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13 Cards in this Set
- Front
- Back
۞ -----CHO:
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• Primary metabolic fuel for humans is glucose
o Diet CHO o Body glycogen stores o Biosynthesis from non-hexose precursors • Constant rate of blood glucose balance between; o Glucose oxidation o Glucose biosynthesis o Glucose storage |
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۞ -----CHO:
Pathway of glucose metabolism varies with the type of cell and physiological demand |
• Liver plays a central role
~ Glucose can be oxidized for energy ~ Glucose can be stored as glycogen ~ Can supply carbons for biosynthesis of fatty acids or amino acids ~ Can release glucose from glycogen ~ Synthesize new glucose • Other tissues (Adipose tissue, skeletal and heart muscle and brain) respond to changes in glucose by altering their internal usage but do not contribute to whole body homeostasis ~ Skeletal muscle and heart glucose can be completely oxidized or it can be stored as glycogen (for own use only not whole body) ~ Adipose tissue under conditions of need release fatty acids to blood supply. ****** Brain is completely dependent on a continuous glucose supply |
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۞ -----CHO:
Glycolysis – breakdown of glucose for energy; (2 pathways) |
anaerobic breakdown= 6-8 atp
aerobic = 4-6 ATP |
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۞ -----CHO:
Glycolysis – breakdown of glucose for energy anaerobic |
1. anaerobic breakdown of glucose to pyruvate in the cytosol of the cell
a. 1 molecule of glucose to 2 molecules of pyruvate ( 4 molecules of ATP produced and 2 molecules of ATP used: net gain 2 ATP *****net gain 2 ATP****** |
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۞ -----CHO:
Glycolysis – breakdown of glucose for energy citric acid cycle |
2. citric acid cycle in mitochondria,is dependent on oxygen, in absence of enough oxygen lactate is formed – can be completely metabolized to CO2 and H2O via the Krebs cycle
****NET GAIN |
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۞ -----CHO:
Glycolysis – breakdown of glucose for energy krebs cycle |
3. Total oxidation via Krebs cycle leads to Total net ATP 38 (acetyl CoA = 2 CO2, 3 molecules of NADH; 3 ATP each and 1 molecule FADH; 2 ATP or 11 ATP). One molecule of ATP produced from GTP by substrate-level phosphorylation at succinyl CoA synthetase step) Total is 12 ATP. There are 3 acetyl CoA for each molecule of glucose or 36 ATP plus 2 ATP from step #1.
36 to 38 ATP |
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۞ -----CHO:
Gluconeogenesis |
– produce glucose from pyruvate, lactate, glycerol and some amino acids.
• This is essentially a reversal of glycolysis, except that not all of the steps were reversible • Occurs primarily in the liver (90%) and to some extent in the kidney (10%) • Critical for tissues that depend on constant level of glucose (brain, CNS, RBC) • Absence of dietary CHO body stores of glycogen depleted in about 18-24 hours, then liver must form new glucose • Hormonal triggers to synthesize glucose from non-glucose sources |
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۞ -----Cori cycles
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• Cori cycle – lactate generated from pyruvate is released from muscle to RBC, transported to liver, converted back to pyruvate and can be used to generate glucose and sent back to the muscle
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۞ -----alanine cycles
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• Alanine cycle – in the muscle alanine is generated from transamination of pyruvate and released. Liver cells deaminate the alanine to pyruvate, substrate for gluconeogenesis, new glucose sent back to the muscle
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۞ -----Glycogen Metabolism
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• Glucose is stored in liver and muscle as glycogen
• Glycogen is a branched chain polymer of glucose • Liver can store 10% of its weight • Muscle about 1% of its weight • Muscle mass is larger than liver so muscle glycogen accounts for twice as much glycogen as contained in the liver • Stored in postprandial state • When blood glucose declines first to be degraded - Glycogenolysis |
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۞ -----Glycogenolysis
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• Liver depleted of glycogen in 18-24 hours
• Glucagon from pancreas promotes glycogen breakdown • Epinephrine from the adrenal medulla promotes glycogen breakdown in both liver and skeletal muscle • Glucagon and epinephrine are insulin antagonists • Muscle uses the glycogen breakdown for its own use • Liver breaks down the glycogen for use by entire body • In skeletal muscle (no glucagon receptors) |
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production atp
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***krebs cycle and ETC= 38-38 ATP
***glycolisis step 1 = 6 to8 ATP ***2 NADH from pyruvate to ACOA = up tp 6 **** |
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from one unit of glucose
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step 1= 6 to 8 atp
step 2 = 6+ atp step 3= 24 atp |