glycolysis

human cells must also perform glycolysis; the drug might also poison them The chemist's drug could have a devastating effect on human cells.

Energy Coupling

in cellular metabolism, the use of energy released from an exergonic reaction to drive an endergonic reaction

Thermal Energy

kinetic energy due to the random motion of atoms and molecules; energy in its most random form; also see heat

Sports physiologists at an Olympic training center wanted to monitor athletes to determine at what point their muscles were functioning anaerobically. They could do this by checking for a buildup of which of the following compounds? a. lactate b. oxygen c. ATP d. ADP e. carbon dioxide

lactate In humans, muscle cells switch to lactate fermentation after becoming anaerobic.

Which type of fermentation would be found to take place in human muscle cells? a. alcoholic fermentation b. lactic acid fermentation

lactic acid fermentation

A molecule becomes more oxidized when it __________. a. gains a hydrogen (H+) ion b. changes shape c. loses a hydrogen (H+) ion d. loses an electron e. gains an electron

loses an electron During oxidation, an electron is removed.

The mechanism of enzyme action is _____ . a. providing energy to speed up the rate of the reaction b. lowering the energy of activation for a reaction c. changing the direction of thermodynamic equilibrium d. changing endergonic into exergonic reactions e. lowering the free energy change of a reaction

lowering the energy of activation for a reaction

During cellular respiration, acetyl CoA accumulates in which location? a. cytosol b. mitochondrial outer membrane c. mitochondrial inner membrane d. mitochondrial intermembrane space e. mitochondrial matrix

mitochondrial matrix

Which of the following is the source of the energy that produces the chemiosmotic gradient in mitochondria? a. the production of NADH b. an ATP-dependent proton pump c. ATP d. movement of electrons down the electron transport chain e. the components of the electron transport chain

movement of electrons down the electron transport chain Energy from the flow of electrons along the electron transport chain is used to pump hydrogen ions (protons) across the inner mitochondrial membrane, creating the chemiosmotic gradient.

NAD+

nicotinamide adenine dinucleotide, a coenzyme that cycles easily between oxidized (NAD+) and reduced (NADH) states, thus acting as an electron carrier

Which of the following is a correct description of the events of cellular respiration in proper sequence? a. glycolysis; oxidative phosphorylation; citric acid cycle; oxidation of pyruvate b. oxidation of glucose to pyruvate; reduction of pyruvate; citric acid cycle; oxidative phosphorylation c. oxidation of pyruvate; citric acid cycle; oxidation of glucose to pyruvate; oxidative phosphorylation d. glycolysis; reduction of pyruvate; citric acid cycle; oxidative phosphorylation e. oxidation of glucose to pyruvate; oxidation of pyruvate; citric acid cycle; oxidative phosphorylation

oxidation of glucose to pyruvate; oxidation of pyruvate; citric acid cycle; oxidative phosphorylation This is the correct sequence of events in cellular respiration.

Carbon dioxide (CO2) is released during which of the following stages of cellular respiration? a. glycolysis and the oxidation of pyruvate to acetyl CoA b. oxidation of pyruvate to acetyl CoA and the citric acid cycle c. the citric acid cycle and oxidative phosphorylation d. oxidative phosphorylation and fermentation e. fermentation and glycolysis

oxidation of pyruvate to acetyl CoA and the citric acid cycle

Most of the ATP produced in cellular respiration comes from which of the following processes? a. reduction of NADH b. substrate-level phosphorylation c. glycolysis d. the citric acid cycle e. oxidative phosphorylation

oxidative phosphorylation After hydrogen ions are pumped into the mitochondrial intermembrane space, they flow back through ATP synthase, which produces most of the ATP associated with cellular respiration.

The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is a. water b. ADP c. oxygen d. NAD+ e. pyruvate

oxygen

During the reaction C6H12O6 + 6 O2 → 6 CO2 + 6 H2O, which compound is reduced as a result of the reaction? a. carbon dioxide b. glucose c. water d. oxygen e. both glucose and carbon dioxide

oxygen In cellular respiration, glucose is oxidized (resulting in the production of carbon dioxide) and oxygen is reduced (resulting in the production of water).

In mitochondria, exergonic redox reactions a. provide the energy that establishes the proton gradient. b. reduce carbon atoms to carbon dioxide. c. are the source of energy driving prokaryotic ATP synthesis. d. are coupled via phosphorylated intermediates to ender-gonic processes. e. are directly coupled to substrate-level phosphorylation.

provide the energy that establishes the proton gradient.

