respiration

Question 1

Why is respiration important?

Answer 1

● Respiration produces ATP (to release energy)
● For active transport, protein synthesis etc.

Question 2

structure of mitochondria

Answer 2

outer membrane
inner membrane - cristae folded
matrix - circ dna, 70 s ribsomes

Question 3

Summarise the stages of aerobic & anaerobic respiration

Answer 3

areobic resp :
- glycolysis - cytoplasm
- link reaction - matrix
- krebs cycle - matrix
ox phos - inner mito mem
anaerobic resp:
- glycolysis - cytoplasm
- nad regeneration - cytoplasm

Question 4

Describe the process of glycolysis

Answer 4

1. Glucose phosphorylated to glucose phosphate
   ○ Using inorganic phosphates from 2 ATP
2. Hydrolysed to 2 x triose phosphate
3. Oxidised to 2 pyruvate
   ○ 2 NAD reduced
   ○ 4 ATP regenerated (net gain of 2)

Question 5

Explain what happens after glycolysis if respiration is anaerobic

Answer 5

1. Pyruvate converted to lactate (animals &
   some bacteria) or ethanol (plants & yeast)
2. Oxidising reduced NAD → NAD regenerated
3. So glycolysis can continue (which needs
   NAD) allowing continued production of ATP

Question 6

Suggest why anaerobic respiration produces less ATP per molecule of
glucose than aerobic respiration

Answer 6

● Only glycolysis involved which produces little ATP (2 molecules)
● No oxidative phosphorylation which forms majority of ATP (around 34 molecules)

Question 7

What happens after glycolysis if respiration is aerobic?

Answer 7

Pyruvate is actively transported into the mitochondrial matrix.

Question 8

Describe the link reaction

Answer 8

1. Pyruvate oxidised (and decarboxylated) to acetate
   ○ CO2 produced
   ○ NAD –> NADH
2. Acetate combines with coenzyme A, forming Acetyl
   Coenzyme A

Question 9

products of link reaction per glucose mol

Answer 9

2 x Acetyl Coenzyme A,
2 X CO2 and 2 X reduced NAD

Question 10

Describe the Krebs cycle

Answer 10

1. Acetyl coenzyme A (2C) reacts with a
   4C molecule
   ○ Releasing coenzyme A
   ○ Producing a 6C molecule that enters the Krebs cycle
2. In a series of oxidation-reduction reactions, the 4C molecule is
   regenerated and:
   ○ 2 x CO2
   lost
   ○ 3x Coenzymes NAD & 1x FAD reduced into NADH and FADH
   ○ Substrate level phosphorylation
   (direct transfer of Pi from
   intermediate compound to ADP)
   → ATP produced
   ADP + pi -> ATP

Question 11

products per glucose mol in the krebs cycle

Answer 11

6 x reduced NAD,
2 x reduced FAD, 2 x ATP and 4 x CO2

Question 12

Give examples of other respiratory substrates

Answer 12

Breakdown products of lipids and amino acids, which enter the Krebs cycle. For example:
● Fatty acids from hydrolysis of lipids → converted to Acetyl Coenzyme A
● Amino acids from hydrolysis of proteins → converted to intermediates in Krebs cycle

Question 13

Describe the process of oxidative phosphorylation

Answer 13

1. NADH/FADH oxidised to release H atoms → split into protons (H+) and electrons (e-)
2. Electrons transferred down electron transfer chain (chain of carriers at decreasing energy levels)
   ○ By redox reactions
3. Energy released by electrons used in the production of ATP from ADP + Pi (chemiosmotic theory):
   ○ Energy used by electron carriers to actively pump protons from matrix → intermembrane space
   ○ Protons diffuse into matrix down an electrochemical gradient, via ATP synthase (embedded)
   ○ Releasing energy to synthesise ATP from ADP + Pi
4. In matrix at end of ETC, oxygen is final electron acceptor (electrons can’t pass along otherwise)
   ○ So protons, electrons and oxygen combine to form water