Biology for CAPE Examinations - Leaf Anatomy and Photosynthesis

Vocabulary flashcards focusing on leaf anatomy, chloroplast structure, photosynthetic pigments, and the stages of photosynthesis.

Petiole

The stalk that connects the leaf blade to the plant stem.

Leaf Arrangement Patterns

The three major arrangements of leaves on plant stems—alternate, opposite, or whorled—organized to maximize the plant's capability to capture sunlight.

Xylem

Vascular tissue within leaf veins that brings water and mineral nutrients from the roots to the leaves.

Phloem

Vascular tissue within leaf veins that transports the products of photosynthesis to other plant parts, such as storage organs.

Trichomes

Epidermal hairs present on the upper and lower surfaces of leaves that help retard water loss.

Stomata

Microscopic pores on the leaf surface that facilitate gaseous exchange (such as $\text{CO}_2$ and $\text{O}_2$) between intercellular spaces and the atmosphere and regulate transpiration.

Guard Cells

Paired epidermal cells surrounding a stoma that regulate its opening and closing via osmotic concentration changes in their vacuoles.

Palisade Mesophyll

The upper layer of leaf mesophyll consisting of compactly stacked, columnar cells oriented at right angles to the epidermis to reduce light-absorbing cell walls between sunlight and chloroplasts.

Spongy Mesophyll

The lower layer of leaf mesophyll composed of irregularly shaped cells with large intercellular air spaces, facilitating gaseous exchange and absorbing higher light wavelengths.

Bundle Sheath

A structure formed by parenchyma cells enclosing leaf veins (vascular bundles), through which all entering or exiting substances must pass.

Chloroplast

The double-membraned organelle in which photosynthesis takes place, containing its own DNA, thylakoids, and stroma.

Thylakoids

Membrane-bound structures within chloroplasts that contain photosynthetic pigments and form the site of light-dependent reactions.

Grana

Stacks of thylakoids arranged one on top of the other like a stack of coins within the chloroplast.

Stroma

The fluid filling the interior of the chloroplast surrounding the thylakoids, where the Calvin cycle occurs.

Light-dependent Reactions

The stage of photosynthesis occurring inside the thylakoid membrane that captures solar energy and converts low-energy electrons from water into $\text{ATP}$ and $\text{NADPH}$.

Calvin Cycle

The light-independent stage of photosynthesis occurring in the stroma that uses $\text{ATP}$ and $\text{NADPH}$ to reduce carbon dioxide into carbohydrates.

Overall Equation of Photosynthesis

The chemical equation summarizing photosynthesis: $6\text{CO}_2 + 12\text{H}_2\text{O} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 + 6\text{H}_2\text{O}$.

Chlorophyll a

The primary photosynthetic pigment present in all photosynthetic organisms, containing a complex chemical ring structure centered around a magnesium atom.

Chlorophyll b

An accessory photosynthetic pigment that has a different absorption spectrum from chlorophyll a.

Accessory Pigment

A photosynthetic pigment (such as chlorophyll b) that absorbs wavelengths of light different from chlorophyll a and transfers energy for photosynthesis.

Carotenoids

Red, orange, and yellow pigments in the thylakoid membrane that absorb blue and blue-green light ($400\text{ nm}$ to $500\text{ nm}$) and act as anti-oxidants to prevent damage to chlorophyll molecules.

NADP

Nicotinamide adenine dinucleotide phosphate, a coenzyme that acts as the oxidised form of the electron acceptor in photosynthesis.

NADPH

The reduced form of nicotinamide adenine dinucleotide phosphate, which temporarily holds energy to reduce carbon dioxide in biosynthetic pathways.

Absorption Spectra and Action Spectrum

Graphs depicting the light absorption of individual photosynthetic pigments (chlorophyll a, chlorophyll b, carotenoids) alongside the overall rate of photosynthesis (measured by $\text{O}_2$ release) across light wavelengths ($400\text{ nm}$ to $700\text{ nm}$).

Photosystems

Pigment-protein units (Photosystem I / $P700$ and Photosystem II / $P680$) responsible for capturing solar energy and passing electrons to drive $\text{ATP}$ synthesis.

Parenchyma Cells

Relatively unspecialised plant cells that carry out various functions, including forming the bundle sheath around leaf veins.

Midrib

The continuation of a leaf's stem along the centre of the leaf that contains the primary vascular bundle.