Specilased Cells

Specialisation

The process where cells develop structures that help them perform a specific job.

Specialised cell

A cell adapted to perform a specific function.

Unicellular organism

An organism made of one cell that carries out all life processes.

Examples of unicellular organisms

Bacteria, Amoeba, Euglena, Paramecium, Yeast.

Advantages of unicellular organisms

Reproduce quickly, need fewer resources, adapt rapidly.

Disadvantages of unicellular organisms

Small size, easily damaged, one cell must perform every function.

Multicellular organism

An organism made of many cells, with different cells performing different jobs.

Examples of multicellular organisms

Humans, dogs, trees, ferns, mushrooms.

Advantages of multicellular organisms

Greater size, specialised functions, can develop complex organs.

Disadvantages of multicellular organisms

Need more energy, require transport systems, more complex organisation.

Muscle cells

Cells that contract and relax to produce movement. They contain many mitochondria.

Skeletal muscle

Found attached to bones. Controls voluntary body movement.

Smooth muscle

Found in the stomach, intestines and blood vessels. Moves substances through organs. Involuntary.

Cardiac muscle

Found only in the heart. Pumps blood continuously. Involuntary and contains many mitochondria.

Nerve cell (neurone)

Carries electrical messages around the body. Long with branched ends to transmit signals quickly.

Red blood cell

Transports oxygen around the body. Disc-shaped, flexible, contains haemoglobin and has no nucleus when mature.

White blood cell

Defends the body against disease. Has a nucleus and can change shape to surround bacteria.

Fat cell (adipose cell)

Stores energy. Large, rounded cells filled with fat droplets.

Root hair cell

Absorbs water and minerals from the soil. Has a large surface area and a thin cell wall.

Guard cell

Controls the opening and closing of stomata to regulate gas exchange and reduce water loss.

Stomata

Tiny openings in leaves that allow carbon dioxide in and oxygen and water vapour out.

Xylem cell

Transports water and minerals through the plant. Hollow, thick-walled cells joined end-to-end.

Phloem cell

Transports sugars produced during photosynthesis. Forms long tubes with sieve-like ends.

Tissue

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

Organ

A structure made of different tissues working together to perform a specific function.

Organ system

A group of organs working together to carry out a major body function.

Why are muscle cells rich in mitochondria?

Movement requires lots of energy, so muscle cells need many mitochondria.

Why do red blood cells have no nucleus?

To create more space for oxygen-carrying haemoglobin.

Why are root hair cells good at absorbing water?

They have a large surface area and a thin cell wall for faster absorption.

Why are xylem cells hollow?

To allow water and minerals to flow easily through the plant.

Why do guard cells change shape?

To open and close the stomata, controlling gas exchange and reducing water loss.