Nutritional Requirements
Marie Černá
A nutritionally adequate diet
satisfies three needs:
• chemical energy for all cellular work of the body,
the generation of ATP by cellular respiration,
from the oxidation of organic molecules
(carbohydrates, proteins and fats)
• the organic raw materials are used in biosynthesis
(carbon skeletons to make many of own molecules)
• essential nutrients,
substances cannot be made from any raw material,
but must be obtained in food in prefabricated form
Nutritional terms
• over nourishment - obesity (caloric excess)
- storing the excess calories in the form of
glycogen (liver and muscles) and fat (adipose tissue)
• undernourishment (caloric deficiency)
- breaking down its own proteins (muscles and brain)
• malnourishment (mineral or protein deficiencies)
- missing one or more essential nutrients
Homeostatic mechanism in
nutritional requirements:
• The human body tends to hoard fat, to
immediately store any excess fat molecules
obtained from food instead of using them for fuel
or biosynthesis.
• By contrast, when we eat an excess of
carbohydrates, the body tends to increase the
rate of carbohydrate consumption.
• Thus, the amount of fat in the diet can have a
more direct effect on weight gain than
carbohydrates.
Paleolithic hunters
Fat hoarding can be a
liability today, but it may
have provided a degree
of fitness for our
hunting/gathering
ancestors.
Individuals with genes
promoting the storage
of high-energy
molecules during feasts
may have been those
that survived famines.
Complex feedback mechanisms
regulate fat storage
Leptin – a hormone produced by adipose cells
↑ of body fat (in adipose tissue) increases leptin levels
in the blood
→ signaling the brain to depress appetite and
increase energy-consuming muscular activity
and body heat production
↓ of body fat (in adipose tissue) decreases leptin levels
in the blood
→ signaling the brain to increase appetite and
weight gain
There are four classes of
essential nutrients:
essential amino acids (9 of 20 required amino acids)
sources: animal products: meat, eggs, cheese
essential fatty acids (unsaturated fatty acids)
for phospholipids in membranes
vitamins (0.01 – 100 mg per day)
- water-soluble (B + C) - their excesses are excreted
in urine, moderate overdoses are harmless
- fat-soluble (A, D, E, K) - their excesses are not
excreted but are deposited in body fat, overdoses
result in their accumulation to toxic levels
minerals (1 – 2500 mg per day)
Vitamins
Water-soluble
Fat-soluble
Vitamin B1 (thiamine)
Vitamin A (retinol)
Vitamin B2 (riboflavin)
Provitamin A (beta-carotene)
Vitamin B6 (pyridoxine) Vitamin D
Vitamin B12
Vitamin E (tocopherol)
Folic acid (folacin)
Vitamin K (phylloquinone)
Pantothenic acid
Niacin
Biotin
Vitamin C (ascorbic acid)
Minerals
higher quantity
Calcium (Ca)
Phosphorus (P)
Sulfur (S)
Potassium (K)
Sodium (Na)
Chlorine (Cl)
Iron (Fe)
Iodine (I)
Fluorine (F)
lower quantity
Magnesium (Mg)
Zinc (Zn)
Cooper (Cu)
Manganese (Mn)
Cobalt (Co)
Selenium (Se)
Chromium (Cr)
Molybdenum (Mo)
Literature
Biology, eighth edition,
Campbell, Reece
Unit seven: Animal Form and Function
Chapter 41: Animal Nutrition
Concept 41.1: An animal’s diet must supply chemical
energy, organic molecules, and essential nutrients
Concept 41.5: Homeostatic mechanisms contribute to
an animal’s energy balance
Pages 875 – 880, 893 – 896