Cellular Respiration

Question 1

What are the two ways ATP can be produced in cellular respiration?

Answer 1

Substrate-level phosphorylation (simple)

Oxidative phosphorylation (complex)

Question 2

What is substrate-level phosphorylation?

Answer 2

The direct generation of ATP in an enzyme-catalyzed reaction by transferring a phosphate group to ADP. This process is endergonic and coupled with an exergonic reaction.

Question 3

What is oxidative phosphorylation?

Answer 3

The chemiosmotic generation of ATP, where energy from electron transport drives proton pumping to create a proton gradient across the membrane, which in turn generates ATP.

Question 4

Describe the structure and function of the mitochondrion.

Answer 4

• Bean shaped
• Double membrane: outer membrane and inner membrane (cristae)
• Own DNA and ribosomes
• Site of oxidative phosphorylation in eukaryotic cells
• Thought to have originated from endosymbiotic bacteria

Question 5

What is glycolysis, and where does it occur?

Answer 5

Glycolysis is the first stage of cellular respiration, occurring in the cytoplasm, where glucose is broken down to produce pyruvate, ATP, and NADH.

Question 6

Chemical reaction for glycolysis.

Answer 6

C₆H₁₂O₆ + 2 ADP + 2 Pi + 2 NAD⁺ → 2 pyruvate + 2 ATP + 2 NADH + 2 H⁺

Question 7

What is the net ATP yield per molecule of glucose in glycolysis?

Answer 7

2 ATP (4 ATP produced, 2 ATP used)

Question 8

What are the three phases of the Calvin Cycle, and why are they important?

Answer 8

Carbon fixation, reduction, and regeneration. Each phase is crucial for synthesizing glucose from CO₂ in the stroma of chloroplasts.

Question 9

What occurs during pyruvate oxidation?

Answer 9

Pyruvate enters the mitochondrial matrix, is decarboxylated to form acetyl-CoA, and produces NADH and CO₂.

Question 10

Chemical reaction for pyruvate oxidation.

Answer 10

2 pyruvate + 2 NAD⁺ + 2 CoA → 2 Acetyl-CoA + 2 NADH + 2 H⁺ + 2 CO₂

Question 11

What is the function of cristae in the mitochondria?

Answer 11

Cristae increase the surface area for oxidative phosphorylation, enhancing ATP production.

Question 12

What role does Acetyl-CoA play in the Krebs Cycle?

Answer 12

Acetyl-CoA combines with oxaloacetate to form citrate, starting the Krebs Cycle.

Question 13

What is the main function of the Krebs Cycle?

Answer 13

To generate high-energy electron carriers (NADH and FADH₂) that supply electrons to the Electron Transport Chain (ETC).

Question 14

How does ATP synthase produce ATP?

Answer 14

Protons flow back into the mitochondrial matrix through ATP synthase, which uses this energy to convert ADP and Pi into ATP.

Question 15

How many ATP are produced from one molecule of NADH?

Answer 15

About 3 ATP

Question 16

How many ATP are produced from one molecule of FADH₂?

Answer 16

About 2 ATP

Question 17

What is chemiosmosis?

Answer 17

The movement of protons down their gradient across a membrane, driving ATP synthesis by ATP synthase.

Question 18

Where in the cell does the Krebs Cycle occur?

Answer 18

In the mitochondrial matrix.

Question 19

What is the final electron acceptor in the Electron Transport Chain?

Answer 19

Oxygen, which combines with electrons and protons to form water.

Question 20

Why is oxygen necessary for aerobic respiration?

Answer 20

Oxygen serves as the final electron acceptor, allowing the Electron Transport Chain to continue and prevent backup of electrons.

Question 21

What is the total ATP yield from one molecule of glucose in cellular respiration?

Answer 21

About 36-38 ATP

Question 22

How does the inner mitochondrial membrane contribute to ATP production?

Answer 22

Its high surface area and embedded proteins facilitate the ETC and ATP synthesis.

Question 23

How does fermentation differ from aerobic respiration?

Answer 23

Fermentation occurs without oxygen, producing less ATP and resulting in byproducts like lactic acid or ethanol.

Question 24

What happens to the electrons as they move along the ETC?

Answer 24

They lose energy, which is used to pump protons into the intermembrane space, creating a proton gradient.

Question 25

What happens to the electrons as they move along the ETC?

Answer 25

They lose energy, which is used to pump protons into the intermembrane space, creating a proton gradient.

Question 26

What is fermentation?

Answer 26

A process where hydrogen atoms from NADH are transferred to organic compounds instead of going through the ETC.

Question 27

Why is pyruvate converted to ethanol or lactate during fermentation?

Answer 27

To regenerate NAD+ so glycolysis can continue in the absence of oxygen.

Question 28

What is the byproduct when pyruvate is converted to acetaldehyde in ethanol fermentation?

Answer 28

Carbon dioxide (CO2).

Question 29

What happens to pyruvate during lactic acid fermentation?

Answer 29

It is converted into lactate, which can later be used in the liver to regenerate glucose.

Question 30

Why does lactic acid buildup occur in muscles during anaerobic respiration?

Answer 30

Because of high-intensity exercise when oxygen is limited, leading to lactate accumulation and muscle fatigue.

Question 31

What is the main difference between aerobic and anaerobic respiration?

Answer 31

Aerobic respiration requires oxygen, while anaerobic respiration occurs without oxygen.

Question 32

How much ATP is produced in aerobic respiration compared to anaerobic respiration?

Answer 32

Aerobic respiration produces about 32 ATP, while anaerobic respiration produces only 2 ATP per glucose molecule.

Question 33

In what form is glucose stored in the body for both aerobic and anaerobic respiration?

Answer 33

As glycogen

Question 34

Why does lactic acid buildup occur only during anaerobic respiration?

Answer 34

Because, in the absence of oxygen, pyruvate is converted into lactic acid instead of entering the Krebs cycle.

Question 35

Why is aerobic respiration more efficient than anaerobic respiration?

Answer 35

Because it produces much more ATP per glucose molecule due to the complete oxidation of glucose.