Photosynthesis

Flashcards on Photosynthesis

Photosynthesis

The process by which plants, some bacteria, and some protistans use energy from sunlight to produce glucose from carbon dioxide and water.

Cellular respiration

Releases adenosine triphosphate (ATP) from glucose.

Chlorophyll

The green pigment associated with the conversion of usable sunlight energy into chemical energy.

Accessory pigments

Absorb energy that chlorophyll a does not absorb, such as chlorophyll b, xanthophylls, and carotenoids.

Chlorophyll structure

A lipid-soluble hydrocarbon tail and a flat hydrophilic head with a magnesium ion at its centre.

Stomata

Allow gas to enter and leave the leaf, guarding against drying out.

Thylakoid

The structural unit of photosynthesis, flattened sacs/vesicles containing photosynthetic chemicals.

Grana

Stacks of thylakoids.

Stroma

The areas between grana in the chloroplast.

Electron excitation

An electron gains energy and is 'excited' when chlorophyll a absorbs light energy.

Photoactivation of chlorophyll a

Results in the splitting of water molecules and the transfer of energy to ATP and NADPH.

Light dependent reactions

Light-dependent series of reactions which occur in the grana, and require the direct energy of light to make energy-carrier molecules.

Light-independent reactions

Light-independent series of reactions which occur in the stroma of the chloroplasts, when the products of the light reaction, ATP and NADPH, are used to make carbohydrates from carbon dioxide.

Photoexcitation

When light energy is absorbed by a chlorophyll molecule its electrons gain energy and move to higher energy levels in the molecule.

Photoionisation

Sufficient energy ionises the molecule, with the electron being 'freed' leaving a positively charged chlorophyll ion.

Photosystem

Consists of a chlorophyll molecule associated with an electron acceptor and an electron donor.

P680

The electron acceptor for PhotoSystem II.

P700

The electron acceptor for PhotoSystem I.

Z scheme

The electron transfer process.

Phosphorylation

Occurs when phosphoric acid and ADP undergo a condensation reaction, eliminating water and forming ATP.

Photosystem II (PSII)

Photoionisation of chlorophyll transfers excited electrons to an electron acceptor.

Chemiosmosis

Electrons passing through the transport chain provide energy to pump H+ ions from the stroma, across the thylakoid membrane into the thylakoid compartment.

Cyclic phosphorylation

Involves only Photosystem I which generates excited electrons.

Carbon fixation

The incorporation of carbon dioxide into organic compounds.

Ribulose 1,5-biphosphate (RuBP)

Carbon dioxide combines with a five-carbon sugar.

Phosphoglycerate (PGA)

The first stable product of the Calvin Cycle.

Limiting factors

Light intensity, carbon dioxide concentration, and temperature.