The energy given up by electrons as they move through the electron transport chain is used in which of the following processes? a. the oxidation of water b. the production of CO2 c. pumping H+ across a membrane d. the production of NADH and FADH2 e. the breakdown of glucose

pumping H+ across a membrane Many of the electron transport molecules in the mitochondrion pump a hydrogen ion into the intermembrane space when they pass an electron along the chain.

What is the oxidizing agent in the following reaction? Pyruvate + NADH + H+ S Lactate + NAD+ a. NAD+ b. oxygen c. pyruvate d. NADH e. lactate

pyruvate

Muscle tissues make lactate from pyruvate to do which of the following? a. get rid of pyruvate produced by glycolysis b. produce additional CO2 c. utilize the energy in pyruvate d. speed up the rate of glycolysis e. regenerate NAD+

regenerate NAD+ Human muscle cells make ATP by lactic acid fermentation when oxygen is scarce. This allows them to regenerate NAD+ so that glycolysis can continue.

Which of the following events accompanies the conversion of pyruvate to acetyl CoA before the citric acid cycle? a. release of CO2 and release of coenzyme A b. regeneration of NAD+ c. removal of coenzyme A d. formation of CO2 and synthesis of ATP e. release of CO2 and synthesis of NADH

release of CO2 and synthesis of NADH The carboxyl group of pyruvate is removed as a carbon dioxide molecule. The remaining two-carbon fragment is oxidized to acetate and NAD+ is reduced to NADH.

Adenosine Triphosphate

see ATP

The ATP made during fermentation is generated by which of the following? a. the electron transport chain b. substrate-level phosphorylation c. chemiosmosis d. oxidative phosphorylation e. aerobic respiration

substrate-level phosphorylation

Most cells cannot harness heat to perform work because a. heat is not a form of energy b. heat must remain constant during work c. cells do not have much heat; they are relatively cool d. heat can never be used to do work e. temperature is usually uniform throughout a cell

temperature is usually uniform throughout a cell

Which of the following is changed by the presence of an enzyme in a reaction? a. the G value for the products b. the magnitude of ΔG c. the sign of ΔG d. the activation energy e. the G value for the reactants

the activation energy

Activation Energy

the amount of energy that reactants must absorb before a chemical reaction will start; also called free energy of activation

Allosteric Regulation

the binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site

Energy

the capacity to cause change, especially to do work (to move matter against an opposing force)

Cellular Respiration

the catabolic pathways of aerobic and anaerobic respiration, which break down organic molecules and use an electron transport chain for the production of ATP

Which of the following processes generates most of the NADH that delivers electrons to the electron transport chain? a. substrate-level phosphorylation b. the citric acid cycle c. glycolysis d. oxidative phosphorylation e. anabolic pathways

the citric acid cycle Most of the NADH is produced during the citric acid cycle, along with some FADH2.

Most CO2 from catabolism is released during a. lactate fermentation. b. oxidative phosphorylation. c. glycolysis. d. electron transport. e. the citric acid cycle.

the citric acid cycle.

Reduction

the complete or partial addition of electrons to a substance involved in a redox reaction

Oxidation

the complete or partial loss of electrons from a substance involved in a redox reaction

Where do the reactions of glycolysis occur in a eukaryotic cell? a. across the inner membrane of the mitochondrion b. the matrix of the mitochondrion c. the inner membrane of the mitochondrion d. in the intermembrane space of the mitochondrion e. the cytosol

the cytosol Glycolysis occurs in the cytosol.

Oxidizing Agent

the electron acceptor in a redox reaction

Reducing Agent

the electron donor in a redox reaction

Acetyl CoA

the entry compound for the citric acid cycle in cellular respiration, formed from a two-carbon fragment of pyruvate attached to a coenzyme

Substrate-Level Phosphorylation

the enzyme-catalyzed formation of ATP by direct transfer of a phosphate group to ADP from an intermediate substrate in catabolism

Energy for synthesizing ATP is obtained by ATP synthase directly from which of the following processes? a. the reduction of oxygen b. the flow of H+ across the inner mitochondrial membrane through the ATP synthase enzyme c. the movement of electrons through a series of carriers d. the oxidation of NADH and FADH2 e. the oxidation of glucose

the flow of H+ across the inner mitochondrial membrane through the ATP synthase enzyme Hydrogen ions flow along an electrochemical gradient across the inner mitochondrial membrane. The gradient is the source of the energy for ATP production.

