Chapter 6

In step 6 of glycolysis, the reaction glyceraldehyde 3-phosphate + NAD+ + Pi leads to which products?

1,3-bisphosphoglycerate + NADH

Which statement regarding glycolysis is true?

Energy from ATP must be expended in the early steps.

Which statement about metabolic pathways is false?

In prokaryotes, reactions in a pathway are located in multiple compartments.

How is free energy that is captured in the molecules NADH and FADH2 passed on in the cell?

It is used to establish a proton gradient across a membrane.

In what processes do proteins in the electron transport chain participate?

Oxidation-reduction reactions and proton pumping

Which process is responsible for the largest amount of ATP production during cellular respiration?

Oxidative phosphorylation

Why is oxygen important in the electron transport pathway and ATP synthesis?

Oxygen accepts electrons at the end of the electron transport chain to free the pathway for a new set of electrons.

Which reaction is not an oxidation-reduction reaction?

R—CH=CH—CH3 + H2O ↔ RCH2—CH(OH)—CH3

Which statement about ATP is true?

The hydrolysis of ATP to ADP and Pi is an exergonic reaction.

How does the quantity of ATP produced as a result of activity by the electron transport chain compare to the quantity produced as a result of glycolysis?

The quantity of ATP produced as a result of electron transport is much more than that produced as a result of glycolysis.

What would happen if regeneration of NAD+ were inhibited during lactic acid fermentation?

The rate of lactic acid production would decrease.

Which of the following statements about photosynthesis is true?

The same number and type of atoms in the reactants of photosynthesis can be accounted for in its products.

Photosynthesis occurs according to the net reaction: 6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2O This equation implies that when you eat an apple, the original source of the carbon atoms you consume is

air.

The chemiosmotic mechanism explains

how a proton gradient is coupled to ATP production.

Fermentation is a process that occurs

in many organisms, including plants and vertebrates.

Cyclic electron transport involves _______ and indirectly generates _______.

photosystem I; ATP

The immediate source of energy for ATP synthesis in chloroplasts is

the electrochemical proton gradient

How many glyceraldehyde-3-phosphate (G3P) molecules are produced by the Calvin cycle when 18 CO2 are fixed?

6

Reduction of carbon dioxide to the level of carbohydrates relies on energy from

ATP and NADPH.

Photophosphorylation requires

ATP synthase.

Which molecule from glycolysis or the citric acid pathway serves as the building block for lipid synthesis?

Acetyl CoA

Which statement about Photosystem I (PSI) and Photosystem II (PSII) is false?

Both photosystems can operate in a cyclic fashion.

How are ATP and NADH similar?

Both structures contain a ribose sugar, an adenine ring, and more than one phosphate group.

In the citric acid cycle, carbon atoms end up as

CO2.

Where does glycolysis occur in the eukaryotic cell?

Cytosol

Ruben and his colleagues knew that photosynthesis could be expressed as the net reaction: 6 CO2 + 12 H2O → C6H12O6 + 6 O2 + 6 H2O Experiments carried out by this group of scientists demonstrated that

H2O is the source of oxygen atoms that end up in O2.

Which statement about the citric acid cycle is true?

It requires NAD+ and FAD.

According to the chemiosmotic mechanism, what is the direct source of the energy used to synthesize ATP from ADP in chloroplasts and in mitochondria?

Proton gradient

Which is most directly derived from intermediates in the citric acid cycle?

Pyrimidines

Which statement about oxidative phosphorylation is false?

The process requires a membrane that is permeable to protons.

Which of the following statements best describes the relationship between photosystem I and photosystem II?

They operate in sequence, with photosystem II supplying electrons to photosystem I.

In which experimental scenario would thylakoids (internal compartments of chloroplasts) be expected to produce the most ATP?

Thylakoids preincubated in a pH 4 solution are moved to a pH 7.5 solution containing ADP and Pi.

Reagents, such as dinitrophenol, increase the permeability of the mitochondrial inner membrane to protons. The addition of dinitrophenol to a suspension of animal cells should, over the short term

inhibit mitochondrial ATP synthesis.

