FOOD20003 Lecture Notes - Lecture 18: Glycogenesis, Glycerol, Acetyl-Coa
28 Jun 2018
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ENERGY METABOLISM
• All three macronutrients = involved in energy metabolism
• Catabolic = breaking down (releases energy)
• Anabolic = making molecules (requires energy)
• Enzymes: facilitate chemical reactions without being changed
o Require organic co-enzyme (helper molecule)
§ Usually vitamins
• Some reactions are coupled: catabolic + anabolic
o Energy from catabolic reactions is captured by “go between” molecules that transfer energy to
other compounds for anabolic reaction (i.e. ATP)
o However, energy released from macronutrients breakdown must be captured in ATP first
GLYCOLYSIS – cytoplasm
• Glucose à 2x pyruvate
o Involves a number of metabolic steps & enzymes
o Pyruvate can be converted back to glucose
o Survival mechanism for when there’s a shortage in carbohydrates
• Yields small amount of energy à inefficient
KREB/TCA/Citric CYCLE – mitochondrial matrix
• Pyruvate moves into mitochondria
• Pyruvate à acetyl CoA + CO2
o Irreversible
o Acetyl CoA can enter the TCA cycle
o or multiple acetyl-CoA joined together à fatty acids if energy is not required
• acetyl-CoA metabolised in aerobic environment – circular pathway
o CO2 = by product
o Bonds broken = release of high energy electrons à binds to H
o Carried to ETC by NADH & FADH2 (coenzymes)
• Must be complemented with new raw material (acetyl-CoA & oxaloacetate)
Cori Cycle:
• during exertion, O2 is inadequately supplied to the mitochondria
• pyruvate converted to lactic acid
• Lactic acid build-up:
o Goes back to the liver
o Enzymes convert it back to glucose
o Requires energy
ELECTRON TRANSPORT CHAIN – inner membrane surface
• Series of proteins mounted in a sequence
• As each carrier protein receives an electron à removes some energy & pass it along to the next protein
o Energy captured = ATP
o At the end of the chain – low energy electrons + oxygen + hydrogen à water
Document Summary
Energy metabolism: all three macronutrients = involved in energy metabolism, catabolic = breaking down (releases energy, anabolic = making molecules (requires energy, enzymes: facilitate chemical reactions without being changed, require organic co-enzyme (helper molecule) Glycolysis cytoplasm: glucose 2x pyruvate. Involves a number of metabolic steps & enzymes: pyruvate can be converted back to glucose, survival mechanism for when there"s a shortage in carbohydrates, yields small amount of energy inefficient. Kreb/tca/citric cycle mitochondrial matrix: pyruvate moves into mitochondria, pyruvate acetyl coa + co2. Cori cycle: during exertion, o2 is inadequately supplied to the mitochondria, pyruvate converted to lactic acid, lactic acid build-up, goes back to the liver, enzymes convert it back to glucose, requires energy. If energy not required, acetyl-coa are re-joined to form fa for storage fat. Protein metabolism: protein can also yield energy, amino acids broken down and nitrogen group removed.