The formation of glucose-6-phosphate from glucose is an endergonic reaction and is coupled to which of the following reactions or pathways? a. the conversion of glucose + fructose to make sucrose b. the hydrolysis of ATP c. the active transport of a phosphate ion into the cell d. the contraction of a muscle cell e. the formation of ATP from ADP + Pi

the hydrolysis of ATP With the help of specific enzymes, the cell is able to couple the energy of ATP hydrolysis directly to endergonic processes by transferring a phosphate group from ATP to some other molecule, such as glucose.

In eukaryotic cells, the components of the electron transport chain are located in or on __________. a. the inner membrane of the mitochondrion b. the matrix of the mitochondrion c. the cytosol d. the intermembrane space of the mitochondrion e. none of the listed locations

the inner membrane of the mitochondrion The electron transport chain is an energy converter that uses the exergonic flow of electrons to pump hydrogen ions across the membrane from matrix to intermembrane space.

Medulla Oblongata

the lowest part of the vertebrate brain, commonly called the medulla; a swelling of the hindbrain anterior to the spinal cord that controls autonomic, homeostatic functions, including breathing, heart and blood vessel activity, swallowing, digestion, and vomiting

Where do the reactions of the citric acid cycle occur in eukaryotic cells? a. across the inner membrane of the mitochondrion b. the cytosol c. the cristae of the mitochondrion d. the intermembrane space of the mitochondrion e. the matrix of the mitochondrion

the matrix of the mitochondrion The citric acid cycle, which takes place in the mitochondrial matrix, completes the degradation of glucose.

Oxygen gas (O2) is one of the strongest oxidizing agents known. The explanation for this is that __________. a. the oxygen atom is very electronegative b. oxygen is so abundant in the atmosphere c. oxygen gas contains a double bond d. oxygen gas is composed of two atoms of oxygen e. oxygen acts as the final electron acceptor in cellular respiration

the oxygen atom is very electronegative The high electronegativity of the oxygen atom is the reason that oxygen is such a strong oxidizing agent.

Proton-Motive Force

the potential energy stored in the form of a proton electrochemical gradient, generated by the pumping of hydrogen ions (H+) across a biological membrane during chemiosmosis

Second Law of Thermodynamics

the principle stating that every energy transfer or transformation increases the entropy of the universe; usable forms of energy are at least partly converted to heat

Oxidative Phosphorylation

the production of ATP using energy derived from the redox reactions of an electron transport chain; the third major stage of cellular respiration

Substrate

the reactant on which an enzyme works

In brewing beer, maltose (a disaccharide of glucose) is __________. a. a sweetener b. the substrate for alcoholic fermentation c. the substrate for aerobic respiration d. one of the enzymes for alcoholic fermentation e. a substitute for pyruvate that cannot be made in yeast

the substrate for alcoholic fermentation In alcoholic fermentation, maltose is cleaved into two glucose molecules, which undergo glycolysis. The resulting pyruvate is converted to ethanol in two steps, one of which regenerates the supply of NAD+ needed for continued glycolysis.

Some bacteria are metabolically active in hot springs because a. they are able to maintain a lower internal temperature b. their enzymes are completely insensitive to temperature c. high temperatures make catalysis unnecessary d. they use molecules other than proteins or RNAs as their main catalysts e. their enzymes have high optimal temperatures

their enzymes have high optimal temperatures

A plot of reaction rate (velocity) against temperature for an enzyme indicates little activity at 10°C and 45°C, with peak activity at 35°C. The most reasonable explanation for the low velocity at 10°C is that __________. a. the enzyme was denatured b. the cofactors required by the enzyme system lack the thermal energy required to activate the enzyme c. the substrate becomes a competitive inhibitor at lower temperature d. there is too little activation energy available e. the hydrogen bonds that define the structure of the enzyme's active site are unstable

there is too little activation energy available The environment usually supplies activation energy in the form of heat. The lower the temperature, the less energy that is available to overcome the activation energy barrier.

Heat

thermal energy in transfer from one body of matter to another

A small amount of ATP is made in glycolysis by which of the following processes? a. attachment of a free inorganic phosphate (Pi) group to ADP to make ATP b. transfer of electrons and hydrogen atoms to NAD+ c. transport of electrons through a series of carriers d. transfer of a phosphate group from a fragment of glucose to ADP by substrate-level phosphorylation e. harnessing energy from the sun

transfer of a phosphate group from a fragment of glucose to ADP by substrate-level phosphorylation Remember that glucose is phosphorylated at the beginning of glycolysis.

