LECTURE 19 - Metabolism Overview: Glycolysis Flashcards
Define “rate limiting step”
The slowest step in the pathway
Define “commitment step”
The first irreversible step unique to the pathway
What is the commitment step in glycolysis
Fructose-6-phosphate → fructose-1,6-bisphosphate
Identify the reducing equivalent produced from catabolism and required for anabolism in humans
NADPH is required for anabolism & produced from catabolism
Define “futile cycle”
Irreversible reactions going in opposite directions running at the same time
– mostly just wastes energy
Give an example of a futile pathway
The liver uses a futile cycle between glucose and glucose 6-phophate as a buffer to
maintain blood glucose levels
List examples of slow regulation methods of metabolism
Transcriptional/translational regulation
Protein degradation
List examples of fast regulation methods of metabolism
Allosteric regulation
Post-translational modification
Compartmentation
Describe the differences between C3 (3 carbon) metabolites and C2 (2 carbon) metabolites
- C3 metabolites are used in GLYCOLYSIS and GLUCONEOGENESIS
- C2 metabolites are past the “point of no return” and are used in the TCA cycle and cataplerotic reactions of intermediates
Identify the 3 irreversible steps in glycolysis (numbers)
Step 1, 3, 10
Describe Step 1 of glycolysis
Irreversible
Glucose is converted to glucose 6-phosphate in the presence of the enzyme hexokinase
Describe Step 3 of glycolysis
Irreversible
Fructose 6-phosphate is converted to fructose 1,6-biphosphate in the presence of the enzyme phosphofructokinase
Describe Step 10 of glycolysis
Irreversible
Phosphoenolpyruvate is converted to pyruvate in the presence of the enzyme pyruvate kinase
What is the branching point for glycolysis and glycogen synthesis?
The branching point between glycolysis
and glycogen synthesis occurs at the molecule glucose-6-phosphate; this molecule can either enter glycolysis directly or be converted to glucose-1-phosphate, which is the form needed for glycogen synthesis
List the different metabolic fates of pyruvate
Lactic Acid Fermentation
Aerobic Respiration
In gluconeogenesis to make glucose
How is pyruvate used in lactic acid fermentation?
Pyruvate –> Lactate
when oxygen is not available
How is pyruvate used in aerobic respiration?
Pyruvate –> Acetyl-CoA
when oxygen is available
How can Pyruvate be used to create glucose?
Through gluconeogenesis IF IT DOES NOT CROSS INTO THE MITOCHONDRIA
Describe the metabolic problem of a fructose-only diet
- Fructose requires different kinases from glycolysis
– The same splitting enzyme (aldolase B) as glycolysis is used, but fructose 1-phosphate is a poor substrate for the enzyme - An excess amount of fructose will accumulate fructose 1-phosphate in liver cells
– Depletes ATP & phosphate
– May cause severe liver damage - TOXICITY
Describe the role of adenylate kinase and AMP in cellular energy sensing
Cells can sense their energy status using AMP as a signal
– When [AMP] is high, [ATP] (energy) is low
HOTSEAT: how much energy is harvested from the conversion of one glucose to two pyruvate molecules?
A. 1 ATP and 1 NADH
B. 4 ATP and 2 NADH
C. 2 ATP and 2 NADH
D. 2 ATP
E. 4 ATP
C. 2 ATP and 2 NADH
