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Energy in a Cell
Unit 3
Chapter 9
Importance of energy

Cells need energy to be able to carry
out important metabolic functions to
sustain life.
– Ex: Active transport, cell division,
movement of flagella or cilia, and
the production, transport, and
storage of proteins
Autotrophs

Plants, algae, some bacteria are able
to store sunlight energy for use.
Heterotrophs


These organisms
cannot store
sunlight energy.
They must eat
(consume) to
have energy.
ATP: the “battery” for a
cell



Adenosine triphosphate
1 adenine + 3 phosphate molecules
bonded together
Each time a phosphate molecule is
removed, energy is released.
Getting energy out of ATP
ATP
Adding 1
phosphate
back to ADP
to make ATP
Remove 1
phosphate
group
ENERGY
RELEASED!
ADP
What process makes
ATP?


Cellular respiration is the primary way
of making ATP molecules from simple
sugars.
How are simple sugars made?
Photosynthesis: the
autotrophic process of making
sugars using sunlight energy
Photosynthesis chemical
equation


6CO2 + 6H2O→C6H12O6 + 6O2
6 carbon dioxide + 6 water makes
simple sugar + 6 oxygen
How autotrophs capture
sunlight energy
Click image to play video.
Pigments


Molecules that absorb specific
wavelengths of light
Autotrophs primarily rely on
chlorophyll pigments to absorb
sunlight.
Where are chlorophyll
pigments found?


Chlorophyll are found
inside the
chloroplast
organelle.
These organelles are
common in the cells
of leaves and
sometimes stems.
How do chlorophyll help
to make sugar?
1.
2.
3.
Chlorophyll absorb sunlight energy.
Electrons become energetic from
light energy that the only way to
lower the energy level is to pass the
electrons from one molecule to
another like playing “hot potato.”
This starts a series of chemical
reactions to break bonds and reform
bonds that sugar is made in the end.
This process is photosynthesis.
What happens to the
sugar?


Plants can store the sugar in roots or
stems (ex: carrot, sugar cane) to
make ATP by cellular respiration as
needed.
Heterotrophs such as humans must
eat complex carbohydrates (ex:
carrots, potatoes) to have sugar to
make ATP by cellular respiration.
Mitochondria

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All eukaryotes have mitochondria.
The mitochondria is necessary to help
break down the sugar to make ATP
molecules (cellular respiration).
Bacteria do not have mitochondria, but
they have the ability to break down
sugars in their cytoplasm to make ATP.