Chapter 6 Mastering

In cellular respiration, most ATP molecules are produced by _____.

oxidative phosphorylation Explanation: This process utilizes energy released by electron transport.

The O2 required for __________ is supplied by __________.

cellular respiration ... breathing

Which energy-rich molecule produced by cellular respiration directly powers cell work?

ATP

Structure A is _____.

ATP synthase Explanation: ATP synthase attaches phosphate groups to ADP molecules to generate ATP.

What molecules belong in space A and B?

glucose and oxygen

What process occurs in Box A?

glycolysis Explanation: Glycolysis occurs in the cytosol.

The proximate (immediate) source of energy for oxidative phosphorylation is _____.

kinetic energy that is released as hydrogen ions diffuse down their concentration gradient Explanation: Concentration gradients are a form of potential energy.

How many NADH are produced by glycolysis?

2

In glycolysis there is a net gain of _____ ATP.

2

Citric Acid Cycle

2 Acetyl CoA--> 2FADH2 + 6NADH+ 2 ATP + 4 CO2

1. The transfer of _____ from one molecule to another is an oxidation-reduction reaction, or redox reaction.

2. In cellular respiration, glucose becomes to carbon dioxide (CO2) as it loses electrons (in hydrogen atoms

In glycolysis, what starts the process of glucose breakdown?

ATP

In nutrient-rich environments (like your mouth), bacteria can use the provided amino acids to synthesize their proteins. However, should the environmental conditions change and become nutrient-poor, bacteria would need to synthesize their amino acids. They can do this using __________.

Citric acid cycle intermediates Explanation: Many intermediates from the citric acid cycle can be siphoned off and used to generate amino acids.

Which of the following molecules is broken down in cellular respiration, providing fuel for the cell?

Glucose

Glycolysis

Glucose --> 2 pyruvic acid+ 2 NADH+ 2 ATP

Given the relatively modest number of calories burned by anything but the most vigorous activities, why can people consume over 2,000 kilocalories a day, yet maintain a healthy body weight?

Most of the energy consumed in food is spent maintaining the body's functions, so only a fraction of food energy needs to be burned in exercise.

Which of these is NOT a product of the citric acid cycle (also called the Krebs cycle)?

acetyl CoA Explanation: Acetyl CoA enters the citric acid cycle.

In muscle cells, fermentation produces _____.

lactate and NAD+ Explanation: These are the products of fermentation as it occurs in muscle cells.

What molecule is indicated by the letter D?

oxygen Explanation: Oxygen is the final electron acceptor of cellular respiration.

The final electron acceptor of cellular respiration is _____.

oxygen Explanation: Oxygen is combined with electrons and hydrogen to form water.

What process occurs within Box B?

the citric acid cycle Explanation: The citric acid cycle transfers electrons to NADH and FADH2.

Which of the following statements regarding glycolysis is FALSE?

Glycolysis evolved in an oxygen-rich environment. Explanation: Glycolysis does not require O2, and likely evolved nearly a billion years before oxygen began accumulating from photosynthesis.

During electron transport, energy from _____ is used to pump hydrogen ions into the _____.

NADH and FADH2 ... intermembrane space Submit Explanation: The energy released as electrons, which have been donated by NADH and FADH2, is passed along the electron transport chain and used to pump hydrogen ions into the intermembrane space.

Which of these enters the citric acid cycle (also called the Krebs cycle)?

acetyl CoA Explanation: Acetyl CoA is a reactant in the citric acid cycle (also called the Krebs cycle).

In an experiment, mice were fed glucose (C6H12O6) containing a small amount of radioactive carbon. The mice were closely monitored, and in a few minutes, radioactive carbon atoms showed up in __________.

carbon dioxide Explanation: Cellular respiration, or the oxidization of glucose, involves the release of CO2.

5. NADH delivers electrons to an electron transport chain, which passes the electrons through carrier molecules in a series of redox reactions to the final electron acceptor ______

oxygen

What process occurs in structure H?

photosynthesis

3. In cellular respiration, oxygen becomes _______ to water (H2O) as it gains electrons (in hydrogen atoms) that came from glucose

reduced

A gram of fat oxidized by cellular respiration produces approximately __________ as much ATP as a gram of carbohydrate.

twice Explanation: Fats are excellent fuels because they store so much energy for their mass.

In eukaryotes, most of the high-energy electrons released from glucose by cellular respiration __________.

reduce NAD+ to NADH, which then delivers them to the electron transport chain Explanation: Most of the high-energy electrons released from the glucose are picked up by NAD+ and sent through the electron transport chain.

Which of these is NOT a product of glycolysis?

