TEXT.  CHAPTER 41, PAGE 792 – 808

I. Introduction

II. Nutritional Requirements

1. Three basic needs a nutritionally adequate diet satisfies.
Chemical energy for all cellular work
Organic raw material used in biosynthesis
Essential nutrients

2. Homeostatic mechanisms manage the intake and consumption of the chemical energy

a. Only the monomers of oxidized organic molecules can be used   as fuel for the generation of ATP by cellular respiration
b. Undernourished person
c. Over nourishment and the cause of obesity
d. Fat storage and use in humans are regulated by a complex feed back mechanisms
Leptin, a hormone produced by adipose cells is a key player

3. A healthy diet must supply essential nutrients and carbon skeletons for biosynthesis

Essential nutrients:
Animals can not make from raw material, have to be obtained in food in preassembled form.

Vitamin C

  Missing one or more essential nutrients
III. Four classes of Essential Nutrients

A. Essential amino acids
Most animals can synthesis about half of the 20 amino acids, the rest of the 10 must be obtained from food in prefabricated form.
Eight of them are essential for human diet.  Histidine is crucial for infants.
Reliable sources of essential amino acids:  meat, egg, cheese and animal products.
Vegetarians have to have a balanced diet, including a variety of vegetables.
(Protein deficiency)

B. Essential fatty acids
Deficiencies are rare, only the unsaturated fatty acids can be short in supply.

C. Vitamins
Organic molecules required in the diet in a small amount.
 0.01 ~ 100 mg/day.  13 vitamins have been identified essential to humans.  Two groups:
a. Water-soluble vitamins
Vitamin B groups, Folic acid, Vitamin C (Ascorbic acid)…

b. Fat-soluble vitamins
Vitamin A, D, E, K.
A:  visual pigments; B: calcium intake; E: oxidation membrane
K: blood clotting
    Table 41.1

D. Minerals
Inorganic nutrients, usually required in very small amount,
1 mg ~ 2500 mg/day.

e.g.  Ca, P, S, and Fe…

    Table 41.2

IV. Food Types and Dietary Categories




V. The Mammalian Digestive System

A. The oral cavity, pharynx, and esophagus initiate food processing

B. The stomach stores food and performs preliminary digestion

C. The small intestine is the major organ of digestion and absorption

D. The large intestine (colon)’s major function is reclaiming water.


Autotroph – an organism that obtains organic food molecules without eating other organisms.  Autotrophs use energy from the sun or from the oxidation of inorganic substances to make organic molecules from inorganic ones. (Plants and algae).

Carnivores – Animals feed on other animals.  Sharks, snakes, etc.

Essential nutrients – Materials that the animal cells cannot make from any raw material, and must be obtained in preassembled form.

Herbivores – Animals feed on autotrophs (plants, algae). For example, gorillas, cow, and hares, etc.

Homeostasis - The steady –state physiological condition of the body.

Malnourished animal – A animal whose diet is missing one or more essential nutrients is said to be a malnourished animal.

Omnivores – Consume animals as well as plant or algae.  Humans.

Over nourishment – Human body tends to hoard fat and store excess fat molecules obtained from food instead of using them for fuel or biosynthesis.

Pharynx – An area in the vertebrate throat where air and food passages cross.

Ruminant – an animal, such as a cow or a sheep, with an elaborate, multicompartmentalized stomach specialized for an herbivorous diet.

Undernourished person – A person whose diet is deficient in calories.  It is common only where drought, war, or some other crisis has severely disrupted the food supply.