Photosynthesis Review
Photosynthesis
1. Define photosynthesis.
Photosynthesis is the process by which
photosynthetic organisms convert solar
energy into chemical energy stored in
sugars.
2. Name several photosynthetic organisms.
Trees
Algae
Cyanobacteria
Photosynthesis
3. Using chemical formulas, write the balanced
equation for photosynthesis.
6CO2 + 6H2O
Sunlight
C6H12O6 + 6O2
4. Now write out the equation using words.
Carbon dioxide + water yields sugar + oxygen
Photosynthesis
5. What organelle in plants is involved in
photosynthesis?
The chloroplast
6. What gives it the green color?
The pigment chlorophyll
Photosynthesis
7. Where in plants are chloroplasts found?
In the cells of soft plant tissue, like the
green stems and leaves of celery .
Note: Chloroplasts are also
found in other colors of soft
plant tissue, like the red leaves
of a burning bush for example.
They use secondary pigments,
like carotenoids (orange color)
and xanthophylls (yellow color)
that are more predominant
than green chlorophyll.
Photosynthesis
8. Identify the chloroplasts in this micrograph of
elodea cells.
Chloroplasts
Elodea plant
Elodea plant cells
Photosynthesis
Identify the following structures of the chloroplast.
9
Photosynthesis
Identify the following structures of the chloroplast.
Outer
membrane
Photosynthesis
Identify the following structures of the chloroplast.
10
Photosynthesis
Identify the following structures of the chloroplast.
Inner
membrane
Photosynthesis
Identify the following structures of the chloroplast.
11
Photosynthesis
Identify the following structures of the chloroplast.
Inner membrane
space
Photosynthesis
Identify the following structures of the chloroplast.
12
Photosynthesis
Identify the following structures of the chloroplast.
Stroma
Photosynthesis
Identify the following structures of the chloroplast.
13
Photosynthesis
Identify the following structures of the chloroplast.
Thylakoids
Photosynthesis
Identify the following structures of the chloroplast.
14
Photosynthesis
Identify the following structures of the chloroplast.
Thylakoid space (lumen)
Photosynthesis
Identify the following structures of the chloroplast.
15
Photosynthesis
Identify the following structures of the chloroplast.
Granum
A stack of
thylakoids
Photosynthesis
16. Photosynthesis occurs in two parts. One is
the light-dependent reaction. What is the
other part called?
The other is the light-independent reaction.
17. Which of these two reactions can occur during
both the daytime and nighttime?
The light-independent reaction
(it doesn’t require light).
Photosynthesis
18. Where in the chloroplast do the light-dependent
reactions occur?
The light-dependent reactions
occur in the thylakoids
Photosynthesis
19. Where in the chloroplast do the lightindependent reactions occur?
The light-independent reactions
occur in the stroma.
Photosynthesis
20. Sometimes the light-independent reaction is
called the “dark” reaction. Why is dark reaction
not an appropriate term to use?
The use of the word dark makes one think that
the reaction only occurs in the dark. This is
not true since the reactions can take place in
the light too—it is just light is not required for
the reaction to occur.
Photosynthesis
21. What is another name for the light-independent
reactions that occur in the stroma?
The light-independent reaction is also called the
Calvin Cycle, in honor of Melvin Calvin, who worked
out the metabolic pathway of photosynthesis.
Chloroplast
Also known as the
light-independent
reaction.
Photosynthesis
The bean-shaped object below represents a chloroplast.
The green disks are thylakoids and the tan area is the
stroma. Identify the outputs and inputs of the lightdependent and light-independent (Calvin cycle) reactions.
23
22
25
26
Chloroplast
24
27
Photosynthesis
The bean-shaped object below represents a chloroplast.
The green disks are thylakoids and the tan area is the
stroma. Identify the outputs and inputs of the lightdependent and light-independent (Calvin cycle) reactions.
