Carbohydrate Metabolism Flashcards
Where does glycolysis take place?
Cytoplasm of all tissues
What does glycolysis produce in aerobic conditions?
Pyruvate (two molecules)
What does glycolysis produce in anaerobic conditions?
Lactate
What is the net gain in ATP molecules from the glycolysis reaction?
2 molecules for each molecule of glucose
Where does the link reaction take place?
Matrix of the mitochondria
What is the link reaction in summary?
Pyruvate (from glycolysis) actively transported into the mitochondria
Pyruvate is converted into Acetyl CoA by the action of pyruvate dehydrogenase
No ATP formation in this reaction but 4 hydrogen atoms are released
Where does Krebs’ Cycle take place?
Mitochondrial matrix
In the Krebs Cycle what happens to Acetyl CoA?
Degraded into carbon dioxide and hydrogen ions
Per glucose molecule what is released from the Krebs’ Cycle?
4 Carbon Dioxide molecules 16 Hydrogen atoms 2 molecules of coenzyme 2 molecules of ATP are formed (one acetyl CoA molecule = one ATP molecule) 6 NADH
What does NAD stand for?
Nicotinamide Adenine Dinucleotide
What percentage of ATP formation occurs in the stage of oxidative phosphorylation?
90%
What molecule is the final electron acceptor in oxidative phosphorylation?
molecular oxygen
What is oxidative phosphorylation?
Formation of ATP by the addition of an inorganic phosphate to ADP in the presence of oxygen
Where is the site of oxidative phosphorylation?
Mitochondrial cristae
Define chemiosmosis
The flow of hydrogen ions
In oxidative phosphorylation, what happens when H+ flow through ATPsynthase?
Drives rotation of the enzymatic part of the protein and causes phosphorylation of ADP forming ATP
What is the maximum theoretical ATP yield from each glucose molecule?
38 ATP molecules
Why is the maximum theoretical ATP yield rarely achieved?
- H+ leakage across mitochondrial membrane
- ATP is used to actively transport pyruvate into the mitochondria
- ATP is used to bring hydrogen from reduced NAD (from glycolysis) into the cytoplasm and into the mitochondria
Why is anaerobic respiration result in a much lower yield of ATP than aerobic respiration?
Glycolysis takes place in anaerobic respiration
Glucose enters cells by GLUT receptors, Which type is found in the liver and which type is found on the adipocytes?
Liver: GLUT2
Adipocytes: GLUT4
Which enzyme phosphorylates glucose to “trap” it in the cell?
Hexokinase I-III
Which enzyme that phosphorylates glucose to “trap” it in the liver has a high activity during high blood glucose concentrations?
Hexokinase IV (Glucokinase)
