Cell Energy:
Photosynthesis & Respiration
Biology 4B
Investigate and Identify cellular
processes including synthesis of
new molecules.
How are plant & animal cells alike &
different?
SYNTHESIS –Cells Make Molecules
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Cells don’t make just anything. They make
molecules. And the process by which cells
make molecules is called synthesis
One important molecule synthesized by plant
cells is glucose. (Made in chloroplasts)
Plant and animal cells use glucose as an energy
source by changing it to ATP (In the
mitochondria)
Today’s Learning Goals
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In plants, chlorophyll (found in
chloroplasts) captures energy
from the sun in order to make
food during photosynthesis
Cells release energy from food
through either cellular
respiration or fermentation
Photosynthesis and Cellular
Respiration are considered to
be opposite. They feed each
other.
How Does a Plant Make It’s Own
Food?
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Plants use carbon dioxide (CO2), water (H2O), and
sun’s energy to make food in the form of glucose.
This is called “photosynthesis”
The glucose gives plants energy
Animals get the
energy stored in
plants when they
eat them.
GLUCOSE
How Do Plants Get Energy From Sun?
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Plants have pigments that absorb
energy from light
Chloroplasts are the site of
photosynthesis. They contain
Chlorophyll (the pigment used in
photosynthesis)
CO2 enters through the stomata;
O2 exits through them
What “Food” do Plants Make?
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The “food” plants
make is a sugar
called glucose
(C6H12O6).
Glucose and oxygen
(O2) are made during
photosynthesis.
How Do Organisms Get Energy
From Food?
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Animals cannot make their own food like plants can.
But, BOTH plants and animals must break down
(digest) food in order to get energy from it (so they
can live, grow, & develop)
Cells do this 2 ways: cellular respiration and
fermentation
Cellular Respiration & Fermentation
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Cellular Respiration uses oxygen (O2) to break down food
Fermentation does not use oxygen
Cellular respiration releases more energy from food than
Fermentation.
So most eukaryotes
(ex: plants & animals)
get their energy through
cellular respiration
Cellular Respiration
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Cellular Respiration is
a chemical process
that happens in cells
In prokaryotes, it
happens in the cell
membranes
In eukaryotes, like our
cells, it happens
mostly in the
mitochondria
Cells that need a lot of energy contain lots
of mitochondria – (Example-heart cells
which are always contacting or sperm cells
which are constantly swimming)
Process of Cellular Respiration
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Food (glucose) is broken down into CO2 and H2O and
energy is released
C6H12O6 + 6 O2  6 CO2 + 6 H2O + energy (ATP)
This energy can be used for:
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Keeping a constant body temperature
Storage (ATP) - to be used later for things like growth
What Do You Notice?
Check It Out! Compare Respiration
& Photosynthesis
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Did you notice
that cellular
respiration is just
the opposite of
photosynthesis?
Photosynthesis
Respiration
Fermentation
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Happens when cells cannot
get the oxygen they need for
cellular respiration
Fermentation is a way to get
energy when oxygen isn’t
available
Ex: In short, fast races you
might get a burning feeling
in you leg muscles because of
a build up of lactic acid
(made during fermentation)
Pop Quiz
1)
2)
3)
4)
5)
In respiration cells use oxygen (____) and glucose
(____) to make energy.
O2 and C6H12O6 are used to make ATP Energy
Which organelle carries on cellular respiration?
MITOCHONDRIA
Do plant or animal cells carry on cellular respiration?
BOTH ANIMAL & PLANT CELLS NEED ENERGY
Do plant or animal cells carry on photosynthesis?
PLANT CELLS BECAUSE ONLY THEY HAVE
CHLOROPLASTS
What is the name for the energy produced by
mitochondria?
ATP (Adenosine Triphosphate)
Pop Quiz
6) Plants use carbon dioxide (____), water (____), and the
sun’s energy to make:
CO2 and H2O are used to make GLUCOSE C6H12O6
7) Which organelle carries on photosynthesis?
CHLOROPLASTS FOUND ONLY IN PLANT CELLS
8) BOTH plants and animals must break down food in
order to get ________from it.
ENERGY IN THE FORM OF ATP
9) How are respiration and photosynthesis related?
THEY ARE THE REVERSE (OPPOSITE) OF EACH
OTHER.
10) Fermentation is a way to get energy when ______
isn’t available. In humans (
) acid is produced.
OXYGEN and LACTIC ACID
Practice Questions
Working muscle cells that are deprived of oxygen
produce:
A. Alcohol
B. Lactic Acid
C. Citric Acid
D. Acetone
Practice Questions
Which of these is a characteristic of body cells that
require large amounts of energy?
A. They have large number of mitochondria
B. They have a supplementary Y chromosome
C. They have a two-layer membrane
D. They have a storage area for albumin proteins.
Practice Questions
Why are photosynthesis and cellular respiration
often considered opposites?
A. Photosynthesis produces twice as many ATP
molecules as cellular respiration does
B. Water is released during photosynthesis and
consumed during cellular respiration
C. Photosynthesis occurs during the day and
cellular respiration occurs at night
D. Oxygen is produced during photosynthesis and
used during cellular respiration
Practice Questions
Which molecule provides most of the energy used to
drive reactions in cells?
A. DNA
B. RNA
C. ATP
D. ADP
Practice Questions
Which structure regulates gas exchange during the
processes of photosynthesis and respiration?
A.
B.
C.
D.
Q
R
S
T
T is pointing to the guard cells
which surround the openings
called stomates. The guard cells
open and close.
To produce 4 molecules of sugar, a plant needsA. 6 molecules of hydrogen
B. 12 molecules of ATP
C. 18 molecules of water
D. 24 molecules of carbon dioxide
DANA
CENTER
ACTIVITY
TIME