In the citric acid cycle, for each pyruvate that enters the cycle, one ATP, three NADH, and one FADH2 are produced. For each glucose molecule that enters glycolysis, how many ATP, NADH, and FADH2 are produced in the citric acid cycle? a. two ATP, six NADH, two FADH2 b. one ATP, three NADH, one FADH2 c. three ATP, three NADH, one FADH2 d. about 38 ATP e. four ATP, six NADH, two FADH2

two ATP, six NADH, two FADH2 Then the NADH and FADH2 go through the electron transport chain.

Which part of the equation ΔG = ΔH - TΔS tells you if a process is spontaneous? a. ΔS b. TΔS c. ΔH d. ΔG e. All of these values reveal the direction in which a reaction will go

ΔG In any spontaneous process, the free energy of a system decreases. The change in free energy equals the change in total energy minus the change in entropy times the temperature.

If, during a process, the system becomes more ordered, then __________. a. ΔG is positive b. ΔG is negative c. ΔH is negative d. ΔS is negative e. ΔH is positive

ΔS is negative In an endergonic reaction, in which order is increased, the change in entropy, symbolized by ΔS, is negative.

When one molecule is broken down into six component molecules, which of the following will always be true? a. ΔS is negative b. ΔS is positive c. ΔG is positive d. An input of free energy is needed e. ΔH is negative

ΔS is positive The large increase in disorder associated with this reaction means that entropy (ΔS) increases.

Metabolism

the totality of an organism's chemical reactions, consisting of catabolic and anabolic pathways, which manage the material and energy resources of the organism

Which of the following is the most correct interpretation of the figure? a. Inorganic phosphate is created from organic phosphate b. Energy from catabolism can be used directly for performing cellular work c. ADP + Pi are a set of molecules that store energy for catabolism d. ATP is a molecule that acts as an intermediary to store energy for cellular work e. Pi acts as a shuttle molecule to move energy from ATP to ADP

ATP is a molecule that acts as an intermediary to store energy for cellular work

How can one increase the rate of a chemical reaction? a. Increase the activation energy needed b. Cool the reactants c. Decrease the concentration of the reactants d. Add a catalyst e. Increase the entropy of the reactants

Add a catalyst

Which of the following statements about allosteric proteins is/are true? a. They are acted on by inhibitors b. They exist in active and inactive conformations c. They are sensitive to environmental conditions d. All of the first three listed responses are correct e. None of the first three listed responses is correct

All of the first three listed responses are correct

Which of the following statements about enzymes is INCORRECT? a. An enzyme lowers the activation energy of a chemical reaction b. Enzymes can be used to accelerate both anabolic and catabolic reactions c. An enzyme is consumed during the reaction it catalyzes d. An enzyme is very specific in terms of the substrate to which it binds e. Most enzymes are proteins

An enzyme is consumed during the reaction it catalyzes If enzymes were consumed during the reaction they catalyzed, they would not be able to act as a catalyst. This statement is incorrect.

Which of the following correctly states the relationship between anabolic and catabolic pathways? a. Energy derived from catabolic pathways is used to drive the breakdown of organic molecules in anabolic pathways b. Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways c. The flow of energy between catabolic and anabolic pathways is reversible d. Catabolic pathways produce usable cellular energy by synthesizing more complex organic molecules e. Degradation of organic molecules by anabolic pathways provides the energy to drive catabolic pathways

Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways The synthesis of complex molecules in anabolic pathways requires an input of energy from catabolic pathways.

Which of the following states the relevance of the first law of thermodynamics to biology? a. Energy is destroyed as glucose is broken down during cellular respiration b. Photosynthetic organisms produce energy in sugars from sunlight c. Living organisms must increase the entropy of their surroundings d. Energy can be freely transformed among different forms as long as the total energy is conserved e. Because living things consume energy, the total energy of the universe is constantly decreasing

Energy can be freely transformed among different forms as long as the total energy is conserved The first law of thermodynamics states that energy can be transformed but can be neither created nor destroyed.

If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously? a. The entropy of the organism's environment must also be decreasing b. The first law of thermodynamics is being violated c. In this situation, the second law of thermodynamics must not apply d. Heat is being used by the organism as a source of energy e. Energy input into the organism must be occurring to drive the decrease in entropy

Energy input into the organism must be occurring to drive the decrease in entropy If the entropy is decreasing, this would tend to make the free energy change associated with this positive. Thus, an input of energy would be required to make this decrease in entropy occur.

