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BIOB32H3 Lecture Notes - Nitrogen Balance, Brown Adipose Tissue, Evaporation

Biological Sciences
Course Code
Kenneth Welch

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Metabolism and Energetics
An Overview of Metabolism
•Metabolism is all the chemical reactions that occur in an organism
•Cellular metabolism
•Cells break down excess carbohydrates first, then lipids
•Cells conserve amino acids
•40% of the energy released in catabolism is captured in ATP
•Rest is released as heat
•Performance of structural maintenance and repairs
•Support of growth
•Production of secretions
•Building of nutrient reserves
Cells and Mitochondria
•cells provide small organic molecules for their mitochondria
•Mitochondria produce ATP used to perform cellular functions
Carbohydrate Metabolism
Most cells generate ATP through the breakdown of carbohydrates
•One molecule of glucose = two pyruvate ions, two ATP, two NADH
•Aerobic metabolism (cellular respiration)
•Two pyruvates = 34 ATP
The chemical formula for this process is
C6H12O6 + 6 O2 6 CO2 + 6 H2O
•The breakdown of glucose to pyruvic acid
•This process requires:
•Glucose molecules
•Cytoplasmic enzymes
•ATP and ADP
•Inorganic phosphate
•NAD (nicotinamide adenine dinucleotide)
•The overall reaction is:
Glucose + 2 NAD + 2 ADP + 2Pi
2 Pyruvic acid + 2 NADH + 2 ATP
Mitochondrial ATP Production
(cellular respiration)
•Pyruvic acid molecules enter mitochondria
•Broken down completely in TCA cycle

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•Hydrogen atoms passed to coenzymes
•Oxidative phosphorylation
Oxidative phosphorylation and the ETS
•Requires coenzymes and consumes oxygen
•Key reactions take place in the electron transport system (ETS)
•Cytochromes of the ETS pass electrons to oxygen, forming water
•The basic chemical reaction is:
2 H2 + O2 2 H2O
•Per molecule of glucose entering these pathways
•Glycolysis has a net yield of 2 ATP
•Electron transport system – yields approximately 28 molecules of ATP
•TCA cycle – yields 2 molecules of ATP
Synthesis of glucose and glycogen
•Synthesis of glucose from noncarbohydrate precursors
•Lactic acid, glycerol, amino acids
•Liver cells synthesis glucose when carbohydrates are depleted
•Formation of glycogen
•Glucose stored in liver and skeletal muscle as glycogen
•Important energy reserve
Lipid catabolism
•Lipids broken down into pieces that can be converted into pyruvate
•Triglycerides are split into glycerol and fatty acids
•Glycerol enters glycolytic pathways
•Fatty acids enter the mitochondrion
Lipid catabolism
•Breakdown of fatty acid molecules into
2-carbon fragments
•Enter the TCA
•Lipids and energy production
•Cannot provide large amounts in ATP in a short amount of time
•Used when glucose reserves are limited
•Almost any organic molecule can be used to form glycerol
•Essential fatty acids cannot be synthesized and must be included in diet
•Linoleic and linolenic acid
Lipid transport and distribution
•5 types of lipoprotein
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