Photosynthesis

Photosynthesis

the process that converts solar energy into chemical energy

autotroph

An organism that produces its own food

heterotroph

An organism that cannot make its own food and must live off of other organisms

photoautotrophs

An organism that uses the energy from light to make its own food

cyanobacteria

Photosynthetic, oxygen-producing bacteria (first photosynthesizers to have evolved)

Chloroplast

An organelle found in plant and algae cells where photosynthesis occurs

mesophyll

the cells that make up the interior tissue of the leaf

stomata

pores on the leaf where O2 exits and CO2 enters

stroma

fluid portion of the chloroplast; outside of the thylakoids; where the Cavin Cycle takes place

thylakoid

A flattened membrane sac inside the chloroplast, used to convert light energy into chemical energy. Where the light reactions take place.

grana

stacks of thylakoids

chlorophyll

A green pigment found in the thylakoid membranes that absorbs light energy

redox reactions

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

oxidation

loss of electrons

reduction

gain of electrons

light

electromagnetic energy made of particles of energy called photons

photons

particles of light

wavelength

The distance between crests of waves

reactants of photosynthesis

6H20 + 6CO2

products of photosynthesis

C6H12O6 + 6O2

NADPH and ATP

molecules that carry chemical energy to the Calvin Cycle from the light reactions

pigments

light absorbing molecules

chlorophyll a

primary photosynthetic pigment that participates directly in the light reactions, which convert solar energy to chemical energy.

Chlorophyll b

An accessory photosynthetic pigment

carotenoids

An accessory pigment, either yellow or orange, in the chloroplasts of plants. By absorbing wavelengths of light that chlorophyll cannot, they broaden the spectrum of colors that can drive photosynthesis and play a role in Photoprotection

photoprotection

A process in which carotenoids absorb and dissipate excessive light energy that would otherwise damage chlorophyll

photosystems

reaction center surrounded by light-harvesting complexes

reaction center

Complex of proteins associated with two special chlorophyll a molecules and a primary electron acceptor.

light-harvesting complex

A complex of proteins associated with pigment molecules (including chlorophyll a, chlorophyll b, and carotenoids) that captures light energy and transfers it to reaction-center pigments in a photosystem.

reaction center of Photosystem I

P700

reaction center of Photosystem II

P680

linear electron flow

the primary pathway, involves both photosystems and produces ATP and NADPH using light energy

cyclic electron flow

uses only photosystem I and produces ATP, but not NADPH

thylakoid lumen

the fluid-filled space inside a thylakoid, where H+ (protons) accumulate during the light reactions

ATP synthase

Enzymes that uses energy from H+ ions to bind ADP and a phosphate group together to produce ATP

Electron Transport Chain (ETC)

series of electron carrier proteins that shuttle high-energy electrons during ATP-generating reactions

G3P

molecule that is made in the Calvin cycle; glucose is formed when two of these molecules combine

RuBP

the molecule that reacts with CO2 during carbon fixation of the Calvin cycle

3-phosphoglycerate

formed at the end of the carbon fixation phase of the Calvin Cycle

carbon fixation

The first phase of the calvin cycle; the initial incorporation of carbon into organic compounds

reduction phase

the second phase of the Calvin cycle which produces G3P

Regeneration of RuBP

last phase of the Calvin cycle. Five G3P molecules are rearranged to form three RuBP molecules. To do this, the cycle must spend three more ATP molecules (one per RuBP)

C3 plants

the most common and the most efficient at photosynthesis in cool, wet climates

Photorespiration

A metabolic pathway that consumes oxygen, releases carbon dioxide, generates no ATP, and decreases photosynthetic output; generally occurs on hot, dry, bright days, when stomata close and the oxygen concentration in the leaf exceeds that of carbon dioxide.

C4 Plants

plants that have adapted their photosynthetic process to more efficiently handle hot and dry conditions

CAM plants

plants close their stomata during the day, collect CO2 at night, and store the CO2 in the form of organic acids in the vacuoles until it is needed during the day for photosynthesis