Glycogen Metabolism And Glycolysis Flashcards
(9 cards)
Flashcard 1
Q: What are carbohydrates, and how does the body use them?
A: Carbohydrates are organic compounds made of carbon, hydrogen, and oxygen. They are broken down into glucose, which serves as the body’s main source of energy. Excess glucose is stored as glycogen in the liver and muscles or converted into fat for long-term storage.
Q: What is glycogen, and why is it important?
A: Glycogen is a polysaccharide composed of glucose molecules. It serves as a storage form of energy, which can be quickly mobilised during fasting, exercise, or stress to maintain blood glucose levels and supply energy to muscles
Q: How do hormones regulate glycogen synthesis and breakdown?
A:
* Insulin: Secreted in response to high blood glucose, activates glycogen synthase to promote glycogen synthesis. It also inhibits glycogen phosphorylase to prevent glycogen breakdown.
* Glucagon: Secreted during fasting, activates glycogen phosphorylase to stimulate glycogen breakdown in the liver, releasing glucose into the bloodstream.
* Adrenaline: Stimulates glycogen breakdown in muscles and liver during stress or exercise by activating glycogen phosphorylase.
What is glycolysis, and why is it important?
A: Glycolysis is a ten-step metabolic pathway that breaks down one molecule of glucose into two molecules of pyruvate. It generates 2 ATP and 2 NADH molecules, providing energy for cellular processes, especially in anaerobic conditions
What are the key steps of glycolysis?
A:
1. Glucose phosphorylation: Glucose is converted into glucose-6-phosphate by hexokinase (requires ATP).
2. Isomerisation: Glucose-6-phosphate is converted into fructose-6-phosphate.
3. Second phosphorylation: Fructose-6-phosphate is converted to fructose-1,6-bisphosphate by phosphofructokinase-1 (PFK-1, requires ATP).
4. Cleavage: Fructose-1,6-bisphosphate is split into two 3-carbon molecules: dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (G3P).
5. Energy generation: Through a series of reactions, G3P is converted to pyruvate, producing 4 ATP (net gain of 2 ATP) and 2 NADH.
Q: What is the net output of glycolysis per molecule of glucose?
A:
* 2 Pyruvate (end product)
* 2 ATP (net gain)
* 2 NADH (electron carriers for oxidative phosphorylation)
Q: How is glycolysis regulated?
A: Glycolysis is regulated at three key enzymes:
1. Hexokinase:
* Inhibited by glucose-6-phosphate (product inhibition).
2. Phosphofructokinase-1 (PFK-1):
* Activated by AMP and fructose-2,6-bisphosphate (signals low energy).
* Inhibited by ATP and citrate (signals high energy).
3. Pyruvate kinase:
* Activated by fructose-1,6-bisphosphate (feed-forward activation).
* Inhibited by ATP and alanine.
Q: What happens to pyruvate after glycolysis?
The fate of pyruvate depends on oxygen availability:
* In aerobic conditions: Pyruvate enters the mitochondria, where it is converted to acetyl-CoA for the citric acid cycle.
* In anaerobic conditions: Pyruvate is converted into lactate (in animals) or ethanol (in yeast) through fermentation.
Q: Why is glycolysis important for energy production in anaerobic conditions?
A: In the absence of oxygen, glycolysis is the sole source of ATP. NAD+ is regenerated by converting pyruvate to lactate, ensuring glycolysis can continue.
