Cell Biology Unit 1 Topic 1 Biology 2025

Prokaryotic cell

A simple cell without a nucleus or membrane-bound organelles (e.g. bacteria).

Eukaryotic cell

A complex cell with a nucleus and membrane-bound organelles (e.g. plant and animal cells).

Nucleus

Controls cell activities and contains DNA.

Mitochondria

Site of cellular respiration; produces ATP.

Rough endoplasmic reticulum (Rough ER)

Transports proteins and has ribosomes attached.

Smooth endoplasmic reticulum (Smooth ER)

Synthesises lipids and detoxifies substances.

Ribosomes

Synthesize proteins; found in cytoplasm or on rough ER.

Golgi apparatus

Modifies, packages and transports proteins and lipids.

Lysosome

Contains enzymes to break down waste and old organelles.

Vacuole

Stores water and other substances; large in plant cells.

Chloroplast

Site of photosynthesis in plant cells.

Mitosis

Cell division that produces two identical daughter cells.

Stem cell

An unspecialised cell capable of self-renewal and differentiation.

Differentiation

The process by which a stem cell becomes specialised.

Totipotent

Can become any cell type, including placental tissues.

Pluripotent

Can become any cell type in the body (but not placental tissues).

Multipotent

Can become a limited range of cell types.

Unipotent

Can become only one specific cell type.

Cell

The basic structural and functional unit of life.

Tissue

A group of similar cells working together to perform a function.

Organ

A structure made of different tissues working together.

Organ system

A group of organs that work together to carry out major body functions.

Multicellular organism

An organism made of many specialised cells.

Digestive system

Breaks down food into nutrients.

Circulatory system

Transports nutrients, gases and wastes.

Respiratory system

Exchanges oxygen and carbon dioxide.

Excretory system

Removes metabolic waste from the body.

Specialised cell

A cell with a structure adapted to perform a specific function.

Surface area-to-volume ratio (SA:V)

The amount of surface area per unit of volume; affects exchange efficiency.

Organelle composition

The type and quantity of organelles present in a cell based on its function.

Cell membrane

A selectively permeable barrier that controls what enters and leaves the cell.

Fluid mosaic model

Describes the flexible structure of the cell membrane with embedded proteins.

Phospholipid

The main structural component of membranes with hydrophilic heads and hydrophobic tails.

Protein channel

Allows specific molecules to pass through the membrane.

Cholesterol

Maintains fluidity and stability of the membrane.

Glycoprotein

A protein with a carbohydrate attached; involved in cell recognition and signalling.

Osmosis

Passive movement of water across a semi-permeable membrane from low to high solute concentration.

Simple diffusion

Passive movement of small, nonpolar molecules across the membrane.

Facilitated diffusion

Passive transport of substances via protein channels.

Active transport

Movement of substances against the concentration gradient using energy (ATP).

Protein-mediated transport

Uses transport proteins for active or facilitated diffusion.

Endocytosis

Active process where the cell membrane folds in to bring substances into the cell.

Exocytosis

Active process where vesicles release substances out of the cell.

Diffusion

The passive movement of molecules from high to low concentration.

Rate of diffusion

How quickly molecules spread; influenced by concentration gradient, temperature and SA:V ratio.

Surface area-to-volume ratio

Influences the efficiency of diffusion and limits cell size.