Chapter 7 Mastering Biology (Unit 2)

Substrate-level phosphorylation accounts for approximately what percentage of the ATP formed by the electron transport chain?

0%

In glycolysis, what starts the process of glucose oxidation?

ATP

Match each product of pyruvate metabolism with the condition under which it is produced. Drag each item to the appropriate bin.

Lactate: fermentation in human muscle Ethanol: fermentation in yeast and bacteria acetyl CoA: aerobic oxidation

Which of the following statements about NAD+ is true?

NAD+ is reduced to NADH during glycolysis.

In the citric acid cycle, ATP molecules are produced by _______.

substrate-level phosphorylation (A phosphate group is transferred from GTP to ADP.)

In glycolysis, ATP molecules are produced by _______.

substrate-level phosphorylation (A phosphate group is transferred from glyceraldehyde phosphate to ADP.)

Which metabolic pathway generates a proton gradient?

the electron transport chain

Which of the following best describes the main purpose of the combined processes of glycolysis and cellular respiration?

transforming the energy in glucose and related molecules in a chemical form that cells can use for work

The electrons stripped from glucose in cellular respiration end up in which compound?

water (At the end of the electron transport chain, the electrons and protons are added to oxygen, forming water.)

Starting with one molecule of isocitrate and ending with fumarate, how many ATP molecules can be made through substrate-level phosphorylation?

1

How many NADH molecules are produced by glycolysis?

2

In glycolysis there is a net gain of _____ ATP.

2 (It takes 2 ATP to produce 4 ATP.)

Approximately how many molecules of ATP are produced from the complete oxidation of two molecules of glucose (C6H12O6) in aerobic cellular respiration?

60-64

In a mitochondrion, if the matrix ATP concentration is high and the intermembrane space proton concentration is too low to generate sufficient proton-motive force, then ________.

ATP synthase will hydrolyze ATP and pump protons into the intermembrane space.

Select the correct statement about cellular respiration.

Cellular respiration and breathing differ in that cellular respiration is at the cellular level, whereas breathing is at the organismal level.

Which of the following is an accurate description of the events that occur along the electron transport chain?

Each electron transfer between carriers results in oxidation of one carrier and reduction of another.

Why is glycolysis described as having an energy investment phase and an energy payoff phase?

Early steps consume energy from ATP, and later steps store an increased amount of energy in ATP and NADH.

Why does the oxidation of organic compounds by molecular oxygen to produce CO2 and water release free energy?

Electrons are being moved from atoms that have a lower affinity for electrons (such as C) to atoms with a higher affinity for electrons (such as O).

Which of these is NOT a product of glycolysis?

FADH2 (FADH2 is a product of the citric acid cycle.)

In the combined processes of glycolysis and cellular respiration, what is consumed, and what is produced?

Glucose is consumed, and carbon dioxide is produced. (The carbon in glucose is oxidized to carbon dioxide during cellular respiration.)

In the oxidation of pyruvate to acetyl CoA, one carbon atom is released as CO2. However, the oxidation of the remaining two carbon atoms—in acetate—to CO2 requires a complex, eight-step pathway—the citric acid cycle. Consider four possible explanations for why the last two carbons in acetate are converted to CO2 in a complex cyclic pathway rather than through a simple, linear reaction. Use your knowledge of the first three stages of cellular respiration to determine which explanation is correct.

It is easier to remove electrons and produce CO2 from compounds with three or more carbon atoms than from a two-carbon compound such as acetyl CoA. (Although it is possible to oxidize the two-carbon acetyl group of acetyl CoA to two molecules of CO2, it is much more difficult than adding the acetyl group to a four-carbon acid to form a six-carbon acid (citrate). Citrate can then be oxidized sequentially to release two molecules of CO2.)

In addition to ATP, what are the end products of glycolysis?

NADH and pyruvate

If pyruvate oxidation is blocked, what will happen to the levels of oxaloacetate and citrate in the citric acid cycle?

Oxaloacetate will accumulate and citrate will decrease.

Sort the following items according to whether they are reactants or products in the anaerobic reduction of pyruvate during lactic acid fermentation. Drag each item to the appropriate bin.

Reactants: pyruvate and NADH Products: lactate and NAD+

Which of the following statements about the chemiosmotic synthesis of ATP is correct?

The chemiosmotic synthesis of ATP requires that the electron transport in the inner mitochondrial membrane be coupled to proton transport across the same membrane. (Chemiosmosis uses the energy of a proton gradient to make ATP; the proton gradient is formed by coupling the energy produced by electron transport with movement of protons across the membrane.)

Which statement about the citric acid cycle is correct?

The last reaction in the citric acid cycle produces a product that is a substrate for the first reaction of the citric acid cycle.

Which of these enters the citric acid cycle?

acetyl CoA

Which of these is NOT a product of the citric acid cycle?

acetyl CoA

Which one of the following is formed by the removal of a carbon (as CO2) from a molecule of pyruvate?

acetyl CoA

During intense exercise, as skeletal muscle cells switch to fermentation, the human body will increase its catabolism of ________.

carbohydrates only.

Which of the following indicates a primary path by which electrons travel downhill energetically during aerobic respiration?

glucose → NADH → electron transport chain → oxygen

The complete oxidation of glucose in aerobic respiration occurs through which of the following sequence of metabolic reactions?

glucose → glycolysis → pyruvate oxidation → citric acid cycle → electron transport chain

Which metabolic pathway is common to both cellular respiration and fermentation?

glycolysis

Which of the following occur(s) in the cytosol of a eukaryotic cell?

glycolysis and fermentation

Where in mitochondria is the enzyme ATP synthase localized?

inner membrane

In muscle cells, fermentation produces _______.

lactate and NAD+

In an oxidation-reduction reaction, the reducing agent ________.

loses electrons and loses potential energy.

Where are the proteins of the electron transport chain located?

mitochondrial inner membrane

The complete reactions of cellular respiration in the presence of oxygen (C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy) result in which of the following?

oxidation of C6H12O6 and reduction of O2

One primary function of both alcohol fermentation and lactic acid fermentation is to ________.

oxidize NADH to NAD+.

In fermentation _______ is reduced and _______ is oxidized.

pyruvate ... NADH (The pyruvate from glycolysis is reduced to either lactate or ethanol, and NADH is oxidized to NAD+.)

In alcohol fermentation, NAD+ is regenerated from NADH by ________.

reduction of acetaldehyde to ethanol.

The primary role of oxygen in cellular respiration is to ________.

serve as an acceptor for electrons and hydrogen, forming water.