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7/31/2019 09 Metabolism Part 2
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BIOENERGETICS Part 2HOW THE BODY CONVERTS FOOD TO ENERGY
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GLUCONEOGENESIS
Production of glucose from non-carbohydrate sources
Lactate
All amino acids except leucine and lysine
Glycerol from fats
Amino acids and glycerol are used only understarvation conditions
Occurs primarily in the liver
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CORI CYCLE
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GLYCOGENESIS
Formation of glycogen from glucose
Occurs in the liver
Influenced by insulin
Inhibits glycogen phosphorylase
Stimulates glycogen synthase andglucokinase
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GLYCOGENOLYSIS
Breakdown of stored glycogen to formglucose
Influenced generally by glucagon andepinephrine in response to low bloodglucose levels
Glycogen phosphorylase is activated
Glycogen synthase is inhibited
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(2) CITRIC ACID CYCLE
Also known as the Krebs Cycle
Final stage of the breakdown of
carbohydrates, fats, and amino acids.
Series of enzymes involved
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KETONES
Formed from beta-oxidation pathway offatty acid metabolism due to low level ofglucose (starvation and fasting)
Low glucose supply slows down citricacid cycle
No glycolysis
No PEP production
Greatly reduced oxaloacetate production As a result, acetyl CoA builds up in the
body
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(3) OXIDATIVE PHOSPHORYLATION
Is a series of reactions which couples theoxidation of NADH and FADH2 to thephosphorylation of ADP to generate ATP
NADH = used to produce 3 ATPs
FADH2= used to produce 2 ATPs
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NUMBER OF ATP PRODUCED BY THECOMPLETE OXIDATION OF ONE MOLECULE
OF GLUCOSE
Glycolysis Substrate-level Phosphorylation 2 ATP
2 NADH x 2 ATP/cytoplasmic NADH 4 ATP
Conversion of 2 pyruvate molecules to 2acetyl CoA molecules
2 NADH x 3 ATP/NADH 6 ATP
Citric Acid Cycle
2 GTP x 1 ATP/GTP 2 ATP
6 NADH x 3 ATP/NADH 18 ATP
2 FADH2 x 2 ATP/FADH2 4 ATP
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CATABOLISM OF THE NITROGENOF AMINO ACIDS
Dietary proteins are hydrolyzed to aminoacids in digestion
Amino acids are primarily used tosynthesize new proteins
Cannot be stored, so excess amino acidsare catabolized for energy production inthe liver
1. Transamination2. Oxidative Deamination
3. Urea Cycle
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TRANSAMINATION
Amino acids transfer their amino group toalpha-ketoglutarate
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OXIDATIVE DEAMINATION
Oxidative deamination of glutamate
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UREACYCLE
Ammoniaisconvertedto urea
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CATABOLISM OF HEME
Red Blood Cells 80 120 days life span
Destroyed by the phagocytic cells
Hemoglobin is metabolized Globin is hydrolyzed to amino acids
Heme is oxidized to biliverdin andfinally reduced to bilirubin
Bilirubin enters the liver
Iron is preserved in ferritin and reused
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