FADH2

1 Glucose + 6 O2 --> 6 Co2 + 6H2O + ATP

Cellular Respiration

What organelle is indicated by the letter C?

mitochondrion

What molecules belong in spaces E and F?

carbon dioxide and water

Which of the following best describes the electron transport chain?

Electrons pass from one carrier to another, releasing a little energy at each step. Answer: 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.

4. In cellular respiration, organic molecules become oxidized as _______ picks up electrons and H+ and becomes reduced to NADH.

NAD+

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 treat people with bacterial infections. However, he can't do this because _____.

human cells also perform glycolysis; the drug might also poison them

We inhale O2 and we exhale CO2. Carbon dioxide is produced __________.

in the reaction that creates acetyl CoA (coenzyme A) from pyruvate Explanation: Carbon dioxide is produced in the transition between glycolysis and the citric acid cycle when the three-carbon pyruvate is cleaved to a two-carbon acetyl molecule with the remaining carbon of pyruvate released as carbon dioxide. Carbon dioxide is also produced in the citric acid cycle itself.

Bacteria have no membrane-enclosed organelles. However, some still generate ATP through cellular respiration. Where might the electron transport chain be found in these organisms?

plasma membrane Explanation: The electron transport chain requires a membrane that will act as a barrier to hydrogen ions that are being pumped across this space. The only membrane in a bacterial cell is the plasma membrane. Note that the inner membrane of a mitochondrion is a bacterial membrane obtained by the eukaryote through endosymbiosis.

In glycolysis, ATP molecules are produced by _____.

substrate-level phosphorylation

Through respiration, humans breathe in O2 and breathe out CO2. However, what would happen if we did not breathe in O2?

We would not make enough ATP to meet our energy requirements Explanation: The electron transport chain accepts electrons from the breakdown products of glycolysis and the citric acid cycle, and it passes these electrons from one molecule to another until they are passed (along with two hydrogen ions) to oxygen to form water.

For each glucose that enters glycolysis, _____ NADH enter the electron transport chain.

10 Explanation: For each glucose molecule that enters glycolosis, a total of 10 NADH are produced -- 2 are produced in glycolysis, 2 are produced in acetyl CoA production, and 6 are produced in the citric acid cycle.

A single glucose molecule produces about 38 molecules of ATP through the process of cellular respiration. However, this only represents approximately 34% of the chemical energy present in this molecule. The rest of the energy from glucose is __________.

converted to heat Explanation: The majority of the energy in a molecule of glucose is lost as heat.

Each turn of the citric acid cycle generates one ATP and ___ additional energy-rich molecules: __________.

four; 3 NADH and 1 FADH2 Explanation: The citric acid cycle generates 3 molecules of NADH and 1 molecule of FADH2. These molecules carry high energy electrons that will be delivered to the electron transport chain.

In the equation shown below, during cellular respiration __________ is oxidized and __________ is reduced.

glucose ... oxygen

Sports physiologists at an Olympic training center want to monitor athletes to determine at what point their muscles begin to function anaerobically. They could do this by checking for a buildup of _____.

lactic acid Explanation: In humans, muscle cells switch to lactic acid fermentation after becoming anaerobic.

A scientist wants to study the enzymes of the citric acid cycle in eukaryotic cells. What part of the cell would she use as a source of these enzymes?

mitochondrial matrix Explanation: The water-soluble citric acid cycle intermediates and enzymes of a eukaryotic cell are found in the mitochondrial matrix, where the newly synthesized NADH and FADH2 diffuse to proteins of the electron transport chain held within the inner mitochondrial membrane. The matrix corresponds to the cytoplasm of the bacterium from which mitochondria are descended.

Some human cells, such as nerve cells, are restricted to aerobic respiration to recycle NADH and FADH2. If these cells are deprived of oxygen, then __________.

oxidative phosphorylation would come to a halt because there wouldn't be any oxygen to "pull" the electrons down the transport chain Explanation: Without electronegative oxygen waiting at the end of the chain, electron flow would cease, along with the action of the protein complexes that create the proton gradients.

2. In cellular respiration, glucose becomes ______ to carbon dioxide (CO2) as it loses electrons (in hydrogen atoms

oxidized

In the citric acid cycle (also called the Krebs cycle), ATP molecules are produced by _____.

substrate-level phosphorylation Explanation: A phosphate group is transferred from GTP to ADP.

Most NADH molecules generated during cellular respiration are produced during __________.

the citric acid cycle Explanation: There are 6 NADH molecules produced by the citric acid cycle per molecule of glucose. Two molecules of FADH2 are also produced by this cycle, which makes it a big source of high energy electron carriers.

6. The energy released from the redox reactions in the electron transport chain is used by the cell to make ______

ATP