Transcript Nutrient Role in Bioenergetics

Nutrient Role in Bioenergetics
Chapter 4 Part 2
Bioenergetics-Glycolysis
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Carbohydrates primary function
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Energy for cellular work.
Breakdown of 1 mole of glucose
liberates 686 kCal of energy.
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233 kCal (34%) usable
The remainder dissipated as heat.
Bioenergetics
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Glucose Degradation - glycolysis
Occurs in two stages:
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1. Anaerobic: Glucose breaks down
relatively rapidly to 2 molecules of
pyruvate → lactate
2. Aerobic: Pyruvate degrades further to
carbon dioxide and water.
Glycolysis
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Occurs in cytoplasm
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ATP required as phosphate donor
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Enzymes
Glucose → glucose-6-phosphate
ATP required as phosphate donor
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Fructose 6-phosphate
Glycogenolysis
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Catabolism of muscle glycogen
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Glycogen phosphorylase
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Glucose-6-phosphate
Epinephrine
Glycolysis
Glycolysis
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Hydrogen ions released during
glycolysis
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NAD → NADH
Additional 5 ATP molecules (ETC)
Bioenergetics
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Aerobic glycolysis
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C3H4O3 – pyruvic acid
Rest, light to moderate levels
Hydrogen + Oxygen → H2O
Bioenergetics
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Anaerobic
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NAD availability
Lactate formation
C3H4O3 + 2H+ → C3H6O3
Pyruvic
Lactic
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Acid
Acid
Bioenergetics
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Aerobic
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C3H4O3 + 2H+
Pyruvic
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Acid

C3H6O3
Lactic
Acid
The Cori Cycle: Lactate As a Fuel
Source
Fig 4.16
Bioenergetics
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Citric Acid Cycle (Krebs cycle).
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The second stage of carbohydrate
breakdown
Pyruvate converts to acetyl-CoA,
degrades
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Carbon dioxide and hydrogen atomsmitochondria
Most important function
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Generate H ions for Electron Transport Chain
(ETC)
Bioenergetics
Bioenergetics
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Stored fat
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Largest source of potential energy.
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Supplies fatty acid molecules
Energy sources for fat catabolism
include:
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Triacylglycerol
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Muscle fiber - stored
Lipoprotein complexes - circulating
Free fatty acids - circulating
Bioenergetics
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Energy metabolism – lipolysis
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FFA + glycerol
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Form intracellular triglycerides
Bind with intramuscular proteins
Bioenergetics
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Adenosine 3’,5’-cyclic monophosphate
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Cyclic AMP -
Hormonal effects
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Epinephrine, norepinephrine, glucagon,
and growth hormone
Bioenergetics
Bioenergetics
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Glycerol
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Provides carbon skeletons for glucose
synthesis
Fatty acids
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Beta (ß)-oxidation converts a free fatty
acid to multiple acetyl-CoA molecules.
Hydrogen ions oxidized through the
respiratory chain.
Bioenergetics
Fats in CHO Flame
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FA breakdown requires CHO
breakdown
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Intermediates of citric acid cycle
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Oxaloacetate (pyruvate)
Malate
Bioenergetics
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Lipogenesis
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The formation of fat
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Cytoplasm of liver cells
Excess glucose or protein not metabolized
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Converted into stored triacylglycerol
The lipogenic process requires:
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ATP energy
B vitamins
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Biotin, niacin, and pantothenic acid.
Bioenergetics
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Protein
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Energy substrate
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Endurance activities
Heavy trainings.
Deamination: Nitrogen removed from
amino acid
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Pyruvate
FA synthesis
Bioenergetics
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Protein
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Catabolism facilitates water loss.
The amine group of protein breakdown
must be eliminated.
“Obligatory” water as the waste products
of protein catabolism leave the body
dissolved in fluid (urine).
Bioenergetics
Bioenergetics
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Metabolic Mill
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The citric acid cycle
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Link
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Food energy and the chemical energy of ATP.
Intermediates
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Mitochondrial membrane into the cytosol to
synthesize bionutrients.
Metabolic Mill