Molecular Biology Ch. 7

photosynthesis

the conversion of light energy into chemical energy.

autotroph

-"self-feeder"
-produce their organic molecules from CO2 in the atmosphere and from inorganic material.
-"producers" of the environment
-plants are autotrophs, using light as energy

heterotrophs

-make their organic material by consuming organic material.
-"consumers"

chloroplast

-site of photosynthesis
-present in all green parts of a plant b/c of chlorophyll pigment.
-leaf has highest amount of chloroplast.

mesophyll

the fleshy part of a leaf where there is the highest concentration of chloroplast

stomata

pores in a leaf used for gas exchange

photosynthesis reaction

6CO2 + 6H2O + Light energy = C6H12O6 + 6O2

-CO2 is reduced
-H2O is oxidized

2 stages of photosynthesis

-light reactions in the thylakoid membrane
-Calvin Cycle in the stroma of the chloroplast

chloroplast pigments

-clustered in the thylakoid membrane
-Chlorophyll A: absorbs blue-violet and red light, reflects green. Participates directly in light reactions.
-Chlorophyll B: absorbs blue and orange light, reflects green-yellow. Transfers all energy to A.
-Carotenoids: reflect orange-yellow. Not involved directly in light reactions, energy provider for A, disperses excess energy.

photosystem

light harvesting unit in the thylakoid membrane

reaction center

-chlorophyll A that accepts all energy and splits water in the photosystem
-H2O = 2H+ + 2e- + 1/2O2

anabolic pathway

-uses energy to make molecules
-3 phases:
1. Carbon fixation- ribulose biphosphate binds w/ CO2. Rubisco is an enzyme which catalyzes the initial fixation of carbon.
2. Reduction phase
3. Regeneration of the CO2 acceptor RuBP

products and energy required of anabolic pathway

-products: 1 G3P, 6 NADP+ & 6P, 9 ADP
-energy required: 9 ATP, 6 NADPH

C3 plants

-take in CO2 directly from atmosphere
-Rubisco fixes CO2

C4 plants

-sugarcane, corn, grass.
-2 types of photosynthetic cells: Mesophyll cell, bundle sheath cell.

CAM plants

-water storing succulents, cacti
-night, stomata open
-day, stomata closed