Cellular Respiration

Question 1

Oxidation

Answer 1

An atom or molecule gains electrons (oxidizes the other substance).
Removal of H atoms from a molecule.
Gain of O atoms to a molecule.

Question 2

Reduction

Answer 2

An atom or molecule loses electrons (reduces the other substance).
Addition of H atoms to a molecule.
Reduction of O atoms from a molecule.

Question 3

Substrate-Level Phosphorylation

Answer 3

ATP that is formed directly by the transfer of a phosphate group to ADP through an enzyme.

Question 4

Oxidative Phosphorylation

Answer 4

ATP that is formed indirectly by the transfer of a phosphate group to ADP through a series of redox reactions.

Question 5

10 stages of glycolysis

Answer 5

Glucose
Glucose 6-phosphate
Fructose 6-phosphate
Fructose 1, 6-bisphosphate
Glyceraldehyde 3-phosphate
1, 3- biphosphoglycerate
3-phosphoglycerate
2-phosphoglycerate
Phosphoenolpyruvate
Pyruvate

Question 6

Products of Glycolysis

Answer 6

Net 2 ATP
2 NADH and 2 H+ produced (NAD+ is reduced).

Question 7

What compound enters the pyruvate oxidation stage?

Answer 7

2 pyruvate enter the pyruvate oxidation stage.

Question 8

What compound enters the Citric Acid Cycle?

Answer 8

2 molecules of acetyl-CoA.

Question 9

What two compounds combine to form citrate in the Citric Acid Cycle?

Answer 9

The acetyl group of acetyl-CoA (2-C) combines with oxaloacetate (4-C) to form citrate (6-C).

Question 10

Why is oxaloacetate important?

Answer 10

• In the citric acid cycle, it is the final product of step 8 and is the reactant in step 1.
• Without it, the citric acid cycle would not be able to occur for the molecules of glucose.
• Oxaloacetate combines with an acetyl group to form citrate (6C), which is necessary for the citric acid cycle to occur.

Question 11

Describe the production of ATP in each stage of cellular respiration.

Answer 11

Glycolysis –> 2 ATP
Pyruvate Oxidation –> No ATP is directly produced
Citric Acid Cycle –> 2 ATP
ETC/Chemiosmosis –> 34 ATP

Question 12

In what stage is ATP produced in the highest quantity? What type of phosphorylation is this?

Answer 12

The most ATP is produced during ETC/chemiosmosis.
This is oxidative phosphorylation.

Question 13

What are the products of ETC/chemiosmosis?

Answer 13

ATP
H2O (water)
NAD+
FAD

Question 14

Where does the energy come from during ATP production in chemiosmosis?

Answer 14

The energy comes from the proton-motive force (electrochemical gradient).
This force is generated by the accumulation of H+ ions in the intermembrane space.

Question 15

Where is NAD+/NADH and FAD/FADH2 oxidized/reduced?

Answer 15

NAD+/NADH and FAD/FADH2 are reduced (gained e- and H+) in glycolysis, pyruvate oxidation and the citric acid cycle.
NAD+/NADH and FAD/FADH2 are oxidized (lost electrons and H+) during ETC and chemiosmosis.

Question 16

At what stage of cellular respiration does coenzyme A become acetyl-CoA?

Answer 16

Coenzyme A becomes acetyl-CoA during pyruvate oxidation.

Question 17

How do electrons enter the ETC? How do electrons “travel through” the ETC?

Answer 17

Electrons enter the ETC from Complexes I, II, III and IV.
Electrons start moving because oxygen pulls them, due to its electronegativity.
Electrons move through the complexes to Complex IV, as it has the highest electronegativity.
Electrons are shuttled through uq and cyt-c between the complexes as well.

Question 18

How many H2O molecules are produced for every glucose molecule?

Answer 18

For every glucose molecule, 6 H2O molecules are produced.

Question 19

Describe the importance of oxygen in cellular respiration. Why is it referred to as the “final electron acceptor”?

Answer 19

Oxygen is important in cellular respiration because due to its high electronegativity, it drives the process of electron transport by pulling electrons from Complex IV/the complexes.
The energy released pumps H+ ions into the intermembrane space, which builds the proton gradient and the proton-motive force.
Oxygen is referred to as the “final electron acceptor” because the oxidation of NADH and FADH is the last reaction in the ETC.
This would not be able to occur without oxygen.
Oxygen combines with hydrogens to produce water.

Question 20

Describe what would happen to the process of cellular respiration if an inhibitor were introduced? How would this affect human health and survival?

Answer 20

If an inhibitor was introduced, there would be a blockage in the production of ATP.
This would quickly cause a decline in the number of ATP molecules in the body.
Lower amounts of ATP cause muscle fatigue, brain fog and slowed nerve signals.
These areas are affected, as there is a high concentration of mitochondria in the brain and muscles.
For example, cyanide kills people because it prevents cells from using oxygen for cellular respiration.

Question 21

Unocoupling

Answer 21

When electron transport and ATP synthesis are uncoupled, free energy that would be used to generate ATP is released as thermal energy.
The H+ ions “leak” back through the membrane without producing ATP.
ATP production is reduced.

