1. Chapter 3: Section 3
Energy in Cells
Minersville Area School Distirct
Mr. Motuk

2. I. Trapping Energy for Life
A. Cells take chemical energy stored in food and
change it into other forms of energy that can be
used in metabolism.
1. Metabolism is the total of all chemical activities of an
organism that enable it to stay alive, grow, and
reproduce.
B. Living Things are broken into two groups
1. Consumers are organisms that cannot make their
own food.
a. Humans, dogs, cats, etc.
2. Producers are organisms that can make their own
food.
a. Plants

3. II. Photosynthesis
A. Photosynthesis-the process of changing light
energy into chemical energy.
1. Producers take energy from the sunlight and use it
to make sugar from carbon dioxide.
B. Steps of photosynthesis
1. Energy from Sun is absorbed by the chlorophyll in
plant cells.
2. In the chloroplasts, the Sun’s energy is used to split
water into oxygen and hydrogen.
a. The light energy is then used to combine these
hydrogen atoms with carbon dioxide to form a
sugar.

4. B. Steps of Photosynthesis (cont’d)
3. Photosynthesis takes place inside chlorplasts.
4. Photosynthesis equation
a. 6CO2 + 6H2O + Light Energy C6H1206 + 6O2
C. Products of Photosynthesis
1. Producers use some of the sugars (C6H1206) they
make for energy. The rest is stored as
carbohydrates or lipids.
2. Consumers eat Producers in order to obtain this
energy.
a. Consumers can also eat other consumers to
obtain energy.

5. Chapter 3: Section 3
III. Releasing Energy for Life
A. Cellular Respiration: Both producers and
consumers break down food molecules in a process
called cellular respiration.
1. In most animals glucose is the food that is
broken down.
2. This process takes place within the mitochondria
and uses that oxygen that you take in as you
breathe.
3. Respiration Equation
a. C6H1206 + 6O2 6CO2 + 6H2O + energy

6. III. Releasing Energy for Life
B. What happens during respiration?
1. Food molecules are broken down to release
stored energy.
2. Respiration of carbohydrates begins in the
cytoplasm.
a. Carbohydrates are broken down into glucose
molecules. (C6H1206)
b. Each glucose molecule is broken down into
simpler molecules, releasing energy.

7. Chapter 3: Section 3 (Energy For Life)
B. What Happens During Respiration (cont’d)
3. Respiration moves into the mitochondria
a. The two simpler molecules are broken down
again, releasing much more energy.
b. This process uses oxygen and produces CO2
and water as wastes.

8. Chapter 3: Section 3 (Energy For Life)
C. Fermentation
1. Fermentation is a form of respiration that converts
energy from glucose when oxygen is insufficient.
a. Lesser amounts of energy are produced by
fermentation.
i. Lactic Acid is formed during this process.
ii. Lactic Acid causes the muscles to burn and be sore
and stiff.
b. Some yeasts and bacteria use alcohol
fermentation to release energy and carbon
dioxide.

9. Chapter 3: Section 3 (Energy For Life)
D. Comparing Photosynthesis and Respiration
1. Both involve complex sets of reactions.
2. Both occur in specific organelles, involve
energy, and require enzymes.
3. The end products of photosynthesis are the starting
blocks for respiration.
a. In many ways photosynthesis is the opposite of
respiration.