Photosynthesis Lecture Practice Flashcards

A comprehensive set of vocabulary-based flashcards covering the process of photosynthesis, including pigments, leaf structures, light-dependent and light-independent reactions, and limiting factors.

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 that absorbs energy from violet-blue and reddish orange-red wavelengths.

Accessory pigments

Pigments such as chlorophyll b, c, d, e, xanthophylls, and carotenoids (e.g., beta-carotene) that absorb light energy that chlorophyll a does not.

Chlorophyll Hydrocarbon Tail

A lipid-soluble component of chlorophyll with the formula $C_{20}H_{39}-$.

Chlorophyll Head

A flat hydrophilic structure with a magnesium ion at its centre, linked to the tail by an ester bond.

Xylem vessels

Specialized plant cells that transport water from the roots up to the leaves.

Stomata

Specialized structures, flanked by two guard cells, that allow gases like carbon dioxide and oxygen 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 fluid-filled areas between the grana in a chloroplast where light-independent reactions occur.

Photoactivation

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

Phosphorylation

The addition of a phosphate group to an organic compound, such as the synthesis of ATP from ADP.

Photolysis

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

NADP

Nicotinamide adenine dinucleotide phosphate, an electron carrier that is reduced to NADPH during the light-dependent reactions.

Photoionisation

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

Photosystem

A core unit consisting of a chlorophyll molecule, an electron acceptor, and an electron donor.

Photosystem II (PSII)

Also known as P680; the first photosystem in the Z scheme that absorbs light most efficiently at $680\,nm$.

Photosystem I (PSI)

Also known as P700; the photosystem that absorbs energy most efficiently at $700\,nm$.

Z scheme

The electron transfer process named for the Z-shaped pattern created by the energy changes during the light-dependent reactions.

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 light-independent reactions without producing NADPH.

Carbon fixation

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

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)

A molecule formed when the unstable six-carbon sugar produced by carbon fixation breaks down.

GALP (Glyceraldehyde 3-phosphate)

A 3-carbon atom molecule formed by the reduction of GP using ATP and NADPH; it is the initial end product of photosynthesis.

Calvin Cycle

The series of light-independent reactions where energy from ATP and NADPH is used to fix carbon and eventually produce glucose.

PGA (Phosphoglycerate)

The first stable 3-carbon product of the Calvin Cycle.

Limiting factors

Environmental variables such as light intensity, carbon dioxide concentration, and temperature that can restrict the rate of photosynthesis.