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)