4 - Carbohydrate Metabolism

V B
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V B
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Describe the two independent ways in which glucose is transported into the muscle. 1) GLUT-4 is a transporter protein which transports glucose across the membrane into the muscle fibre. Insulin stimulates GLUT-4 2)PA involves muscle contraction which transports glucose into the muscle fibre
Name the three processes for carbohydrate metabolism. Glycogenolysis - breaking down glycogen Glycolysis - breaking down glucose Glycogenesis - synthesis of glycogen
What does a postfix of lysis mean? What does a postfix of esis mean? Splitting Formation
Which hormones regulate a) glycogenolysis b) glycogenesis Adrenaline Insulin
What is a carbohydrate with 3-7 carbons called? Name the specific name and example for each number. Monosaccharide 3 - trioses eg dihydroxyacetone 4 - tetroses eg erythrose 5 - pentoses eg ribose 6 - hexoses eg glucose/fructose
What are two monosacccharides joined together called? What is the bi-product when this occurs? Give examples Disaccharides Water Glucose + glucose = maltose + water Galactose + glucose = lactose + water Glucose + fructose = sucrose and water
What is it called when there is > 10 monosaccharides? Give examples 10-20 = glucose polymers > 1000 - starch in plants, glycogen in animals
Draw a glucose molecule LEARN HOW TO DRAW THIS FOR THE EXAM
Draw a Maltose molecule What type of bond joins the two glucose molecules?
What is regulation of CHO metabolism? The biochemical processes that regulate how our body transports, stores and uses CHO for energy, in this case how it produces ATP from CHO
What are the main sites involved in CHO metabolism? (1-3) 1) Transportation of glucose into the muscle fibre 2) Glucose is transformed into Glucose-6-Phosphate (G-6-P Either glycolysis occurs to produce ATP OR it's transformed into G-1-P and stored as glycogen
What are the main sites involved in CHO metabolism? (4) 4. The electron transport chain, by this stage we have pyruvate. In the absence of O2 it is used to produce ATP with a bi-product of lactic acid OR with O2 the pyruvate is transported into the mitochondria and made into Acetyl-CoA
What are the main sites involved in CHO metabolism? (5,6) 5) Acetyl CoA enters the krebs cycle 6) Glycogenolysis occurs - the formation of glycogen
What are the two key regulators of blood glucose? 1) The pancreas - insulin stimulates GLUT-4. Glucagon splits glycogen (glycogenolysis) so that the liver can maintain blood glucose levels 2)Muscle contraction (exercise) does not require insulin to transport glucose into the muscle
What is GLUT-4 A glucose transporter protein
What are the 6 steps for insulin to transport glucose? 1) It is outside the muscle fibre 2) Binds to a receptor inside the plasma membrane 3) Is phosphorylated - adding a phosphate group turns the molecule on 4) P13 kinase is activated 5) This activates AKt 6) Activated AS160 allowing translocation of GLUT-4 into the sarcolemma
How does exercise (muscle contraction) transport glucose? 1) During exercise ATP is expended = an increase in the ratio of AMP:ATP 2) When this ratio is high AMP kinase is activated 3. This activates AS160 allowing translocation of GLUT-4 into the sarcolemma
Where is glucose stored and in what amounts? 5g floating in the bloodstream 100g stored in the liver 400g stored in the muscle (close to the mitochondria so available for quick use)
To utilise more muscle glycogen than fat what must we do to exercise intensity? Increase exercise intensity
What is the equation for breaking glycogen down to glucose-1-phosphate What enzyme catalyses this reaction? LEARN FOR EXAM Glycogen (n units) + Pi -> Glycogen (n-1 units) + Glucose-1-phosphate Glycogen Phosphorylase
What is the equation for breaking glucose-1-phosphate down to glucose-6-phosphate What enzyme catalyses this reaction? LEARN FOR EXAM Glucose-1-phosphate -> Glucose-6-phosphate Phosphoglucomutase
What regulates glycogen phosphorylase and how? It is regulated through covalent modification via hormonal activation See notes for diagram
What affect does adrenaline have during moderate exercise? Increases glycogenolysis, PDH activation and CHO oxidation
What does an increase of ADP and AMP do to glycogen phosphorylase? Causes it to be switched on even more so it can transform more glycogen into glycogen-1-phosphate
What is the formula for glycolysis? What is the net gain? Glucose + 2ADP + 2Pi + 2NAD+ -> 2 pyruvate + 2ATP + 2NADH + 2H+ 2ATP
What regulates the glycolysis reaction? What does it specifically do? What inhibits this enzyme? Hexokinase Transforms glucose to glucose-6-phosphate. This is an irreversible reaction Too much G-6-P from glycogenolysis
What is phosphofructokinase (PFK)? PFK is the regulatory enzyme in glycolysis
What affects how much PFK is switched on? Amount of ADP, AMP, Pi, cAMP
What slows down PFK? Excess H+, ATP and citrate
What is the link reaction? What is it facilitated by? Turning pyruvate into Acetyl-CoA PDH. The regulatory hormone for CHO oxidation
What does any phosphatase do? eg. PDH phosphatase Remove a phosphate group
What does any kinase do? eg PDH kinase Any kinase adds a phosphate
What does adding a phosphate do to PDH? Makes in inactive
Which hormones regulate glycogenesis, and therefore inhibits glycogenolysis? Insulin
Which hormones regulate glycogenolysis, and therefore inhibits glycogenesis? Adrenaline
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