Ch 14 Metabolism

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Ch 14 Metabolism

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

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