Photosynthesis and Plant Biology

This set of vocabulary flashcards covers the process of photosynthesis, including pigments, leaf and chloroplast structures, the light-dependent and light-independent reactions, and limiting factors.

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

The primary green pigment present in all photosynthetic organisms that absorbs energy from violet-blue and reddish orange-red wavelengths.

Accessory pigments

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

Chlorophyll Structure

Consists of a lipid-soluble hydrocarbon tail ($C_{20}H_{39}-$) and a flat hydrophilic head with a magnesium ion at its centre, linked by an ester bond.

Xylem vessels

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

Stomata

Specialized structures flanked by two guard cells that allow gas to enter and leave the leaf; the plural of stoma.

Cuticle

A protective waxy layer covering the leaf that 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 in a chloroplast; the site of light-independent reactions.

Photoactivation

The process where chlorophyll a absorbs light energy, causing an electron to become 'excited' and transferred to a primary electron acceptor.

Photolysis

The light-dependent splitting of water into oxygen, hydrogen ions, and free electrons: $2H_2O \rightarrow 4H^+ + O_2 + 4e^-$.

Photophosphorylation

The process of trapping light energy by chlorophyll to make ATP from ADP and phosphate.

NADP+

The oxidized form of nicotinamide adenine dinucleotide phosphate, an electron carrier molecule.

Photoionisation

The process where light energy ionises a chlorophyll molecule, freeing an electron and leaving a positively charged chlorophyll ion.

Z scheme

The electron transfer process named for the Z shape formed by the energy changes accompanying the photosystems.

Photosystem II (PSII)

Also known as $P_{680}$, it is the photosystem that occurs first in the Z scheme despite being discovered and named second.

Photosystem I (PSI)

Also known as $P_{700}$, it is the photosystem that absorbs energy most efficiently at $700 \text{ nm}$ and is involved in both cyclic and non-cyclic phosphorylation.

Chemiosmosis

The process where energy from the electron transport chain pumps $H^+$ ions to create an electrochemical gradient, driving the production of ATP.

Cyclic phosphorylation

A process involving only Photosystem I that generates extra ATP for light-independent reactions without forming NADPH.

Carbon fixation

The incorporation of carbon dioxide from the atmosphere into organic compounds during the light-independent reactions.

RuBP

Ribulose 1,5-biphosphate; a five-carbon sugar that combines with carbon dioxide at the start of the Calvin cycle.

Glycerate 3-phosphate (GP)

Also known as phosphoglycerate (PGA), it is a 3-carbon molecule formed when the unstable 6-carbon sugar from carbon fixation breaks down.

GALP

Glyceraldehyde 3-phosphate (also known as PGAL); a 3-carbon molecule used to either create glucose or reform RuBP.

Limiting factors

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