Chloroplasts and Mitochondria
Plant cells and some Algae contain an organelle called the
chloroplast. The chloroplast allows plants to harvest energy from sunlight
to carry on a process known as Photosynthesis. Specialized pigments in the
chloroplast (including the common green pigment chlorophyll) absorb
sunlight and use this energy to combine carbon dioxide and water and make
GLUCOSE and OXYGEN. The complete the chemical reaction for
Photosynthesis is:
6 CO2 + 6 H2O + energy (from sunlight)
RAW MATERIALS
ENERGY
C6H12O6 + 6 O2
PRODUCTS
In this way, plant cells manufacture glucose and other carbohydrates
that they can store for later use. Photosynthetic cells found mainly in the
leaves may have thousands of chloroplasts.
QUESTIONS:
1. What type of cells contains chloroplasts?
2. What is the energy autotrophs use to make their own food?
3. The food making process is called ___________________.
4. What are the raw materials for photosynthesis?
5. What simple sugar is produced?
6. What gas is USED? ________________ RELEASED? ________
7. Where are most photosynthetic cells in plants found?
8. About how many chloroplasts can be found in photosynthetic cells?
1
Chloroplasts are double membrane organelles with a smooth outer
membrane and an inner membrane folded into disc-shaped sacs called
thylakoids. Color and label the outer membrane light green. Thylakoids,
containing chlorophyll and other accessory pigments (red, orange, yellow,
brown), are in stacks called granum (grana, plural). Color and label the
grana (STACK) dark green in Figure 1. Grana are connected to each other
by structures called lamellae, and they are surrounded by a gel-like
material called stroma. Color and label the lamellae brown in figure 1.
Color and label the stroma light blue in Figure 1.
FIGURE 1-CHLOROPLAST
9. How many membranes surround a chloroplast?
10. The outer membrane is S____________.
11. The INDIVIDUAL SACS formed by the inner membrane are called
_________________ and are arranged in ___________ like
pancakes.
12. What pigment is found inside a thylakoid? What color will it be?
13. Other pigments that trap sunlight are called A_____________
pigments. What colors are these pigments?
2
14. STACKS of thylakoids are called G___________ (plural) or
GRANUM (singular).
15. Stacks or grana are connected to each other by _____________.
Light-capturing pigments in the grana are organized into photosystems.
On Figure 2, color and label a single thylakoid (SINGLE DISK) dark green.
In figure 2, color and label a granum (STACK) red.
FIGURE 2-THYLAKOID
Mitochondria are the powerhouses of the cell because they “burn” or
break the chemical bonds of glucose to release energy to do work in a
cell. Remember that this energy originally came from the sun and was
stored in chemical bonds by plants during photosynthesis. Glucose and
other carbohydrates made by plants during photosynthesis are broken
down by the process of aerobic cellular respiration (requires oxygen) in
the mitochondria of the cell. This releases energy (ATP) for the cell.
The more active a cell (such as a muscle cell), the more mitochondria it
will have. The mitochondria are bout the size of a bacterial cell and are
often peanut-shaped. Mitochondria have their own DNA and a double
membrane like the nucleus and chloroplast. The outer membrane is
smooth, while the inner membrane is convoluted into folds called cristae
in order to increase the surface area.
3
16. Why are mitochondria called the powerhouse of the cell?
17. What cell process occurs in the mitochondria?
18. Why do some cells have MORE mitochondria? Give an example.
19. What simple sugar is broken down in the mitochondria?
20. Where does the energy in glucose come from ORIGINALLY?
21. Where is this energy stored in glucose?
22. Why is cellular respiration an aerobic process?
23. What energy is released when the chemical bonds of glucose are
broken?
24. Name two other organelles besides the mitochondria that contain
DNA and have a double membrane.
25. Describe the outer membrane of the mitochondria.
26. Why is the inner mitochondrial membrane folded?
27. What are the folds called?
4
Color and label the outer membrane pink and the cristae red on
figure 3. This greatly increases the surface area of the membrane so
that carbohydrates (simple sugars) can combine with oxygen to produce
ATP, adenosine triphosphate (the energy molecule of the cell). The
electron transport chain takes place across the membranes of the
cristae (crista, singular). Inside the folds or cristae is a space called
the matrix that contains enzymes needed for the Kreb's Cycle? Color
and label the matrix yellow on figure 3.
FIGURE 3 - MITOCHONDRIA
Mitochondria
Adenosine triphosphate (ATP) is the energy molecule used by all cells
to do work. It is a nucleotide consisting of a nitrogen-containing base
(adenine, thymine, cytosine, or guanine), a 5-carbon sugar, and 3 phosphate
groups. ATP is able to store and transport chemical energy within cells.
The LAST TWO phosphate groups (PO4), are joined by HIGH-ENERGY
bonds. When these bonds are broken, energy is released for cells to use
and ADP forms. Enzymes help to break and reform these high-energy
bonds.
28. What does ATP stand for?
29. What three main things make up an ATP molecule?
30. How many high-energy bonds does ATP contain?
5
31. Where are these high-energy bonds found in ATP?
32. What helps weaken these bonds so energy can be released and then
later help reform them?
