chapter7
TRANSCRIPT
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Energy Energy MetabolismMetabolism
Chapter 7Chapter 7
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IntroductionIntroduction
• Energy• Heat, mechanical, electrical, chemical
• Photosynthesis• Metabolism
• Release of energy, water, and carbon dioxide
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Chemical Reactions in the Chemical Reactions in the BodyBody
• Energy metabolism• How body obtains & uses energy from food
• Cells• Liver cells
• Anabolism • Requires energy
• Catabolism• Releases energy
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A Typical CellA Typical Cell
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Anabolic and Catabolic Anabolic and Catabolic Reactions ComparedReactions Compared
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Chemical Reactions in the Chemical Reactions in the BodyBody
• Transfer of energy in reactions – ATP • Released during breakdown of glucose, fatty
acids, and amino acids• Form of phosphate groups
• Negative charge – vulnerable to hydrolysis
• Provides energy for all cell activities• Coupled reactions
• Efficiency
• Heat loss
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Capture and Release of Energy Capture and Release of Energy by ATPby ATP
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Chemical Reactions in the Chemical Reactions in the BodyBody
• Enzymes • Facilitators of metabolic reactions
• Coenzymes• Organic• Associate with enzymes• Without coenzyme, an enzyme cannot
function
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Breaking Down Nutrients for Breaking Down Nutrients for EnergyEnergy
• Digestion• Carbohydrates – glucose (& other
monosaccharides)• Fats (triglycerides) – glycerol and fatty acids• Proteins – amino acids
• Molecules of glucose, glycerol, amino acids, and fatty acids• Catabolism
• Carbon, nitrogen, oxygen, hydrogen
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Breaking Down Nutrients for Breaking Down Nutrients for EnergyEnergy
• Two new compounds• Pyruvate
• 3-carbon structure
• Can be used to make glucose
• Acetyl CoA• 2-carbon structure
• Cannot be used to make glucose
• TCA cycle and electron transport chain
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Simplified Overview of Energy-Simplified Overview of Energy-Yielding PathwaysYielding Pathways
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Breaking Down Nutrients for Breaking Down Nutrients for Energy – Glucose Energy – Glucose
• Glucose-to-pyruvate• Glycolysis
• 2 pyruvate molecules
• Hydrogen atoms carried to electron transport chain
• Pyruvate can be converted back to glucose• Liver cells and kidneys (to some extent)
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Breaking Down Nutrients for Breaking Down Nutrients for Energy – Glucose Energy – Glucose
• Pyruvate’s options• Quick energy needs – anaerobic
• Pyruvate to lactate
• Slower energy needs – aerobic• Pyruvate to acetyl CoA
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Breaking Down Nutrients for Breaking Down Nutrients for Energy – Glucose Energy – Glucose
• Pyruvate-to-lactate• Pyruvate accepts hydrogens
• Converts pyruvate to lactate
• Occurs to a limited extent at rest• Produces ATP quickly
• Mitochondrial ability
• Accumulation of lactate in muscles• Effects
• Cori cycle
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Pyruvate-to-Lactate Pyruvate-to-Lactate
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Breaking Down Nutrients for Breaking Down Nutrients for Energy – Glucose Energy – Glucose
• Pyruvate-to-Acetyl CoA• Pyruvate enters mitochondria of cell
• Carbon removed – becomes carbon dioxide
• 2-carbon compound joins with CoA becoming acetyl CoA – irreversible
• Acetyl CoA pathways
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Pyruvate-Acetyl CoA Pyruvate-Acetyl CoA
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The Paths of Pyruvate and The Paths of Pyruvate and Acetyl CoA Acetyl CoA
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Glucose Enters the Energy Glucose Enters the Energy Pathway Pathway
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Breaking Down Nutrients for Breaking Down Nutrients for Energy – Glycerol & Fatty Acids Energy – Glycerol & Fatty Acids
• Glycerol-to-pyruvate• Glycerol can be converted
• Glucose
• Pyruvate
• Fatty acids-to-Acetyl CoA• Fatty acid oxidation
• 2-carbon units at a time then join with CoA
• Hydrogens and electrons carried to electron transport chain
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Fatty Acids-to-Acetyl CoA Fatty Acids-to-Acetyl CoA
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Fats Enter the Energy Pathway Fats Enter the Energy Pathway
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Breaking Down Nutrients for Breaking Down Nutrients for Energy – Amino AcidsEnergy – Amino Acids
• Deamination of amino acids • Amino acids-to-energy
• Several entry points in energy pathway• Converted to pyruvate (glucogenic)
• Converted to acetyl CoA (ketogenic)
• Enter TCA cycle directly (glucogenic)
• Amino acids-to-glucose
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Review of Energy-Yielding Nutrient Endpoints
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Final Steps of Energy Final Steps of Energy MetabolismMetabolism
• TCA Cycle• Inner compartment of mitochondria• Circular path
• Acetyl CoA
• Oxaloacetate – made primarily from pyruvate
• Carbon dioxide release• Hydrogen atoms and their electrons
• Niacin and riboflavin
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Final Steps of Energy Final Steps of Energy MetabolismMetabolism
• Electron transport chain• Captures energy in ATP• Series of proteins
