Week 5 - Carbohydrate metabolism Flashcards
What happens when a substrate is oxidised?
It gives up 2 hydrogen atoms - 1 is passed as a hydride ion (h-) to NAD+ (to make NADH) or FADH (to make FADH2) and the other is released as a proton (H+) to the aqueous environment (lowers pH).
Is glycolysis aerobic or anaerobic?
Anaerobic
Where does glycolysis take place?
Cytosol
What is the reactant, and products of glycolysis?
Reactant - Glucose
Products - Pyruvate (3C)x2 and NADH
What are the 2 key phases to glycolysis?
Investment phase
Pay-off phase
What are the 4 ways in which exercise can speed up glycolysis?
- Substrate availability – increased glycogenolysis favours glycolysis to proceed.
- Physiological factors – greater flow of blood with exercise increases flow of glucose molecules towards active muscle.
- Cellular factors – increased glucose uptake by glucose transporters, such as GLUT4.
- Molecular factors – allosteric activation of pyruvate kinase and phosphofructokinase involved with glycolysis.
Is the Krebs/Citric acid cycle aerobic or anaerobic?
Aerobic
Where does the krebs cycle occur?
Mitochondrial matrix
What are the reactants and products of the krebs cycle?
Reactant - Acetyl coA
Products - ATP, NADH, FADH2
What enzyme oxidises pyruvate to acetyl coA?
pyruvate dehydrogenase. This in turn generates NADH
As NADH is impermeable to mitochondrial membrane, how does it transfer its electrons into the mitochondria?
It transfers its electrons through a membranal enzyme to FADH.
What happens to Gibbs free energy as electrons are transferred to NADH and FADH?
Gibbs free energy falls
Is oxidative phosphorylation an aerobic or anaerobic pathway?
Aerobic
Where does oxidative phosphorylation occur?
Mitochondrial intermembrane space and matrix
What are the reactants and products of oxidative phosphorylation?
Reactants - 8 NADH & 4 FADH2
Products - 26 ATP, 6CO2, 6 H20
What does the ETC do to NADH and FADH2?
Re-oxidises them back to their oxidised form, releasing H-
During oxidative phosphorylation, in what direction are H+ ejected?
From the matrix to the intermembrane space, creating a concentration gradient
What is the limiting factor of anaerobic metabolism?
Regeneration of ATP, NOT OXYGEN.
During anaerobic respiration, what enzyme converts pyruvate to lactate?
Pyruvate dehydrogenase
What is gluconeogenesis?
Where carbon skeletons from other molecules are used to synthesis glucose for energy provision in muscle
Describe the cori cycle
When lactate leaves the working muscle, it enters the liver via the blood and reforms pyruvate, which can then be used as a substrate for gluconeogenesis. Glucose is then shuttled back to the active muscle.
