Biology, Chapter 8 review questions

Anaerobic respiration occurs sans oxygen; it passes NADH down an ETC that uses inorganic substance like NO3 - and/ or SO42- as electron acceptors; produces relatively reduced inorganic substances. Fermentation is an anaerobic pathway with no ETC; produces relatively reduced organic compounds like alcohol and lactate.

How are anaerobic respiration and fermentation different?

They're anaerobic processes

How are anaerobic respiration and fermentation similar?

NADH and FADH2 enter the electron transport chain at different places.

How does the ETC handle NADH and FADH2 differently?

prokaryotes: occurs in cytosol; eukaryotes: occurs in mitochondria

How does the formation of acetyl CoA stage differ between prokaryotes and eukaryotes?

Transformed into metabolic intermediates. Amino acids undergo deamination; carbon backbone converted into multiple intermediates. Fats: glycerol converted to G3P; fatty acids converted to acetyl CoA (about 40 ATP yield from a six carbon fatty acid).

How is it that other nutrients (e.g., amino acids, lipids) can be metabolized to yield ATP?

The electrons entering the electron transport chain have a relatively high energy content. They lose some of their energy at each step as they pass along the chain of electron carriers. As this energy is lost from the electrons, some of this energy is used to move protons (H+) across a membrane (in eukaryotes, the inner mitochondrial membrane to the intermembrane space).

How is the ETC coupled to ATP synthesis (i.e., what does the ETC do that helps to synthesize ATP?)

2 ATPs per molecule

How many ATP does one FADH2 yield?

Up to 3 ATPs per molecule

How many ATP does one NADH yield?

2 NADH

How many energy carriers (ATP, NADH, and/or FADH2) does Formation of Acetyl CoA produce?

32-34 ATP

How many energy carriers (ATP, NADH, and/or FADH2) does Oxidative phosphorylation produce?

2 net ATP (4 ATP produced, but 2 ATP used); 2 NADH

How many energy carriers (ATP, NADH, and/or FADH2) does glycolysis produce?

2 ATP, 6 NADH, 2 FADH2

How many energy carriers (ATP, NADH, and/or FADH2) does the Citric acid cycle produce?

When a phosphorylated intermediate transfers 2 electrons to ADP, creating ATP; occurs in steps 7 and 8 of glycolysis.

Substrate-level phosphorylation

The endergonic reactions that require ATP ("energy investment phase") and the exergonic reactions yielding ATP and NADH ("energy capture phase").

What are the 2 major phases of glycolysis?

Glycolysis, formation of acetyl coenzyme A, Citric Acid (Kelvin) cycle, and oxidative phosphorylation

What are the four stages of aerobic respiration?

relatively reduced organic compounds like alcohol or lactate

What are the reduced products formed by fermentation?

All of the complexes back up, and we can't pass on electrons - the last cytochrome in the chain retains its electrons (each remains in its reduced state), and the entire chain is blocked all the way back to NADH.

What happens if oxygen isn't present as a final electron acceptor?

Including all steps preceding the citric acid cycle, 74 ATP could be produced from 4 turns of the citric acid cycle. Only including the ATP from the NADH and FADH2 generated from the citric acid cycle, 68 ATP could be generated from 4 turns of the cycle (or one molecule of glucose).

How much ATP could be produced from 4 turns of the citric acid cycle?

4 ATP

How much ATP could be produced from one molecule of glycerol that can produce 4 G3P?

Production of ATP using energy derived from transferring electrons in the ETC of mitochondria; occurs by chemiosmosis. It is an anabolic reaction with a positive delta G, but it's a coupled reaction, so there is a net negative delta G.

Oxidative phosphorylation

oxidative phosphorylation/ chemiosmosis; also substrate-level phosphorylation

The mechanism(s) of ATP synthesis for Aerobic Respiration

substrate-level phosphorylation only (during glycolysis)

The mechanism(s) of ATP synthesis for Fermentation

oxidative phosphorylation/ chemiosmosis; also substrate-level phosphorylation

The mechanism(s) of ATP synthesis for anaerobic respiration are

water

The reduced products formed by Aerobic Respiration

relatively reduced inorganic substances

The reduced products formed by Anaerobic respiration

oxygen (O2)

The terminal electron acceptor in the ETC for Aerobic Respiration

Inorganic substances such as NO3 - and/ or SO42-

The terminal electron acceptor in the ETC for Anaerobic respiration

no ETC

The terminal electron acceptor in the ETC for Fermentation

Oxygen, which is reduced to water.

