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30 Cards in this Set
- Front
- Back
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What is glycolysis?
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first stage of glucose metabolism
only energy source in RBCs |
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What is the glucose paradox?
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direct vs. indirect pathways of liver glycogen synthesis
direct - direct uptake for liver glycogen formation indirect - degradation of glucose to lactate and conversion to glycogen in liver |
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How is blood glucose maintained during exercise?
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it's a constant challenge because of muscle uptake
liver increases output from 1.8mg/kg BM/min to 3.5mg/kg BM/min at 50% VO2 max |
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how does glycolysis work?
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split 6 carbon sugar in 2, 3 carbon carboxylic acids
dissociate an H+ and are therefore acids standard free energy of LDH is very high, therefore lactate production is inevitable if pyruvate is not immediately taken up by mitochondria |
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describe the NAD/NADH ration REDOX potential
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NAD serves to transport reducing equivalents within the cells
glycolysis involves reduction of NAD to yield NADH NADH shuttles H and e- to mitochondria |
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describe the formation of lactate or pyruvate
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depends on relative glycolytic and mitochondrial activities - not the presence of oxygen
lactate is formed simply because the LDH has the highest Vmax Keq of any glycolytic enzyme |
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What are the shuttle systems?
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malatae-aspartate and glycerol-phosphate
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what is the malate-aspartate shuttle system's role in glycolysis?
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shuttles reducing equivalents from the cytosol to the electron transport chain in mitchondria in the heart
produces 3 ATP (NADH) |
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what is the glycerol-phosphate shuttle system's role in glycolysis?
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it shuttle reducing equivalents from the cytosol to the electron transport chain in mitochondria in skeletal muscle
prduces 2 ATP (FADH) |
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What is the Intracellular lactate shuttle?
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lactate is the link between glycolytic and anaerobic metabolism
lactate shuttle transports NADH and substrate into mitochondria when glycolysis is fast lactate is then oxidized to pyruvate and pyruvate is then oxidized by the TCA cycle |
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what are the feed forward factors that control glycolysis?
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stimulation of glycogenolysis (epinephrine and contraction) and glucose uptake (contractions and insulin) stimulate enzymes to increase G6P levels
known as coarse gain |
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what are the feed back factors that control glycolsis?
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involves changes in metabolite levels that result from glycolysis
known as fine tuning |
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what is the most important feedback control?
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decline in blood glucose which usually resides in PFK - rate limiting enzym in muclse when glycolysis is rapid - and results in stimulation or inhibition
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how does the cellular energy charge control glycolysis?
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if ATP level is high, adenylate energy charge is high
If it's low, ATP is degraded to ADP and AMP |
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how do the GLUT transporters affect glycolysis?
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at rest GLUT-1 non-insulin dependent
when insulin is high or during exercise, GLUT-4 transporters take up glucose and translocate from intracellular locations to the cell surface |
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What is the thermodynamic control of glycolysis?
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hexokinase, PFK, PK and LDH are all exergonic reactions that move the pathway to product formation
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what is the LDH control of glycolysis?
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has a high energy of activiation and Keq
lactate is always formed even in resting muslce most important factor determining whether a tissue is a consumer or producer of lactate is the presence of LDH in mitochondria |
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what is PDH control of glycolysis?
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PDH is regulated by phosphorylation in mitochondria
when PDH is active, lactate can be diverted to the mitochondria competes with LDH for pyruvate and thus indirectly afect NADH/NAD and the rate of glycolysis |
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how does the redox of NADH/NAD control glycolysis?
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the ratio affects G-3PD whichr equires NADH as a cofactor
increased NADH/NAD slows glycolysis, and descreased NADH/NAD speeds glycolysis |
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what is glycogenolysis?
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glycogen breakdown
80% of glucose comes from this |
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how does glycogenolysis control glycolysis?
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during exercise glycogen is the major precursor for glycolysis
glycogen breakdown at 65% VO2 max can exceed glucose uptake by 4-5x |
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how does the phophorylase enzyme control glycogenolysis?
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it is hormonally mediated (EP,cAMP)
Pi and calcium ion and AMP speed up phosphorylase during heavy exercise cAMP - amplifies Pi and calcium effects and mobilizes glycogen in inactive muslce to provide lactate as a fuel and a gluconeogenic (cori cycle) precursor |
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what is the cell-cell lactate shuttle?
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lacatate is shuttle from type IIb fibers to type I fibers for use which diffuses to adjacent type I fibers
much of the lactate produced is consumed in the muscle it is produced |
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what is the MCT protein?
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transports lactate between lactate producing and lactate consuming muscle
MCT1 is mitochondrial lactate/pyruvate transporter training increases amount of mitochondrial and sarcolemmal MCT1 |
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what is gluconeogenesis?
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there is little capacity for formation of glucose in muslce and it participates in gluconeogenesis via cori cycle
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what are the effects of training on glycolysis?
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significant increase in hexokinase, decreases total LDH activity but increases Mitochondrial LDH content
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what is good about the significant hexokinase increase that comes with endurance training?
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it facilitates entry of sugars from blood into the glycolytic pathway of muscle
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what is good about the decrease in total LDH activity but the increase in mitchondrial LDH content
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it decreases lactate accumulation and allows some muscle fibers to take up and oxidize lactate produced in other fibers
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describe glucose use during exercise
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increases with increasing exercise intensity
after training at some absolute intensity glucose use decreases only 10-25% of CHO energy protective mechanism to prevent fall in blood glucose muscle relies on endogenous glycogen and lactate shuttle |
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what are the effects of exercise and endurance training on lactate concentration, appearance and clearance rates?
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exercise increases lactate concentration but training decreases lactate concentration measured at absolute or relative exercise intensities
lactate appearance is related to metabolic rate training results in better clearance due to increased MCT |
