Photosynthesis and Plant Physiology Flashcards

This set of vocabulary flashcards covers the process of photosynthesis, including pigment structures, leaf anatomy, the light-dependent and light-independent reactions, and the Z scheme.

Photosynthesis

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

Chlorophyll a

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

Accessory pigments

Pigments that absorb energy that chlorophyll a does not; examples include chlorophyll b, c, d, 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 (singular: stoma) flanked by two guard cells that allow gases to enter and leave the leaf.

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

Collective term for stacks of thylakoids arranged like pancakes within the chloroplast.

Stroma

The areas between the grana in a chloroplast where the 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, such as the synthesis of ATP from ADP.

Photolysis

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

NADP+

Nicotinamide adenine dinucleotide phosphate in its oxidized state; it acts as an electron carrier.

Photoionisation

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

Photosystem II (PSII)

Also known as P680, this photosystem occurs first in the light-dependent reactions and is involved in the photolysis of water.

Photosystem I (PSI)

Also known as P700, this photosystem absorbs energy most efficiently at $700\,nm$ and is involved in both cyclic and non-cyclic phosphorylation.

Z scheme

The name given to the electron transfer process because the energy changes accompanying the reactions form a Z shape when graphed.

Non-cyclic phosphorylation

A process involving both PSII and PSI that produces both ATP and NADPH.

Chemiosmosis

The process where an electrochemical gradient of H+ ions across the thylakoid membrane drives the production of ATP.

Cyclic phosphorylation

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

Carbon fixation

The incorporation of carbon dioxide from the atmosphere into organic compounds.

Ribulose 1,5-biphosphate (RuBP)

A five-carbon sugar that combines with carbon dioxide at the start of the light-independent reactions.

Glycerate 3-phosphate (GP)

A molecule formed when the unstable six-carbon sugar produced from RuBP and $CO_2$ breaks down.

Glyceraldehyde 3-phosphate (GALP/PGAL)

A 3-carbon molecule formed by the reduction of GP using ATP and NADPH; it is used to make glucose or reform RuBP.

Calvin Cycle

The series of light-independent reactions where $CO_2$ is fixed and converted into carbohydrates like glucose.

Limiting factors

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