EOY IGCSE BIOLOGY – SECTION 1: PLANTS

Vocabulary terms and definitions covering photosynthesis, leaf structure, and plant transport mechanisms based on the IGCSE Biology curriculum.

Photosynthesis

The process by which green plants use energy from sunlight to convert carbon dioxide from the air and water from the soil into glucose and oxygen.

Glucose

A type of sugar used for energy and growth produced during photosynthesis with the chemical formula $C_6H_{12}O_6$.

Word equation for photosynthesis

$$\text{Carbon dioxide} + \text{Water} \rightarrow \text{Glucose} + \text{Oxygen}$$

Balanced chemical equation for photosynthesis

$$6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$$

Limiting factor

The factor that is in the shortest supply and therefore limits the rate of photosynthesis.

Waxy cuticle

A waterproof layer on the surface of the leaf that reduces water loss through evaporation.

Upper epidermis

The transparent layer of a leaf that allows sunlight to pass through to the cells below.

Palisade mesophyll

The main site of photosynthesis in the leaf containing cells with large numbers of chloroplasts.

Spongy mesophyll

A leaf layer containing air spaces that allow carbon dioxide to diffuse quickly through the leaf and oxygen to diffuse out.

Stomata

Tiny pores found mainly on the underside of the leaf where carbon dioxide enters and oxygen and water vapour leave.

Guard cells

Cells that surround each stoma and control whether it is open or closed.

Root hair cells

Long and thin cells that provide a large surface area for the absorption of water from the soil.

Osmosis

The movement of water molecules from a region of high water potential to a region of lower water potential through a partially permeable membrane.

Xylem

A transport tissue made of dead cells with walls reinforced with lignin that carries water and mineral ions from the roots to the leaves.

Lignin

A substance that reinforces the walls of xylem vessels to prevent them from collapsing.

Transpiration

The loss of water vapour from the leaves through the stomata.

Transpiration stream

The continuous movement of water being pulled upward through the xylem as water leaves the leaf.

Phloem

A transport tissue made of living cells that moves food substances, such as sucrose and amino acids, throughout the plant in both directions.

Translocation

The movement of sucrose and amino acids through the phloem from the leaves to areas where they are needed, such as roots, flowers, and fruits.