2. Photosynthesis
• An anabolic, endergonic, carbon dioxide
(CO2) requiring process that uses light energy
(photons) and water (H2O) to produce organic
macromolecules (glucose).
6CO2 + 6H2O C6H12O6 + 6O2
glucose
SUN
photons
7. Stomata (stoma)
• Pores in a plant’s cuticle through which water
and gases are exchanged between the plant
and the atmosphere.
Guard Cell
Guard Cell
Carbon Dioxide
(CO2)
Oxygen
(O2)
11. Chloroplast
• Organelle where photosynthesis takes place.
Granum
Thylakoid
Stroma
Outer Membrane
Inner Membrane
Chloroplast is an organelle that contains the photosynthetic
pigment chlorophyll that captures sunlight and converts it
into useful energy, thereby, releasing oxygen from water.
12.
13. Chloroplasts are found in all green plants and algae. They are the
food producers of plants. These are found in the guard cells
located in the leaves of the plants. They contain a high
concentration of chlorophyll that traps sunlight.
22. Chlorophyll Molecules
• Located in the thylakoid membranes.
• Chlorophyll have Mg+ in the center.
• Chlorophyll pigments harvest energy (photons)
by absorbing certain wavelengths (blue-420
nm and red-660 nm are most important).
• Plants are green because the green
wavelength is reflected, not absorbed.
23.
24. Wavelength of Light (nm)
400 500 600 700
Short wave Long wave
(more energy) (less energy)
27. Fall Colors
• In addition to the chlorophyll pigments, there are
other pigments present.
• During the fall, the green chlorophyll pigments
are greatly reduced revealing the other
pigments.
• Carotenoids are pigments that are either red or
yellow.
28.
29.
30. Redox Reaction
• The transfer of one or more electrons from
one reactant to another.
• Two types:
1. Oxidation
2. Reduction
31. There are several types of pigments distributed among various phototrophic
organisms. Chlorophyll is the primary light-harvesting pigment in all
photosynthetic organisms. Chlorophyll is a tetrapyrrole which contains
magnesium at the center of the porphyrin ring. It contains a long hydrophobic
side chain that associates with the photosynthetic membrane. Cyanobacteria
have chlorophyll a, the same as plants and algae. The chlorophylls of the
purple and green bacteria, called bacteriochlorophylls are chemically different
than chlorophyll a in their substituent side chains. This is reflected in their light
absorption spectra. Chlorophyll a absorbs light in two regions of the spectrum,
one around 450nm and the other between 650 -750nm; bacterial chlorophylls
absorb from 800-1000nm in the far red region of the spectrum
32. Chlorophyll a (Chl-a)
1. It is the principal photosynthetic pigment
2. It is present in all phototrophs other than bacteria
3. Blue green in pure state
4. Empirical formula is C55H77O5N4Mg
5. The 3rd carbon of the side group is methyl group (-CH3)
6. Molecular weight is 873
Chlorophyll b (Chl-b)
1. It is the accessory photosynthetic pigment
2. It is present in all phototrophs other than diatoms, cyanobacteria, red and
brown algae
3. Olive green in pure state
4. Empirical formula is C55H70O6N4Mg
5. Side group at the 3rd carbon is aldehyde group (-CHO)
6. Molecular weight is 907
33. Absorption of blue light excites the chlorophyll to a higher
energy state than absorption of red light because the energy of
photons is higher when their wavelength is shorter.
34. Photosystems
• Photosystem I uses chlorophyll a, in the form referred to as P700. It
absorbs light at 700 nm. Photosystem II uses a form of chlorophyll a
known as P680. It absorbs light at 680 nm.
• The accessory pigments (chlorophyll b, carotenes, 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. 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.
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.
Graphic: http://kvhs.nbed.nb.ca/gallant/biology/photosystem.jpg
37. Phosphorylation
• Phosphorylation: The chemical addition of a
phosphate group (phosphorous and oxygen) to
a compound. i.e. adding Pi to ADP to get ATP
• Photophosphorylation is addition of a
phosphate using the sun’s energy!
• There are two types of photophosphorylation;
cyclic and non-cyclic