Which of the following statements about enzyme function is correct? a. Enzymes can greatly speed up reactions, but they cannot change the net energy output because they cannot change the activation energy b. Enzymes can greatly speed up reactions, but they cannot change the activation energy because they cannot change the net energy output c. Enzymes can change the equilibrium point of reactions, but they cannot speed up reactions because they cannot change the net energy output d. Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output e. None of the listed responses is correct

Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output Enzymes lower the activation energy barrier of a reaction but do not change the free energy of the products.

Which of the following statements about enzymes is/are true? a. Enzymes react with their substrate (form chemical bonds), forming an enzyme-substrate complex, which irreversibly alters the enzyme b. Enzymes increase the rate of a reaction by raising the activation energy for reactions c. The more heat that is added to a reaction, the faster the enzymes will function d. Enzymes speed up the rate of the reaction without changing the ΔG for the reaction e. All of the listed responses are correct

Enzymes speed up the rate of the reaction without changing the ΔG for the reaction Enzymes speed up reactions by lowering the activation energy barrier for the reaction. Enzymes cannot change the DG for the reaction.

Under most conditions, the supply of energy by catabolic pathways is regulated by the demand for energy by anabolic pathways. Considering the role of ATP formation and hydrolysis in energy coupling of anabolic and catabolic pathways, which of the following statements is most likely to be true? a. High levels of ADP result in allosteric inhibition of anabolic pathways b. High levels of ATP result in allosteric activation of anabolic pathways c. High levels of ADP result in allosteric inhibition of catabolic pathways d. High levels of ATP result in allosteric activation of catabolic pathways e. High levels of ADP result in allosteric activation of catabolic pathways

High levels of ATP result in allosteric activation of catabolic pathways

When 1 mole of ATP is hydrolyzed in a test tube without an enzyme, about twice as much heat is given off as when 1 mole of ATP is hydrolyzed in a cell. Which of the following best explains these observations? a. Cells are less efficient at energy metabolism than reactions that are optimized in a test tube b. In the cell, the hydrolysis of ATP is coupled to other endergonic reactions c. Cells have the ability to store heat; this cannot happen in a test tube d. The amount of heat released by a reaction has nothing to do with the free energy change of the reaction e. In cells, ATP is hydrolyzed to ADP and Pi, but in the test tube it is hydrolyzed to carbon dioxide and water

In the cell, the hydrolysis of ATP is coupled to other endergonic reactions The coupling of ATP to other endergonic processes in cells means that less of the free energy is released as heat. When ATP is hydrolyzed without this coupling, all of the energy is released as heat.

What do the sign and magnitude of the ΔG of a reaction tell us about the speed of the reaction? a. The sign determines whether the reaction is spontaneous, and the magnitude determines the speed b. Neither the sign nor the magnitude of ΔG has anything to do with the speed of a reaction c. The more negative the ΔG, the faster the reaction is d. The sign does not matter, but the larger the magnitude of ΔG, the faster the reaction e. The sign does not matter, but the smaller the magnitude of ΔG, the faster the reaction

Neither the sign nor the magnitude of ΔG has anything to do with the speed of a reaction The speed of a reaction is determined by the activation energy barrier of the reaction and the temperature (which determines how many reactants have the energy to overcome the barrier).

Which of the following environments or actions would NOT affect the rate of an enzyme reaction? a. cooling the enzyme b. substrate concentration c. heating the enzyme d. pH e. None of the listed responses is correct

None of the listed responses is correct Changes in temperature, substrate concentration, and pH are all likely to affect enzyme activity.

Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description? a. The metabolism of an organism is isolated from its surroundings b. Heat produced by the organism is conserved in the organism and not lost to the environment c. Organisms acquire energy from, and lose energy to, their surroundings d. Because energy must be conserved, organisms constantly recycle energy and thus need no input of energy e. All of the listed responses are correct.

Organisms acquire energy from, and lose energy to, their surroundings Open systems are those in which energy and materials can be exchanged between the system and its surroundings.

Which of the following is an example of the second law of thermodynamics as it applies to biological reactions? a. The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water b. All types of cellular respiration produce ATP c. Cellular respiration releases some energy as heat d. The first and second choices are correct e. The first, second, and third choices are correct

The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water The second law of thermodynamics states that every energy transformation makes the universe more disordered—carbon dioxide and water are more disordered than glucose.

