chp 9

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What is the term for metabolic pathways that release stored energy by breaking down complex molecules?

catabolic pathways

The molecule that functions as the reducing agent (electron donor) in a redox or oxidation-reduction reaction

loses electrons and loses potential energy.

When electrons move closer to a more electronegative atom, what happens?

The more electronegative atom is reduced, and energy is released.

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 the following statements describes the results of this reaction?
C6H12O6 + 6 O2 6 CO2 + 6 H2O + Energy

C6H12O6 is oxidized and O2 is reduced.

When a glucose molecule loses a hydrogen atom as the result of an oxidation-reduction reaction, the molecule becomes

oxidized.

When a molecule of NAD+ (nicotinamide adenine dinucleotide) gains a hydrogen atom (not a proton), the molecule becomes

reduced.

Which of the following statements describes NAD+?

NAD+ is reduced to NADH during glycolysis, pyruvate oxidation, and the citric acid cycle.

Where does glycolysis take place in eukaryotic cells?

cytosol

The ATP made during glycolysis is generated by

substrate-level phosphorylation.

The oxygen consumed during cellular respiration is involved directly in which process or event?

accepting electrons at the end of the electron transport chain

Which process in eukaryotic cells will proceed normally whether oxygen (O2) is present or absent?

glycolysis

An electron loses potential energy when it

shifts to a more electronegative atom.

Why are carbohydrates and fats considered high energy foods?

They have a lot of electrons associated with hydrogen.

During glycolysis, when each molecule of glucose is catabolized to two molecules of pyruvate, most of the potential energy contained in glucose is

retained in the two pyruvates.

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

NADH and pyruvate

In glycolysis, for each molecule of glucose oxidized to pyruvate

two molecules of ATP are used and four molecules of ATP are produced.

A molecule that is phosphorylated

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

Which kind of metabolic poison would most directly interfere with glycolysis?

an agent that closely mimics the structure of glucose but is not metabolized

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

It uses stored ATP and then forms a net increase in ATP.

The transport of pyruvate into mitochondria depends on the proton-motive force across the inner mitochondrial membrane. How does pyruvate enter the mitochondrion?

active transport

Which of the following intermediary metabolites enters the citric acid cycle and is formed, in part, by the removal of a carbon (CO2) from one molecule of pyruvate?

acetyl CoA

During cellular respiration, acetyl CoA accumulates in which location?

mitochondrial matrix

How many carbon atoms are fed into the citric acid cycle as a result of the oxidation of one molecule of pyruvate?

two

Carbon dioxide (CO2) is released during which of the following stages of cellular respiration?

oxidation of pyruvate to acetyl CoA and the citric acid cycle

During aerobic respiration, electrons travel downhill in which sequence?

food NADH electron transport chain oxygen

Where are the proteins of the electron transport chain located?

mitochondrial inner membrane

In cellular respiration, the energy for most ATP synthesis is supplied by

a proton gradient across a membrane.

During aerobic respiration, which of the following directly donates electrons to the electron transport chain at the lowest energy level?

FADH2

The primary role of oxygen in cellular respiration is to

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

Inside an active mitochondrion, most electrons follow which pathway?

citric acid cycle NADH electron transport chain oxygen

During aerobic respiration, H2O is formed. Where does the oxygen atom for the formation of the water come from?

molecular oxygen (O2)

In chemiosmotic phosphorylation, what is the most direct source of energy that is used to convert ADP+Pi to ATP

energy released from movement of protons through ATP synthase, down the electrochemical gradient

Energy released by the electron transport chain is used to pump H+ into which location in eukaryotic cells?

mitochondrial intermembrane space

The direct energy source that drives ATP synthesis during respiratory oxidative phosphorylation in eukaryotic cells is

the proton-motive force across the inner mitochondrial membrane.

When hydrogen ions are pumped from the mitochondrial matrix across the inner membrane and into the intermembrane space, the result is the

creation of a proton-motive force.

Where is ATP synthase located in the mitochondrion?

inner membrane

Which of the following produces the most ATP when glucose (C6H12O6) is completely oxidized to carbon dioxide (CO2) and water?

oxidative phosphorylation (chemiosmosis)

The synthesis of ATP by oxidative phosphorylation, using the energy released by movement of protons across the membrane down their electrochemical gradient, is an example of

an endergonic reaction coupled to an exergonic reaction.

