Glycolysis Flashcards
(24 cards)
what is glycolysis?
glycolysis is the breakdown of glucose into smaller molecules producing ATP. Effectively it is the conversion of glucose to pyruvate.
where does glycolysis take place?
in the cytoplasm of cells.
what provides the nicotinamide part of NAD?
Vitamin B3, niacin
Which part of NAD does vitamin B3 (niacin) provide?
nicotinamide part
what does a lack of vitamin B3 result in?
pellagra (sunlight sensitivity), alopecia, dermatitis, weakness, ataxia
how is NAD+ regenerated?
regenerated in aerobic conditions as NADH passes through the electron transfer chain and receives hydrogen atoms and electrons from glyceraldehyde-3-phosphate which combines them with molecular oxygen to form water.
What does the electron transfer chain generate?
NAD+ and ATP
How is NAD+ regenerated in anaerobic conditions?
NADH is re-oxidised by reducing pyruvate to lactate. Lactate is what is responsible for muscle aches experienced after prolonged exercise.
How does yeast regenerate NAD+ in anaerobic conditions?
Converts pyruvate into ethanol.
What are the three key enzymes in glycolysis?
Hexokinase
Phosphofructokinase
Pyruvate kinase
Which step in glycolysis does hexokinase regulate?
step 1: phosphorylation of glucose into glucose-6-phosphatee
Which step in glycolysis does phosphofructokinase regulate?
step 3: fructose-6-phosphate –> fructose-1,6,biphopshate
Which step in glycolysis does phosphofructokinase regulate?
step 9: converstion of phospoenol pyruvate to pyruvate
Which is the most important enzyme in glycolysis and why?
Phosphofructokinase - it is the most inhibitory. it is inhibited by:
- high concentration of ATP allosterically
- low pH (lactate accumulation)
- high concentration of citric acid
However it is stimulated by a high concentration of fructose-6-phosphate
What are the 9 steps in glycolysis?
STEP 1 - phosphorylation STEP 2 - isomerization STEP 3 - phosphorylation STEP 4 - isomerization and cleavage STEP 5 - phosphorylation and oxidation STEP 6 - transfer of phosphate STEP 7 - molecular rearrangement STEP 8 - dehydration STEP 9 - transfer of phosphate
What happens in the first step of glycolysis?
Hexokinase enzyme. Glucose is converted into glucose-6-phosphate which is trapped in cells as there is no transporter. ATP converts to AD.
What happens in the second step of glycolysis?
glucose-6-phopshate is converted into fructose-6-phopshate, they both have the same molecular weight.
What happens in the third step of glycolysis?
fructose-6-phosphate is converted into fructose-1,6-biphosphate. Phosphofructokinase enzyme. ATP is converted into ADP.
What happens in the fourth step of glycolysis?
fructose-1,6-biphosphate is converted into dihydroxyacetonephosphate and glyceraldehyde-3-phosphate. dihydroxyacetonephosphate can be converted into glyceraldehyde-3-phosphate which is then normally metabolised.
What happens in the fifth step of glycolysis?
NAD+ –> NADH. NAD is a cofactor and collects hydrogen ions and electrons in the electron transport chain. glyceraldehyde-3-phosphate is simultaneoulsy oxidised and phosphorylated.
What happens in the sixth step of glycolysis?
ATP is formed. 1,3-biphopshoglycerate is converted into 3-phosphoglycerate. 2 ATP per glucose are consumed at this stage.
What happens in the seventh step of glycolysis?
3-phosphoglycerate is converted into 2-phosphoglycerate.
What happens in the eigth step of glycolysis?
2-phopshoglycerate is converted into phosphenol pyruvate, water is lost.
What happens in the ninth (last) step of glycolysis?
phosphenol pyruvate is converted to pyruvate and 2 ATP are formed for each glucose molecule.
