Transcript Chapter 21. Nutrition

Nutrition
AP Biology
Chapter 21
21.14: Overview: A healthy diet satisfies three
needs
All animals must obtain:
Fuel to power body activites
Organic molecules to build their own molecules
Essential nutrients that the animal cannot make
on its own
Eating too little or too much food or the
wrong mixture can endanger the animals
health
21.15: Chemical energy powers the body
 Every activity your body performs requires fuel in
the form of chemical energy
 Cellular metabolism produces ATP by oxidizing
molecules digested from food
 Cells use carbohydrates and fats as fuel sources
If these are in short supply, the body uses protein
 The energy content of food is measured in kilo
calories
1 kcal = 1000 calories
 Metabolic rate:the rate of energy consumption; sum of
all the energy requiring bio-chemical reactions over a
given time
 Metabolism must drive several processes such as:
 cell maintenance
 Breathing
 Beating of the heart
 Basal Metabolic Rate: number of kilocalories a resting
animal requires to fuel essential processes
 Cells store extra energy in various forms
 The liver and muscles store energy in the form of glycogen
 Also store extra energy as fat
21.16: An animal’s diet must supply
essential nutrients
 Essential nutrients: materials that must be obtained in
preassembled form, the animal cannot make them.
 Four classes of essential nutrients:
 Essential fatty acids
 Essential amino acids
 Vitamins
 Minerals
 Undernourishment: results from a diet chronically
deficient in calories
 Malnourishment: results from long-term absence of one
or more essential nutrients from the diet
Essential fatty acids must be obtained
from the diet
Example: linoleic acid, used to make some
phospholipids for the cell membrane
Adult humans cannot make 8 of the 20
amino acids needed to synthesize proteins
Those eight are known as the essential amino
acids
21.17: Vegetarians must obtain all 8
essential amino acids
Vegetarian diets range from avoiding meat
to avoiding all meat by-products such as
cheese, eggs and milk.
On such a limited diet, people can become
protein deficient because they lack certain
amino acids
Must eat a variety of plant foods that
together supply enough of all the essential
amino acids
21.18: A healthy diet includes 13 vitamins
and many essential minerals
 Vitamin: organic nutrient that is obtained from the diet
but required in minute amounts
 Water-soluable vitamins include the b complex and
vitamin C
 B vitamins function as coenzymes; vitamin c is required to
produce connective tissue
 Fat-Soluble vitamins include vitamins A,D,E,and K
 Minerals: simple, inorganic nutrients required in small
amounts
 Humans require large amounts of calcium and
phosphorus to construct and maintain the skeleton
 See tables 21.18 A and B (page 444 and 445)
21.19: Do you need vitamin and mineral
supplements?
 A varied diet should provide enough vitamins
and minerals
 It is considered the best source for these
nutrients
 Recommended Dietary Allowances: minimum
amounts of nutrients needed each day;
determined by a national scientific panel
 Some people argue RDAs are too low for some
vitamins; research is far from complete
 Unless recommended by a doctor, stay away
from megavitamins-supplements that exceed
daily recommended doses
21.20: What do food labels tell us?
The Food and Drug Administration (FDA)
requires various types of information to be
given on food labels
Several nutrition facts are on food labels:
Serving size of the food is defined
Energy content in calories is listed per serving
Food labels emphasize nutrients believed
to be associated with disease risks and
healthy diets
21.21: the problem of obesity may reflect
on our evolutionary past
 Overnourishment: consuming more food energy
than the body needs for normal metabolism;
causes obesity
 Obesity contributes to diabetes, colon and
breast cancer and cardiovascular disease
 Inheritance is once factor in obesity
Leptin-deficiency-leptin is produced by fat cells. As fat
increases, leptin levels rise which cues the brain to
suppress appetite.
 Fat hoarding may have been an advantage in
the past
Ancient ancestors were hunter-gatherers
Natural selection may have favored those
that ate more fatty foods when they were
available
21.22: What are the health risks and
benefits of weight loss plans?
 Many weight loss plans have focused on reduced
intake of carbohydrates
 Some lose weight quickly on these plans, however,
much of the initial weight loss is water loss
 Gastric bypass surgery reduces the size of the
stomach and the length of the small intestine
For very obese individuals
 Sustainability is major problem with many diets
 Best way to lose weight is a combination of increased
exercises and a restricted but balanced diet
21.23: Diet can influence cardiovascular
disease and cancer
 A diet rich in saturated fats is linked to high
blood cholesterol levels which are linked to
cardiovascular disease
 Cholesterol travels through the body in blood
lipoproteins
 Low-density lipoproteins: high blood levels of
lipoproteins, generally correlate with tendency to
develop blocked blood vessels
High Density Lipoproteins are just the opposite
 A diet high in saturated fats increase LDL levels
Saturated fats are found in eggs, butter,and most meats
 Trans-fats increase LDL levels and lower HDL
levels
 Eating mainly unsaturated fats tends to lower
LDL levels and raise HDL levels
 There may be a link between diets heavy in fats
and breast cancer
 Other foods may help fight cancer, such as fruits
and vegetables
 The American Cancer society recommends
eating a variety of healthy foods, with an
emphasis on plant sources