Glycolysis Flashcards
What are the three stages of catabolism?
- Hydrolysis of complex molecules into constituent monomers
- Conversion to acetyl CoA
- Oxidation of acetyl CoA - produces ATP and NADH
Describe anabolism.
- Endergonic
- Requires reducing coenzymes - NADH
Define cellular respiration
- Set of metabolic reactions - CATABOLIC
- Convert chemical energy from oxygen to cellular energy, ATP and CO2
Describe glycolysis.
- Occurs in cytoplasm
- Can occur aerobically or anaerobically depending on oxygen availability
- Allows production of ATP even in anaerobic conditions
Describe the energy investment phase.
- Phosphate group from ATP transferred to glucose by glucokinase/hexokinase, forming G6P
- Isomerisation - converted to F6P
- Phosphorylation of F6P by PFK to form F 1,6-Bisphosphate.
- PFK allosterically inhibited by high ATP
Describe the cleavage phase.
- F1,6-Bisphosphate cleaved. by aldolase to form G3P and DHAP
- DHAP converted to G3P
What is the rate-limiting step in glycolysis?
- PHOSPHORYLATION by PFK (during energy investment phase)
Describe the generation phase in glycolysis. PART 1
- G3P oxidised and phosphorylated to 1,3-BPG. NAD+ reduced to NADH
- Phosphate transfer from 1,3-BGP to ADP. Forms 3-phosphoglycerate and ATP
Describe the generation phase in glycolysis. PART 2
- 3-PG isomerised to 2-PG - dehydrates to form PEP
- Pyruvate kinase transfers phosphate group from PEP and ADP produciong pyruvate and ATP
What occurs following aerobic glycolysis?
- Pyruvate enters mitochondria, oxidised to acetyl CoA and enters TCA cycle
- Reduction of NAD+ and FAD to NADH and FADH2
- Carry electrons to ETC - oxidative phosphorylation occurs
Why are the following steps irreversible?
-G6P production
- F-1,6 BP production
- Phosphoenol pyruvate to pyruvate
- Highly negative ΔG values
Describe anaerobic glycolysis. PART 1
- Aerobic metbaolism no longer keeps up with energy demands
- Lactic acid formation
- Less efficient method of ATP production
- Lactate converted to glucose in liver - carried to muscles
Describe anaerobic glycolysis PART 2
- Pyruvate reduced to lactate by LDH
- Reduction allows NADH oxidisation to NAD+
- NAD+ re-enters glycolysis to synthesise ATP
- Takes place in areas without oxygen - eye, cornea and RBCs
Describe hexokinase
- Found in blood, tissues.
- Low Km and Vmax.
- Inhibited by G6P - efficient at low glucose
Describe glucokinase
- Found in liver, pancreas.
- High Km, Vmax.
- Regulated by insulin. High insulin = high GK activity
What inhibits and activates PFK?
- Inhibited by citrate, ATP and H+
- Activated by AMP and Fructose 1,6-bisphosphate
Describe pyruvate kinase regulation.
- ALLOSTERIC - Activated by high Fructose 1,6-BP. Inhibited by high ATP
- HORMONAL - INSULIN AT HIGH GLUCOSE activates PK. Glucagon at LOW GLUCOSE increases AMP, inhibit PK
How does insulin regulate glycolysis?
- Stimulate uptake of glucose from blood at high glucose
- Activates GK, PFK and PK
How does glucagon regulate glycolysis?
- At low glucose, stimulates conversion of glycogen from liver into glucose
- Inhibits GK, PFK and PK
Give an example of hemolytic anaemia.
- Pyruvate kinase deficiency e.g G6PD deficiency
- Autosomal recessive
- Reduced glycolysis and ATP production.
- Premature RBC lysis (no ATP to maintain sodium-potassium ATPase to maintain cell shape)
