Midterm 2

Question 1

Where does glycolysis take place?

Answer 1

• cytoplasm
• aerobic: cardiac muscle, brain, liver
• anaerobic: RBC, muscle

Question 2

How is glycolysis regulated?

Answer 2

Phosphofructokinase:
\+ F, 2-6 P, AMP
- ATP, citrate, H
Pyruvate kinase:
\+ F, 1-6 P
- ATP, alanine

Question 3

Energy Production of glycolysis

Answer 3

glucose -> glucose-6-P = -1 ATP
fructose -> fructose 1-6 PP = -1 ATP
1,3 bisphosphofructose (x2) -> 3PG = +1 ATP
PEP -> pyruvate (x2) = +1 ATP 
net = +2 ATP

Question 4

Where does glyconeogenesis take place?

Answer 4

• cytoplasm
• liver (kidney, especially in prolonged
  starvation)

Question 5

How is glyconeogenesis regulated?

Answer 5

Pyruvate carboxylase
\+ acetyl CoA
Fructose, 1-6 P
\+ ATP, citrate
- AMP

Question 6

What is gluconeogenesis?

Answer 6

Gluconeogenesis is the synthesis of
glucose/ glycogen by non-carbohydrate
precursors (lactate, glycerol, amino acids
and in Ru propionate)

Question 7

Energy Balance of GNG?

Answer 7

2 lactate + 7 ATP -> 1 glucose unit + 7 ADP

Question 8

Amino acids of GNG?

Answer 8

Almost all amino acids are glucogenic (except leucine)
Alanine -> pyruvate
Glutamic acid -> alpha-keto glutarate
Aspartic acid -> oxaloacetate

Question 9

Hormonal control of GNG?

Answer 9

• Glucagon: +GNG - Stimulates mobilisation of aa. in muscle. Stimulates uptake of aa in the liver. Raises cAMP levels in adipose cells.
• Glucocorticoids: + GNG - Favours synthesis of glucose by aa.
• Insulin: -GNG - Antagonist of glucagon.

Question 10

Oxidation of pyruvate to AcCoA

1. What kind of reaction is it?
2. Where does it happen?
3. Reaction equation
4. What does it require?
5. Regulation?

Answer 10

1. Oxidative decarboxylation
2. Mitochondrial matrix
3. Pyruvate + HSCoA + NAD+ -> AcCoA + CO2 + NADH + H+
4. Requires the pyruvate dehydrogenase complex:
   - Enzymes: pyruvate decarboxylase, dihydrolipyl transacetone, dihydrolipoic acid dehydrogenase
   - Cofactors: thiamine (TPP), pantothenic acid (HSCoA), nicotinic acid (NAD+), riboflavin (FAD), lipoic acid
5. Pyruvate dehydrogenase complex is inhibited by ATP.

Question 11

Citric acid cycle

1. Another word for it?
2. Where?
3. Energy gain?
4. Regulation

Answer 11

1.Tricarboxylic acid cycle
2.Mitochondrial matrix (not in RBCs)
3.3NADH + H + = 9 ATP
1FADH2 = 2 ATP
1 GTP
= 12ATP x 2 = 24 ATP
4.Citrate synthase: + ADP, NAD, - ATP, NADH, Isocitrate dehydrogenase: - ADP, NADH, Succinate dehydrogenase: + succinate, - oxaloacetate

Question 12

THE RESPIRATORY CHAIN

1. What is it?
2. Where?

Answer 12

1. A series of e- carriers which are red. and ox. The released E can be used to form ATP via ox.ppr.
2. inner membrane of mitochondria

Question 13

Steps of resp.chain

Answer 13

1.From the glycerol phosphate shuttle NADH+H+ is
ox. to NAD+ by substrate dehydrogenase
2.The 2 e- generated are used to red. the FMN -> FMNH2 by NADH dehydrogenase in the Fe-S complex 1 (4H+)
3.The e- are transferred to coQ. Oxidised = ubiquinone, reduced = coQ.
4.Between CoQ and oxygen are the cytochromes which are e- carrying proteins that contain a haem prosthetic
group. The iron atom in the haem alternates between a
red. Fe2+ and ox. Fe3+ state.
5-8: -CoQ —Fe3+ -> Fe2+ —>cytochrome B (Complex III)
-cytochrome B —Fe2+ -> Fe3+ —> cytochrome C
-cytochrome C —Fe3+ -> Fe2+ —cytochrome a + a3 (Cu2+
Complex IV)
-cytochrome a + a3 is reoxidised by O2 and prod. H2O

