The Digestive System and Body Metabolism

1. The Digestive System and Body Metabolism

2. I. Nutrition and Metabolism 1) A small amount of the food nutrients are used to build cellular molecules and structures 2) The majority is used to produce ATP through cellular respiration 3) Kilocalories (Calories) unit of energy for food 4) Nutrient: any substance in food that is used by the body to promote normal growth, maintenance and repair

3. 5) Major nutrients: carbohydrates, lipids, protein, vitamins, minerals, water 6) A balanced diet normally guarantees adequate amounts of these nutrients 7) Sources of nutrients a) Carbohydrates: plants b) Lipids: 1. Saturated fats: Meat, dairy and coconut 2. Unsaturated fats: seeds, nuts oils,egg yolk, meats and milk products

4. c) Proteins: 1. Complete: eggs, milk and meat 2. Incomplete (low in certain a.a.): legumes, nuts and cereals 8) Vitamin: organic nutrients obtained from various foods, most function as coenzymes 9) Coenzyme: molecule necessary for an enzyme to function 10) Mineral: inorganic substances needed by the body (Appendix C)

5. II. Metabolism: 1) Metabolism: all the chemical reactions of the body necessary to maintain life 2) Catabolism: reactions breaking down material 3) Anabolism: reactions building up material 4) Carbohydrate metabolism

6. a) The preferred energy source for cells is glucose (blood sugar) b) Catabolism breaks down materials into ATP through cellular respiration c) Cellular respiration: Process using oxygen to breakdown food into energy C6H12O6 + 6O2 6CO2 + 6H2O + 36 ATP d) Glycolysis: process breaking down glucose into pyruvic acid and a small amount of ATP

7. e) Krebs cycle: produces CO2, water, small amount of ATP and molecules for ETC f) ETC: Hydrogen atoms split into H+ and high energy electrons, as the electrons move through a series of carriers, energy is released and used to form ATP & water g) Glycogenesis: formation of glycogen from excess glucose

8. Glycolysis D-glucose + ATP (hexokinase & Mg)  glucose-6-phosphate + ADP (Phosphoglucoisomerase)  Fructose-g-phosphate + ATP (phosphofructokinase)  Fructo 1-6 diphosphate + ADP (fructose diphosphate aldose)  phosphoglyceraldehyde (PGAL) + Pi + NAD+ (glyceraldehydes phosphate dehydrogenase)  phosphoglycerol phosphate + NADH (phosphoglycerate kinase)  phosphoglycerate + ATP (phosphoglycomutase)  phosphoglycerate (enolase)  PEP (pyruvate kinase)  ATP + pyruvate (pyruvate dehydrogenase)  CO2 + NADH + Acetyle -CoA

9. Krebs

10. Metabolic Pathways Involved in Cellular Respiration Figure 14.19a

11. Metabolic Pathways Involved in Cellular Respiration Figure 14.18

12. h) Glycogenolysis: breakdown of glycogen into glucose 5) Fat metabolism: a) Liver cells handle most lipid metabolism, using part of it for energy b) Fats are also used to form: blood protein, cholesterol, membranes, hormones, myelin, cushions, store energy

13. c) Fat stores about twice the energy per gram, but takes longer to metabolize and can cause acidosis d) Ketogenesis: Process breaking down lipids to form ketones used in Kreb’s cycle 6) Protein metabolism a) Only used as a major source of energy during starvation or when an excess is present

14. b) Protein metabolism is actually amino acid metabolism c) Essential amino acids: the 9 amino acids that cannot be produced by the cells d) Deamination: removal of the amino group to produce ammonia and a molecule for the Kreb’s cycle 7) Role of the liver:

15. a) Without the liver, we die within 24 hours b) We have an excess of liver tissue and it can regenerate c) Functions: 1. Bile production 2. Detoxification 3. Hormone degradation

16. Metabolic Functions of the Liver Figure 14.21

17. 4. Production of cholesterol, blood proteins, lipoproteins 5. Food metabolism 8) Cholesterol metabolism a) Functions as the structural basis of steroid hormones & Vit. D and in making membranes b) They are transported by lipoproteins

18. 1. LDLs (bad): transport cholesterol and lipids to the cells (high numbers can cause atherosclerosis) 2. HDLs (good): transport cholesterol and lipids to the liver for elimination

19. III. Metabolic rate 1) Energy intake = total energy output (heat + work + storage) 2) If more energy is taken in than used as heat and work than fat storage occurs 3) Basal metabolic rate (BMR): amount of energy used to maintain body at rest (Table 14.3) 4) Total metabolic rate (TMR): amount of energy needed to do all activities

20. 5) During exercise TMR may increase 15-20 times normal and remain elevated for hours 6) For good weight loss a person needs to eat a balanced diet, reduce calories and exercise 7) Temperature regulation: a) Most energy released escapes as heat (less than 40% becomes ATP)

21. b) Body temp should remain about 98.6 F or 37C c) Low body temps cause vasoconstriction and shivering to conserve heat d) Hypothermia: extreme drop in body temperature e) Heat is lost by radiation or evaporation f) High body temp causes BV dilation in the skin

22. g) If the outside temp is equal to or higher than body temp heat cannot radiate h) Evaporation doesn’t work well in high humidity i) Heat exhaustion: heat collapse resulting from excessive loss of fluids, causes low BP, rapid HB cool clammy skin (mechanisms work)

23. j) Heat stroke: Body temp increases, increases metabolic rate, which increase heat production, the body temp can cause permanent brain damage and death 8) Fever: controlled hyperthermia in response to an infection, helps speed healing, inhibit bacterial growth, but can cause brain damage if too high

24. Body Temperature Regulation Figure 14.22