Photosynthesis and Plant Biology

Comprehensive vocabulary flashcards covering the process of photosynthesis, leaf structure, 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 including chlorophyll b, c, d, and e, xanthophylls, and carotenoids (such as beta-carotene) that absorb energy that chlorophyll a does not.

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

Stacks of thylakoids arranged like pancakes within the chloroplast.

Stroma

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

Photoactivation

The process where chlorophyll a absorbs light energy and an electron becomes excited and is transferred to a primary electron acceptor.

Phosphorylation

The addition of a phosphate group to an organic compound.

Photophosphorylation

The process of using light energy trapped by chlorophyll to make ATP.

Photolysis

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

Photoionisation

The process in which a chlorophyll molecule is ionised by light energy, freeing an electron and leaving a positively charged chlorophyll ion.

Photosystem II (PSII)

A photosystem also known as $P680$ that occurs first in the electron transfer process.

Photosystem I (PSI)

A photosystem also known as $P700$ that is involved in the reduction of $NADP^+$ to NADPH.

Z scheme

The name for the electron transfer process based on the Z-shaped energy changes accompanying the reactions in the photosystems.

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 which generates excited electrons that are transported back to PSI to produce extra ATP without forming NADPH.

Carbon fixation

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

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 3-carbon molecule formed when the unstable six-carbon sugar resulting from carbon fixation breaks down.

Glyceraldehyde 3-phosphate (GALP)

A 3-carbon molecule (also known as PGAL) formed by the reduction of phosphorylated GP using NADPH.

Calvin cycle

The series of light-independent reactions where carbon dioxide is fixed and energy from ATP and NADPH is used to produce carbohydrates.

Limiting factors

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