Question 14

OXIDATIVE PHOSPHORYLATION

1. Where?
2. Role?
3. What does it do?
4. Role of NADH + H+ and FADH2
5. What is the net result?

Answer 14

1.inner membrane of mitochondria
2.to generate ATP
3.Generates a proton gradient across the inner mitochondrial membr. Once established, the protons will flow through the ATPase complex back into the mitochondrial matrix. As they lose E, this E is utilised by the ATPase complex to phosphorylase and therefore generate ATP (11 molecules).
4.serve as H/e- donors and cofactors for the protein complexes in the electron transport chain.
5.an influx of protons into the inter membranous
space.

Question 15

Uncouplers of ox.ppr?

Answer 15

Protons pumped out are carried by the uncoupler back to the matrix preventing a pH/ electrical gradient.

• Thermogenin: in brown adipose tissue of newborns and hibernating mammals. Stimulates resp. and heat prod. (non-shivering thermogenesis).
• Dinitrophenol: a yellow toxin that affects cattle

Question 16

Transamination

1. Why do we have it?
2. What does it do?
3. What catalyses it?

Answer 16

1.Aa can´t be stored by the body, so a surplus is degraded and excreted as urea, while their carbon skeletons are converted into major metabolic
intermediates.
2.Ultimately all amino groups are collected by alpha-keto
glutarate yielding glutamate. Glutamate enters the
mitochondria where:
A. It is deaminated by L-glutamate dehydrogenase or
B. Its amino group is transferred to oxaloacetate to yield
aspartate
3.Transaminases

Question 17

Oxidative deamination?

1. What is it?
2. Regulation?
3. Localisation?

Answer 17

1.The alpha-amino groups from the aa. end up as the amine group of L-glutamate. Glutamate undergoes oxidative deamination by mitochondrial L-glutamate
dehydrogenase.
2.+ ATP, GTP, - ADP, GDP
3.liver

Question 18

THE UREA CYCLE

1. localisation?
2. regulation?
3. Reaction equation?

Answer 18

1.only in the liver. Mitochondria until citrulline leaves to the cytosol
2.carbamoyl phosphate synthetase + N-acetyl glutamate
3.CO2 + NH3 + 3ATP + 2H2O -> urea + 2ADP + 2Pi
+ AMP + PP

Question 19

LIPOLYSIS

1. localisation
2. What is it?
3. Enzyme?

Answer 19

1. adipose tissue
2. the breakdown of fats and other lipids by hydrolysis to release fa.
3. Hormone-sensitive lipase

Question 20

What is adenylate cyclase in the lipolysis, how is it activated and what does it cause?

Answer 20

Catalyses the synthesis of cAMP.
Activated when adrenaline, noradenaline, glucagon or ACTH bind to receptors on the cell membr. cAMP activates protein kinase A which activates after a cascade of reactions hormone-sensitive lipase.

Question 21

Lipogenesis

1.localisation?

Answer 21

1.cytoplasm and adipose tissue, liver, mammary gland

Question 22

BETA-OXIDATION

1. What does it do?
2. Regulation?
3. Example?
4. Energy yield?
5. Localization?

Answer 22

1.Triacylglycerides are split into fa. and glycerol. Fa. are transported into mitochondria in the blood bound to albumin.
2.Regulation: CAT 1
(+) allosterically and by high conc. of free fa.
(+) adrenaline and glucagon indirectly
(-) by malonyl CoA
(-) insulin indirectly
3.Example: palmitoyl CoA (C = 16, 7 cycles (n/2 - 1))
4.Energy yield of palmiotyl CoA:
8 acetyl CoA 8 x 12 = 96 ATP
7 FADH2 7 x 2 = 14 ATP
7 NADH 7 x 3 = 21 ATP
= 131 ATP
Energy yield of stearic acid (+2C)
1 acetyl CoA = 12 ATP
1 FAHD2 = 2 ATP
1 NADH = 3 ATP
= 17 ATP per cycle
5. mitochondrial matrix, liver and muscle (skeletal and cardiac)