Session 4 Flashcards
(42 cards)
What is Glycogen synthesis called?
Glycogenesis
What enzyme catalyses the first step in Glycogenesis?
Hexokinase
What enzyme catalyses the second step in Glycogenesis?
Phosphoglucomutase
What enzyme catalyses the fourth step in Glycogenesis?
Glycogen synthase & Branching enzyme
What enzyme catalyses the first step in Glycogen breakdown?
Glycogen phosphorylase attacks the alpha 1,4 bonds & Debranching enzyme attacks alpha 1,6
What enzyme catalyses the second step in Glycogen breakdown?
Phosphoglucomutase
What enzyme catalyses the third step in Glycogen breakdown?
Glucose 6-phosphatase
Contrast the Glycogen stores in Muscles and the Liver
Muscle - G6P, muscle only
Liver - Glucose for all tissues of the body
Explain the clinical consequences of Glycogen storage disease
Abnormality in enzymes of Glycogen metabolism; Tissue damage if excessive storage Fasting hypoglycaemia Poor exercise tolerance Glycogen structure may be abnormal
Define Gluconeogenesis
The process where Glucose is produced when there are no Carbohydrates.
Liver is the main site
Reversible steps of glycolysis used in gluconeogenesis, irreversible bypassed.
Name some of the substrates for Gluconeogenesis
Pyruvate Lactate Glucerol AA NOT Acetyl CoA
WHat 3 steps of Glycolysis are bypassed in Gluconeogenesis?
1, 3 & 10
How are steps 1 & 3 of Glycolysis bypassed in Gluconeogenesis?
Thermodynamically spontaneous reactions catalysed by glucose 6-phosphatase and fructose 1,6-bisphophatase
How is step 10 of Glycolgysis bypassed in Gluconeogenesis?
2 reactions catalysed by pyruvate carboxylase and PEPCK (Use ATP)
Which reaction provides a ‘link’ between the Krebs cycle and Gluconeogenesis?
Step 10 reaction enables products of AA catabolism (intermediates of TCA cycle) to synthesise glucose.
How is Gluconeogenesis regulated?
Hormonal control on PEPCK and Fructose 1,6-bisphosphonate
Increased by Glucagon, decreased by Insulin
What controls Triacylglycerol storage?
Promoted by Insulin
Depleted by anti insulin hormones (Glucagon, Adrenaline, Cortisol, Thyroxine, GH)
How are Fatty acids degraded?
Beta oxidation. 2C removed at a time (As Acetyl CoA) until only 2 left.
Needs NAD+, FAD & O2
How are fatty acids synthesised?
Lipogenesis - Synthesised from Acetyl CoA using ATP and NADPH
Fatty acid synthase complex adds 2Cs at a time by adding 3Cs and having CO2 lost
How is Lipogenesis controlled?
Acetyl~CoA carboxylase enzyme (Converts Acetyl CoA to 3C compound)
Allosteric regulation - citrate activates and AMP inhibits
Regulation by covalent modification - Insulin activates by promoting dephosphorylation. Glucagon & Adrenaline inhibit the enzyme by promoting phosphorylation
How are Amino acids catabolised?
Each has its own pathway;
Amino group removed –> Urea (Deamination/Transamination)
Remaining C skeleton reused
What are Ketogenic Amino acids?
Ones that can produce Acetyl CoA as it goes on to make Ketone bodies
What are Glucogenic Amino acids?
Ones that produce molecules which can be used for Glucose synthesis in Gluconeogenesis
What enzymes are used in Transamination?
Aminotransferases