Metabolism

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Metabolism

• Chapter 24
• Biology 2122

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Metabolism overview

• 1. Metabolism
• Anabolic and Catabolic Reactions
• 2. Cell respiration -catabolic reaction
• 3. Metabolic pathways
• 4. Cell Respiration
• Digestion and absorption of nutrients
• In the cell anabolic process build up lipids,
  proteins, glycogen
• Aerobic respiration in the mitochondria will
  produce ATP

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Important Aspects of Metabolism

• 1. Metabolic pathways enzyme mediated
• 2. Glucose is oxidized
• other compounds are reduced.
• 3. Coenzymes become reduced
• compounds electron and proton carriers.
• 4. Phosphorylation
• Hydrolysis of ATP
• Transfer of an inorganic phosphate from ATP

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Oxidation and reduction

• 1. Glucose - oxidized in the cell
• C6H12O6 6O2 ---------? 6CO2 6H2O ATP Heat
  
• Oxidation
• gain of oxygen or loss of a hydrogen
• Loss of electrons
• Reduction - gain of hydrogen and electrons
• Cellular respiration oxygen is reduced
• Any compound that receives electrons and
  hydrogens are reduced
• OIL RIG
• Dehydrogenases
• Enzymes that remove hydrogen atoms from organic
  compounds

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Role of coenzymes

• When hydrogen and electrons are being transferred
  from one compound to another, which compounds
  will accept them?
• 2. Coenzymes
• Organic compounds (enzyme with a vitamin)
• NAD (nicotinamide adenine dinucleotide) (niacin)
• FAD (flavin adenine dinucleotide) (flavin)
• 3. What will they do after they are reduced?
• Carry hydrogen and electrons to the electron
  transport chain and unload them
• Final production of ATP

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Phosphorylation and ATP synthesis

• Transfer of a phosphate group to another compound
  
• Metabolic pathways
• Produce ATP
• Substrate-level phosphorylation
• Oxidative phosphorylation

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ATP formation
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Glycolysis

• In the Box
• Glucose (6-C) and Oxygen

• Out of the Box
• Pyruvic Acid (3-C)

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Glycolysis

• 1. Sugar Activation
• 2. Sugar Cleavage
• Fructose 1,6-bisphosphate splits into (2) 3-C
  compounds
• 3. ATP and Pyruvate formation
• Final produce is (2) 3-C pyruvate
• Net Totals
• 2 ATP 2 NADH H

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Preparing for the Krebs cycle

• 1. What happens to the 3-C pyruvate?
• 2. If oxygen is not available (anaerobic)
• Undergo lactic acid fermentation
• Only 2 ATP produce and lactic acid which causes
  soreness in the muscles
• 3. If oxygen is available (aerobic) then pyruvate
  is processed
• In the cytosol of mitochondria pyruvate loses a C
  (CO2) and becomes acetic acid decarboxylation
• Coenzyme A attaches to Acetic Acid ---?2-C Acetyl
  CoA

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Krebs cycle

• In the Box
• Acetyl CoA

• Out of the Box
• CO2
• FADH2
• NADH
• ATP

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Krebs cycle

• 2-C acetyl CoA is picked up by 4-C oxaloacetate
• 6-C compound - citric acid
• Formation of intermediates
• 1. Reactions
• Decarboxylation
• substrate-level phosphorylation produces ATP
• Reduction of FADH2 and NADH H
• 2. Net (Remember the cycle turns twice)
• 2 ATP, 8 NADH, 2 FADH2 , 6 CO2

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Oxidative phosphorylation

• In the Box
• NADH
• FADH2

• Out of the Box
• ATP

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Electron transport chain and oxidative
phosphorylation

• NADH H and FADH2 lose their electrons
• Hydrogen
• When hydrogen ions are released they are move
  through channel proteins from the mitochondrial
  matrix to the intermembrane space
• They form an electrochemical gradient
• Electrons
• Accepted by flavins, proteins that contain Fe and
  S, cytochromes (pigments with Fe)
• They are passed from one to the other down the
  chain
• Finally accepted by ½ O2 to produce water
• Movement of these electrons provide the energy to
  drive the hydrogen ions across the membrane