The binding of an allosteric inhibitor to an enzyme causes the rate of product formation by the enzyme to decrease. Which of the following best explains why this decrease occurs? a. The allosteric inhibitor lowers the temperature of the active site b. The allosteric inhibitor binds to the substrate and prevents it from binding at the active site c. The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site d. The allosteric inhibitor binds to the active site, preventing the substrate from binding e. The allosteric inhibitor causes free energy change of the reaction to increase

The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site In general, any allosteric regulator functions by changing the structure of the enzyme to change the ability of the active site to bind the substrate.

According to the second law of thermodynamics, which of the following is true? a. The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists b. The entropy of the universe is constantly decreasing c. All reactions produce some heat d. Energy conversions increase the order in the universe e. The total amount of energy in the universe is constant

The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists The second law of thermodynamics demands that total entropy increase with any reaction.

What is meant by the "induced fit" of an enzyme? a. The presence of the substrate in solution induces the enzyme to slightly change its structure b. The shape of the active site is nearly perfect for specifically binding the enzyme's substrate or substrates c. The substrate can be altered so that it is induced to fit into the enzyme's active site d. The enzyme changes its shape slightly as the substrate binds to it e. The enzyme structure is altered so that it can be induced to fit many different types of substrate

The enzyme changes its shape slightly as the substrate binds to it The enzyme changes slightly to bind to the substrate and catalyze the reaction.

Which of the following statements correctly describe(s) the role or roles of heat in biological reactions? a. Heat from the environment is necessary for substrates to get over the activation energy barrier b. The kinetic energy of the substrates is increased as the amount of heat in the system is increased c. Increasing the amount of heat in a system will always increase the rate of enzyme-catalyzed reactions d. The first and second choices are correct e. The second and third choices are correct

The first and second choices are correct As the heat energy in a system increases, so does the kinetic energy of the reactants. As the kinetic energy of the reactants increases, the reactants are more likely to interact (with each other directly, or with the active site of an enzyme). Subsequently, the reaction rate would increase.

Above a certain substrate concentration, the rate of an enzyme-catalyzed reaction drops as the enzymes become saturated. Which of the following would lead to a faster conversion of substrate into product under these saturated conditions? a. an increase in concentration of enzyme b. increasing the temperature by a few degrees c. increasing the substrate concentration d. The first and second listed responses are correct e. The first, second, and third listed responses are correct

The first and second listed responses are correct Either increasing the enzyme concentration or slightly increasing the temperature will increase the rate of product formation.

Metabolic pathways in cells are typically far from equilibrium. Which of the following processes tend(s) to keep these pathways away from equilibrium? a. the continuous removal of the products of a pathway to be used in other reactions b. an input of free energy from outside the pathway c. an input of heat from the environment d. The first and second listed responses are correct e. The first, second, and third listed responses are correct

The first and second listed responses are correct Pathways can be displaced from equilibrium either by adding free energy or by removal of the products of the pathway by other reactions.

Which of the following best characterizes the role of ATP in cellular metabolism? a. The charge on the phosphate group of ATP tends to make the molecule very water-soluble b. The ΔG associated with its hydrolysis is positive c. The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate d. The release of free energy during the hydrolysis of ATP heats the surrounding environment e. It is catabolized to carbon dioxide and water

The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate This is one way a cell can use an exergonic reaction to drive an endergonic reaction.

Molecules A and B contain 110 kcal/mol of free energy, and molecules B and C contain 150 kcal/mol of energy. A and B are converted to C and D. What can be concluded? a. A and B will be converted to C and D with a net release of energy b. The conversion of A and B to C and D is spontaneous c. The reaction that proceeds to convert A and B to C and D is endergonic; the products are more organized than the reactants d. The entropy in the products, C and D, is higher than in the reactants, A and B e. The conversion of A and B to C and D is exergonic; the products are less organized than the reactants

The reaction that proceeds to convert A and B to C and D is endergonic; the products are more organized than the reactants

Which of the following is (are) true for anabolic pathways? a. They do not depend on enzymes b. They are usually highly spontaneous chemical reactions c. They consume energy to build up polymers from monomers d. They release energy as they degrade polymers to monomers

They consume energy to build up polymers from monomers

Which of the following statements correctly describes some aspect of ATP hydrolysis being used to drive the active transport of an ion into the cell AGAINST the ion's concentration gradient? a. This is an example of energy coupling b. Both ATP hydrolysis and active transport are spontaneous because they result in an increase in entropy of the system c. The hydrolysis of ATP is endergonic, and the active transport is exergonic d. Neither ATP hydrolysis nor active transport is spontaneous e. ATP is acting as a transport protein to facilitate the movement of the ion across the plasma membrane

This is an example of energy coupling The free energy released from the hydrolysis of ATP is coupled to the energy-requiring active transport of the ion across a membrane.

