Respiration (7.3–7.7)

Question 1

What are the 4 stages of respiration?

Answer 1

Glycolysis, link reaction, Krebs cycle, electron transport chain

Question 2

Explain the process of glycolysis

Answer 2

1- (6C) glucose is phosphorylated forming phosphorylated glucose using ATP (6C,2Pi)

2- Phosphorylated glucose splits into 2 triose phosphates.

3- Triose phosphate is oxidised (releases H atom) which then joins NAD to form reduced NAD.

4- 2 ATP molecules per triose phosphate is formed

5- 2 Pyruvates are formed

Question 3

Explain the link reaction

Answer 3

• Pyruvate (3C) is decarboxylated (-CO2) and dehydrogenated (-H).
• The CO2 is released into the atmosphere and the 2H turn NAD into reduced NAD.
• Acetyl (2C) CoA is formed.

Question 4

Explain the Krebs cycle

Answer 4

1. -Acetyl CoA (2C) join with a 4C compound forming a 6C compound.
2. 6C compound releases a CO2 and 2H (2H forms reduced NAD) 5C compound is formed
3. -5C compound loses:
   1. *CO2
   2. *ATP
   3. *2H– NAD > Reduced NAD
   4. *2H– NAD > Reduced NAD
   5. *2H– FAD > Reduced FAD

Question 5

Explain the electron transport chain in respiration

Answer 5

1- Reduced coenzyme (eg NAD or FAD) carries 2H+ and electrons to electron transport chain on inner mitochondrial membrane.

2- Electrons pass from one electron carrier to the next in a series of oxidation and reduction reactions.

3- Protons (H+) move across inner mitochondrial membrane creating high H+ concentrations in the intermembrane space.

4- H+ diffuse back into the mitochondrial matrix down the electrochemical gradient.

5- H+ Diffusion allows ATP synthase to catalyse ATP synthesis.

6- Electrons and H+ ions recombine to form H atoms which then combine with oxygen to form water.

*if the supply of oxygen stops the electron transport chain and ATP synthesis will also stop.

Question 6

What is the overall reaction of aerobic respiration?

Answer 6

The splitting of the respiratory substrate, to release carbon dioxide as a waste product and reuniting hydrogen with atmospheric oxygen with the release of large amounts of energy.

Question 7

Where does glycolysis take place?

Answer 7

cytoplasm

Question 8

Where does the link reaction happen?

Answer 8

mitochondrial matrix

Question 9

Where does the Krebs cycle occur?

Answer 9

mitochondrial matrix

Question 10

Where does chemiosmosis occur?

Answer 10

inner mitochondrial membrane

Question 11

What factors might effect the rate of respiration?

Answer 11

enzyme concentration, substrate concentration, temperature and pH

Question 12

How does ATP control respiration?

Answer 12

When ATP is present the enzyme responsible for glucose phosphorylation has a shape that makes it inactive so cannot catalyse the reaction. But when ATP is broken down the enzyme is converted back to its active form and can catalyse the phosphorylation of glucose.

Question 13

How does anaerobic respiration work

Answer 13

The pyruvate produced at the end of glycolysis is reduced to lactate and the oxidised form of of NAD is regenerated. The person can continue as glucose is partially broken down to produce a small amount of ATP.

Question 14

Why does aerobic respiration stop without oxygen?

Answer 14

As without oxygen to accept the hydrogen ions and electrons at the end of the end of the electron transport chain the process ceases. The reduced NADs created cannot therefore be oxidised.

Question 15

What happens when lactate builds up?

Answer 15

It forms lactic acid meaning that the pH of the cell falls inhibiting the enzymes that catalyse the glycolysis reactions.

Question 16

Why do enzymes stop working when lactate builds up?

Answer 16

Hydrogen ions from the lactic acid accumulate in the cytoplasm they neutralise the negatively charged groups in the active site of the enzyme. So the attraction between the charged groups will be affected and the substrate may no longer bind.

Question 17

How do animals get rid of lactate?

Answer 17

Lactate is converted back to pyruvate. It is oxidised directly to CO2 and water via the Krebs cycle, thus releasing energy to synthesise ATP. So oxygen uptake is greater than normal in the recovery period.

Question 18

What is oxygen debt or post exercise oxygen consumption?

Answer 18

the amount of oxygen needed to oxidise lactic acid to carbon dioxide and water

Question 19

How is the immediate regeneration of ATP achieved?

Answer 19

Creatine phosphate which is stored in the muscles and can be hydrolysed to release energy. Creatine phosphate + ADP –> creatine + ATP

Question 20

What are the 3 energy systems

Answer 20

ATP-PC, anaerobic, aerobic

Question 21

How is adequate oxygen supply maintained?

Answer 21

Increased cardiac output, faster rate of breathing and deeper breathing.