AP Bio Chapter 9: Cellular Respiration and Fermentation

Explain the overall concept of how ATP synthase uses the flow of hydrogen ions to produce ATP.

H+ ions flow down their gradient and enter binding sites within a rotor, changing the shape of each subunit so that the rotor spins within the membrane, before leaving the rotor and passing through a second half channel into the mitochondrial matrix. The spinning of the rotor causes an internal rod to spin, activating catalytic sites in the knob that produce ATP.

Oxygen stabilizes the electrons by combining with two hydrogen ions to form what compound?

water

Why is the total count 36 or 38 ATP molecules rather than a specific number?

→Ratio of NAD⁺ to ATP is not a whole number → ATP yield varies depending on type of shuttle used to transport → Use of proton-motive force generated by the redox reactions of respiration to drive other work.

What are the three steps of the conversion process in the citric acid cycle?

1.) Pyruvate's carboxyl group is removed & given off as a molecule of CO₂ 2.) The remaining two-carbon fragment is oxidized, forming acetate. Extracted electrons are are transferred to NAD⁺ storing energy in the form of NADH. 3.) CoA is attached by its sulfur atom to the acetate forming acetyl CoA.

What three organic macromolecules are often utilized to make ATP by cellular respiration?

1.) proteins 2.) carbohydrates 3.) fats

How many ATPs are formed in the citric acid cycle?

2

How many FADH₂ have been formed in the citric acid cycle?

2

How many times does the citric acid cycle occur for each molecule of glucose?

2

How many NADHs formed in the citric acid cycle?

3

Each NADH can form a maximum of ______________ ATP molecules. Each FADH, which donates electrons that activate only two proton pumps, makes ______________ ATP molecules.

3 2

In the energy investment phase which two steps use ATP? In the energy payoff phase which two steps from ATP and which step forms NADH?

3 & 1 7 & 10; 6

How many total carbons are lost as pyruvate is oxidized in the citric acid cycle?

4

What are coenzymes?

An organic molecule serving as a cofactor. EX: Most vitamins function as coenzymes in metabolic reactions

Explain how AMP stimulates cellular respiration while citrate and ATP inhibit it.

As ATP is used up, AMP accumulates which signals more ATP to be made. The more ATP there is, the slower glycolysis is.

What is the function of the electron transport chain in cellular respiration?

Breaks the fall of electrons.

Alcohol fermentation starts with glucose and yields ethanol. Explain this process, and be sure to describe how NAD⁺ is recycle.

CO₂ releases from the pyruvate & is converted to acetaldehyde. Acetaldehyde is reduced by NADH to ethanol which regenerates the supply of NAD⁺ needed for glycolysis to continue.

Explain the difference in energy usage between the catabolic reactions of cellular respiration and anabolic pathways of biosynthesis.

Catabolic: energy is generatedanabolic: energy is consumed

Give the formula (with names) for the catabolic degradation of glucose by cellular respiration.

C₆H₁₂O₆ + 6 O₂ → 6 CO₂ + 6 H₂O + Energy (ATP + Heat) Glucose + Oxygen → Carbon Dioxide + Water + Energy (ATP + Heat)

What two stages can glycolysis be divided into?

Energy investment phase and energy payoff

Explain the difference between fermentation and cellular respiration.

Fermentation is the partial degradation of sugars or other organic fuel without oxygen while cellular respiration uses oxygen.

Explain what has happened to each of the 6 carbons found in the original glucose molecule.

For each pyruvate molecule formed from the original glucose molecule, the pyruvate is broken down to three CO₂ molecules, including the molecule of CO₂ releases during the conversion of pyruvate to acetyl CoA.

What is the meaning of glycolysis? What occurs in this step of cellular respiration?

Glycolysis means sugar splitting. During glycolysis chemical energy is harvested by oxidizing glucose to pyruvate.

Two key terms are chemiosmosis and proton-motive force. Relate both of these terms to the process of oxidative phosphorylation.

In oxidative phosphorylation, chemiosmosis uses energy stored in the form of H⁺ and proton-motive force is an H⁺ gradient.

Electron transport involves a series of electron carriers. Where are these found in eukaryotic cells? Where are these found in prokaryotic cells?

Inner mitochondrial membrane Plasma membrane.

The oxidation of pyruvate accounts for two additional reduced __________ molecules and two molecules of CO₂.

NADH

The two electron carrier molecules that feed electrons into the electron transport system are __________________ and ____________.

NADH; FADH₂

What electron carrier is hydrogen transferred to first?

NAD⁺

Describe what happens when NAD⁺ is reduced. What enzyme is involved?

NAD⁺ receives two negatively charged electrons and one positively charged electron which neutralized its charge and is reduced to NADH. Dehydrogenase is the enzyme involved.

What is the electron acceptor in fermentation?

Organic molecules (pyruvate or acetaldehyde)

What is the difference between oxidation and reduction?

Oxidation is the loss of electrons from one substance and reduction is the gain of electrons to another substance.

What strongly electronegative atom, pulling electrons down the transport chain, is the final electron acceptor?

Oxygen

Oxygen is ultimate electron acceptor. Why is this?

Oxygen has high electronegativity which pulls electrons toward it.

Phosphofructokinase is an allosteric enzyme that catalyzes an important step in glycolysis. Explain how this step is a control point in cellular respiration.

Phosphofructokinase is the pacemaker of cellular respiration.

Lactic acid fermentation starts with glucose and yields lactate. Explain this process, and be sure to describe how NAD⁺ is recycled.

Pyruvate is reduced by NADH to form lactate with no release of CO₂.

What is the role of electron transport chain in forming the H⁺ gradient across the inner mitochondrial membrane?

The chain is an energy converter that uses the exergonic flow of electrons from NADH to FADH₂ to pump H⁺ across the membranes from the mitochondrial matrix to the intermembrane space. The H⁺ has a tendency to move back across the membrane, diffusing own its gradient. And the ATP synthases are the only sites that provide a route through the membrane for H⁺.

Explain how the electron transport chain is utilized in oxidative phosphorylation.

The electron transport chain accepts electrons from the breakdown products of the first two stages of cellular respiration and passes the electrons from one molecule to the next.

Xe⁻ + Y → X + Ye⁻ Which component is oxidized and which component is reduced? _________________is the reducing agent in this reaction, and ________________ is the oxidizing agent.

Xe⁻ is oxidized and Y is reduced Y; Xe⁻

Notice that glycolysis occurs in the __________ of the cell. Is oxygen required?

cytosol (cytoplasm); no

Each member of the electron transport chain is lower in free __________ than the preceding member of the chain, but higher in _________. The molecule at zero free energy, which is _____________, is lowest of all the molecules in free energy and highest in electronegativity.

energy; NADH; oxygen

When compounds lose electrons, they ________________ energy; when compounds gain electrons, they _______________ energy.

gain; lose

The starting point of glycolysis is the six-carbon sugar ___________, and the ending products are two ______________-carbon molecules of pyruvate.

glucose; organic; pyruvate

Is NAD⁺ oxidized or reduced? Lower or higher potential energy? Is NADH oxidized or reduced? Lower or higher potential energy?

oxidized; lower reduced; higher

Fermentation allows for production of ATP without using either ____________ or any ____________.

oxygen; electron transport chain