Energy I Flashcards
Why do we need energy
Metabolism
- Synthesis of new molecules
- Establishing ion gradients
- Mechanical work
- keeping warm
Define catabolism
The breakdown of complex molecules to release energy to carry out mechanical work
Catabolism pathway
Carbohydrates, fats proteins > degradation > heat
02 to CO2
Anabolism
Synthesis of new molecules from less complex compounds
Anabolism pathway
Amino acids, nucleotides, sugars and fats > biosynthesis > new cells
What does ATP do
Acs as both an acceptor and donator of energy
It acts a short term reservoir of energy
What are the major oxidative pathways
- Glycolysis
- Citric acid cycle
- Electron transport coupled to oxidative phosphorylation
- Fatty acid oxidation
Glycolysis pathway
- Glucose is phosphorylated into glucose-6-phosphate using 1 ATP
- Which is then isomerised into fructose-6-phosphate
- This is then phosphorylated into fructose 1,6 bisphosphate using 1 ATP
- This splits into two 3 carbon molecules; dihydroxyacetone phosphate and glyceraldehyde-3-phosphate
- These molecules are made into phosphoenol pyruvate as NAD+ and Pi are made into NADH and one ATP is generated from ADP and Pi
- This is then made into pyruvate as 1 ATP is generated again
What are the overall net gain of glycolysis
- 2 ATP molecules
- 2 NADH molecules
Where can glycolysis be regulated and how
Where there are enzymes catalysing irreversible reactions
How are these enzymes regulated
- Reversible binding of allosteric effectors
- Covalent modification
- transcription
What are the 3 regulatory kinases used and how they regulated
- Hexokinase - Regulated by its product, G-P-6
- Phosphate-fructokinase - Regulated by ATP, citrate and H+ and stimulated by F26BP and AMP
- Pyruvate kinase - regulated by ATP
How is PFK (phosphate-fructokinase) inhibited
High concentrations of ATP inhibit PFK by lowering the affinity for its substrate fructose-6-phosphate
Its also inhibited by low pH
Inhibition of PF leads to inhibition of hexokinase because of the backup of substrates
What are the differences between hexokinase and glucokinase
- Glucokinase has a higher Km so its only really active at high glucose concentrations
- Hexokinase is inhibited by G-P-6 but glucokinase isn’t
- Glucokinase is induced by insulin
How are tumours and exercising muscles similar
Both rely on anaerobic respiration for the generation of ATP
What is a limiting factor of anaerobic respiration
NAD+ since it limits the production of pyruvate
How is NAD+ resynthesised
Lactate is made from pyruvate so NADH is metabolised back into NAD+
Why does muscle fatigue and how does it counteract it
Lactate is highly acidic because of H+ ion production
Low pH is an inhibitor of glycolysis
The muscle overcomes this by exporting lactate back to the liver, here it is metabolise back to glucose
Why do tumours use glycolysis
When tumours outgrown their blood supply, oxygen delivery is reduced and therefore tumour cell metabolism reverts to glycolysis
How does tumour physiology change to accommodate glycolysis
A reduction in O2 leads to he activation of the transcription factor HIF-1 alpha
HIF-1 alpha regulates the expression of a number of enzymes in the glycolytic pathway such as hexokinase and phosphate-fructokinase
HIF-1 alpha also leads to blood vessel growth
