CH. 25 – NUTRITION, METABOLISM & TEMP. REGULATION
I. NUTRITION
A. NUTRIENTS - for energy & building blocks
1. Carbohydrates
2. Proteins
3. Lipids
4. Vitamins - Coenzymes for rxns
5. Minerals = Inorganic nutrients
6. H2O
7. Essential - need in diet, can’t synthesize
8. Kilocalorie = Calorie = energy available per unit of food
a. Carbos & proteins = 4 cal./gram
b. Fats = 9 cal./gram
[*Also read CH. 24, p. 906-913, Fig. 24.28, p. 907]
B. CARBOHYDRATES
1. DIGESTION - Mouth, Small Intestine
a. MouthèSalivary amylaseèDisaccharides 3-5%
b. Stomach - NONE to very little - too acidic
c. Small Intestine
i. Pancreatic amylase
ii. Disaccharidases - on villi
2. ABSORPTION of MONOSACCHARIDES (Fig. 24.29, p. 908)
a. ACTIVE Cotransport w/ Na+ into cells
b. Facilitated transport from cells - into capillaries
3. TRANSPORT (Fig. 24.29, p. 908)
CapillariesèHepatic Portal veinèLiver (converts
all to glucose or stores as glycogen) èglucose into blood è
into cells by facilitated transport
4. METABOLISM - glucose + O2èATP + H2O + CO2 (Fig. 25.4, p. 934)
C. LIPIDS
1. DIGESTION - Mostly Small Intestine (Fig. 24.30, p. 909)
a. Emulsification via bile salts from liver into droplets
b. Pancreatic lipases breakdown triglycerides
2. ABSORPTION
a. MICELLES - droplets coated w/ bile salts
- DIFFUSE into epith cells
b. Triglycerides reformed in smooth E.R.
c. Protein “coat” = CHYLOMICRONS - EXOCYTOSIS into LACTEALS
3. TRANSPORTATION
a. LACTEALSèLymphaticèbloodèadipose & liver
b. Stored as fat or used as energy
4. METABOLISM (Fig. 25.10, p. 942)
D. PROTEINS
1. DIGESTION - Stomach & Small Intestine (Fig. 24.33 p. 912)
a. Stomach - Pepsin breaks proteinsèpolypeptides
- 10-20% digested
b. Pancreas - Free proteasesèsmall peptide chains
c. Sm. Intes. - Tri & Dipeptidases attached to wallèA.A.
2. ABSORPTION
a. ACTIVE Cotransport w/ Na+ èA.A. into epithelium
b. ACTIVE TRANSPORT from epithilium into capillaries
3. TRANSPORTATION
a. ACTIVE TRANSPORT ècapillariesèhepatic portal veinè
liver & cellsèblood
b. ACTIVE TRANSPORT into cells from blood
4. METABOLISM (Figs. 25.11 - 25.13, p. 944 & 945)
E. INTERCONVERSION (Fig. 25.14, p. 946)
1. Meet body’s metabolic needs - building blocks & energy
2. Maintain homeostasis
II. METABOLISM - ALL Chem. rxns in body
- Goal = maintain homeostasis, grow, repair, etc.
= ATP production, “Universal energy currency of cells”
A. ANABOLISM - synthesis, energy-requiring rxns
B. CATABOLISM - breakdown, energy-releasing rxns
C. METABOLIC STATES
1. ABSORPTIVE - meal + 4 hours (Fig. 25.15, p. 948)
a. Digest, absorb, energy use, storage
b. Glucoseè Glycogen
2. POSTABSORPTIVE - >4 hours after meal (Fig. 25.16, p. 948)
a. Breakdown of stored nutrientsè energy
b. GlycogenèGlucose
D. METABOLIC RATE = energy expended per unit of time
1. BMR - energy needed to keep body functional at REST (60%)
2. Muscular activity - (30%), can vary greatly
3. Assimilation/Thermic energy - to digest & absorb food (10%)
E. BODY TEMP REGULATION = THERMOREGULATION (Fig. 25.18, p. 952)
1. Balance between heat gain vs. heat loss
2. Hypothalamus regulates
3. Negative feedback mechanism