Glycolysis Flashcards
What is the definition of metabolism?
Process through which living systems acquire and utilize the free energy they need to carry out their various functions
ex: breakdown of food, ATP synthesis, heat loss, chemical waste, work, organic wastes
What is the reaction and ∆G˚’ of the full breakdown of glucose?
C6H12O6 + 6 O2 → 6 CO2 + 6 H2O
∆G˚’ = -2,870 kJ/mol
What is the reaction and ∆G˚’ of the full breakdown of lipids?
C16H32O2 + 23 O2 → 16 CO2 + 16 H2O
∆G˚’ = -9,781 kJ/mol
What is the reaction and ∆G˚’ of the hydrolysis of ATP?
ATP + H2O → ADP + Pi
∆G˚’ = -32.2 kJ/mol
How many calories is 1 kJ?
1 kJ = 0.239 kcal
How could catabolism and anabolism be summarized?
Catabolism: complex → simple (exergonic)
Anabolism: simple → complex (endergonic)
*Both coupled with ATP hydrolysis
What are the 3 stages of metabolism?
- Polymers and complex lipids → monomeric intermediates
- Monomeric sugars, amino acids and lipids → simpler organic compounds
- Degradation or synthesis of inorganic compounds including CO2, H2O and NH3
What are futile cycles?
When 2 metabolic pathways run simultaneously in both directions
It is an example of how cells regulate many pathways
Ex: Fatty acid synthesis and degradation occurred simultaneously (use ATP) → no useful work done and all ATP consumed
Solution → do these reaction in separate compartement (acetyl-CoA → Fatty acids uses ATP in cytosol ///// Fatty acids → Acetyl-CoA releasing ATP in Mitochondria)
What are the major intermediates of glycolysis?
Polysaccharides → Monosaccharides → GLYCOLYSIS [Glucose → Glyceraldehyde-3-phosphate (ATP/NAD step) → pyruvate] → To fermentation of respiration
Which tissues are responsible for synthesis of glucose and responsible for glucose use as a primary energy source?
Tissues that synthesize glucose:
- Liver
- Kidney cortex
Tissues that use glucose as their primary energy source:
- Brain
- Muscle
- Kidney medulla
- Erythrocytes
- Testes
Where does glycolysis occur in the cell?
In the cytosol
What are the net starting materials and products of glycolysis?
- Glucose
Energy investment phase: - Invest 2 ATP (→ADP)
Energy generation phase (2 trise phosphates (3C)):
3. Produces 4 ATP (from ADP)
4. Produces 2 NADH (from NAD+)
5. 2 Pyruvates
Net:
Glucose → 2 pyruvates
2 ADP → 2 ATP
2 NAD+ → 2 NADH
What explains the fact that glycolysis is a fermentation? (reaction)
NADH produced ealier in the pathway is reoxidized to NAD+ by transfer of electrons to some electron acceptor → ensures that there is enough NAD+ available for the cell to continue to produce ATP via glycolysis under anaerobic conditions
Lactate dehydrogenase reaction:
Pyruvate + NADH + H+ ↔ L-lactate + NAD+
∆G˚’ = -25.1 kJ/mol
Lactate is then excreted
Fermentation rxn: a biochemical reaction that extracts energy from carbohydrates without using oxygen
What are the 10 steps fo glycolysis?
Energy Investment phase:
1. Phosphorylation (Hexokinase)
2. Isomerization (Glucose-6-phosphate isomerase)
3. Phosphorylation (phosphofructokinase)
4. Cleavage (aldolase)
5. Isomerization (Triose phosphate isomerase)
Energy Generation phase:
6. Oxidation and phosphorylation (Glyceraldehyde-3-phosphate dehydrogenase)
7. Substrate-level phosphorylation (phosphoglycerate kinase)
8. Isomerization (phosphoglycerate mutase)
9. Dehydration
10. Substrate-level phosphorylation (pyruvate kinase)
End with 2 pyruvates
What occurs in step 1 of Glycolysis?
Step 1 = Phosphorylation by Hexokinase
Glucose → (Hexokinase) → G6P
Uses 1 ATP to phosphorylate the 6th carbon of glucose → traps glucose inside the cell (glucose enters by selective transporter)
*Hexokinase has very high affinity (low Kd) so will phosphorylate very low amounts of glucose coming in.
- Also has sites for both reactions
*Needs to be coupled with ATP hydrolysis, just glucose + phosphate in the test-tube → no reaction