• Electron “carriers”
• Inner membrane of mitochondria
• Electrons passed to next carrier• Join oxygen at end of chain – water released
• ATP synthesis
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Final Steps of Energy Metabolism
• kCalorie-per-gram secret• Fat provides most energy per gram• Carbon-hydrogen bonds • More ATP = more kcalories
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Feasting – Excess Energy Feasting – Excess Energy
• Metabolism favors fat formation• Regardless of excess from protein, fat, or
carbohydrates• Excess protein
• Excess carbohydrate
• Excess fat – most direct and efficient conversion
• Fuel mix
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Transition from Feasting to Transition from Feasting to Fasting Fasting
• Glucose, glycerol, and fatty acids are used then stored• Fasting state draws on these stores
• Glycogen and fat are released
• Basal metabolism • Fasting versus starving
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Feasting and Fasting Feasting and Fasting
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Fasting – Inadequate EnergyFasting – Inadequate Energy
• Carbohydrate, fat, and protein are all eventually used for energy
• Begin with release of glucose and fatty acids• Acetyl CoA
• Low blood glucose levels signal • Fat breakdown• Release of amino acids from muscles
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Fasting – Inadequate EnergyFasting – Inadequate Energy
• Adaptation: making glucose• Nervous system and red blood cells
• Amino acids yielding pyruvate
• Breakdown of body proteins
• Adaptation: creating an alternate fuel• Use fat to fuel brain
• Ketone bodies
• Slows the rate of body protein breakdown
• Ketosis induces a loss of appetite
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Ketone Body FormationKetone Body Formation
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Energy Balance – FastingEnergy Balance – Fasting
• Adaptation: conserving energy• Hormones• Reduces energy output• Supports weight loss but not fat loss• Symptoms of starvation
• Physical symptoms
• Psychological symptoms
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Low-Carbohydrate DietsLow-Carbohydrate Diets
• Metabolism similar to fasting• Uses glycogen stores first• Gluconeogenesis when glycogen is depleted
• Body tissues used somewhat even when protein provided in diet
• Urine monitoring• Ketosis
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Adverse Side Effects of Low-Carbohydrate, Ketogenic Diets
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Alcohol in the Alcohol in the BodyBody
Highlight 7Highlight 7
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Alcohol in the BodyAlcohol in the Body
• Potential health benefits
• Alcohols• Glycerol
• Ethanol
• Lipid solvents• Moderation
• Definition of “drink”
• Proof
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AlcoholAlcohol’’s Influences Influence
• Alcohol’s special privileges• No digestion• Quick absorption
• Slowing absorption
• Stomach• Alcohol dehydrogenase
• Small intestine• Priority over nutrients
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AlcoholAlcohol’’s Influences Influence
• In the liver• Liver cells
• First to receive alcohol-laden blood
• Alcohol dehydrogenase• Disrupts liver activity• Can permanently change liver cell structure• Rate of alcohol metabolism
• Acetaldehyde
• Acetate
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Alcohol MetabolismAlcohol Metabolism
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AlcoholAlcohol’’s Influence s Influence
• In the liver• Niacin coenzyme
• Glycolysis
• TCA cycle
• Electron transport chain
• Development of fatty liver• Damage to central nervous system• Inflammation of joints• Amino acid and protein metabolism
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Alternate Route for Acetyl Alternate Route for Acetyl CoA: To FatCoA: To Fat
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AlcoholAlcohol’’s Influence s Influence
• In the liver• Immune system functioning• Alcohol interferes with drug metabolism
• Microsomal ethanol-oxidizing system (MEOS)
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AlcoholAlcohol’’s Influences Influence
• In the brain• Sedates inhibitory nerves
• Acts as central nervous system depressant
• Blood alcohol levels and brain responses• Death of liver and brain cells• Depression of antidiuretic hormone (ADH)
• Loss of body water
• Loss of important minerals
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AlcoholAlcohol’’s Effects on the Brains Effects on the Brain
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Alcohol Doses & Approximate Blood Level Percentages for Men & Women
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Alcohol Blood Levels and Alcohol Blood Levels and Brain ResponsesBrain Responses
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AlcoholAlcohol’’s Damages Damage
• Dehydration• Antidiuretic hormone (ADH)• Water loss
• Loss of minerals
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Alcohol’s Damage
• Malnutrition • Can contribute to body fat and weight gain
• 1 ounce of alcohol represents 0.5 ounce of fat
• Central obesity• Substituted energy
• 7 kcalories per gram
• Nutrient displacement• B vitamins
• Wernicke-Korsakoff syndrome
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AlcoholAlcohol’’s Effectss Effects
• Short-term effects• Excessive drinking
• Heavy drinking
• Binge drinking
• Long-term effects• Third leading preventable cause of death in
U.S.
• Sobering up
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Signs of Alcoholism
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