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Chemiosmosis

• Hydrogen ions will move passively through ATP
  synthase
• 2. As they move through, the protein spins
  providing energy to phosphorylate ADP and
  produce ATP
• 3. A total of 34 ATP are produced
• 1 Glucose 36 net ATP (2-Krebs 2 Glycolysis)

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Summary
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Glycogenesis and Glycogenolysis

• Excess ATP is accumulated
• Glycolysis declines
• Excess glucose stored as glycogen or fat
• Glycogenesis occurs
• Glycogenolysis
• Glucose blood levels drop
• Glycogen phosphorylase
• Muscle cells
• Glucose-6 phosphate cannot move across the
  membrane
• Glucose-6-phosphatase

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Gluconeogenesis/Lipid oxidation

• When glucose levels are very low the liver can
  synthesize glucose
• Amino acids glycerol to produce glucose
• Prevents hypoglycemia
• Lipid Metabolism
• More energy than carbohydrates (9 kcal/g)
• Glycerol (from neutral fats)--? glyceraldehyde
  phosphate --? Krebs (18 ATP/glycerol)
• F.A. (from neutral fats)-----? 2-C acetic acid
  CoA (coenzyme A) ---? acetyl CoA -------?Krebs
• Beta oxidation

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Lipid oxidation
TRIGLYCERIDE METABOLISM Animation
BETA-OXIDATION
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Lipid metabolism

• Lipogenesis
• excess lipids are not metabolized will be stored
  as adipose in the hypodermis (50) as well as
  other parts of the body
• Lipogenesis or triglyceride synthesis
• occurs when ATP and glucose levels are high
  (enough energy available to the cells)
• Lypolysis breaking down of stored fats
• Glycerol converted to energy
• Fatty acids

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What happens if you deny yourself carbohydrates?

• 1. If carbohydrate levels are low
• 2. Oxaloacetic acid is converted to glucose
  (fuels the brain).
• 3. Oxaloacetic acid levels become low and acetyl
  CoA cannot enter the Krebs cycle
• Ketogenesis and ketone bodies
• Ketosis - ketone bodies accumulate in the urine
• pH levels drops to dangerous levels

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Protein metabolism

• Deamination before proteins can be oxidized for
  energy must lose ammine group
• Converted to pyruvate or intermediates of the
  Krebs
• Events (notes)
• 1. transamination
• 2. oxidative deamination
• 3. ketoacid modification

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Interconversions
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Absorptive states
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Post-absorptive state
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Insulin
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Glucagon and glucose
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Liver Metabolism and cholesterol

• Cholesterol - Animation
• is an important component of bile salts
  formation of vitamin D, plasma membrane and
  steroid hormones
• 15 from the diet - the rest is made from acetyl
  CoA in the liver, intestinal cells
• Cholesterol and Triglycerides are insoluble in
  water
• Transported via lipoproteins
• Proteins regulate lipid entry and exit in the
  cells
• Types are HDL (high protein) LDL (lower
  protein) VLDL Chylomicrons

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Cholesterol transport

• 1. Liver produces VLDL ---? transport
  triglycerides to adipose and other tissues
  ------?converted to LDL (much cholesterol)------?
  transports cholesterol to peripheral tissues
• 2. HDL transports excess cholesterol from
  peripheral tissues to liver ---? broken down and
  becomes parts of bile
• 3. HDL is made in a collapsed form -----? moves
  from liver to blood and picks up cholesterol
  from the tissue cells and some pulled from
  artery walls

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Cholesterol Levels

• 1. Liver will stimulate the production of a basal
  amount of cholesterol (85)
• Dieting will not override genetics up to a
  certain point
• 2. Saturated fats ------? stimulate liver
  production of cholesterol and inhibit secretion
• 3. Unsaturated fats -------? increase excretion
  of cholesterol
• Hydrogenation and trans-fatty acids
• Omega 3s lower cholesterol levels fatty fish
• Levels
• HDL (lt130) is good LDL (gt60) is good

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Feeding centers
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Body temperature regulation