Wk5ch7
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Transcript of Wk5ch7
IntroductionIntroduction
• Energy• Heat, mechanical, electrical, chemical
• Photosynthesis• Metabolism
• Release of energy, water, and carbon dioxide
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
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
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
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
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
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)
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
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
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
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
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
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
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
Final Steps of Energy Metabolism
• kCalorie-per-gram secret• Fat provides most energy per gram
• Carbon-hydrogen bonds • More ATP = more kcalories
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
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
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
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
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
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
Alcohol in the BodyAlcohol in the Body
• Potential health benefits
• Alcohols• Glycerol
• Ethanol
• Lipid solvents• Moderation
• Definition of “drink”• Proof
AlcoholAlcohol’s Influence’s Influence
• Alcohol’s special privileges• No digestion
• Quick absorption• Slowing absorption
• Stomach• Alcohol dehydrogenase
• Small intestine• Priority over nutrients
AlcoholAlcohol’s Influence’s 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
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
AlcoholAlcohol’s Influence ’s Influence
• In the liver• Immune system functioning
• Alcohol interferes with drug metabolism• Microsomal ethanol-oxidizing system (MEOS)
AlcoholAlcohol’s Influence’s 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
AlcoholAlcohol’s Damage’s Damage
• Dehydration• Antidiuretic hormone (ADH)
• Water loss• Loss of minerals
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
AlcoholAlcohol’s Effects’s Effects
• Short-term effects• Excessive drinking
• Heavy drinking
• Binge drinking
• Long-term effects• Third leading preventable cause of death in
U.S.
• Sobering up