CHAPTER 4: FOOD
AND DIGESTION
Miss Sabia
Section 1
FOOD AND ENERGY
1. Why do we need food?
2. What are the six nutrients?
Do Now
What is your favorite part of
Thanksgiving dinner?
We all need food!
• Nutrients: substances in food that provide
the raw materials and energy the body needs
to carry out all the essential processes
• 6 kinds:
–
–
–
–
–
–
Carbohydrates
Fats
Proteins
Vitamins
Minerals
Water
Carbohydrates
• Body’s main source of energy!
• Examples: sugar, potatoes, noodles, rice,
bread
Proteins
• Made of amino acids
• Make up cell membrane, make up many
organelles, make up hair, etc.
• Examples—meat, eggs, fish, nuts, and beans
2013: “The International Year
of the Quinoa”
• (according to the Food and Agricultural
Organization of the United Nations)
• A complete protein source—contains all
the essential amino acids!
Lipids
• Used for storing energy in the body
• Cholesterol is a lipid found in food that
comes from animals…too much cholesterol
can clog your blood vessels
• Saturated or unsaturated
Water
• Without water, most chemical
reactions that take place in cells
would not happen!
• Water also helps cells keep their size
and shape
Vitamins
• Act as helper molecules in a variety of
chemical reactions within the body
Fat soluble
A, D, E, K
or
Water soluble
B, C
• Nutrients that are not made by living things—
they are present in soil and absorbed by plants
through their roots
Calcium
Fluorine
Iron
chlorine
sodium
Potassium
Magnesium
Section 2
HEALTHY EATING
What is a calorie?
• Energy in food is measured in calories
• A calorie is the amount of energy needed to
raise 1 gram of water 1 °C
• # of calories in each food varies
• # of calories each person needs varies
TIME TO PLAY
http://calorieguesser.com/
Keeping a Balance
• To maintain a balanced state
(homeostasis), all organisms
have a minimum daily intake of
each type of nutrient based on
species, size, age, sex, activity,
etc.
• An imbalance in any nutrients
might result in weight gain,
weight loss, or a diseases state
% Daily Value
indicates how the
nutrition content of
one serving fits into
the diet of a person
who consumes
2,000 calories a day
Americans Guess What 100 Calories Looks Like
Is Holiday Coffee Worth the Calories?
Metabolism
• Metabolism is the sum of all the life
processes that occur within a living organism
Sections 3 & 4
THE DIGESTIVE SYSTEM
Do Now
• Draw what you think the path of the
digestive system in your body looks like
1. What are the major organs of the digestive
system?
2. What does a basic diagram of the digestive
system look like?
The Digestive System
• The bodily system that enables us to eat and
digest our food
• The main players:
– Mouth (including teeth and tongue)
– Esophagus
– Stomach
– Small Intestine
– Large Intestine
– Rectum & Anus
ENTER
EXIT
Other Organs & Structures
Involved
•
•
•
•
Pharynx
Liver
Pancreas
Gallbladder
Functions of the Digestive
System
• Digestion: breaking down food into smaller
molecules
• Absorption: nutrient molecules pass
through the wall of your digestive system
into your blood
– Materials that are not absorbed are eliminated
as waste
The Mouth
• Mechanical digestion—chewing breaks food into
smaller pieces
• Chemical digestion—breaking down complex
molecules into simpler ones
– Saliva starts the breakdown of carbohydrates
Unsalted cracker challenge
The Esophagus
• Epiglottis: flap of tissue that
seals off your windpipe and
prevents food from entering
• Esophagus: muscular tube that
connects mouth and stomach
• Mucus: thick, slippery
substance that makes food
easier to be swallowed and
moved along
• Peristalsis: involuntary muscle
contractions that move food
The Stomach
• Stomach: J-shaped muscular pouch located in
abdomen
– Expands to hold food as you eat
• The average adult’s stomach can hold 2 Liters of
food
The Stomach (continued)
• Most mechanical digestion occurs here
– Muscles of stomach contract to produce a
churning motion that mixes food and fluids
• Chemical digestion occurs too!
– Churning mixes food with digestive juice
– Digestive juice contains pepsin (enzyme that
breaks down proteins)
– Digestive juice contains hydrochloric acid (kills
bacteria you swallow, allows pepsin to work)
Do Now
FIRST, place your hand
palm-side down on a
table, keeping your
thumb and fingers tightly
together. Lay a string
along the outline of your
hand, and then measure
the string.
SECOND, place your hand
palm-side down, but this
time spread your fingers.
Lay a string along the
outline of your hand and
then measure the string.
The Small Intestine
• Almost all chemical
digestion and absorption of
nutrients occurs here
• 6 meters long, makes up 2/3
of the digestive system
– Called “small” because of its
diameter, only 2-3 cm wide
The Small Intestine (cont’d)
• Enzymes in small intestines are produced by
other organs
– Liver  bile (breaks down fats)
– Gallbladder  stores bile
– Pancreas  enzymes (break down starches, proteins,
and fats)
The Small Intestine (cont’d)
• Villi cover the
surface of the inner
lining to increase
the surface area, to
allow for max
absorption
– Nutrient molecules
pass from the villi
into blood vessels
– If all the villi were
laid out, the total
surface area of the
small intestine
would be about as
large as a tennis
court
The Large Intestine
• 1.5 meters long
– Large diameter, about 4-6 cm
wide
• The last section of the
digestive system
– As material moves through,
water is absorbed into the
bloodstream
– Everything else is readied for
elimination
Large Intestine (cont’d)
• Ends in the rectum, a
short tube that
compresses waste into
a solid form
• Waste is eliminated
through the anus, a
muscular opening at
the end of the rectum