Chapter 24: Nutrition, Metabolism, and Body Temperature Regulation
is a substance in food that is used by the body to promote normal growth,
maintenance, and repair.
There are six categories of nutrients: carbohydrates, lipids, proteins, vitamins,
minerals, and water.
Essential nutrients are those that cannot be made by the body and must be obtained
in the diet.
Except for milk sugar (lactose) and small amounts of glycogen found in meats, all the
carbohydrates we ingest are derived from plants.
Glucose is the carbohydrate molecule ultimately used by the body as fuel to make
The most common dietary lipids are the neutral fats, triglycerides or triacylglycerols,
which occur as saturated fats and unsaturated fats.
Cholesterol is another dietary lipid that is found in egg yolk, meats, and milk products.
Dietary fats are essential as the major source of fuel for hepatocytes and skeletal
muscle, for absorption of fat-soluble vitamins, and as components of the myelin
sheaths and cellular membranes of the body.
Animal products contain the highest-quality proteins, those with the greatest amount
and best ratio of amino acids.
a. Proteins in eggs, milk, and meats are considered to be complete proteins that
meet all the body’s amino acid requirements for tissue maintenance and growth.
b. Legumes, nuts, and cereals are protein-rich but not complete, but when cereal
grains and legumes are ingested together they provide all the essential amino
Proteins are important as structural materials of the body, enzymes, and hormones:
proteins are only broken down for fuel to make ATP during starvation.
a. All amino acids needed to make a particular protein must be present in a cell at
the same time and in sufficient amounts for the protein to be made.
b. For optimal protein synthesis the diet needs sufficient carbohydrate or fat calories
for ATP production.
c. The body is in nitrogen balance
when the amount of nitrogen ingested in proteins
is equal to the amount lost in urine and feces.
d. Anabolic hormones