From the equation ΔG = ΔH - TΔS it is clear that __________. a. a decrease in the system's total energy will increase the probability of spontaneous change b. increasing the entropy of a system will increase the probability of spontaneous change c. increasing the temperature of a system will increase the probability of spontaneous change d. a decrease in the system's total energy will increase the probability of spontaneous change, and increasing the entropy of a system will increase the probability of spontaneous change e. a decrease in the system's total energy will increase the probability of spontaneous change, increasing the entropy of a system will increase the probability of spontaneous change, and increasing the temperature of a system will increase the probability of spontaneous change

a decrease in the system's total energy will increase the probability of spontaneous change, increasing the entropy of a system will increase the probability of spontaneous change, and increasing the temperature of a system will increase the probability of spontaneous change This is the best response.

Cooperativity

a kind of allosteric regulation whereby a shape change in one subunit of a protein caused by substrate binding is transmitted to all the other subunits, facilitating binding of additional substrate molecules to those subunits

Enzyme

a macromolecule serving as a catalyst, a chemical agent that increases the rate of a reaction without being consumed by the reaction; most enzymes are proteins

Entropy

a measure of disorder, or randomness

Spontaneous Process

a process that occurs without an overall input of energy; a process that is energetically favorable

Metabolic Pathway

a series of chemical reactions that either builds a complex molecule (anabolic pathway) or breaks down a complex molecule to simpler molecules (catabolic pathway)

Competitive Inhibitor

a substance that reduces the activity of an enzyme by entering the active site in place of the substrate, whose structure it mimics

If an enzyme in solution is saturated with substrate, the most effective way to obtain a faster yield of products is to a. add a noncompetitive inhibitor b. add an allosteric inhibitor c. add more substrate d. add more of the enzyme e. heat the solution to 90°C

add more of the enzyme

If an enzyme solution is saturated with substrate, the most effective way to obtain a faster yield of products is to a. add more of the enzyme b. heat the solution to 90°C c. add more substrate d. add an allosteric inhibitor e. add a noncompetitive inhibitor

add more of the enzyme

The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule outside the active site is an example of __________. a. allosteric activation b. competitive inhibition c. feedback inhibition d. cooperativity e. noncompetitive inhibition

allosteric activation The molecule in this example would be termed an allosteric activator.

ATP (Adenosine Triphosphate)

an adenine-containing nucleoside triphosphate that releases free energy when its phosphate bonds are hydrolyzed; this energy is used to drive endergonic reactions in cells

Cofactor

any nonprotein molecule or ion that is required for the proper functioning of an enzyme; cofactors can be permanently bound to the active site or may bind loosely and reversibly, along with the substrate, during catalysis

The study of energy flow through a living organism defines... a. metabolism b. catabolism c. anabolism d. bioernergetics e. none of the above are correct

bioernergetics

How do enzymes lower activation energy? a. by increasing reactivity of products b. by locally concentrating the reactants c. by harnessing heat energy to drive the breakage of bonds between atoms d. The first two responses are correct e. The second and third choices are correct

by locally concentrating the reactants One of the ways enzymes work is to increase the concentrations of reactants at a single place.

Bacterial production of the enzymes needed for the synthesis of the amino acid tryptophan declines with increasing levels of tryptophan and increases as tryptophan levels decline. This is an example of ... a. competitive inhibition b. noncompetitive inhibition c. feedback inhibition d. positive feedback e. irreversible inhibition

feedback inhibition

Which of the following reactions would be endergonic? a. HCl → H+ + Cl- b. glucose + fructose → sucrose c. ATP → ADP + Pi d. C6H12O6 + 6 O2 → 6 CO2 + 6 H2O e. All of the listed responses are correct

glucose + fructose → sucrose In this case, the product is more complex (lower entropy) than the reactants, and like many anabolic reactions, this one requires an input of energy.