Under anaerobic conditions, pyruvate

is fermented to lactate or alcohol.

If 0.5 mole of glucose is oxidized by glycolysis and lactic acid fermentation, the amount of ATP generated in the cytosol would be

1 mole

If hydrolysis of one mole of ATP generates 7.3 kilocalories (kcal), the total amount of free energy captured as ATP from the complete oxidation of 0.1 mol glucose is

23.4 kcal.

The hydrolysis of ATP can be summarized by the equation below. ATP + H2O → ADP + Pi ΔG = -7.3 kcal/mol How many moles of ATP will a man hydrolyze in a day if he expends 2,300 kilocalories of free energy through this process?

315 mol

In a reaction catalyzed by the enzyme rubisco, CO2 combines with a _______ molecule (ribulose 1,5-bisphosphate) to form two molecules of a _______ molecule (3-phosphoglycerate).

5-carbon; 3-carbon

What is catabolic interconversion?

A metabolic pathway in which a large molecule is broken down into its constituent molecules and releases energy

Which statement best describes step 4 of glycolysis, in which fructose 1,6-bisphophate is converted to glyceraldehyde 3-phosphate?

A six-carbon molecule is broken down into two three-carbon molecules.

Which statement regarding the Calvin cycle is false?

ATP is required during carbon fixation

To be metabolized, glucose first must be converted to glucose 6-phosphate. However, under cellular concentrations of ADP and phosphate, this cannot occur. How do cells circumvent this problem?

ATP, not Pi, is used as the donor of the phosphate group, and thus the overall reaction is exergonic

In the early 1880s, German scientist Theodor Engelmann combined a photosynthetic filamentous alga with aerobic, oxygen-seeking bacteria in a tube of water. The alga was long and narrow and lined up in the same direction as the long tube, while the bacteria were much smaller and moved freely within the tube. When Engelmann exposed the tube to white light, the bacteria moved about randomly. When he placed a prism between the light and the tube, the bacteria gathered in two distinct regions along the length of the filamentous alga that corresponded to different colors of light from the prism. What did Engelmann's experiment demonstrate?

An action spectrum

Why did researchers include bacteriorhodopsin in experiments designed to elucidate the chemiosmotic mechanism?

Bacteriorhodopsin provided researchers with a way to add a light-driven proton pumping function to a simple vesicle.

Which is an example of a catabolic interconversion?

C16 fatty acid to 8 acetyl CoA

Which of the following statements about the Calvin cycle is true?

Carbon atoms from atmospheric CO2 are incorporated into carbohydrates.

Which sequence describes the general flow of free energy in the cell?

Catabolic reactions → NAD+ reduction → phosphoanhydride bond of ATP → anabolic reactions

If four molecules of ribulose 1,5-bisphosphate (RuBP) were added to a solution containing rubisco and CO2, what would be the product(s) of the reaction?

Eight molecules of 3-phosphoglycerate (3PG)

Which is the correct sequence of phases in the Calvin cycle?

Fixation of CO2, reduction and sugar production, ribulose 1,5-bisphosphate regeneration

The reactions making up the citric acid cycle are important because they capture free energy in the form of

GTP, FADH2, and NADH.

Which is an example of an anabolic interconversion?

Gluconeogenesis

Triglycerides are major energy storage molecules. Which statement about the complete oxidation of triglycerides to CO2 and water and the oxidation of glucose to two molecules of pyruvate is true?

Glucose oxidation and triglyceride oxidation use glycolysis

In the complete oxidation of glucose, 6 CO2 molecules are formed per glucose molecule oxidized. From the list below, choose the correct numbers of CO2 molecules released by glycolysis (Gly), the citric acid cycle (CAC), and pyruvate oxidation (Pyr).

Gly 0; CAC 4; Pyr 2

What role does water play in photosynthesis?

It acts as a source of oxygen atom found in the product O2. It acts as an electron donor. It serves as a reactant. It serves as a solvent.

How does a compound that uncouples ATP synthesis from electron transport help a person lose weight?

