Ch 14 Metabolism
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Ch 14 Metabolism






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    Ch 14 Metabolism Ch 14 Metabolism Presentation Transcript

    • Chapter 14 The Digestive System and Body Metabolism
      • Nutrients – used for growth, maintenance & repair
        • Carbohydrates - Most from plants; Exceptions: lactose from milk and some glycogens from meats
        • Lipids - Saturated fats from animals, Unsaturated fats from plants, Cholesterol from egg yolk, meats, and milk products
        • Proteins - Complete proteins –all essential amino acids, Most from animals, Legumes and beans also have proteins, but are incomplete
        • Vitamins - used as cofactors and act with enzymes, in all major food groups
        • Minerals - many roles in the body, mineral-rich foods are vegetables, legumes, milk, and some meats
        • Water
      • Metabolism
      • Chemical reactions necessary to maintain life
      • Catabolism – substances are broken down to simpler substances
      • Anabolism – larger molecules are built from smaller ones
      • Energy is released during catabolism
      • Carbohydrate Metabolism
      • The body’s preferred source to produce cellular energy (ATP)
      • Glucose (blood sugar) is the major breakdown product and fuel to make ATP
      • Fat Metabolism
      • Handled mostly by the liver
        • Use some fats to make ATP
        • Synthesize lipoproteins, thromboplastin, and cholesterol
        • Release breakdown products to the blood
      • Body cells remove fat and cholesterol to build membranes and steroid hormones
      • Protein Metabolism
      • Proteins are conserved by body cells because they are used for most cellular structures
      • Ingested proteins are broken down to amino acids
      • Cells remove amino acids to build proteins
      • Synthesized proteins are actively transported across cell membranes
      • Amino acids are used to make ATP only when proteins are overabundant or there is a shortage of other sources
      • Role of the Liver in Metabolism
      • Detoxifies drugs and alcohol
      • Degrades hormones
      • Produce cholesterol, blood proteins (albumin and clotting proteins)
      • Plays a central role in metabolism
      • Converts ammonia to urea which is eliminated in urine
      • Metabolic Functions of the Liver
      • Cholesterol Metabolism
      • Functions of cholesterol
        • Structural basis of steroid hormones & vit D
        • Major building block of plasma membranes
      • Most cholesterol is produced in the liver and is not from diet
      • Cholesterol Transport
      • Cholesterol and fatty acids cannot freely circulate in the bloodstream
      • They are transported by lipoproteins (lipid-protein complexes)
        • Low-density lipoproteins (LDLs) transport to body cells
        • High-density lilpoproteins (HDLs) transport from body cells to the liver
      • Body Energy Balance
      • Energy intake = total energy output
      • = (heat + work + energy storage)
        • Energy intake is liberated during food oxidation
        • Energy output
          • Heat is usually about 60%
          • Storage energy is fat or glycogen
      • Metabolic Rate & Body Heat Production
      • Basic metabolic rate (BMR) – amount of heat produced by the body per unit of time at rest
      • Influencing factors:
      • Surface area – small body
      • higher BMR
      • Gender – males higher BMR
      • Age – children & adolescents
      • higher BMR
      • Thyroxine - most important control factor
      • Total Metabolic Rate (TMR)
      • Total amount of kilocalories the body must consume to fuel ongoing activities
      • TMR increases with an increase in body activity
      • TMR must equal calories consumed to maintain homeostasis and maintain a constant weight
      • Body Temperature Regulation
      • Most energy is released as foods are oxidized
        • - Protein – 4 Kcal/g
        • - Carbs – 4 Kcal/g
        • - Fats – 9 Kcal/g
      • Most energy leaves as heat
      • body temp 35.6° - 37.8°C (96° to 100° F)
      • thermostat is hypothalamus
      • - Initiates heat-loss or heat-promoting mechanisms
      • Heat Mechanisms
      • Heat Promoting Mechanisms
        • Vasoconstriction of blood vessels
        • Blood rerouted to deeper, more vital body organs
        • Shivering – contraction of muscles produces heat
      • Heat Loss Mechanisms
        • Heat loss from the skin via radiation and evaporation
        • Skin blood vessels and capillaries are flushed with warm blood
        • Evaporation of perspiration cools the skin
      • Developmental Aspects – fetal/baby
      • Continuous tube by the 5 th week
      • Digestive glands bud from the mucosa of the alimentary tube
      • fetus receives nutrients through placenta
      • In newborns, feeding frequent, peristalsis is inefficient, and vomiting is common
      • Developmental Aspects
      • Teething ~ age six mos
      • Metabolism decreases with age
      • Middle age
        • Ulcers
        • Gall bladder problems
      • Old age
        • Fewer digestive juices
        • Peristalsis slows
        • Diverticulosis & cancer more common