Nutrition

Food provides basic organic molecules that animals cannot synthesize. An example is the acetyl group:

from which is made (or which is used in combination to make) more complex molecules.

e.g.

• Vitamin a
• Steroid hormones
• Citrate
• Fatty acids
• Amino acids (with -NH₂)

Amino acids

However, there are eight essential amino acids that are derived from food (see table 3.1 in chapter 3). E.g. Leucine, lysine, tryptophan, valine. All eight are present in meat, eggs, milk. All eight can be obtained by appropriate mixture of plant foods.

Minerals

(see table 47.1).

Seven minerals (macronutrients) are required for major functions, tissue construction, maintenance, tissue detoxification.

Ten minerals (micronutrients) required for many enzymes, certain hormones, certain metabolic pathways.

Vitamins

(see table 47.2)

Act as coenzymes, in visual pigments, antioxidants, clotting.

Digestion - the Gut

The gut is compartmentalized.

• Mouth amylase carbohydrate breakdown
• Stomach pepsin, HCL starts protein digestion produces chyme. Stomach wall can absorb caffeine, alcohol. See fig. 47.12
• Small intestine (not small: is 6m long has area equivalent to tennis court) wall is microvillar. See figs 47.10, 47,16.
• Duodenum ------ digests
• Jejunum and ileum ------absorb
• Pancreas and liver:
• Liver provides an emulsifier called bile
• Pancreas provides enzymes and bicarbonate. See table 47.3 for enzymes

Control of digestion is hormonal.

(see fig. 47.18)

Absorption and postabsorption

Insulin is the key player in promoting glucose uptake during absorption.

During postabsorption, insulin is reduced. Reduction blocks glucose uptake and promotes fat and glycogen breakdown. (see figs. 47.19, 47.20).

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