33. When ATP loses a phosphate group __________ is released for cells
and a molecule of _________ forms.
In Figure 4, COLOR the 5-carbon sugar RED and LABEL it RIBOSE.
COLOR and LABEL the nitrogen-base DARK BLUE. COLOR and LABEL
the 3 phosphate groups YELLOW, and COLOR & LABEL the 2 highenergy bonds GREEN.
FIGURE 4 – ATP MOLECULE
Questions:
34. What is the energy molecule of the cell called?
35. What macromolecule made by plants is "burned" in the mitochondria?
36. Where is chlorophyll found in the chloroplast?
37. In which part of a plant would you expect to find the most chloroplasts and why?
38. How would the number of mitochondria in an insect's wing compare to the amount
found in other cells in an insect's body? Explain your answer.
6
39. What are the raw materials for photosynthesis?
40. What product of photosynthesis is used in cellular respiration?
41. What is the advantage of having a folded inner membrane in the mitochondria?
42. What is the energy for photosynthesis?
43. Besides chlorophyll, what other pigments are found in the chloroplasts?
Photosynthesis Review Worksheet
Part A
Match the terms below with the correct description
Chlorophyll
Chloroplast
Electromagnetic spectrum
Electron transport chain
Grana
Light-dependant reactions
Light-independent reactions
Photon
Photosynthesis
Photosystem
Stroma
Thylakoid
a. __________________ packet of solar energy
b. __________________energy-capturing portion of photosynthesis that takes place in thylakoid
membranes of chloroplasts and cannot proceed without solar energy, it produces ATP and
NADPH
c. __________________green pigment that absorbs solar energy and is important in
photosynthesis
d. __________________ large, central compartment in a chloroplast that is fluid filled and
contains enzymes used in photosynthesis
e. __________________ membrane-bounded organelle with chlorophyll – containing
membranous thylakoids; where photosynthesis takes place
f. __________________Photosynthetic unit where solar energy is absorbed and high-energy
electrons are generated; contains a pigment complex and an electron acceptor
g. __________________Passage of electrons along a series of carrier molecules form a higher to
a lower energy level; the energy released is used for the synthesis of ATP.
h. __________________Process usually occurring within chloroplasts whereby chlorophyll traps
solar energy and carbon dioxide is reduced to a carbohydrate.
7
i. __________________ Series of photosynthetic reactions in which carbon dioxide is fixed and
reduced in the chloroplast.
j. __________________Synthesis portion of photosynthesis that takes place in the stroma of
chloroplasts and does not directly require solar energy; it uses the products of the light
dependant reactions to reduce carbon dioxide to a carbohydrate
Part B
Answer the following questions
1. Explain the difference between autotrophs and heterotrophs. Give two examples of each.
2. Below draw a molecule of ATP. Label: ADP, adenosine, adenine, ribose, phosphate groups,
chemical bond that would be broken if energy needed to be released.
3. Below draw a diagram of chloroplast and label the following: chloroplast membrane, thylakoid,
granum (grana), stroma, thylakoid membrane, thylakoid innerspace, location of pigments.
4. Explain why chloroplasts are green. (use the correct information from the electromagnetic spectrum)
5. What is NADPH? What is the difference between NADP+ and NADPH? How does NADP+ turn
into NADPH?
8
6. Write the chemical equation for the process of photosynthesis.
7. What are the reactants and products of Light Dependant Reactions? Where in the chloroplast do they
occur?
Reactants:
Products:
Location:
8. What are the reactants and products of Light-Independent Reactions? Where in the chloroplast do
they occur?
Reactants:
Products:
Location:
Part C
The Light Dependent Reactions of photosynthesis occur on the thylakoid membranes of the
chloroplast. Below is a diagram that describes the path of the electrons throughout the L-D reactions.
Use it to answer the next set of questions.
1. Describe the first set of Light-Dependant reactions.
9
2. Every time a photon is absorbed in the chlorophyll a 2 electrons are excited. They are not
recycled. Where does the supply of electrons come from and where do they end up at the end of
L-D set of reactions?
3. What products result specifically from Photosystem I and Photosystem II?
4. When a water molecule is split, what is it split into? Where do all the resulting components end
up?
5. At what steps of L-D reactions is ATP made. What is it specifically used for? (this will be
different depending when and where is it produced)
6. Describe the action of protein carrier: ATP synthase? Explain why is it important to build up a
Hydrogen ion concentration gradient in order to have it properly function?
Part D
1. What are Light-Independent Reaction often called?
2. Why is there a need to go on with Light – Independent reactions? Why not stop with the Light
–Dependant Reactions since ATP and NADPH are energy carrying molecules?
3. Where does the Carbon Dioxide come from? What will happen to it and what will it eventually
become?
4. How many molecules of carbon dioxide enter one Calvin Cycle? How many molecules of highenergy sugars are produced as a result of one Calvin Cycle?
5. Look at the diagram below and complete it by filling in the products, reactants or descriptions
of what happens at each step.
10
6. What are the steps of the Calvin Cycle where ATP is needed?
7. Explain how temperature, intensity of light and water affect the rates of photosynthesis?
11