Anaerobic Metabolism

Question 1

Structure of glucose

Answer 1

• Monosaccharide
• 6 Membered hexose Ring
• form alpha 1-4 glycosidic bonds

Question 2

Describe the structure glucose?

Answer 2

• 10g in plasma
• Osmotically active
• Immediate energy source – glycolysis
• Synthesis from non-carbohydrate sources – gluconeogenesis

Question 3

Structure of glycogen

Answer 3

• Polysaccharide
• alpha 1-6 glycosidic bonds in structure

Question 4

Describe and function of glycogen?

Answer 4

Approx. 400 g in tissue stores
* Low osmolarity
* Medium term fuel source
* Synthesis and breakdown (later lecture)

Question 5

Sources of Glucose for glycolysis

Answer 5

1. Sugars & starch from diet
2. Breakdown of stored glycogen from the liver
3. Recycled glucose (from lactic acid or amino acids or glycerol)

Question 6

Glycolysis definition, location?

Answer 6

Definition: glucose C6 —-> 2 pyruvate C3

Location: cytosol
(10 soluble enzymes)

Tissues: all tissues

Question 7

Function of glycolysis

Answer 7

• ‘energy’ trapping
  (ATP synthesis)
• intermediates for fat synthesis
• intermediates for amino acid synthesis

Question 8

4 Stages of glycolysis

Answer 8

1. Activation (using up ATP )
2. Splitting the 6 C sugar into half
3. Oxidation (removing 2H atoms)
4. Synthesis of ATP

Question 9

Reaction 1 activation stages of glycolysis
Enzymes involved?

Answer 9

D-glucose ———> glucose-6-phosphate (Adds a phosphate group to molecule - so is IRREVERSIBLE) - NEED TO KNOW
Uses ATP (ATP ->ADP)
Catalysed by enzymes: Glucokinase or Hexokinase

Question 10

Reaction 2 activation stage of glycolysis

Answer 10

REVERISIBLE
Glucose 6-phosphate ——>< Fructose-6-phosphate
Catalysed by Phosphohexose isomerase

Question 11

Reaction 3 activation stage of glycolysis

Answer 11

IRREVERSIBLE Regulatory step - NEED TO KNOW -
Fructose 6-phosphate —-> Fructose 1,6-bisphosphate
Catalysed by enzyme: PHOSPHOFRUCTOKINASE - Have to use to slit and put phosphate on other side of molecule
Uses ATP (ATP —-> ADP)

Question 12

What enzymes are used in reaction 1 and 3

Answer 12

Reaction 1 - Glucokinase or Hexokinase
Reaction 3 - PHOSPHOFRUCTOKINASE

Question 13

Describe the 2nd stage of gylcolysis
Reactions 4 and 5

Answer 13

Splitting of 6C Sugar to 3C Units
Fructose 1,6-bisphosphate —-> Glyceraldehyde 3-phosphate and Dihydroxyacetone
phosphate (revesible between two molecules produced)

Catalysed by: Aldolase - used to split molecule in half - not symmeyrical molecules produced
Triose phosphate isomerase enzyme used to convert between molecules

Question 14

What is stage 3? Describe the reaction? (Reaction 6)

Answer 14

OXIDATION step (payoff phase) - removing 2H atoms
- Reversible reaction

Glyceraldehyde 3-phosphate —–> 1,3-Bisphosphoglycerate
NAD+ + Pi –> NADH + H+ (reducing NAD+)

Catalysesd by: Glyceraldehyde 3-phosphate dehydrogenase

Question 15

What is Stage 4 of glycolysis process?
What is Produces and used?

Answer 15

ATP Synthesis stages
Reactions 7,8,9 (reversible)
Rection 10 - irreversible
Final product - Pyruvate
2 ATP Molecules
1 H20 molecule

Question 16

Reaction 7 of glycolysis? (ATP Synthesis stages)

Answer 16

SUBSTRATE LEVEL PHOSPHORALATION - IMPORTANT -
1,3-Bisphosphoglycerate —–> 3-phosphoglycerate
**ATP molecule produced from ADP **
Catalysed by: phosphoglycerate kinase

Question 17

Reaction 8 of glycolysis? (ATP Synthesis stages)

Answer 17

ISOMERISATION
Reverisible

3-phosphoglycerate —-> 2-phosphoglcerate
Catalysed by **phosphoglycerate mutase **

Question 18

Reaction 9 of glycolysis? (ATP Synthesis stages)

Answer 18

2-phosphoglycerate –>< Phosphoenol pyruvate
REVERSIBIBLE
Water (H20) released
Catalysed by: Enolase

Question 19

Reaction 10 of glycolysis? (ATP Synthesis stages)

Answer 19

Substrate level phosphorylation’ - IRREVERSIBLE - Phosphate produced
Phosphoenolpyruvate —–>pyruvate
Catalysed by **pyruvate kinase **
Produces a molecule of ATP from ADP

Question 20

Structure of pyruvate

Answer 20

3 carbon vertical
central carbon 4 bonds:
Double bond = to oxygen
Bond to = methyl group (CH3)
Bond to = COO-

Question 21

Yields of ATP from Glycolysis

Answer 21

Early stages use 2 ATP
Later stages make 4 ATP
Net yield = 2 ATP (plus further ATP from mitochondrial metabolism)
NADH produced
H20 Released

Question 22

What happens after glycolysis stage in anaerobic respiration?
Why?

Answer 22

• When oxygen supplies to the tissues are limited, pyruvate is not metabolised to CO2
• Pyruvate converted to lactate in order to convert the cofactor NADH back to NAD+

Question 23

Metabolic fates of Pyruvate with and without O2 or mitochondria?

Answer 23

Question 24

Structure of lactate

Answer 24

3 carbon vertical
central carbon 4 bonds:
Double bond = to oxygen
Bond to = methyl group (CH3)
Bond to = O=C-OO-
Bond to = OH
Bond to H

Question 25

How is glycolysis regulated?

Answer 25

The pathway is under Allosteric control Hormonal control

Question 26

Example of glycolysis by allosteric regulation?

Answer 26

Allosteric control of the **enzyme phosphofructokinase** Allosteric inhibition of phosphofructokinase **by ATP** When ATP binds to the regulatory site, reaction rate slows dramatically

Question 27

Specialised functions in skeletal muscle, Red blood cells,brain for respiration?

Answer 27

Skeletal muscle: ATP production during intense exercise Red blood cells: only pathway for ATP production (no mitochondria) Brain: major source of ATP (cannot use fats as fuels)