Photosynthesis Definition

Light-dependent reactions

reactions of photosynthesis where light energy is captured and used to produce ATP and NADPH. Involves 2 linked photosystems.

Carbon fixation

the conversion of CO2 into organic compounds during photosynthesis. (first stage of dark reactions- CO2 from air combined with RuBP)

Light-independent reactions

reactions of photosynthesis where ATP and NADPH from the light-dependent reactions are used to reduce CO2 and make glucose

Chlorophyll

green pigment in plants that absorb light to start

Stroma

liquid that surrounds thylakoids in chloroplasts- dark reactions happen here

Photosystems

an organized complex of chlorophyll, other pigments, and proteins that traps light energy as excited electrons.

ATP

energy currency in all organisms. Made during light reactions of photosynthesis and is used in the dark reactions.

NADPH

energy storing molecules made (along with ATP) during the light reactions and used in the dark reactions to convert CO2 to glucose

Pigments

molecule that absorbs light

Photons

a particle of light absorbed by pigments during photosynthesis

Absorption spectrum

indicate which wavelengths are absorbed maximally for a particular pigment

Chlorophyll A

main photosynthetic pigment in plants. absorbs blue and red wavelengths the best

Accessory pigment

secondary light-absorbing pigments (chlorophyll b, carotenoids) that absorb different wavelengths than chlorophyll a

Phycobiloproteins

accessory pigment in cyanobacteria and some algae that can absorb green light

Antenna complex

hundreds of pigment molecules in a photosystem that collects photons and feeds the light energy to a reaction center

Reaction center

part of the photosystem that gets energy from the antenna complex causing the electrons to get excited

Phtosystem I

receives excited electrons from Photosytem II

Photosytem II

passes an excited electrons through electron transport chain to NADPH. (lost electrons are replaced by oxidation of water

Noncyclic photophosphorylation

the phosphorylation that produces ATP and NADPH in Photosystem II and Photosytem I in series

Cytochrome/b6-f complex

proton pump in thylakoid membrane that uses energy from excited electrons to set up a proton gradient

ATP synthase

enyzme responsible for using a proton gradient to produce ATP in oxidative phosphorylation

Thylakoid

discs that contain photosystems involved in light reactions

Grana

stacked column of thylakoids in a chloroplast

Calvin cycle

another name for the dark reactions of photosythesis

RuBP

5 carbon sugar that CO2 is attached to during the Calvin Cycle

PGA

Compound made during CO2 fixation during the Calvin Cycle.

Rubisco

Enzyme that catalyzes carbon fixation (the joining of CO2 to RuBP).

Photorespiration

When rubisco oxidizes RuBP and releases fixed CO2- reduces yield of photosynthesis

Stoma

opening in epidermis of leaves that allows CO2 in and water out. Surrounded y guard cells.

Guard Cells

One of a pair of sausage-shaped cells flanking a stoma. They control the opening and closing of the stoma

C3 Plants

Plants that fix carbon using only the Calvin cycle. Carbon dioxide binds to RuBP to form two PGA molecules.

C4 Plants

Plants that reduce photorespiration by capturing CO2 in one cell and performing decarboxylation.

CAM Plants

Plants that use C4 carbon fixation at night and store the product to use during the day without having to open their stomates and risk drying out.