What is the final electron acceptor in the ETC?

C6H12O6 + 6O2 --> 6CO2 + 6H2O + ATP + heat

What is the overall chemical reaction for cellular respiration?

36 to 38 ATP

What is the total ATP yield of one molecule of glucose?

NAD+, FAD, ATP, H2O

What is/are the product(s) of Oxidative Phosphorylation?

Acetyl CoA, NADH, CO2

What is/are the product(s) of formation of Acetyl CoA?

pyruvate, ATP, NADH

What is/are the product(s) of glycolysis?

CO2, NADH, FADH2, ATP

What is/are the product(s) of the citric acid cycle?

4-carbon oxaloacetate regenerated at the end of cycle

What makes the citric acid cycle a true cycle?

NADH, FADH2, ADP + Pi, O2

What molecule(s) is/are needed to start Oxidative Phosphorylation?

Pyruvate, NAD+, CoA

What molecule(s) is/are needed to start formation of Acetyl CoA?

glucose, ATP, NAD+, ADP, and Pi

What molecule(s) is/are needed to start glycolysis?

Acetyl CoA, oxaloacetate, H2O, NAD+, FAD, ADP, and Pi

What molecule(s) is/are needed to start the citric acid cycle?

2 pyruvate and 2 NADH

What molecule(s) is/are passed on to later stages of cellular respiration from glycolysis?

6 NADH and 2 FADH2

What molecule(s) is/are passed on to later stages of cellular respiration from the citric acid cycle?

2-carbon acetate formed and combined with coenzyme A for each pyruvate formed, also, 2 NADH

What molecule(s) is/are passed on to later stages of cellular respiration from the formation of acetyl CoA step?

NADH and FADH2 enter the ETC and pass their high energy electrons to other acceptors.

What products of earlier reactions enter the ETC?

Anaerobic respiration: ETC; Fermentation: organic molecule

Where are electrons from NADH transferred during anaerobic respiration? Where are they transferred for fermentation?

ETC

Where are electrons from NADH transferred to in aerobic respiration?

Anoxic environments like waterlogged soil, stagnant ponds, and the intestines (the bacteria in the intestines).

Where do we see anaerobic respiration occurring?

The cytosol of cells; like muscle cells, yeast, bacteria (like in yogurt), and fungi.

Where does fermentation occur?

Mitochondrial matrix

Where in the cell does formation of acetyl CoA occur?

Cytosol

Where in the cell does glycolysis occur?

Inner mitochondrial membrane

Where in the cell does oxidative phosphorylation: occur?

Mitochondrial matrix

Where in the cell does the citric acid cycle occur?

Glucose is oxidized to carbon dioxide; oxygen is reduced to water.

Which molecules are oxidized and which are reduced during cellular respiration?

Their electrons enter at different places

Why do FADH2 molecules yield fewer ATP than NADH molecules?

Because the inner mitochondrial membrane is not permeable to NADH, so the NADH molecules can't diffuse into the mitochondria to transfer their electrons. Instead, they send their electrons in, which works well for the liver, kidney, and heart cells. However, the brain, skeletal muscle, and some other types of cells have shuttles requiring more energy, so the electrons are at lower energy levels by the time they reach the entrance to the electron transport chain. This means they yield less ATP (2/NADH instead of 3/NADH).

Why do the NADH molecules from glycolysis yield fewer ATP?

Without the ETC, you run out of NAD+, and glycolysis stops. In fermentation, NAD+ is regenerated when NADH transfers H atoms to organic molecules. (For example, pyruvate is converted to acetaldehyde, which accepts H from NADH to become ethyl alcohol.)

Why is fermentation necessary (i.e., why can't glycolysis simply go on indefinitely?)

Fermentation is so inefficient because the sugar is only partially oxidized - it only yields 2 ATP.

Why is fermentation so inefficient?