Biochem Exam 3 Flashcards
What is glycolysis?
A universal and ancient metabolic pathway occurring in the cytosol that degrades glucose to pyruvate, generating ATP and NADH.
It consists of 10 steps catalyzed by 10 enzymes.
What are the two main phases of glycolysis?
- Preparatory Phase (Steps 1-5)
- Payoff Phase (Steps 6-10)
The preparatory phase invests ATP to activate glucose, while the payoff phase recoups ATP and creates additional ATP.
What occurs during the preparatory phase of glycolysis?
ATP is invested to activate glucose through phosphorylation and degrades glucose to two 3-carbon sugars.
This phase includes rearrangement of carbons.
What are the key regulatory steps in glycolysis?
- Step 1: Hexokinase
- Step 3: Phosphofructokinase 1 (PFK1)
- Step 10: Pyruvate Kinase
These steps are crucial for controlling the flow of metabolites through the pathway.
What is the role of hexokinase in glycolysis?
Transfers phosphate from ATP to glucose, trapping glucose in the cell.
Hexokinase has four isozymes with different properties.
How does phosphofructokinase 1 (PFK1) regulate glycolysis?
Adds a second phosphate to fructose-6-phosphate (F6P) to form fructose-1,6-bisphosphate (F1,6BP).
It is regulated by ATP (inhibitor) and AMP (activator).
What is the final step of glycolysis?
Pyruvate Kinase transfers phosphate from phosphoenolpyruvate (PEP) to ADP, forming ATP.
This step is crucial for energy production.
What is the overall free energy change (ΔG’°) of glycolysis?
-85 KJ/mol
This indicates that the pathway is energetically favorable.
What happens to pyruvate in aerobic conditions?
Enters the TCA cycle for complete degradation.
This process is crucial for cellular respiration.
What are the two types of fermentation that occur in anaerobic conditions?
- Lactic acid fermentation
- Ethanol fermentation
Lactic acid fermentation reduces pyruvate to lactate, while ethanol fermentation converts pyruvate to ethanol (in yeast).
How is fructose processed in glycolysis?
Phosphorylated by hexokinase to fructose-1-phosphate (F1P), then split into glyceraldehyde and DHAP.
Glyceraldehyde is further phosphorylated by triose kinase.
What is the role of glucokinase in glucose transport?
Active at higher glucose concentrations and helps maintain blood glucose homeostasis.
It is found in the liver, pancreas, hypothalamus, and intestines.
What are the types of carbohydrates?
- Simple: Monosaccharides (glucose, fructose, galactose)
- Complex: Starch (amylose, amylopectin)
- Non-starch: Cellulose, hemicellulose, pectin
Understanding carbohydrate types is essential for digestion and metabolism.
What is the function of α-amylases in carbohydrate digestion?
Cleaves glycosidic bonds in carbohydrates.
α-Amylases are present in saliva and intestines.
What is reciprocal regulation in glycolysis and gluconeogenesis?
Ensures that glycolysis and gluconeogenesis are not simultaneously active to prevent futile cycling.
Shared effectors produce opposite effects on the two pathways.
What hormones regulate glucose metabolism?
- Insulin
- Glucagon
Insulin signals energy use and storage, while glucagon signals glucose production.
