Glycolysis Flashcards
Definition of glycolysis:
Breakdown of glucose into smaller molecules
Produce ATP
Where does glycolysis take place?
Cytoplasm of cells
What ring does glucose form?
6 member Pyranose ring
What ring does fructose form?
5 members furanose ring
Structure of amino acid:
Amino group and carboxyl group
What happens when two amino acids Bon?
Peptide bond formed between amino group on one and carboxyl group on the other
What is an amino acid called with a carbonyl group?
Keto acids
What are keto acids common in?
Metabolism - important for transamination
What essentially is converted in glycolysis?
Glucose converted to pyruvate
What is glucose first converted to?
Glucose-6-Phosphate
Phosphorylation
What happens in first phophorylation of glucose?
ATP consumed
Hexokinase traps glucose in cell because glucose-6-P is ionised
Significance of glucose-6-P being ionised:
Unable to cross cell membrane
What happens after phosphorylation go glucose into glucose-6-P?
Isomerisation of Glucose-6-P into fructose-6-P
What happens in isomerisation of glucose—P into fructose-6-P?
Pyranose ring -> fruranose ring
What is fructose-6-P then converted into?
Fructose 1,6 -biphosphate
Phosphorylation
Costumes ATP
Enzyme phosphofructokinase
What is fructose-1,6 -biphosphate further split into?
2x glyceraldehyde-3-phosphate
Process of forming 2x glyceraldehyde-3-P:
Cleavage and isomerization
Forms dihydroxyacetone which is then converted into 1x glyceraldehyde-3-P
What happens to glyceraldehyde-3-P?
Simultaneously oxidised and phosphorylated by oxidative phosphorylation
Forms 1,3 - Biphosphoglycerate
What happens in oxidative phosphorylation of glyceraldehyde 3-P?
H+ and 2e- passed to NAD+ to form NADH
Phosphate is also added to each glyceraldehyde 3-P
What is NAD+?
Co-factor
Collects hydrogen and electrons
What’s NAD+ made of?
Nicotinamide
Ribose
Adenosine
What’s the reactive site of NAD+?
Nicorinamide = head group
What does NAD+ stand for?
Nicotinamide adenine dinucleotide
What provides nicotinamide part of NAD+?
Vitamin B3
Lack of niacin:
Pellagra - sensitivity to sunlight
NAD+ into NADH:
NAD+ + H+ + 2e- ——> NADH
What then happens to 2x 1,3-Biphophoglycerate?
Phosphate transferred to ADP to produce ATP (2xATP per 1 molecule glucose)
3-phosphogylerate is produced
What then happens to 3-Phosphoglycerate?
Molecular rearrangement of phosphate group - isomerisation
2-Phosphoglycerate formed
What then happens to 2-phosphoglycerate?
Dehydration
Water produced
Forms phosphoenol pyruvate
What then happens to 2x phosphoenol pyruvate?
Phosphate is transferred to ADP to produce ATP (2xATP produced per 1 molecule glucose)
2x Pyruvate formed
Enzyme pyruvate kinase
Net ATP produced in glycolysis:
2
How is NAD+ regenerated under aerobic conditions?
NADH passes electrons and H+ (from glyceraldehyde-3-P) through electron transfer chain system
Electrons and H+ combine with oxygen to produce water
What else does electron transfer chain generate?
ATP
What happens in absence of oxygen (anaerobic)?
NADH builds up as NAD+ can’t be regenerated
Could stop glycolysis continuing
Anaerobic conditions: what must be done to regenerate NAD+?
NADH re-oxidised
Pyruvate is reduced lactate
How is pyruvate reduced to lactate?
Pyruvate + NADH + H+ ———> Lactate + NAD+
What enzyme converts pyruvate to lactate?
Lactate dehydrogenase
How does yeast overcome problem of anaerobic conditions?
Converts pyruvate to ethanol
Important enzymes in glycolysis:
Hexokinase
Phosphofructokinase
Pyruvate kinase
What inhibits phosphofructokinase?
High ATP concentration
Low pH
High citric acid concentration
What stimulates phosphofructokinase?
High fructose-6-P concentration
