Photosynthesis: Processes and Adaptations in Plants

Photosynthesis

the conversion of light energy to chemical energy

Autotrophs

Organisms that produce their own food (organic molecules) from simple substances in their surroundings

Heterotrophs

Organisms unable to make their own food so they live off of other organisms

Cyanobacteria

early prokaryotes capable of photosynthesis

Chloroplast

organelle for the location of photosynthesis

Stomata

pores in leaves that allow CO2 in and O2 out

Stroma

aqueous internal fluid of chloroplasts

Thylakoids

form stacks known as grana in chloroplasts

Chlorophyll

green pigment in thylakoid membranes

Photosynthesis Simplified Formula

6 CO2 + 6 H2O + light energy C6H12O6 + 6 O2

Redox reaction

reaction involving complete or partial transfer of one or more electrons from one reactant to another

OIL RIG

Oxidation is loss of e-; Reduction is gain of e-

Light

electromagnetic energy made up of particles of energy called photons

Wavelength

the distance from the crest of one wave to the crest of the next

Electromagnetic spectrum

the entire range of wavelengths of light

Photosynthetic Pigments

molecules that absorb visible light

Chlorophyll a

Primary pigment involved in the light reactions; blue/green pigment

Chlorophyll b

Accessory pigment; yellow/green pigment

Carotenoids

yellow/orange pigments that broaden the spectrum of colors that drive photosynthesis

Photorespiration

occurs on very hot days when plants close their stomata, causing less CO2 to be present and more O2

C4 Plants

plants that have spatial separation of steps in carbon fixation and partially close stomata to conserve water

CAM Plants

plants that open stomata at night and close during the day to conserve water

Calvin Cycle

cyclic electron flow that uses ATP and NADPH to reduce CO2 to sugar (G3P)

Phase 1: Carbon Fixation

CO2 is incorporated into the Calvin cycle one at a time, catalyzed by the enzyme rubisco

Phase 2: Reduction

each molecule of 3-phosphoglycerate is phosphorylated by ATP and reduced to G3P

Phase 3: Regeneration of RuBP

5 G3P molecules are used to regenerate 3 molecules of RuBP using 3 ATP

Inputs of Calvin Cycle

3 CO2, 9 ATP, 6 NADPH

Outputs of Calvin Cycle

1 G3P, 9 ADP, 6 NADP+

Light Reactions

occur in the thylakoid membrane, converting solar energy to chemical energy in the forms of NADPH and ATP

NADP+ reductase

catalyzes the transfer of electrons from Fd to NADP+

Photoprotection

Carotenoids absorb and dissipate excessive light energy that could damage chlorophyll or interact with oxygen

Photosystems

Reaction center and light capturing complexes

Reaction center

Complex of proteins associated with chlorophyll a and an electron acceptor

Light capturing complexes

Pigments associated with proteins (AKA antenna for the reaction centers)