Transcript Photosynthesis 1

PHOTOSYNTHESIS
Pigments & Chlorophyll
Teachers' Domain: Photosynthesis
Discussion questions:
• Do you think that the factory is a good analogy for
the process of photosynthesis in plants?
• Why did von Helmont think that plants got their
nourishment from soil?
• Why did he eliminate soil as a source of
nourishment and focus on water?
• What did he measure to find out if the willow plant
got its nourishment from soil?
• What do you think von Helmont concluded when he
measured the change in weight of the plant and the
soil?
PHOTOSYNTHESIS OVERVIEW
6CO2 + 6H2O + energy (sun)  C6H12O6 + 6O2
PHOTOSYNTHESIS OVERVIEW
• Photosynthesis is the conversion of
light energy to chemical energy.
• It involves two stages:
1. Light reaction.
2. Dark reaction (Calvin Cycle)
STRUCTURE OF A LEAF
• Leaves are a plant's main
photosynthetic organs.
• Leaves must permit carbon dioxide
access to the photosynthetic cells but
impede water from diffusing out.
• The oxygen that is a waste product of
photosynthesis must be allowed to
escape from the leaf.
STRUCTURE OF A LEAF
• In
which cells does photosynthesis take place?
STRUCTURE OF A LEAF
• Mesophyll cells are specialized for
photosynthesis.
• These cells in the middle of the leaf
contain many chloroplasts, the
organelles that perform
photosynthesis.
STOMA
• The stoma allows for the plant to
exchange gasses with its environment.
Stoma
Guard cells
PIGMENTS & CHLOROPHYLL
• Pigment: any substance that absorbs
light of a specific wavelength.
• Photosynthetic Pigments absorb light
(solar) energy and convert it to
chemical energy.
• Chlorophyll by itself can’t carry out
photosynthesis - it will absorb light
but radiate it back at a different
wavelength.
PIGMENTS & CHLOROPHYLL
• Electron Acceptors must also be
present for photosynthesis.
• Chlorophyll is found embedded in
flattened membranes called
Thylakoids in the Chloroplast.
• Thylakoids are arranged I
interconnected stacks called Granna.
PIGMENTS & CHLOROPHYLL
PIGMENTS & CHLOROPHYLL
PLANT PIGMENT
COLOR
Chlorophyll A and B
Green
Carotins
orange
Xanthophyll
red
PHOTOSYSTEMS
• Photosystems are arrangements of
chlorophyll and other accessory
pigments packed into thylakoids.
• Many prokaryotes have only one
photosystem, Photosystem I. Eukaryotes
have Photosystem I plus Photosystem II.
PHOTOSYSTEMS
• The accessory pigments
(chlorophyll b, carotenoids , and
xanthophylls) play an indirect role in
the formation of glucose through
photosynthesis.
• These pigments provide chlorophyll a
with the energy that they have
captured from the sun.
PHOTOSYSTEMS
• These pigments capture varying
wavelengths of light and thus allow
the plant to receive sun energy across
a greater spectrum.
• Accessory pigments absorb energy
that chlorophyll a does not absorb.
• Some carotenoids play a role in
energy absorption rather than in
photosynthesis. They absorb light to
prevent damage to chlorophyll. The
energy is lost as heat.
PHOTOSYSTEMS
Nova: Illuminating photosynthesis
Discussion Questions:
• Does the plant give off oxygen at night or when the
shade is down?
• Does the plant use oxygen at night or when the shade
is down?
• The person takes in oxygen and gives off carbon
dioxide. Do plants do this as well?
• How does the process of photosynthesis help the
plant?
• What organisms can carry out photosynthesis?
The photosynthesis song!
PHOTOSYSTEMS
• Why do leaves of deciduous trees turn
pretty colors in autumn?