Glycolysis Flashcards
Where does glycolysis take place ?
Cytoplasm of the cell
Which ring structure does glucose usually form ?
How many membered-ring is that ?
Pyranose
6-membered ring
Which ring structure does fructose usually form ?
How many membered-ring is that ?
Furanose
5-membered ring
What is the starting and end product of glycolysis ?
Glucose
Pyruvate
What is the name of each big step of glycolysis ?
What is the acronym for it ?
Phosphorylation Isomerisation Cleavage + Isomerisation Oxidative Phosphorylation Transfer of Phosphate Molecular Rearrangement Dehydration Transfer of Phosphate
PICOT MDT
How is the glucose used in glycolysis brought into the cell ?
By a transporter
Describe the main features of the first step of glycolysis.
PHOSPHORYLATION
- In 6th carbon (Glucose to Glucose-6-P)
- Consumes ATP (ATP –> ADP)
- Traps glucose inside the cell (ionised)
Describe the main features of the second step of glycolysis.
ISOMERISATION
- Glucose-6-P converted to fructose-6-P
- Enzyme used (no ATP needed)
Describe the main features of the third step of glycolysis.
PHOSPHORYLATION
- Fructose 6-P to Fructose 1,6-biphosphate
- Consumes ATP (ATP –> ADP)
Describe the main features of the fourth step of glycolysis.
CLEAVAGE + ISOMERISATION
- Fructose 1,6-biphosphate converted to glyceraldehyde-3-P and dihydroxyacetone-P
- dihydroxyacetone-P converted to glyceraldehyde-3-P
Describe the main features of the fifth step of glycolysis.
OXIDATIVE PHOSPHORYLATION
- glyceraldehyde-3-P converted to 1, 3- biphosphoglycerate
- Phosphorylation occurs thanks to phosphate in the cytosol (not phosphate from ATP)
- Hydrogen and electrons from glyceraldehyde-3-P passed to nicotinamide adenine dinucleotide (NAD+ to NADH)
What are the constituents of NADP/NAD ?
Nicotinamide, ribose, adenine, ribose
What molecule provides the nicotinamide part of the NAD+ molecule ? Do we get it in the diet or can we synthesise it ?
Vitamin B3 (niacin) In diet
What condition is a possible consequence of lack of niacin ?
Pellagra:
Sensitivity to sunlight, dermatitis, alopecia, glossitis, weakness, ataxia
Describe the main features of the sixth step of glycolysis.
TRANSFER OF PHOSPHATE
- 1, 3- biphosphoglycerate to 3-phosphoglycerate
- Produces ATP (ADP –> ATP)
What is the ratio of ATP molecules produced per glucose molecule consumed ?
2 ATP : 1 glucose
Describe the main features of the seventh step of glycolysis.
MOLECULAR REARRAGEMENT
-3-phosphoglycerate to 2-phosphoglycerate
Describe the main features of the eight step of glycolysis.
DEHYDRATION
-2-phosphoglycerate to phosphoenol pyruvate
Describe the main features of the ninth step of glycolysis.
TRANSFER OF PHOSPHATE
- Phosphoenol pyruvate to pyruvate
- Produces ATP (ADP –> ATP)
What is the difference in the way glycolysis takes place between aerobic and anaerobic conditions ?
AEROBIC:
-NAD+ regenerated because NADH passes the electrons and the hydrogen atoms which it receives from glyceraldehyde-3-P through a system known as the ELECTRON TRANSFER CHAIN which combines them with molecular oxygen to form water (also forms ATP)
ANAEROBIC:
- NADH builds up because NAD+ cannot be regenerated
- In humans: NADH is re-oxidized (hence regenerating NAD+) by reducing pyruvate to lactate
- In yeast: NAD+ regenerated by converting pyruvate to ethanol
Which molecule is responsible for muscle aches after prolonged exercise ?
Lactate
Which enzymes are key targets to affect the rate of glycolysis ?
Which reaction does each enzyme catalyse ?
- Hexokinase
(Catalyses: glucose → glucose-6-P) - Phosphofructokinase
(Catalyses: fructose-6-P → fructose-1,6- bisphosphate) - Pyruvate kinase
(Catalyses: phosphoenolpyruvate → pyruvate)
Which of the 3 enzymes is the most important point at which glycolysis is regulated ?
phosphofructokinase
What are some ways in which to affect phosphofructokinase ?
- High [ATP] allosterically inhibits the enzyme
- Low pH inhibits the enzyme (lactate accumulation, stabilises low pH)
- High [citric acid] inhibits
- High [fructose-6-P] stimulates the enzyme (more substrate)
What is the full molecular equation for the reaction catalysed by phosphofructokinase ?
Fructose 6-phosphate + ATP –> Fructose 1,6-biphosphate + ADP + H+
What is the point of glycolysis rate being controlled ?
Glucose stores are only drawn on when energy is required and when conditions will allow sugars to be broken down