Resp/photosyn

Question 1

Metabolic control of glycolysis

Answer 1

1. Glucose transport
2. Phosphorylation of glucose
3. PFK1
4. F-2,6-BP
5. Pyruvate kinase

Question 2

Glucose transport

Answer 2

Glut123 (insulin ind) in liver and brain

Glut4 (insulin dep) in muscle and fat

Question 3

Phosphorylation of glu

Answer 3

Glucokinase in liver (only active at high glucose)

Hexokinase in muscle (inhibited by G6P)

Question 4

PFK1

Answer 4

Allosterically inhibited by ATP, effect amplified by citrate

allosteric activation by AMP/ADP

Question 5

F-2,6-BP

Answer 5

Allosteric activator of PFK1

Glucagon causes decrease in F-2,6-BP, reducing glycolysis, stimulates gluconeogenesis

Question 6

Pyruvate kinase

Answer 6

F-1,6-BP stimulates pyruvate kinase; feed forward

Question 7

TCA cycle replenish carbons

Answer 7

Anaplerosis:

Pyruvate carboxylase converts pyruvate to oxaloacetate (adding one CO2)

Question 8

Metabolic control of TCA Cycle

Answer 8

Pyruvate Dehydrogenase (PDH)
PDH Kinase inactivates it, PDH phosphatase activates it. 

Citrate Synthase
Allosterically inhibited by ATP (pyruvate used in gluconeogenesis instead)

Purine nucleotide cycle
Generates fumurate to prime TCA cycle with more oxaloacetate

Glutamate (neurotransmitter) converted to glutamine and carbon used in TCA cycle

Question 9

ETC complexes 1 and 2

Answer 9

Complex I: e from NADH to FMN PS to FeS clusters to ubiquinone (Protons pumped)

Complex 2: FADH2 to FeS clusters to ubiquinone

Question 10

Complexes 3 and 4

Answer 10

Complex 3: receives e from Ubiquinone to cytochrome C (q-cycle transient storage by haem groups)

Complex 4:
Cytochrome C transports e and cytochrome c oxidase transfers e to molecular oxygen, forming water and pumping H+

Question 11

Evidence for chemiosmosis

Answer 11

Detergents disrupting inner membrane abolish proton pumping

Uncoupling agents and proteins (eg UCP1) abolish H+ gradient and prevent ATP synthesis

Inhibitors of ATP synthase (oligomycin) abolish e- transfer

Artificially reconstituted pmf (bacteria rhodopsin and ATP synthase on liposome)

Question 12

ATP synthase structure

Answer 12

Beta subunit
Loose binds to ADP and Pi
tight combined to form ATP
open releases ATP

Rotation of gamma subunit drives alterations in conformations of beta

Question 13

Light harvesting

Answer 13

LHC excite electrons resonance e transfer to RC

OEC replenishes e- in PSII by oxidising water (Mn buffers redox changes)

Question 14

Photosynthesis e- transfer

Answer 14

In PSII:
e- transferred by quinone A and B within PSII, released from PSII in plastoquinol
To cytochrome b6f complex to plastocyanin to PSI (excited again, charge separation) to FeS clusters to ferredoxin
FNR catalyses reduction of NADP+ to NADPH
Formation of proton gradient used for ATP synthesis

Question 15

Discovery of Calvin cycle

Answer 15

Pulse-chase with 14CO2
Immediately after, only a few organic compounds labelled
After many minutes, many organic compounds labelled

Question 16

How RuBisCo sucks

Answer 16

Wasteful oxygenate reaction forms phosphoglycolate - inhibits photosynthetic enzymes

Misfire reaction to form XuBP

Question 17

Damage repair

Answer 17

XuBP converted to Xu5P which re enters Calvin cycle

NADPHX formed from GAPDH rxn - NADPHX dehydratase converts S epimer to NADPH, epimerase converts between R and S form

Question 18

Nitrogenase enzyme

Answer 18

Mini ETC
Fe generates high E electron by oxidation of ferredoxin
MoFe binds N2

Question 19

Assimilation of N

Answer 19

Entry point is via glutamate

Reductive amination of 2-oxoglutarate by glutamate dehydrogenase to form glutamate

GS converts glutamate and NH4 to form glutamine
GOGAT transfers amino group from glutamine to form glutamate

Transamination and anaplerotic reaction

Question 20

A ferroxidans

Answer 20

Electrons from Fe2+ to Fe3+ passed to Cytochrome C
Passed to rusticyanin - then can either go to cytochrome bc1 for reducing power (NADH) or cytochrome c oxidase to form PMF