Photosynthesis and Leaf Structure

Practice flashcards covering the biological processes of photosynthesis, leaf anatomy, the light-dependent and light-independent reactions, and factors affecting photosynthetic rates.

Photosynthesis

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

Chlorophyll

A complex molecule and green pigment associated with the conversion of usable sunlight energy into chemical energy.

Accessory pigments

Pigments that absorb energy that chlorophyll a does not absorb, including chlorophyll b, c, d, e, xanthophylls, and carotenoids.

Xylem vessels

Specialized plant cells through which water is transported from the root up to the leaves.

Stomata

Specialized structures that allow gas to enter and leave the leaf; the singular form is stoma.

Guard cells

Two cells that flank the stoma and regulate its opening and closing.

Cuticle

A protective waxy layer covering the leaf which carbon dioxide cannot pass through.

Thylakoid

The structural unit of photosynthesis consisting of flattened sacs or vesicles containing photosynthetic chemicals.

Grana

Stacks of thylakoids arranged like pancakes within the chloroplast.

Stroma

The areas between the grana inside the chloroplast where light-independent reactions occur.

Photoactivation

The process where chlorophyll a absorbs light energy, resulting in an excited electron and the splitting of water molecules.

Phosphorylation

The addition of a phosphate group to an organic compound.

Light-dependent reactions

The first stage of photosynthesis occurring in the grana that requires direct light energy to produce ATP and NADPH.

Photolysis

The light-driven splitting of water into oxygen, hydrogen ions, and free electrons, represented by the equation $2H_2O \rightarrow 4H^+ + O_2 + 4e^-$.

Light-independent reactions

A series of reactions occurring in the stroma where ATP and NADPH are used to fix carbon dioxide into carbohydrates.

Photoionisation

The process where light energy ionises a chlorophyll molecule, causing an electron to be freed and leaving a positively charged ion.

Photosystem

A core unit consisting of a chlorophyll molecule associated with an electron acceptor and an electron donor.

Z scheme

The term for the electron transfer process involving Photosystem II and Photosystem I, named after the Z shape created by the energy changes.

Chemiosmosis

The process where the diffusion of $H^+$ ions across an electrochemical gradient drives the production of ATP.

Carbon fixation

The incorporation of carbon dioxide into organic compounds.

Ribulose 1,5-biphosphate (RuBP)

A five-carbon sugar that combines with carbon dioxide during the initial stage of the Calvin cycle.

Glycerate 3-phosphate (GP)

A molecule formed when the unstable six-carbon sugar produced by carbon fixation breaks down.

Glyceraldehyde 3-phosphate (GALP)

A 3-carbon molecule formed by the reduction of glycerate diphosphate using NADPH; also known as phosphoglyceraldehyde (PGAL).

Limiting factors

The main factors that affect the rate of photosynthesis, specifically light intensity, carbon dioxide concentration, and temperature.

P680

The wavelength of light ($680\,nm$) at which Photosystem II (PSII) absorbs energy most efficiently.

P700

The wavelength of light ($700\,nm$) at which Photosystem I (PSI) absorbs energy most efficiently.