Glycolysis_Flashcards
What is glycolysis?
A 10-step enzyme-catalyzed process that converts glucose into pyruvate.
Where does glycolysis occur?
In the cytosol of most differentiated cells.
What is the net ATP gain from glycolysis?
2 ATP per glucose molecule.
What are the two main stages of glycolysis?
Hexose stage (ATP-consuming) and triose stage (ATP-generating).
Which cofactor is reduced in glycolysis?
NAD+ is reduced to NADH.
What enzyme catalyzes Step 1 of glycolysis?
Hexokinase.
What happens in Step 1 of glycolysis?
Glucose is phosphorylated to glucose-6-phosphate.
Which enzyme catalyzes Step 2?
Glucose-6-phosphate isomerase.
What is the function of phosphofructokinase-1 (PFK-1) in Step 3?
It phosphorylates fructose-6-phosphate, committing it to glycolysis.
Which enzyme catalyzes Step 4, and what does it do?
Aldolase; it splits fructose-1,6-bisphosphate into DHAP and G3P.
What enzyme converts DHAP to G3P in Step 5?
Triose phosphate isomerase.
What type of reaction occurs in Step 6, catalyzed by G3P dehydrogenase?
A redox reaction where NAD+ is reduced to NADH.
Which enzyme catalyzes Step 7 and what does it produce?
Phosphoglycerate kinase; produces ATP.
What type of reaction occurs in Step 8, catalyzed by a mutase?
A phosphoryl shift within the molecule.
What is formed in Step 9, catalyzed by enolase?
Phosphoenolpyruvate (PEP), a high-energy intermediate.
What enzyme catalyzes the final step of glycolysis?
Pyruvate kinase.
What is the final product of glycolysis?
Pyruvate.
What is the main regulatory enzyme of glycolysis?
Phosphofructokinase-1 (PFK-1).
What activates PFK-1?
AMP and fructose-2,6-bisphosphate.
What inhibits PFK-1?
ATP and citrate.
How is hexokinase regulated?
Inhibited by glucose-6-phosphate (feedback inhibition).
How is pyruvate kinase regulated?
Activated by fructose-1,6-bisphosphate; inhibited by ATP.
What is the Pasteur effect?
Glycolysis slows in the presence of oxygen.
What are the metabolic fates of pyruvate?
Acetyl-CoA (aerobic), lactate (anaerobic), ethanol (fermentation).
Which enzyme converts pyruvate to lactate?
Lactate dehydrogenase.
What process converts pyruvate to acetyl-CoA?
Pyruvate decarboxylation by pyruvate dehydrogenase.
What enzyme catalyzes ethanol fermentation?
Alcohol dehydrogenase.
What is the Cori cycle?
Lactate recycling between muscles and liver.
How does fructose enter glycolysis?
Converted to G3P via fructokinase and aldolase.
How does galactose enter glycolysis?
Converted to glucose-6-phosphate.
How does mannose enter glycolysis?
Converted to fructose-6-phosphate.
What is gluconeogenesis?
Biosynthesis of glucose from non-carbohydrate sources.
Where does gluconeogenesis occur?
Mostly in the liver and kidney cortex.
What are the three irreversible steps in glycolysis?
Steps catalyzed by hexokinase, PFK-1, and pyruvate kinase.
Which enzyme converts pyruvate to oxaloacetate in gluconeogenesis?
Pyruvate carboxylase.
Which enzyme converts oxaloacetate to PEP?
PEP carboxykinase.
Which enzyme bypasses PFK-1 in gluconeogenesis?
Fructose-1,6-bisphosphatase.
Which enzyme bypasses hexokinase in gluconeogenesis?
Glucose-6-phosphatase.
What is the pentose phosphate pathway?
An alternative glucose metabolism pathway producing NADPH and ribose-5-phosphate.
What are the two stages of the PPP?
Oxidative (NADPH production) and non-oxidative (sugar interconversion).
What is the main enzyme of the oxidative phase?
Glucose-6-phosphate dehydrogenase.
What is the function of transketolases and transaldolases?
Transfer carbon groups between sugars.
Which cofactor does transketolase require?
Thiamine pyrophosphate (TPP).
How many ATPs are produced in glycolysis per glucose?
4 ATP (gross), 2 ATP (net).
How many NADH molecules are produced per glucose?
2 NADH.
How many ATPs can be generated per NADH in the electron transport chain?
Around 2.5 ATP.
Why is glycolysis essential for red blood cells?
It is their only source of ATP.
How is glycolysis linked to the citric acid cycle?
Pyruvate is converted to acetyl-CoA.
What is substrate-level phosphorylation?
ATP generation without the electron transport chain.
Why is glycolysis one of the oldest metabolic pathways?
It is anaerobic and found in nearly all living organisms.
