Photosynthesis
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Transcript Photosynthesis
Chapter 4
Is the Earth Warming?
Photosynthesis
Copyright © 2007 Pearson Prentice Hall, Inc.
Photosynthesis
• Photosynthesis
– Removes carbon
dioxide from the air
and turns it into sugar
(food)
6 CO2 + 6 H2O + light energy
C6H12O6 + 6 O2
carbon dioxide + water + light
glucose + oxygen +energy
•
In photosynthesis, plants use light
energy to rearrange the atoms of
CO2 and H2O into carbohydrates
Photosynthesis
• Plants are not the only organisms that can
photosynthesize
• Algae
• Photosynthetic bacteria can photosynthesize without
chloroplasts
Transpiration
Xylem sap (water and
dissolved minerals from soil)
travel up inside a plant
Water vapor is lost from leaves
When water evaporates, the forces of cohesion
and adhesion create tension
Tension causes water molecules from the xylem
to be drawn out into the leaf to replace the water
that has evaporated
This, in turn, increases tension on the water
molecules immediately below them in the
xylem
This causes water to move towards the leaves,
and so on
•
Transpiration relies on
– The sun to cause evaporation
– Hydrogen bonding
•
Plants can modify the rate of transpiration
by regulating stomata size
http://www.youtube.com/watch?v=At1BJJD
cXhk
• Chloroplasts are structures in plant cells
that allow them to carry out photosynthesis
• Pigment molecules called chlorophyll are on the surface
of the thylakoid membrane
• Chlorophyll molecules absorb and capture light energy
from the sun
• Chlorophyll gives plants their green color
• The electromagnetic spectrum is made up of
several types of light, each having a different
energy level and wavelength
http://academic.kellogg.edu/herbr
andsonc/bio111/animations/0053.
swf
The Light Reactions
and Calvin Cycle
• Step 1: photo– Light reactions
• Light energy is
harvested
•
Step 2: -synthesis
– Calvin cycle
• Sugar is made
Light Reaction**Occurs in
thylakoid
http://dendro.cnre.vt.edu/forestbiology/photosynthesis.swf\
Uses Water and light
Produces Oxygen, ATP, and
NADPH
http://www.science.smith.edu/depart
ments/Biology/Bio231/ltrxn.html
“Calvin cycle”
**Occurs in stroma
Uses CO2 ,
ATP, & NADPH
s,,
Produces
Sugar
http://highered.mc
grawhill.com/sites/9834
092339/student_vi
ew0/chapter39/cal
vin_cycle.html
http://www.science.smith.edu/dep
artments/Biology/Bio231/calvin.ht
ml
C3, C4, and CAM Plants
• Stomatal openings
through which plant
cells bring CO2 into
leaves are surrounded
by guard cells that
open and close
• Water can also move
through the stomatal
openings in
transpiration
• Photorespiration
involves the closing of
stomatal openings to
prevent water loss
C3, C4, and CAM Plants
• C3 plants – normal
photosynthesis
• C4 plants – live in hot
climates; need to
conserve water; can
make sugar, but this
takes more ATP than
normal
Sugarcane
crabgrass
• CAM plants –stored as
acid until daytime
houseplants