The overall process of photosynthesis produces sugars that ...€¦ · Photosynthesis Sections...
Transcript of The overall process of photosynthesis produces sugars that ...€¦ · Photosynthesis Sections...
Photosynthesis Sections 4.2-4.3
The overall process of
photosynthesis produces
sugars that store chemical
energy.
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Overview • All energy on earth comes from the sun.
• We depend on:
– Plants
– Algae (underwater plants)
– Cyanobacteria (photosynthetic bacteria)
• To provide this energy to us!
Overview
Overview • Photosynthetic organisms are producers.
• Producers make their own source of
chemical energy.
• Plants use photosynthesis and are
producers.
• Photosynthesis captures energy from
sunlight to make sugars.
Overview • Carbon dioxide and water are taken in by
plants
• Plants absorb light energy and convert it to a usable form. – ATP
• Energy is used to “fix” carbon dioxide into sugar molecules – Chemical energy
• Sugar is converted to starch and stored for use by the plant, and by animals when they eat plants.
Chlorophyll
• Chlorophyll is a
molecule that
absorbs light
energy.
• In plants,
chlorophyll is
found in organelles
called
chloroplasts. leaf
leaf cell
chloroplast
Plants are green because of the pigment chlorophyll.
(which absorbs light energy)
• During the fall, the green chlorophyll
pigments are greatly reduced revealing
the other pigments, this is the reason
leaves turn brown in the fall.
• Carotenoids are pigments that are
either red or yellow.
• Photosynthesis
takes place in two
parts of
chloroplasts.
–grana
(thylakoids)
–stroma
chloroplast
stroma
grana (thylakoids)
Chloroplasts • Have TWO
membranes
– A “bi-bilayer!”
• The inner membrane is called the thylakoid.
• The thylakoid is folded and looks like stacks of coins called granum (grana=singular).
• The stroma is the space surrounding the granum.
Image source: http://www.daviddarling.info/encyclopedia/C/chloroplasts.html
Chloroplasts • Chlorophyll
molecules are
embedded in the
thylakoid membrane
• Act like a light
“antenna”
• These molecules
can absorb sunlight
energy. Image from Biology 11: College Preparation. Pg 73. Nelson,
Toronto. 2003.
Light (dependent)Reactions
• Happen ONLY in sunlight
– Hence they depend on light!
– Water is also required
1. Light energy is absorbed by chlorophyll
molecules in the thylakoid
2. The energy generates molecules of ATP
(ADP converted to ATP)
3. Convert NADP+ to NADPH (Electron
Carriers)-Energy then goes to Light
Independent reaction
4. Produce Oxygen (O2) gas
Light (dependent)Reactions
Image from: Biology 11: College Preparation. Pg 74. Nelson, Toronto. 2003.
Light (dependent)Reactions
Light Independent Reactions
(formerly the “dark reactions”) • Happen in sunlight, and in the dark.
– Hence “independent of light”
– Makes sugars
1. Takes place in the stroma.
2. CO2 enters from the atmosphere
3. ATP generated by sunlight drives the Calvin Cycle.
4. Monosaccarides (eg. glucose) are manufactured in the
cycle.
5. Monosaccarides are used to “build” polysaccharides (eg.
Starch).
Light Independent Reactions
(formerly the “dark reactions”)
Image from: Biology 11: College Preparation. Pg 74. Nelson, Toronto. 2003.
Light Independent Reactions
(formerly the “dark reactions”)
Overall Reaction What is the equation for photosynthesis?
carbon dioxide + water glucose + oxygen + energy
6CO2 + 6H2O C6H12O6 + 6O2 + energy
C6H12O6
granum (stack of thylakoids)
thylakoid
1 six-carbon sugar
6H2O
6CO2
6O2
chloroplast 1
2
4 3
energy
stroma (fluid outside the thylakoids)
Factors that affect the rate
of Photosynthesis are…
• Availability of Water
• Temperature
• Intensity of Light
• Concentration of CO2
S
u
n
L
I
G
H
T
H2O CO2
Light
Dependent
Reactions
Calvin Cycle
CHLOROPLAST
Sugars O2