Metabolism COPY Flashcards
What is the basic reaction by which food is converted to ATP?
Oxidation
- Which enzyme(s) are responsible for initial glucose phosphorylation after entry into the cell?
- Which enzyme reverses this reaction?
- Glucokinase - liver
Hexokinase - other tissues
- Glucose-6-phosphatase
GLYCOGENESIS
glucose 6-phosphate is converted to glucose-1-phosphate and then uridine diphosphate glucose before becoming glycogen.
Which is the important enzyme involved in glycogenolysis?
Glycogen phosphorylase
How many moles of ATP are formed from a single mole of glucose?
38
What is the end product of the glycolytic pathway?
Two pyruvic acid molcules
How many ATPs are formed from glycolysis?
4 are formed but 2 are required in the initial phosphorylation of glucose so the net gain is two ATP
What vitamin is acetyl-CoA a derivative of?
Vitamin B5 - patothenic acid
What is the net reaction of the CAC following the processing of one molecule of glucose?
What is the starting molecule of the CAC?
Oxaloacetate
Which vitamin is required to form NADH?
Nicotinamide (vitamin B3)
What group of enzymes splits hydrogen from substrates in glucose breakdown pathways?
Dehydrogenases
What group of enzymes splits away CO2 in the various glucose breakdown pathways?
Decarboxylases
What is oxidation vs. reduction?
Oxidation = removal of electrons
Reduction = addition of electrons
What is the role of cytochrome oxidase in the electron transport chain?
To reduce oxgen by combining it with H20.
Summarise ATP formation during the breakdown of glucose
- Glycolysis - formation of net 2 ATP
- CAC - 2 ATP
- 24 hydrogens produced from the above, which are then oxidised in the mitochondrial chemiosmotic mechanism.
= 38 ATP molecules
What is the importance of the enzyme phosphofructokinase in the glucose metabolic pathway?
It is involved in the formation of fructose 1,6-diphosphate (early stage in glycolysis).
PPK can be inhibited by ATP and this represents a feedback mechanism by which cellular energy metabolism is regulated.
Citrate also inhibits PPK
What are the most common fatty acids present in human triglycerides?
- Stearic acid
- Oleic acid
- Palmitic acid
What is the plasma T½ of a chylomicron?
Approz. 1h
What is the role of lipoprotein lipase and where is it located?
Its role is to release triglycerides from chylomicrons so that they can diffuse into cells.
Location = capillary wall (particularly of adipose tissues)
What is the role of apoliprpteins (e.g. Apo E and Apo B) in lipid metabolism?
They mediate clearance of chylomicron remnants from the blood by the liver.