2.2 - Cellular Respiration

Question 1

Cellular Respiration

Answer 1

Cellular respiration is a series of metabolic pathways that are connected to many other pathways.

Question 2

Aerobic Respiration

Answer 2

Aerobic respiration is a three-stage process:
1. Glycolysis
2. Citric Acid Cycle
3. Electron Transport Chain

Question 3

Glycolysis Definition

Answer 3

Glycolysis is the breakdown of glucose to pyruvate in the cytoplasm.

Question 4

Energy Investment Phase

Answer 4

ATP is required for the phosphorylation (addition of a phosphate group) of glucose and intermediates.

Question 5

Pay-Off Stage

Answer 5

As glucose is broken down, more ATP is generated in a pay-off stage. This gives a net gain of ATP.

Dehydrogenase enzymes remove hydrogen ions and electrons and pass them to the co-enzyme NAD. This forms NADH which moves to the electron transport chain.

Question 6

Preperation of Pyruvate

Answer 6

If oxygen is present (aerobic conditions) then pyruvate is broken down into an acetyl group. the acetyl group combines with coenzyme A to form acetyl coenzyme A.

Question 7

Citric Acid Cycle

Answer 7

Occurs in the matrix of the mitochondria.

1. The acetyl group from the acetyl coenzyme A combines with oxaloacetate to form citrate.
2. Citrate goes through a series of enzyme mediated reactions to get back to oxaloacetate.
3. ATP is generated from ADP and Pi and carbon dioxide is released as carbons are lost from the citrate as the cycle takes place.
4. Dehydrogenase enzymes remove hydrogen ions and electrons anf pass them to NAD to form NADH.

Hydrogen ions and electrons are passed to the electron transport chain.

Question 8

Electron Transport Chain

Answer 8

Electron Transport Chain is a series of carrier proteins attached to the inner mitochondria membrane. Occurs in the inner mitochondrial membrane.

1. Electrons from glycolysis and the citric acid cycle are passed along the electron transport chain which releases energy.
2. This energy allows hydrogen ions to be pumped across the inner mitochondrial membrane. As the ions flow back through a protein called ATP synthase, ATP is produced
3. The hydrogen ions and electrons combine with oxygen to form water.

Question 9

Role of ATP

Answer 9

ATP is used to transfer energy to cellular processes which require energy e.g protein synthesis.
ADP ATP
Adenosine-Pi-Pi + Pi ⇌ Adenosine-Pi-Pi-Pi
+ free energy

Question 10

Fermentation

Answer 10

Fermentation occurs if no oxygen is present after glycolysis in the cytoplasm.
This results in much less ATP being produced compared to aerobic respiration.

Question 11

Fermentation (Animal Cells)

Answer 11

In animal cells, pyruvate is converted to lactate. This is a reversible reaction

Glucose
↓
Pyruvate
↓↑
Lactate

Question 12

Fermentation (Plants and Yeast)

Answer 12

In plants and yeast, pyruvate is converted to ethanol and carbon dioxide. This is an irrevrsible reaction.

Glucose
↓
Pyruvate
↓
Ethanol + CO2