Enzyme activity is affected by pH because __________. a. most substrates do not function well at high or low pH b. low pH will denature all enzymes c. changes in pH can cause loss of cofactors from the enzyme d. the binding of hydrogen ions to the enzyme absorbs energy and thus there may not be enough energy to overcome the activation energy barrier e. high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site

high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site Each enzyme has an optimal pH at which it is most active, and variations in pH can alter the enzyme's structure, changing activity.

The free energy derived from the hydrolysis of ATP can be used to perform many kinds of cellular work. Which of the following is an example of the cellular work involved in the production of electrochemical gradients? a. the beating of cilia b. proton movement against a gradient of protons c. facilitated diffusion d. the chemical synthesis of ATP e. chromosome movement on microtubules

proton movement against a gradient of protons Protein pumps that hydrolyze ATP can generate electrochemical gradients.

An exergonic (spontaneous) reaction is a chemical reaction that _____. a. occurs only when an enzyme or other catalyst is present b. cannot occur outside of a living cell c. releases energy when proceeding in the forward direction d. is common in anabolic pathways e. leads to a decrease in the entropy of the universe

releases energy when proceeding in the forward direction

An exergonic (spontaneous) reaction is a chemical reaction that __________. a. occurs only when an enzyme or other catalyst is present b. cannot occur outside of a living cell c. releases energy when proceeding in the forward direction d. is common in anabolic pathways e. leads to a decrease in the entropy of the universe

releases energy when proceeding in the forward direction Exergonic reactions proceed with a net release of free energy, and they occur spontaneously.

In general, the hydrolysis of ATP drives cellular work by __________. a. acting as a catalyst b. releasing heat c. changing to ADP and phosphate d. lowering the activation energy of the reaction e. releasing free energy that can be coupled to other reactions

releasing free energy that can be coupled to other reactions With the help of specific enzymes, the cell can couple the energy of ATP hydrolysis directly to endergonic processes.

Active Site

the specific region of an enzyme that binds the substrate and that forms the pocket in which catalysis occurs

Thermodynamics

the study of energy transformations that occur in a collection of matter; see also first law of thermodynamics and second law of thermodynamics

Kinetic Energy

the energy associated with the relative motion of objects; moving matter can perform work by imparting motion to other matter

Potential Energy

the energy that matter possesses as a result of its location or spatial arrangement (structure)

Which of the following determines the sign of ΔG for a reaction? a. the free energy of the products b. the enzyme catalyzing the reaction's having a high affinity (strength of binding) for the reactants c. the free energy of the reactants d. the enzyme catalyzing the reaction's having a low affinity for the products e. the free energy of the reactants and the free energy of the products

the free energy of the reactants and the free energy of the products By subtracting the free energy of the reactants from the free energy of the products, the ΔG can be calculated and the difference in these values determines the sign of the difference.

Much of the suitability of ATP as an energy intermediary is related to the instability of the bonds between the phosphate groups. These bonds are unstable because __________. a. the bonds between the phosphate groups are unusually strong and breaking them releases free energy b. the valence electrons in the phosphorus atom have less energy on average than those of other atoms c. they are hydrogen bonds, which are only about 10% as strong as covalent bonds d. the negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP e. the phosphate groups are polar and are attracted to the water in the cell's interior

the negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP Negative charges repel each other. Loss of the terminal phosphate removes some of the repulsion.

Free Energy

the portion of a biological system's energy that can perform work when temperature and pressure are uniform throughout the system; the change in free energy of a system (ΔG) is calculated by the equation ΔG = ΔH − TΔS, where ΔH is the change in enthalpy (in biological systems, equivalent to total energy), ΔT is the absolute temperature, and ΔS is the change in entropy

A chemical reaction is designated as exergonic rather than endergonic when __________. a. activation energy is required b. the products are less complex than the reactants c. it absorbs more energy d. the potential energy of the products is less than the potential energy of the reactants e. activation energy exceeds net energy release

the potential energy of the products is less than the potential energy of the reactants If a reaction is exergonic, the formation of new bonds releases more energy than was invested in breaking the old bonds.

First Law of Thermodynamics

the principle of conservation of energy: energy can be transferred and transformed, but it cannot be created or destroyed

Some bacteria are metabolically active in hot springs because a. they are able to maintain a cooler internal temperature b. high temperatures make catalysis unnecessary c. their enzymes have high optimal temperatures d. their enzymes are completely insensitive to temperature e. they use molecules other than proteins or RNAs as their main catalysts

their enzymes have high optimal temperatures