Download 49-1 Digestive System

49-1 Digestive System
1. List the four organic nutrients needed by the human body.
A. Nutrients – chemical substances organisms need to grow and function properly.
B. Four nutrients—carbohydrates, proteins, fats, and vitamins—are organic compounds
because they contain the elements carbon, hydrogen, and oxygen.
2. Summarize the functions that the six nutrients perform in the body.
A. There are 6 basic food ingredients:
1. Carbohydrates – sugars
2. Proteins – chains of amino acids. The body’s major structural and functional
material.
3. Lipids – fats. Highest energy source but bad in excess.
4. Vitamins – complex organic molecules that serve as coenzymes (they help enzymes
function). There are water and fat-soluble vitamins.
5. Minerals – inorganic substances required for the normal functioning of the body.
6. Water – most reactions that maintain life can only take place in water. It makes up
most of the blood, which carries the nutrients, and is also the medium in which waste
products are dissolved and carried away from body tissues.
B. Carbohydrates
1) Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen
in a ratio of about two hydrogen atoms to one oxygen atom and one carbon atom.
a) Carbohydrates are broken down in aerobic respiration to provide most of the
body’s energy.
b) Although proteins and fats also supply energy, the body most easily uses the
energy provided by carbohydrates.
c) Carbohydrates contain sugars that are quickly converted into the usable energy
ATP, while proteins and fats must go through many chemical processes before
the body can obtain energy from them.
C. Proteins
1) Proteins are the major structural and functional material of body cells.
a) Proteins from food help the body to grow and to repair tissues.
b) Proteins consist of long chains of amino acids.
D. Lipids
1) Why does the human body store fat?
a) The answer is that stored fats are beneficial unless they are excessive.
b) A light layer of body fat beneath the skin provides insulation in cold weather.
c) Fat surrounding vulnerable organs, such as the kidneys and liver, acts as
protective padding.
d) And most important, fat reserves are a source of energy.
e) While you cannot live off just your body fat, the body can use its fat for energy,
especially when carbohydrates are unavailable.
E. Vitamins
1) Vitamins are complex organic molecules that serve as coenzymes.
2) Vitamins activate the enzymes and help them function.
F. Minerals
1) Minerals are inorganic substances required for the normal functioning of the body.
G. Water
1) Most of the reactions that maintain life can take place only in water.
2) Water makes up over 90 percent of the fluid part of the blood, which carries
essential nutrients to all parts of the body.
3) It is also the medium in which waste products are dissolved and carried away from
body tissues.
4) Water also helps regulate body temperature.
Chapter 49 Digestive and Excretory Systems
 The human body needs six nutrients—carbohydrates, proteins, lipids, vitamins, minerals,
and water—to grow and function.
 Carbohydrates provide most of the body’s energy. Monosaccharides are quickly processed
by the body. Cellulose cannot be digested but is needed for fiber.
 Proteins help the body grow and repair tissues. Amino acids must be obtained from foods.
 Lipids are used to build cell membranes.
 Vitamins act as coenzymes. The body can synthesize vitamin D.
 Minerals are inorganic substances that are needed in small amounts.
 Water helps regulate body temperature and transports nutrients and wastes.
Vocabulary List
Carbohydrate
Dehydration
Lipids
Minerals
Nutrients
Proteins
Vitamins
Water