W5 Energy I

Question 1

Catabolism

Answer 1

Breakdown of complex molecules to release energy or carry out mechanical work

Question 2

Anabolism

Answer 2

Synthesis of new molecules from less complex components

Question 3

How much ATP do we need?

Answer 3

Total ATP in body = 100g

Total amount of energy available from the hydrolysis of ATP is 65kj/mole

Usage at rest = 40Kg/24hour

Usage during exercise = 0.5Kg/minute

Question 4

Glycolysis

Answer 4

Glucose to G6P (ATP used) (Hexokinase)

G6P to F6P

F6P into fructose 1,6 bisphosphate (ATP used) (Phosphofructokinase)

Fructose 1,6 bisphosphate into dihydroxyacetone phosphate + glyceraldehyde 3 phosphate (these 2 are intermediates in equilibrium w/each other)

3 carbon intermediate into phosphoenol pyruvate (2 * ATP + NADH made)

Phosphoenol into pyruvate (2 * ATP made) (Pyruvate kinase)

2 pyruvate made
2 ATP
2 NADH

Question 5

Regulation of trancription

Answer 5

Enzymes catalysing irreversible reactions = potential sites
for regulation

Activity of such enzymes can be regulated by:

Reversible binding of allosteric effectors

Covalent modification

Transcription

Question 6

Phosphorylation

Answer 6

Can have +/- effect

G6P inhibits G to G6P

ATP, citrate and H+ inhibit F6P to fructose 1,6 bisphosphate (AMP stimulates)

ATP inhibits phosphoenol pyruvate into pyruvate

Question 7

Regulation of muscle glycolysis to meet need for ATP

Answer 7

ADP + ADP → ATP + AMP (adenylate kinase)

AMP signal for low energy state

PFK is the most important control point

High concentrations of ATP inhibit PFK
by lowering the affinity for fructose 6 phosphate

Also inhibited by low pH

Inhibition of PFK leads to inhibition of hexokinase

Question 8

Why AMP not ATP

Answer 8

AMP much better signal of activity than ATP itself because ADP will be present anyway for resynthesis of ATP

Question 9

Why AMP and not ADP

Answer 9

ATP can be made from ADP by adenylate kinase 2ADP gives ATP + AMP therefore AMP is a better indicator of energy state

Question 10

Regulation of glycolysis in the liver

Answer 10

High concentrations of ATP inhibit PFK
PFK is inhibited by citrate
PFK is stimulated indirectly by a build up of F6P
Hexokinase is inhibited by G6P
But the liver also has glucokinase which is not inhibited by G6P

Low pH is not a problem as the liver does not normally produce lactate

Question 11

Example of feed forward regulation in liver

Answer 11

Indirect activation by F6P which is converted to F26bisP when blood glucose is high

Question 12

Tumours and exercising muscles have what in common

Answer 12

Anaerobiccally respire

Growth of tumour outweighs/outstetches the availibility of oxygen delivered by blood supply

Question 13

Lactate

Answer 13

Toxic as acidic
H+ inhibit
So lactate exported into blood + taken up by liver

Question 14

Why do tumours use glycolysis

Answer 14

When tumours outgrow their blood supply oxygen delivery is reduced, tumour cell metabolism reverts to glycolysis

Reduction in O2 leads the
activation of the transcription
Factor HIF-1α (hypoxia-inducible factor)

HIF-1α regulates the expression
of a number enzymes in the
glycolytic pathway + blood vessel growth

Question 15

Functions of glycolysis

Answer 15

Degrades glucose to generate ATP and provides building blocks for the synthesis of cellular components

Three non-reversible steps phosphofructokinase is inhibited by ATP and citrate and activated by AMP and fructose 2-6 bisphosphate

Hexokinase inhibited by G6P. ATP and alanine inhibits PK.
PK activity max when energy charge is low and glycolytic intermediates accumulate