Photosynthesis and Leaf Structure Flashcards

A comprehensive set of vocabulary flashcards covering the biological processes, chemical reactions, and structures involved in photosynthesis as detailed in the lecture notes.

Photosynthesis

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

Chlorophyll a

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

Accessory pigments

Pigments that absorb energy that chlorophyll a does not; includes chlorophyll b, c, d, e, xanthophylls, and carotenoids such as 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 center, 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 while also permitting water loss.

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 grana within the chloroplast where light-independent reactions occur.

Photoactivation

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

Phosphorylation

The addition of a phosphate group to an organic compound.

Photolysis

The process occurring during light-dependent reactions where water is split into oxygen, hydrogen ions, and free electrons: $2H_2O \rightarrow 4H^+ + O_2 + 4e^-$.

Photoionisation

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

Photosystem II (PSII)

Also known as P680, this photosystem occurs first in the electron transfer process and absorbs light most efficiently at $680\,nm$.

Photosystem I (PSI)

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

Z scheme

The name for the electron transfer process illustrating the Z-shaped pattern of energy changes accompanying PSII and PSI.

Chemiosmosis

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

Cyclic phosphorylation

A process involving only Photosystem I that generates excited electrons to produce extra ATP without forming NADPH.

Carbon fixation

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

Ribulose 1,5-biphosphate (RuBP)

A five-carbon sugar that combines with carbon dioxide to start the light-independent reaction cycle.

Glycerate 3-phosphate (GP)

Molecules formed from the breakdown of the unstable six-carbon sugar during carbon fixation.

Glyceraldehyde 3-phosphate (GALP)

A 3-carbon molecule formed when GP is phosphorylated by ATP and reduced by NADPH; it is used to make carbohydrates or reform RuBP.

Limiting factors

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