General features of metabolic pathways:
- Multiple uses for each metabolite
- Cyclic
- Redundant
- Far from equilibrium
- Steady state
Focusing on glycolysis:
- Can be reversed in gluconeogenesis
- Net imputs are glucose, ADP and NAD+
- Net outputs are pyruvate, NADH and ATP
Focusing on Hexokinase:
- Irreversible
- Low KmAllosteric inhibition by G6P (-ve feedback)
- Traps glucose in cell
- Gives a chemical ‘handle’ for subsequent steps
Questions:
Enzymes work by:
A. altering the equilibrium position
B. preventing unwanted side reactions
C. binding the product far more tightly than the reactant
D. lowering the activation energy of the reaction
E. removing product from the chemical environment, driving the reaction to the left.
The final electron acceptor in fermentation is _______, while in the electron transport chain it is _______.
A. oxygen, pyruvate
B. pyruvate, oxygen
C. water, lactate
D. lactate, water
E. glucose, pyruvate
What is the advantage of hexokinase having a low Km?
References:
Campbell et al Biology Ch. 9 (esp. pg. 160-170)
Kimball, J Biology Hypertext Book “Glycolysis”
Ophardt, C Virtual Chembook “Carbohydrate metabolism overview”
Answers: D, B, Hexokinase can work at very low concentrations.