Light energy
23
25
26
Chloroplast
24
27
Photosynthesis
The bean-shaped object below represents a chloroplast.
The green disks are thylakoids and the tan area is the
stroma. Identify the outputs and inputs of the lightdependent and light-independent (Calvin cycle) reactions.
Water H2O
Light energy
25
26
Chloroplast
24
27
Photosynthesis
The bean-shaped object below represents a chloroplast.
The green disks are thylakoids and the tan area is the
stroma. Identify the outputs and inputs of the lightdependent and light-independent (Calvin cycle) reactions.
Water H2O
Light energy
Oxygen
25
26
Chloroplast
O2
27
Photosynthesis
The bean-shaped object below represents a chloroplast.
The green disks are thylakoids and the tan area is the
stroma. Identify the outputs and inputs of the lightdependent and light-independent (Calvin cycle) reactions.
Water H2O
Light energy
Oxygen
ATP
26
Chloroplast
O2
27
Photosynthesis
The bean-shaped object below represents a chloroplast.
The green disks are thylakoids and the tan area is the
stroma. Identify the outputs and inputs of the lightdependent and light-independent (Calvin cycle) reactions.
Water H2O
Light energy
Oxygen
ATP
CO2
Chloroplast
O2
27
Carbon dioxide
Photosynthesis
The bean-shaped object below represents a chloroplast.
The green disks are thylakoids and the tan area is the
stroma. Identify the outputs and inputs of the lightdependent and light-independent (Calvin cycle) reactions.
Water H2O
Light energy
Oxygen
ATP
CO2
Carbon dioxide
Chloroplast
O2
C6H12O6
Sugar (glucose)
Photosynthesis
28. What do plants do with the sugars they make
from photosynthesis?
The sugars are used to
help the plant live, grow,
and reproduce. Some
sugars are used to make
other compounds, and
some end up at the
mitochondria to be
converted into ATP,
which is then used to
drive cellular reactions.
Everything above can be made from sugars
Photosynthesis
29. What do plants do with the excess sugars they
make during photosynthesis?
The excess sugars are stored as starch.
Starch grains
(stained purple)
in plant cells.
Photosynthesis
30. What will happen if a plant is placed in the dark
for 48 hours?
Since it will not be able to make glucose
through photosynthesis, the plant must access
glucose from starch reserves. The plant will
most likely deplete its starch supply in that
time. Thus the plant will be destarched.
Photosynthesis
An Experiment in photosynthesis
a. Destarch a plant by leaving it in the dark for 48 hrs.
b. Next, cover a section of one leaf with cardboard.
c. Finally, expose the leaf to light for 24 hours
Photosynthesis
An Experiment in photosynthesis (continued)
d. Remove cardboard and pick off the leaf.
e. Put the leaf in hot water for a few minutes.
Photosynthesis
An Experiment in photosynthesis (continued)
f. Remove the leaf.
g. Test for starch using iodine solution.
Iodine
Solution
Photosynthesis
An Experiment in photosynthesis (continued)
31. What do you think will happen?
Iodine
Solution
Photosynthesis
An Experiment in photosynthesis (continued)
31. What do you think will happen?
No light,
The leaf cells under
no starch
the cardboard
would not receive
any light and thus
would not make
sugars or store any
starch.
Exposure to light
Positive for starch
The areas exposed
to light would
store starch and
test positive with
iodine, turning a
black color.
Photosynthesis
32. As previously mentioned, chlorophyll is green. Why
is chlorophyll green and not some other color?
White light is made
up of many colors.
Chlorophyll absorbs
all of these colors
except green, which
is reflected back
into our eyes.
Photosynthesis
33. Study the chart below. What color(s) of light does
chlorophyll absorb best?
Chlorophyll absorbs
red and blue light
energies the best.
Photosynthesis
34. What would happen to the health of a plant that
was grown under red and blue filters?
The plant will do
poorly since the red
and blue light
energies chlorophyll
absorbs best are
being reflected
away by the filters.