the digestive system and body metabolism

ELAINE N. MARIEB

EIGHTH EDITION

14

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings

PowerPoint® Lecture Slide Presentation by Jerry L. Cook, Sam Houston University

ESSENTIALSOF HUMANANATOMY

& PHYSIOLOGY

PART D

The Digestive System and Body Metabolism


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


5) Major nutrients: carbohydrates, lipids, protein, vitamins, minerals, water

6) A balanced diet normally guarantees adequate amounts of these nutrients

7) Sources of nutrientsa) Carbohydrates: plantsb) Lipids:

1. Saturated fats: Meat, dairy and coconut

2. Unsaturated fats: seeds, nuts oils,egg yolk, meats and milk products


c) Proteins:1. Complete: eggs, milk and meat2. 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)


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


a) The preferred energy source for cells is glucose (blood sugar)b) Catabolism breaks down materials into ATP through cellular respirationc) Cellular respiration: Process using oxygen to breakdown food into energyC6H12O6 + 6O2 6CO2 + 6H2O + 36 ATPd) Glycolysis: process breaking down glucose into pyruvic acid and a small amount of ATP


e) Krebs cycle: produces CO2, water, small

amount of ATP and molecules for ETCf) 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


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


Krebs

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 14.19a

Metabolic Pathways Involved in Cellular Respiration

Copyright © 2006 Pearson Education, Inc., publishing as Benjamin CummingsFigure 14.18

Metabolic Pathways Involved in Cellular Respiration


h) Glycogenolysis: breakdown of glycogen into glucose

5) Fat metabolism:a) Liver cells handle most lipid metabolism, using part of it for energyb) Fats are also used to form: blood protein, cholesterol, membranes, hormones, myelin, cushions, store energy


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 metabolisma) Only used as a major source of energy during starvation or when an excess is present


b) Protein metabolism is actually amino acid metabolismc) 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:


a) Without the liver, we die within 24 hoursb) We have an excess of liver tissue and it can regenerate

c) Functions:1. Bile production2. Detoxification 3. Hormone degradation


Metabolic Functions of the Liver

Figure 14.21


4. Production of cholesterol, blood proteins, lipoproteins

5. Food metabolism8) Cholesterol metabolism

a) Functions as the structural basis of steroid hormones & Vit. D and in making membranesb) They are transported by lipoproteins


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


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


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)


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 evaporationf) High body temp causes BV dilation in

the skin


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)


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


Body Temperature Regulation

Figure 14.22

the digestive system and body metabolism

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