Anaerobic Metabolism Flashcards
Structure of glucose
- Monosaccharide
- 6 Membered hexose Ring
- form alpha 1-4 glycosidic bonds
Describe the structure glucose?
- 10g in plasma
- Osmotically active
- Immediate energy source – glycolysis
- Synthesis from non-carbohydrate sources – gluconeogenesis
Structure of glycogen
- Polysaccharide
- alpha 1-6 glycosidic bonds in structure
Describe and function of glycogen?
Approx. 400 g in tissue stores
* Low osmolarity
* Medium term fuel source
* Synthesis and breakdown (later lecture)
Sources of Glucose for glycolysis
- Sugars & starch from diet
- Breakdown of stored glycogen from the liver
- Recycled glucose (from lactic acid or amino acids or glycerol)
Glycolysis definition, location?
Definition: glucose C6 —-> 2 pyruvate C3
Location: cytosol
(10 soluble enzymes)
Tissues: all tissues
Function of glycolysis
- ‘energy’ trapping
(ATP synthesis) - intermediates for fat synthesis
- intermediates for amino acid synthesis
4 Stages of glycolysis
- Activation (using up ATP )
- Splitting the 6 C sugar into half
- Oxidation (removing 2H atoms)
- Synthesis of ATP
Reaction 1 activation stages of glycolysis
Enzymes involved?
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
Reaction 2 activation stage of glycolysis
REVERISIBLE
Glucose 6-phosphate ——>< Fructose-6-phosphate
Catalysed by Phosphohexose isomerase
Reaction 3 activation stage of glycolysis
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)
What enzymes are used in reaction 1 and 3
Reaction 1 - Glucokinase or Hexokinase
Reaction 3 - PHOSPHOFRUCTOKINASE
Describe the 2nd stage of gylcolysis
Reactions 4 and 5
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
What is stage 3? Describe the reaction? (Reaction 6)
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
What is Stage 4 of glycolysis process?
What is Produces and used?
ATP Synthesis stages
Reactions 7,8,9 (reversible)
Rection 10 - irreversible
Final product - Pyruvate
2 ATP Molecules
1 H20 molecule
Reaction 7 of glycolysis? (ATP Synthesis stages)
SUBSTRATE LEVEL PHOSPHORALATION - IMPORTANT -
1,3-Bisphosphoglycerate —–> 3-phosphoglycerate
**ATP molecule produced from ADP **
Catalysed by: phosphoglycerate kinase
Reaction 8 of glycolysis? (ATP Synthesis stages)
ISOMERISATION
Reverisible
3-phosphoglycerate —-> 2-phosphoglcerate
Catalysed by **phosphoglycerate mutase **
Reaction 9 of glycolysis? (ATP Synthesis stages)
2-phosphoglycerate –>< Phosphoenol pyruvate
REVERSIBIBLE
Water (H20) released
Catalysed by: Enolase
Reaction 10 of glycolysis? (ATP Synthesis stages)
Substrate level phosphorylation’ - IRREVERSIBLE - Phosphate produced
Phosphoenolpyruvate —–>pyruvate
Catalysed by **pyruvate kinase **
Produces a molecule of ATP from ADP
Structure of pyruvate
3 carbon vertical
central carbon 4 bonds:
Double bond = to oxygen
Bond to = methyl group (CH3)
Bond to = COO-
Yields of ATP from Glycolysis
Early stages use 2 ATP
Later stages make 4 ATP
Net yield = 2 ATP (plus further ATP from mitochondrial metabolism)
NADH produced
H20 Released
What happens after glycolysis stage in anaerobic respiration?
Why?
- 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+
Metabolic fates of Pyruvate with and without O2 or mitochondria?
Structure of lactate
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
How is glycolysis regulated?
The pathway is under
Allosteric control
Hormonal control
Example of glycolysis by allosteric regulation?
Allosteric control of the enzyme phosphofructokinase
Allosteric inhibition of phosphofructokinase by ATP
When ATP binds to the regulatory site, reaction rate slows dramatically
Specialised functions in skeletal muscle, Red blood cells,brain for respiration?
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)
