Carbohydrate Metabolism: Glycolysis Flashcards
What is Glycolysis
1st step of cellular respiration
It is a series of reactions that extract energy from glucose by splitting it into two three-carbon pyruvate
What is the net product of glycolysis? Where does it happen?
It produces 2 ATP and occurs in the cytoplasm
What are the irreversible steps in glycolysis?
1: When hexokinase or glucokinase add a phosphate group and traps the sugar (converting it from glucose to glucose-6-phosphate
2: The rate-limiting step of phophofructokinase-1 which converts fructose-6-phosphate to fructose 1,6-bisp
3: Finally when pyruvate kinase converts phosphoenolypyruvate to 2 pyruvate
What are the important enzymes in glycolysis?
Glucokinase Hexokinase Phosphofructokinase-1 (PFK-1) Phosphofructokinase-2 (PFK-2) Glyceraldehyde-3-phosphate dehydrogenase 3-phosphoglycerate kinase Pyruvate kinase
What is the role of glucokinase? Where is it found?
It is present in only liver and pancreatic beta cells
Is inhibited by insulin in hepatocytes
Acts proportionally to the concentration of glucose
Phosphorylates glucose
What is the role of hexokinase? Where is it found?
It is present in all tissue
Phosphorylates glucose to trap it in cells
Difference between hexokinase and glucokinase
Hexokinase is present in most tissues while glucokinase is only present in hepatocytes and pancreatic beta cells
Hexokinase is more present at low glucose levels while glucokinase acts proportionally to glucose concentrations
Hexokinase is inhibited by glucose-6-phosphate and glucokinase is inhibited by insulin in hepatocytes
What is the role of phosphofructokinase-1 (PFK-1)?
This is the rate-limiting step in glycolysis
What is the role of phosphofructokinase-2 (PFK-2)?
PFK-2 produces F2,6-BP which activates PFK-1
What is the role of glyceraldehyde-3-phosphate dehydrogenase
It produces NADH (which is either then oxidized aerobically in electron transport chain or anaerobically by cytoplasmic lactate dehydrogenase)
What is the role of 3-phosphoglycerate kinase?
Performs substrate-level phosphorylation (produces ATP)
This is the only type of anaerobic production of ATP in glycolysis
What is the role of pyruvate kinase?
Performs substrate-level phosphorylation (produces ATP)
This is the only type of anaerobic production of ATP in glycolysis
What is the importance of glycolysis in erythrocytes?
Ethrocytes (red blood cells) deliver oxygen to cells so they must produce energy anaerobically as to not use up the oxygen they’re delivering.
Additionally, 1,3-bisP converts to 2,3-bisP which helps to deliver the oxygen off of red blood cells, which causes a Bohr effect (decrease in oxygen affinity)
General overview of glycolysis