Question 22

Uncoupling –> Hibernation

Answer 22

Uncoupling in the cells of animals such as bears allows free energy that would be used to generate ATP to be released as thermal energy and maintain their body temperature while they hibernate.

Question 23

Uncoupling –> Diet pills

Answer 23

The chemical DNP used to be used in diet pills.
It reduces the rate of production of ATP, so cells consume stored fat more rapidly, which causes people to lose weight.
Had harmful side effects, such as overheating.

Question 24

Uncoupling –> Luft Syndrome

Answer 24

Cells metabolize food, but much of their activity is dissipating metabolic thermal energy.
This causes symptoms such as…
Always hot
Always sweating
Flushed skin
Weak and thin

Question 25

What products of the citric acid cycle are used by the ETC?

Answer 25

NADH, FADH2 and H+.

Question 26

Explain what would happen to energy production in the mitochondria if ATP synthase stopped functioning.

Answer 26

H+ wouldn’t be able to move through the protein into the matrix. This would cause H+ to leak back into the membrane, which produces thermal energy.

Question 27

List 3 reasons why glycolysis is the most fundamental and most ancient metabolic pathway.

Answer 27

It is universal, as it is found in almost all organisms (in eukaryotes and prokaryotes). It does not require oxygen, which only became abundant in the atmosphere 1.5 billion years after life on Earth began. It occurs in the cytosol and does not require complex organelles to operate.

Question 28

What carriers supply the electrons that pass through the ETC? At what stages of respiration are these electrons produced?

Answer 28

The energy carriers are NADH and FADH2. NADH is produced during glycolysis (2), pyruvate oxidation (2) and the citric acid cycle (6). FADH2 is produced during the citric acid cycle (2).

Question 29

Is the BMR the same for an elderly woman and a baby? Explain your reasoning.

Answer 29

Basal Metabolic Rate: The metabolic rate of an organism when it is at rest. No, the BMR is not the same. The baby has a higher BMR because their tissues and bones are growing and developing while they are at rest, while the woman’s body is no longer growing or developing. The woman may be less physically active than the baby, which slows down your BMR.

Question 30

Glycolysis only produces a small percentage of the energy that would be produced if the same quantity of glucose was completely oxidized. What happens to the rest of the energy in the glucose?

Answer 30

The rest of the energy is released as thermal energy.

Question 31

If you were a dietitian and a client wanted to increase their BMR, what major change would you suggest?

Answer 31

I would suggest building more muscle. A higher percentage of body fat reduces BMR. A higher percentage of muscle increases BMR.

Question 32

Many eukaryotic organisms do not produce the maximum of 38 ATP for every glucose molecule that is oxidized through aerobic respiration. Explain why.

Answer 32

The NADH to FADH2 to ATP ratio is inexact. Energy from the H+ flow may be lost due to uncoupling proteins or used for other mitochondrial processes, such as the mitochondria’s uptake of pyruvate. Cells that use a glycerol-phosphate shuttle produce 2 fewer ATPs per glucose.

Question 33

List the key steps that take place from the end of glycolysis until the beginning of the citric acid cycle.

Answer 33

2 pyruvate enter pyruvate oxidation. In pyruvate oxidation, pyruvate is oxidized, 2 acetyl-CoA are produced, CO2 is released and NAD+ is reduced. Acetyl-CoA enters the citric acid cycle.

Question 34

Compare substrate-level oxidation with oxidative phosphorylation. Which process is responsible for generating more ATP?

Answer 34

Substrate-Level Phosphorylation: When ATP is formed directly by the transfer of a phosphate group to ADP through an enzyme. Oxidative Phosphorylation: When ATP is formed indirectly by the transfer of a phosphate group to ADP through a series of redox reactions. Oxidative phosphorylation generates more ATP (in ETC/chemiosmosis).

Question 35

Describe how the proton-motive force is established during aerobic cellular respiration and explain its importance in ATP synthesis.

Answer 35

The accumulation of H+ in the intermembrane space creates a proton gradient and an intermembrane force (electrochemical gradient). This is important, as it movies H+ down ATP synthase (which catalyzes ATP) into the matrix.

Question 36

Cyanide inhibits cyt-c. Based on this information, explain why cyanide is toxic to humans. Which tissues would be most affected if you ingested a sub-lethal dose of cyanide? Explain why.

Answer 36

Cyanide is toxic to humans because it inhibits cyt-c, which is needed to carry electrons from Complex III to Complex IV. If cyt-c is inhibited, ETC and cellular respiration can not function and ATP can not be produced. The brain and muscles would be most affected, as they have a high concentration of ATP.

Question 37

A human can survive without oxygen for a few minutes, q without water for a few days and without food for several weeks. Use your understanding of cellular respiration to explain why.

Answer 37

Oxygen: Oxygen is needed in ETC/chemiosmosis to make ATP (energy) in cellular respiration. Water: Water provides the body with necessary H and O atoms for hydrolysis reactions in cellular respiration. Food: The body is able to break down stored fat and glucose for energy.

Question 38

Some metabolic disorders cause the ionophore channels across the mitochondrial membrane to leak. What impact would this have on the normal functioning of the body?

Answer 38

This causes H+ to leak back into the membrane. This would reduce the production of ATP. This would also produce thermal energy and cause symptoms such as sweating.