Table of Contents
Chapter 9: Cell Processes
Section 1: Chemistry of Life
Section 2: Moving Cellular Materials
Section 3: Energy for Life
Energy for Life
3
A. Trapping and Using Energy
1. All of the activities of an organism involve
chemical reactions in some way.
2. The total of all chemical reactions in an
organism is called metabolism.
3. The chemical reactions of metabolism need
enzymes.
4. Enzymes in cells cause a change, but the
enzyme is not changed and can be used
again.
Energy for Life
3
A. Trapping and Using Energy
5. Enzymes also can cause molecules to join.
6. Without the right
enzyme, a chemical
reaction in a cell
cannot take place.
7. Each chemical
reaction in a cell
requires a specific
enzyme.
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Energy for Life
3
B. Photosynthesis
1. Living things are divided into two
groups— producers and consumers—
based on how they obtain their food.
2. Organisms that make their own food, such
as plants, are called producers.
3. Organisms that cannot make their own
food are called consumers.
Energy for Life
3
B. Photosynthesis
4. Plants and many other
producers can convert light
energy into another kind of
energy—chemical energy.
5. The process they use is called
photosynthesis.
6. During photosynthesis, producers use light
energy to make sugars, which can be used as
food.
Energy for Life
3
C. Producing Carbohydrates
1. Producers that use photosynthesis are usually
green because they contain a green pigment
called chlorophyll (KLOR uh fihl).
2. Chlorophyll and other pigments are used in
photosynthesis to capture light energy.
3. In plant cells, these pigments are found in
chloroplasts.
Energy for Life
3
C. Producing Carbohydrates
4. The captured light energy is used to drive
chemical reactions during which the raw
materials, carbon dioxide and water, are
used to produce sugar and oxygen.
5. For plants, the raw materials come from air
and soil.
Energy for Life
3
C. Producing Carbohydrates
6. Some of the
captured light
energy is stored
in the chemical
bonds that hold
sugar molecules
together.
Energy for Life
3
D. Storing Carbohydrates
1. Plants make more sugar during
photosynthesis than they need for survival.
2. Excess sugar is changed and stored as
starches or used to make other carbohydrates.
3. Plants use carbohydrates as food for growth,
maintenance, and reproduction.
4. Consumers take in food by eating producers
or other consumers.
Energy for Life
3
E. Respiration
1. Some of the energy from the food you eat is
used to make you move.
2. Some of it becomes thermal
energy, which is why you
feel warm or hot when you
exercise.
3. Most cells also need oxygen
to break down food.
Energy for Life
3
E. Respiration
4. During respiration, chemical reactions
occur that break down food molecules into
simpler substances and release their stored
energy.
5. Just as in photosynthesis, enzymes are
needed for the chemical reactions of
respiration.
Energy for Life
3
F. Breaking Down Carbohydrates
1. The type of food molecules most easily
broken down by cells is carbohydrates.
2. Respiration of carbohydrates begins in the
cytoplasm of the cell.
3. The carbohydrates are broken down into
glucose molecules.
4. Each glucose molecule is broken down
further into two simpler molecules.
Energy for Life
3
F. Breaking Down Carbohydrates
5. As the glucose molecules are broken down,
energy is released.
6. The two simpler molecules are broken
down again. This breakdown occurs in the
mitochondria of the cells of plants, animals,
fungi, and many other organisms.
7. This process uses oxygen, releases much
more energy, and produces carbon dioxide
and water as wastes.
Energy for Life
3
F. Breaking Down Carbohydrates
8. When you exhale you
breathe out carbon
dioxide and some of
the water.
9. Respiration occurs in
the cells of all living
things.
Energy for Life
3
G. Fermentation
1. When cells do not have enough oxygen for
respiration, they use a process called
fermentation to release some of the
energy stored in glucose molecules.
2. Like respiration, fermentation begins in
the cytoplasm.
Energy for Life
3
G. Fermentation
3. Again, as the glucose molecules are broken
down, energy is released.
4. But the simple molecules from the
breakdown of glucose do not move into the
mitochondria.
5. Instead, more chemical reactions occur in
the cytoplasm.
Energy for Life
3
G. Fermentation
6. These reactions release some energy and
produce wastes.
7. Depending on the type of cell, the wastes
may be lactic acid, alcohol, and carbon
dioxide.
8. The presence of lactic acid is why your
muscle cells might feel stiff and sore after
you exercise.
Energy for Life
3
H. Related Processes
1. During photosynthesis and respiration,
what is produced in one is used in the
other.
2. Photosynthesis produces sugars and
oxygen, and respiration uses these
products.
Section Check
3
Question 1
_______ is the total of all chemical reactions in
an organism.
Answer
The answer is metabolism. All of the
activities of an organism involve chemical
reactions in some way.
Section Check
3
Question 2
Which does this equation represent?
A. respiration
B. fermentation
C. photosynthesis
D. chemosynthesis
Section Check
3
Answer
The answer is C. During photosynthesis, plants
take in carbon dioxide and water and combine
it with light energy to make sugars, which they
use for food.
Section Check
3
Question 3
_______ is the type of food molecules most
easily broken down by cells.
Answer
The answer is carbohydrates. As
carbohydrates are broken down, energy is
released.
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