It diverts some of the chemical energy coming from glucose into heat instead of into ATP formation.

Which statement about rubisco is true?

It generates a six-carbon molecule that splits into two 3-phosphoglycerate (3PG) molecules.

Cyanide binds to and inhibits the enzyme cytochrome oxidase. How does this property of cyanide explain its effect as a lethal poison?

It shuts down movement of electrons along the electron transport chain.

Which statement accurately describes the primary difference between lactic acid fermentation and alcoholic fermentation?

Lactic acid fermentation produces a three-carbon molecule, and alcoholic fermentation produces a two-carbon molecule.

Which organelle contains enzymes necessary for aerobic cellular energy production in eukaryotes?

Mitochondria

Electrons are shuttled to the respiratory chain from glycolysis via _______ and from the citric acid cycle via _______.

NADH; FADH2 and NADH

Which step in glycolysis is an example of substrate-level phosphorylation?

Step 7: 1,3-bisphosphoglycerate + ADP + Pi → 3-phosphoglycerate + ATP Step 10: phosphoenolpyruvate + ADP + Pi → pyruvate + ATP

Which molecule shuttles energy from the leaf to the root cells in many plants?

Sucrose

In the mitochondrial electron transport chain, cyanide inhibits the enzyme that reduces O2 to water. Which statement is the most accurate with respect to the effects of cyanide on glucose catabolism in muscle cells?

The citric acid cycle would be inhibited, but glycolysis would not. Lactic acid would accumulate.

Organisms regulate certain metabolic enzymes in cells to maintain

a constant pool of metabolites.

A metabolic pathway is

a series of separate chemical reactions that together accomplish a complex chemical transformation.A set of chemical transformational steps, each with a specific enzyme. a set of chemical transformational steps, each with a specific enzyme. A means for transforming cellular energy. a means for transforming cellular energy. Vulnerable to inhibitors and activators that target some key enzymes. vulnerable to inhibitors and activators that target some key enzymes.

An important property of 14C that helped Calvin and his coworkers elucidate the pathway of carbon fixation was the fact that

chemically, 14C behaves virtually identically to nonradioactive 12C.

Pyruvate oxidation to acetyl CoA is a complex reaction because

it is a multistep chemical reaction involving five different coenzymes and 60 individual proteins

The ultimate source of energy for ATP synthesis in chloroplasts is

light.

Photosystem I and photosystem II function to absorb _______ energy and donate _______ to proteins in electron transport chains.

light; electrons

The mitochondrial ATP synthase

makes ATP at the expense of the proton gradient established by electron transport.

The difference between oxidation and reduction is that

oxidation reduces the number of electrons in a reactant, while reduction increases the number of electrons

The difference between oxidation and reduction is that

oxidation reduces the number of electrons in a reactant, while reduction increases the number of electrons.

During photosynthesis in green plants, water is

oxidized to O2 in the light.

Cellular respiration refers to the metabolic process that

oxidizes organic molecules to obtain a useful form of energy.

The mitochondrial electron transport chain

oxidizes the intermediate electron carriers, NADH and FADH2

Under anaerobic conditions, _______ is absent.

oxygen

Light is needed for photosynthesis, because it

provides energy, which is converted to chemical energy.

In photosynthesis, NADPH is used for the

reduction of 3-phosphoglycerate (3PG).

Fermentation

results in the formation of lactic acid or ethanol.

ATP synthase is the protein complex that

rotates when protons flow through it, causing ADP and Pi to combine.

The major product of photosynthesis that is exported from the leaves to the rest of the plant is/are

sucrose

Proteins are built from carbons that come from

the citric acid cycle.

The conversion of malate to oxaloacetate in the citric acid cycle takes place with the conversion of NAD+ to NADH. In this reaction, NAD+ is

the oxidizing agent.

All of the following can happen when a photon comes into contact with a pigment molecule except

the photon lowers the ground state of the molecule.

An action spectrum measures

the relative rate of photosynthesis as a function of wavelength.

The most important wavelengths of light for photosynthesis are

the visible wavelengths between 400 and 525 nm and between 600 and 700 nm.