Unit 1: Aerobic respiration (energy released from food)

Question 1

where does the link reaction occur and what are the enzyme/ co-enzymes involved?

Answer 1

occurs in mitochondrial matrix

pyruvate dehydrogenase - assisted by 5 co-factors: lipoic acid/ coA/ NAD/FAD/ TPP

Question 2

What are the net products of the link reaction?

Answer 2

2 x acetyl coA
2 x NADH
2 x CO2

Question 3

how is link reaction regulated?

Answer 3

adenylate control of PDC - inhibited by products

Question 4

where does the krebs cycle occur and what are the net products?

Answer 4

occurs in mitochondrial matrix
6 x NADH
2 x FADH2
2 x GTP

Question 5

describe the role of two electron shuttles and why are they needed?

Answer 5

needed because inner mitochondrial membrane is impermeable
Glycerol -3 P shuttle: e- enters 2nd complex - mainly found in skeletal muscle - yields 1.5 ATP (simpler/faster)
malate-aspartate shuttle: e- enters 1st complex - mainly found in heart/liver - yields 2.5 ATP (more efficient but more complex)

Question 6

what type of translocase is powered bythe electron transport chain?

Answer 6

ADP-ATP translocase - saps 25% of gradient because exchange of ATP and ADP requires charge difference created by H+ ions

Question 7

describe how ETC works

Answer 7

complex 1 accepts electrons from NADH and transfers them to ubiquinone - provides energy for pumping of 4 H+ from matrix to intermembranal space
complex 2 accepts electrons from FADH2 and also transfers to ubiquinone but does not pump h+ ions
complex 3 accepts electrons from ubiquinone and transfers to complex 4 via cytochrome C - pumps 4 H+ ions (2 from matrix/ 2 from ubiquinone)
complex 4 accepts electrons from cytochrome C- pumps 4H+ ions - 2 of which contributes to formation of water
- electrochemical gradient produced leads to production of ATP by ATP synthase

Question 8

how many ATP produced overall

Answer 8

glycolysis - 2 ATP/ 5 ATP (from 2 NADH)
link reaction - 5 ATP (from 2 NADH)
krebs cycle - 15 ATP (from 6 NADH)/ 3 ATP (2 from FADH2)/ 2 ATP (from 2 GTP)

overall: 32 ATP

Question 9

How does antimycin work and what is its antidote?

Answer 9

inhibits complex III- no transfer onto cytochrome C

antidote -ascorbic acid

Question 10

How do cyanide/ carbon monoxide and azide inhibit oxidative metabolism?

Answer 10

inhibits complex IV - no ATP produced

Question 11

how does oligomycin work and how can it be restored?

Answer 11

inhibits ATP synthase so accumulation of protons - no gradient
- gradient can be restored by DNP - poison moves protons from intermembranal space to matrix

Question 12

how do plants/ mold toxins affect respiration?

Answer 12

inhibit ADP-ATP translocase