Photosynthesis Mr. Zito

General Formula

I. Energy A. The sun is the source of energy for almost all life on earth. 1. Autotrophs -“Self Feeders” a. Sun light and/ or inorganic compounds are used to produce organic compounds.

*phototrophic- plants, algae, and certain bacteria

*chemotrophic- bacteria in hostile environments 6CO2 + 6H2O + 3 H2S  C6H12O6 + 3H2SO4 Bacteria that thrive on the energy-rich chemical compounds transported by hydrothermal fluids forming a food chain that does not depend on the energy of the Sun or photosynthesis.

Instead of photosynthesis, vent ecosystems derive their energy from chemicals in a process called “chemosynthesis.” Both methods involve an energy source (1), carbon dioxide (2), and water to produce sugars (3). Photosynthesis gives off oxygen gas as a byproduct, while chemosynthesis produces sulfur (4) Image courtesy Woods Hole Oceanographic Institution.Graphic from: http://science.nasa.gov/headlines/y2001/ast13apr_1.htm

B. ATP- adenosine triphosphate 1. Structure 2.ATP is the “stored energy currency” of the cell- can be made available when needed.

II. Leaf Structure

Leaves are the primary photosynthetic organ of plants-large surface area for light to strike. 1. Cuticle- waxy layer on epidermis a. protection b. prevent water loss 2. Epidermis- single layer of flat cells. a. used for protection

3. Palisade Mesophyll- elongated cells a. most chloroplast=most photosynthesis 4. Spongy Mesophyll-air pockets for gas exchange and circulation of water a. fewer chloroplasts

5. Vascular Bundle/Veins (xylem/phloem) a. xylem: carries water and minerals upward to leaf cells from the stem and roots. b. phloem: carries food made in the leaves to the stem and the roots for use and storage.

6. Stomata/stomate- tiny openings that exchange gases and water with the atmosphere. 7. Guard Cell- one on each side of the stomata to regulate its opening and closing. (open day/ closed night- prevent water loss)

III. Chloroplast Structure

(inner- most membrane) Thylakoids: Membrane “discs” arranged in stacks called grana. (inner- most membrane) 1.Contain chlorophyll and other important molecules. 2. Site where solar energy is trapped and converted into chemical energy. (light- dependant reaction)

1. Site of carbon fixation. (light- independent (dark) reactions) B. Photosystems: clusters of proteins, chlorophyll, and other pigments in the thylakoid membrane. C. Stroma: Thick enzyme-rich fluid filled area surrounding the thylakoid membrane. 1. Site of carbon fixation. (light- independent (dark) reactions)

IV. Light and Pigments Light absorbing molecules- PIGMENTS. Pigments absorb certain wavelengths and reflect others. Chlorophyll- primary green pigment in photosynthesis. Absorbs blue- violet and orange-red best. (BEST LIGHT) Reflects green and yellow (WORST LIGHT) Carotinoids- yellow and orange pigments.