Chemiosmotic ATP synthesis (oxidative phosphorylation) occurs in

all respiring cells, both prokaryotic and eukaryotic, using either oxygen or other electron acceptors.

What is proton-motive force?

the force exerted on a proton by a transmembrane proton concentration gradient

In liver cells, the inner mitochondrial membranes are about five times the area of the outer mitochondrial membranes. What purpose must this serve?

It increases the surface for oxidative phosphorylation.

In prokaryotes, the respiratory electron transport chain is located

in the plasma membrane

Which catabolic processes may have been used by cells on ancient Earth before free oxygen became available?

glycolysis, pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation, using an electron acceptor other than oxygen

Which of the following normally occurs regardless of whether or not oxygen (O2) is present?

glycolysis

Which of the following occurs in the cytosol of a eukaryotic cell?

glycolysis and fermentation

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

glycolysis

The ATP made during fermentation is generated by which of the following?

substrate-level phosphorylation

In the absence of oxygen, yeast cells can obtain energy by fermentation, resulting in the production of

ATP, CO2, and ethanol (ethyl alcohol).

In alcohol fermentation, NAD+ is regenerated from NADH by

reduction of acetaldehyde to ethanol (ethyl alcohol).

One function of both alcohol fermentation and lactic acid fermentation is to

oxidize NADH to NAD+.

Why is glycolysis considered to be one of the first metabolic pathways to have evolved?

It does not involve organelles or specialized structures, does not require oxygen, and is present in most organisms.

When an individual is exercising heavily and when the muscle becomes oxygen-deprived, muscle cells convert pyruvate to lactate. What happens to the lactate in skeletal muscle cells?

It is taken to the liver and converted back to pyruvate.

When skeletal muscle cells are oxygen-deprived, the heart still pumps. What must the heart muscle cells be able to do?

continue aerobic metabolism when skeletal muscle cannot

When skeletal muscle cells undergo anaerobic respiration, they become fatigued and painful. This is now known to be caused by

buildup of lactate.

You have a friend who lost 7 kg (about 15 pounds) of fat on a regimen of strict diet and exercise. How did the fat leave her body?

It was released as CO2 and H2O.

Even though plants carry on photosynthesis, plant cells still use their mitochondria for oxidation of pyruvate. When and where will this occur?

in all cels all the time

What is the purpose of beta oxidation in respiration?

breakdown of fatty acids

Where do the catabolic products of fatty acid breakdown enter into the citric acid cycle?

acetyl CoA

What carbon sources can yeast cells metabolize to make ATP from ADP under anaerobic conditions?

glucose

High levels of citric acid inhibit the enzyme phosphofructokinase, a key enzyme in glycolysis. Citric acid binds to the enzyme at a different location from the active site. This is an example of

allosteric regulation.

During intense exercise, as skeletal muscle cells go into anaerobiosis, the human body will increase its catabolism of

carbohydrates only.

Yeast cells that have defective mitochondria incapable of respiration will be able to grow by catabolizing which of the following carbon sources for energy?

glucose

In the presence of oxygen, the three-carbon compound pyruvate can be catabolized in the citric acid cycle. First, however, the pyruvate (1) loses a carbon, which is given off as a molecule of CO2, (2) is oxidized to form a two-carbon compound called acetate, and (3) is bonded to coenzyme A.

acetyl CoA, NADH, H+, and CO2.

Exposing inner mitochondrial membranes to ultrasonic vibrations will disrupt the membranes. However, the fragments will reseal "inside out." These little vesicles that result can still transfer electrons from NADH to oxygen and synthesize ATP. If the membranes are agitated further, however, the ability to synthesize ATP is lost.


After the further agitation of the membrane vesicles, what must be lost from the membrane?

ATP synthase, in whole or in part

The immediate energy source that drives ATP synthesis by ATP synthase during oxidative phosphorylation is the

H+ concentration across the membrane holding ATP synthase.

Which metabolic pathway is common to both fermentation and cellular respiration of a glucose molecule?

glycolysis

In mitochondria, exergonic redox reactions

provide the energy that establishes the proton gradient.

The final electron acceptor of the electron transport chain that functions in aerobic oxidative phosphorylation is

oxygen

When electrons flow along the electron transport chains of mitochondria, which of the following changes occurs?

The pH of the matrix increases.

Most CO2 from catabolism is released during

the citric acid cycle.

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