Citric Acid Cycle and Oxidative Phosphorylation Regulation of Metabolism Flashcards

Question

muscle tissue/metabolism

Answer 1

major fuels: glucose, FA and ketone bodies, rested and well fed stores 1-2% of its mass as glycogen. - glycogen more rapidly mobilised than fat - glucose can be metabolised anaerobically (FA cannot) - muscle cannot export glucose - muscle carbohydrate metabolism serves only muscle - extreme exertion: muscle contraction is anaerobic, driven by ATP hydrolysis - at rest: sk muscle users 30% of body O2 - heavy load: 25x more O2 used, higher demand for ATP

Answer 2

maximum flux of glycolysis exceeds CAC, so much of the glucose is degraded anaerobically to lactate, muscle fatigue caused by pH drop caused by lactate build-up This explains why lactate has to travel from the muscle to the liver. Excess lactate produced in muscle goes to Liver - Cori cycle

Answer 3

Heart is a muscular organ - Continuous action - different to skeletal muscle - Relies entirely on aerobic metabolism - Has many mitochondria (40% of cytosol) - Metabolises - glucose, pyruvate, lactate, fatty acids, ketone bodies - rest: fuel is FA - heavy work: small glycogen store, converted to glucose

Answer 4

function to store and release FAs, distributed in skin, abdomen and muscle - FA storage from circulating lipoproteins --> triacylglyerols - inc glucose --> inc insulin --> FA mobilisation - insulin --> glucose uptake --> glycerol-3-phosphate --> triacylglycerol - lipase --> FFA + glycerol during fasting - Intakes glucose by insulin dependent mechanism - Pyruvate is oxidised to Acetyl CoA which is used in the de novo synthesis of fatty acids - Adipose tissue has the capacity for gluconeogenesis and glycogenolysis - much more limited than in muscle & heart - therefore fatty acid synthesis is favoured

Answer 5

- Central metabolic clearing house - Acts as a blood glucose buffer - Takes up and releases glucose in response to BGL & hormones - Converts to glucose-6-phosphate: glucose, glycogen, Acetyl CoA, Pentose Phosphate Pathway - Contains enzymes for gluconeogenesis

Answer 6

- Central metabolic clearing house - Can synthesise or degrade Fatty Acids - During High Metabolic Demand (ie low fuel), Can synthesise ketone bodies but not use them (Lacks enzyme for reconversion) and FA are preferred fuel - During Low Metabolic Demand (ie high fuel): Fatty acids --> TAG --> adipose tissue

Answer 7

- Amino Acids are metabolic fuels - Can be completely oxidized to O2 & H2O - Converted to glucose - Converted to ketone bodies

Answer 8

- liver has the greatest number of ways to utilise glucose - takes up glucose by insulin (independent mechanism) - uses PPP extensively for NADPH production: required for reductive synthesis, reduced glutathione, Er enzyme systems, provides ribose phosphate for nucleotide - uses glucose for glycogen synthesis - glucose used the glucoronic pathway (drug and bilirubin detoxification) - glycolysis: pyruvate --> acetyl CoA --> CAC - use Acetyl CoA for de novo fatty acid synthesis - Liver can convert lactate, pyruvate, glycerol, alanine into glucose by gluconeogenesis to meet the needs of other cells in the body.

Answer 9

- Anaerobic glycolysis in Muscle - Pyruvate --> Lactate - transported in blood - Lactate --> Liver --> pyruvate --> glucose/glycogen - Rescues Lactate & Recovery of glucose - Object of anaerobic glycolysis not to produce lactate but to re-oxidise NADH & thus permit continued ATP production from glycolysis.

Answer 10

- Increased Lactate DH in muscle therefore NADH is rapidly re-oxidised, this leads to increased rate of glycolysis - Useful in fight & flight situation - rapid exercise means that energy requirements outstrip O2 supply. - Anaerobic metabolism - ie glycolysis has the advantage that although only 2ATP are generated per molecule of glucose (as opposed to 38ATP with complete oxidation in presence of O2) Relatively vast amounts of glucose can be broken down - difference between being eaten or not. - Short time later, increased heart rate, dilation of blood vessels increase O2 supply and oxidative regeneration of NAD+ increases - Excess lactate produced in the muscle must travel to the liver where it is converted to pyruvate and can then be used to generate glucose via gluconeogenesis - Effects 1. rescues lactate for further use 2. counteracts lactic acidosis (too much lactate => dec blood pH)

Answer 11

Extremely active muscles use glycogen as their energy source, generating lactate via glycolysis. During recovery, some of this lactate is transported to the liver and converted to glucose via gluconeogenesis. This glucose is released to the blood and returned to the muscles to replenish their glycogen stores. The overall pathway (glucose --> lactate --> glucose) constitutes the Cori cycle

Answer 12

- Initially liver breaks down glycogen --> glucose - Then gluconeogenesis (GNG) is required. The liver needs substrates from other tissues to form glucose using GNG. - ie glucogenic amino acids mostly from the muscle (muscle switches to using FFA’s and ketones for energy, spares use of glucose) - After a few days of fasting most of the energy requirements of the the body are met by fat catabolism = glucose sparing mechanism. TAG’s in adipose tissues are broken down to FFAs and these circulate to the Liver and muscle. - Remainder is supplied by glucogenic amino acids - The brain adapts to using ketones

Answer 13

- Liver makes inc Acteyl CoA when fat is mobilised & glucose is reduced - inc Acteyl CoA normally --> TAG synthesis but if glucose is dec --> dec TAG - Therefore excess Acteyl CoA - -> ketones --> leads acidosis in starvation - The liver maintains glucose output using the amino acids for gluconeogenesis that come from muscle

Answer 14

Occurs via - Availability of substrates - Hormones - Nervous System to the liver, adipose, muscle and brain

Answer 15

- Metabolism also under hormonal control - Insulin --> uptake of glucose, dec glucose synthesis - Glucagon --> release of glucose inc glucose synthesis - Epinephrine --> inc glucose synthesis