Mastering Biology: Chapter 9 Review

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

oxygen.

What are two types of fermentation?

Two common types of fermentation are alcohol fermentation and lactic acid fermentation.

How does glycolysis go about netting 2 ATP via substrate-level phosphorylation, whether oxygen is present or not?

Under anaerobic conditions, either anaerobic respiration or fermentation can take place. In anaerobic respiration, an electron transport chain is present with a final electron acceptor other than oxygen. In fermentation, the electrons from NADH are passed to pyruvate or a derivative of pyruvate, regenerating the NAD+ required to oxidize more glucose.

In how many organisms does glycolysis occur?

Glycolysis occurs in nearly all organisms and is thought to have evolved in ancient prokaryotes before there was oxygen in the atmosphere.

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

I believe it is C, glycolysis. Correct.

What are oxidation and reduction?

Oxidation is the loss of electrons from one substance, while reduction is the addition of electrons to the other.

ATP synthases are found in the prokaryotic plasma membrane and in mitochondria and chloroplasts. What does this suggest about the evolutionary relationship of these eukaryotic organelles to prokaryotes? How might the amino acid sequences of the ATP synthases from the different sources support or refute your hypothesis?

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What are the three stages in which aerobic respiration occurs?

1. Glycolysis. 2. Pyruvate oxidation and the citric acid cycle. 3. Oxidative phosphorylation (electron transport and chemiosmosis).

What % of a glucose molecule is transferred to ATP?

About 34% of the energy stored in a glucose molecule is transferred to ATP during cellular respiration, producing a maximum of about 32 ATP. I wonder if we have been able to extract all the energy to transfer it into ATP. Is that possible? What enzymes would we need to do this in order to produce lets say 100 ATP for our bodies to use?

Compare and contrast fermentation and anaerobic or aerobic respiration.

All three processes use glycolysis to oxidize glucose, but they differ in their final electron acceptor and whether an electron transport chain is used (respiration) or not (fermentation. Respiration yields more ATP; aerobic respiration, with O2 as the final electron acceptor (because it is so electronegative!) yields about 16 times as much ATP as does fermentation.

Which process yields more ATP, fermentation or anaerobic respiration? Explain

Anaerobic respiration yields more ATP. The 2 ATP produced by substrate-level phosphorylation in glycolysis represents the total energy yield of fermentation. NADH passes its "high-energy" electrons to pyruvate or a derivative of pyruvate, recycling NAD+ and allowing glycolysis to continue. Anaerobic respiration uses an electron transport chain to capture the energy of the electrons in NADH via a series of redox reactions; ultimately, the electrons are transferred to an electronegative other than oxygen. And additional molecules of NADH are produced in anaerobic respiration as pyruvate is oxidized.

How does mitochondria store energy as a proton-motive force (H+ gradient)?

At certain steps along the electron transport chain, electron transfer causes protein complexes to move H+ from the mitochondrial matrix (in eukaryotes) to the intermembrane space, storing energy energy as a proton-motive force. As H+ diffuses back into the matrix through ATP synthase, its passage drives the phosphorylation of ADP, a process called chemiosmosis.

How do electrons travel in the electron transport chain?

First NADH and FADH2 transfer electrons to the electron transport chain. Electrons move down the chain, losing energy in several energy-releasing steps. Finally, electrons are passed to O2, reducing it to H2O.

What happens in aerobic respiration?

Here, oxygen is used as a reactant. Glucose is oxidized to CO2 and oxygen is reduced to water. Electrons lose their PE during their transfer from glucose or other organic compounds to oxygen. Electrons are usually passed first to NAD+, reducing it to NADH, and then from NADH to an electron transport chain, which conducts them to oxygen in energy-releasing steps. The energy is used to make ATP.

In mitochondria, exergonic redox reactions

I believe it is C, provide the energy that establishes the proton gradient. Correct

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

I think B or C. It is D. The H+ concentration across the membrane holding ATP synthase.

