glycolysis Flashcards
Where are all the enzymes of glycolysis located?
In the cytosol.
What is the general mechanism for ATP generation in glycolysis?
Rearrangement of phosphorylated monosaccharides into high-energy compounds that transfer phosphate to ADP.
What is substrate-level phosphorylation?
The direct transfer of a phosphate group from an intermediate to ADP, forming ATP.
Why must ATP be used after being generated in glycolysis?
To regenerate ADP, which is required to sustain glycolysis.
How does glucose enter glycolysis after being transported into the cell?
It is phosphorylated to glucose-6-phosphate by hexokinase, using ATP as a phosphate donor.
Is the phosphorylation of glucose reversible?
No, it is irreversible under physiological conditions.
What inhibits hexokinase?
Its product, glucose-6-phosphate (allosteric inhibition).
What is the difference between hexokinase and glucokinase?
Hexokinase (in most tissues) has a low Km (high affinity) and is inhibited by glucose-6-phosphate. Glucokinase (in the liver) has a high Km (low affinity) and is NOT inhibited by glucose-6-phosphate.
Where is glucokinase found, and how does it function?
In the liver, with a higher Km than normal plasma glucose, allowing it to function when glucose levels are high.
How is glucose transport regulated in muscle and adipose tissue?
It is stimulated by insulin.
How is glucose used in muscle?
For glycolysis or glycogen synthesis.
How is glucose used in adipose tissue?
For lipogenesis.
Why is glucose transport important in glycolysis regulation?
It acts as a barrier when transport activity is low, limiting glucose uptake and overall glycolysis rate.
Insulin-dependent glucose transporter?
GLUT-4
Glucose transporter in erythrocytes?
GLUT-1
Site of glycolysis in the cell?
Cytosol
End product of aerobic glycolysis?
Pyruvate
End product of anaerobic glycolysis?
Lactate
Enzyme converting glucose to glucose-6-phosphate?
Hexokinase
Rate-limiting enzyme of glycolysis?
PFK-1
Enzyme converting phosphoenolpyruvate (PEP) to pyruvate?
Pyruvate kinase
Type of phosphorylation in glycolysis?
Substrate-level
Number of ATP molecules produced per glucose in glycolysis?
2
Tissue where insulin resistance reduces GLUT-4?
Muscle (also Adipose)
Glycolysis pathway also called?
Embden-Meyerhof
Rate-limiting enzyme of gluconeogenesis?
Fructose-1,6-bisphosphatase
Energy source in hypoxic cancer cells?
Glycolysis
Glucose-6-phosphate inhibits which enzyme?
Hexokinase
Rate-limiting enzyme of glycolysis?
PFK-1
Enzyme inhibited by glucose-6-phosphate?
Hexokinase
Liver enzyme that phosphorylates glucose?
Glucokinase
PFK-1 activator that overrides ATP inhibition?
Fructose 2,6-bisphosphate
Enzyme that synthesizes fructose 2,6-bisphosphate?
PFK-2
Enzyme that degrades fructose 2,6-bisphosphate?
Fructose 2,6-bisphosphatase
PFK-2 is active in which state?
Dephosphorylated
Pyruvate kinase is inactivated by?
Phosphorylation
Hormone that inhibits hepatic glycolysis?
Glucagon
Second messenger controlling PFK-2 activity?
cAMP
RBC pathway that produces 2,3-BPG?
Rapaport-Leubering cycle
Enzyme converting 1,3-BPG to 2,3-BPG?
Bisphosphoglycerate mutase
Enzyme hydrolyzing 2,3-BPG?
Bisphosphoglycerate phosphatase
Percentage of glycolytic glucose shunted to 2,3-BPG synthesis?
15-25%
Effect of 2,3-BPG on hemoglobin?
Decreases oxygen affinity
Condition where 2,3-BPG increases?
Hypoxia
Effect of high altitude on 2,3-BPG?
Increases
Major tissue needing 2,3-BPG for oxygen delivery?
Fetal tissue
Pathway glycolysis follows in RBCs to avoid ATP production?
2,3-BPG shunt
Why does RBC glycolysis prioritize 2,3-BPG over ATP?
Oxygen unloading
