Photosynthesis Lecture Notes

Comprehensive vocabulary flashcards covering the biological and chemical processes of photosynthesis as described in the lecture notes.

Photosynthesis

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

ATP

Adenosine triphosphate, an energy-releasing molecule produced by cellular respiration from pyruvate.

Chlorophyll a

A green 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, including chlorophyll b, c, d, e, xanthophylls, and carotenoids like beta-carotene.

Chlorophyll tail

A lipid-soluble hydrocarbon tail with the chemical formula $(C_{20}H_{39} -)$.

Chlorophyll head

A flat hydrophilic head with a magnesium ion at its centre, linked to the tail 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 evolved by land plants to allow gas to enter and leave the leaf; the singular form is stoma.

Cuticle

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

Guard cells

A pair of cells that flank the stoma and regulate gas exchange.

Thylakoid

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

Grana

Stacks of thylakoids arranged like pancakes within a chloroplast.

Stroma

The fluid-filled areas between the grana where light-independent reactions occur.

Photoactivation

The process where chlorophyll a absorbs light energy, leading to an excited electron, the splitting of water, and energy transfer to ATP and NADP.

Phosphorylation

The addition of a phosphate group to an organic compound.

Photolysis

The light-dependent splitting of water molecules summarized by the equation $2H_2O \rightarrow 4H^+ + O_2 + 4e^-$.

NADP

Nicotinamide adenine dinucleotide phosphate, which exists in an oxidized state $(NADP^+)$ and a reduced state $(NADPH)$.$

Light-independent reactions

A series of reactions occurring in the stroma using ATP and NADPH to make carbohydrates from carbon dioxide.

Photoionisation

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

Photosystem

A unit consisting of a chlorophyll molecule, an electron acceptor, and an electron donor; examples include PSII (P680) and PSI (P700).

Z scheme

The electron transfer process named for the Z-shaped energy changes that occur during the sequence of reactions.

Non-cyclic phosphorylation

The Z scheme process where both ATP and NADPH are produced using both Photosystem II and Photosystem I.

Chemiosmosis

The production of ATP driven by the diffusion of $H^+$ ions across an electrochemical gradient from the thylakoid compartment to the stroma.

Cyclic phosphorylation

A process involving only Photosystem I that generates extra ATP for light-independent reactions but does not form NADPH.

Carbon fixation

The incorporation of carbon dioxide into organic compounds.

RuBP

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

GP

Glycerate 3-phosphate, a 3-carbon molecule formed when the unstable six-carbon sugar from RuBP and CO2 breaks down.

GALP

Glyceraldehyde 3-phosphate, a molecule formed from GP using ATP and NADPH; also known as phosphoglyceraldehyde (PGAL).

Calvin cycle

The sequence of light-independent reactions where the first stable product is phosphoglycerate (PGA).

Limiting factors

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