What role does Acetyl CoA play in cellular respiration?

In eukaryotic cells, pyruvate enters the mitochondrion and is oxidized to acetyl CoA, which is further oxidized in the citric acid cycle.

What is cellular respiration?

It is a more complete breakdown of glucose.

What is fermentation?

It is a partial degradation of glucose without the use of oxygen.

How does glycolysis harvest chemical energy?

It is harvested by oxidizing glucose to pyruvate. Here 2 pyruvates, 2 ATP's, and 2 NADH's are produced.

How do the catabolic pathways of the cell funnel electrons from many kinds of organic molecules during respiration?

Many carbohydrates enter glycolysis, most often after conversion to glucose. Amino acids of proteins must be deaminated before being oxidized. The fatty acids of fats undergo beta oxidation to two carbon fragments and then enter the citric acid cycle as acetyl CoA. Anabolic pathways can use small molecules from food directly or build other substances using intermediates of glycolysis or the citric acid cycle. Cellular respiration is controlled by allosteric enzymes at key points in glycolysis and the citric acid cycle.

Describe the difference between the two processes in cellular respiration that produce ATP: oxidative phosphorylation and substrate-level phosphorylation.

Most of the ATP produced in cellular respiration comes from an oxidative phosphorylation, in which the energy released from redox reactions in an electron transport chain is used to produce ATP. In substrate-level phosphorylation, an enzyme directly transfers a phosphate group to ADP from an intermediate substrate. All ATP production in glycolysis occurs by substrate-level phosphorylation; this form of ATP production also occurs at one step in the citric acid cycle.

Describe how the catabolic pathways of glycolysis and the citric acid cycle intersect with anabolic pathways in the metabolism of a cell.

The ATP produced by catabolic pathways is used to drive anabolic pathways. As, many of the intermediates of glycolysis and the citric acid cycle are used in the biosynthesis of a cell's molecules.

In the 1930s, some physicians described low doses of a compound called dinitrophenol (DNP) to help patients lose weight. This unsafe method was abandoned after some patients died. DNP uncouples the chemiosmotic machinery (Which allows for a proton gradient - more acidic on one side) by making the lipid bilayer of the inner mitochondrial membrane leaky to H+. Explain how this could cause weight loss and death.

The body the intermembrane would become more acidic over time and have a consistent working of the ATP synthase, where ATP would be constantly produced. I am not sure of how to reach an answer. (search Google.)

How does the cell utilize redox reactions?

The cell tapes the energy stored in food molecules through redox reactions, in which one substance partially or totally shifts electrons to another.

Briefly explain the mechanism by which ATP synthase produces ATP. List three locations in which ATP synthases are found.

The flow of H+ through the ATP synthase complex causes the rotor and attached rod to rotate, exposing catalytic sites in the knob portion that produce ATP from ADP and phosphate. ATP synthases are found in the inner mitochondrial membrane, the plasma membrane of prokaryotes, and membranes within chloroplasts.

What is the source of energy for the formation of ATP and NADH in glycolysis?

The oxidation of the three carbon sugar, glyceraldehyde 3-phosphate, yields energy. In this oxidation, electrons and H+ are transferred to NAD+, forming NADH, and a phosphate group is attached to the oxidized substrate. ATP is then formed by substrate-level phosphorylation when this phosphate group is transferred to ADP.

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

The pH of the matrix increases.

What molecular products indicate the complete oxidation of glucose during cellular respiration?

The release of six molecules of CO2 (did not know this) represents the complete oxidation of glucose. During the processing of two pyruvates to acetyl CoA, the fully oxidized carboxyl group (-COO-) is given off as CO2. The remaining four carbons are released as CO2 in the citric acid cycle as citrate is oxidized back to oxaloacetate.

Most of the CO2 from catabolism is released

during the citric acid cycle.

What is the oxidizing agent in the following reaction Pyruvate + NADH + H+ -> Lactate + NAD+

pyruvate. (why pyruvate..? I thought it was lactate)