Aerobic Respiration

Question 1

Define aerobic respiration

Answer 1

The release of lare quantities of ATP energy from glucose or another organic substrate in the presence of oxygen. Carbon dioxide is produced.

Question 2

Define anaerobic respiration

Answer 2

Takes place in the absence of oxygen and produced lactate in animal cells and carbon dioxide and ethanol in yeast cells, together with a small yield of ATP energy.

Question 3

What are 2 substrates that can be used to release energy in respiration?

Answer 3

Glucose and fatty acids

Question 4

Most of the energy released during respiration is used to synthesise ATP. How is the rest of the energy released?

Answer 4

Heat energy

Question 5

How does respiration release energy?

Answer 5

Respiration oxidises glucose in a series of small reactions to release energy in the form of ATP

Question 6

Why is ATP often called the ‘universal energy currency’?

Answer 6

Because ATP provides energy in all cells in all reactions in all organisms

Question 7

What is the role of ATP in protein synthesis?

Answer 7

ATP required for amino acid activation in the cytoplasm

Question 8

What is the role of ATP in active transport?

Answer 8

ATP changes the shape of transport proteins to move molecules against a concentration gradient

Question 9

What is the role of ATP in bulk transport?

Answer 9

Packaging and transport of secretory products, like enzymes in vesicles

Question 10

What is the role of ATP in nerve transmission?

Answer 10

Sodium/potassium pumps actively transport ions across the axon membrane

Question 11

What is the role of ATP in muscle contraction?

Answer 11

Energy is required for contraction of muscle fibres

Question 12

What is the role of ATP in DNA replication?

Answer 12

Synthesis of DNA from nucleotides during DNA replication at interphase

Question 13

Name 6 different processes ATP is required for

Answer 13

• Protein synthesis
• Active transport
• Bulk transport
• Nerve transmission
• Muscle contraction
• DNA replication

Question 14

Describe the formation of ATP

Answer 14

The enzyme ATP synthase combines ADP and Pi in a condensation reaction. This requires an input of energy (30.6kJmol) in an endergonic reaction. The addition of this phosphate to ADP is called phosphorylation.

Question 15

Describe the hydrolysis of ATP

Answer 15

The enzyme ATPase hydrolyses the terminal phosphate bond releasing a small packet of energy (30.6kJmol) in an exergonic reaction. This forms ADP and Pi

Question 16

How are the properties, structure and formation of ATP linked to its role in cells?

Answer 16

1. The hydrolysis of ATP to ADP releases immediate energy. The hydrolysis of glucose takes much longer and involves many intermediate reactions.
2. Only one enzyme is needed to release energy from ATP, whereas many are needed in the case of glucose.
3. ATP releases energy in small packets when and where it is needed.
4. ATP is the universal energy currency in many reactions in all living organisms
5. ATP is easily transported across membranes

Question 17

Name the 4 stages of respiration and state where they occur

Answer 17

1. Glycolysis: cytoplasm of cell
2. Link reaction: mitochondrial matrix
3. Krebs cycle: mitochondrial matrix
4. Electron transport chain: inner mitochondrial membrane

Question 18

State 2 examples of redox reactions in respiration

Answer 18

2 co-enzymes act as hydrogen carriers
- NAD+ is reduced to form reduced NAD
- FAD is reduced to form reduced FAD

Question 19

Describe the 5 stages of glycolysis

Answer 19

• Glucose (6C) is phosphorylated to form hexose phosphate (6C). This requires the addition of 2 ATP molecules
• Hexose phosphate (6C) splits into two triose phosphate molecules (3C)
• Each triose phosphate molecule is oxidised to pyruvate (3C). This means that hydrogen is removed by a dehydrogenase enzyme in a dehydrogenation reaction. The hydrogen is accepted by NAD forming reduced NAD
• The production of pyruvate from triose phosphate also results in phosphorylation of 2 ADP molecules to produce 2 ATP (substrate level phosphorylation)
• Overall in glycolysis 2 reduced NAD and 2 pyruvate are produced. There is also a net gain of 2 ATP molecules as 4 ATP molecules were produced but 2 were required in the first stage of the pathway to phosphorylate glucose