4.1.1.3 Cell specialisation

What is Specialisation

Adaptations which help to carry out particular function

Differentiation

When cells become specialised

Sperm cell function

specialised to carry the males DNA to the egg cell (ovum) for successful reproduction

Sperm cell adaptations

Streamlined head and long tail to aid swimming and making it easier

many mitochondria, where respiration happens, which supply the energy to allow the cell to move and swim

The acrosome (top of the head) has digestive enzymes which break down the outer layers of membrane of the egg cell

Nerve cell function

Specialised to transmit electrical signals quickly from one place in the body to another

Send electrical impulses around the body

Nerve cell adaptation

The Axon is long, enabling the impulses to be carried,

long distances

The axon is covered with myelin which insulates the axon and speeds up the transmission of nerve impulses

The end of the axon has synapses. These are junctions which allow the impulse to pass from one nerve cell to another

The cell body of the nerve cell has dendrites, these increase the surface are so that the other nerve cells can connect more easily

the nerve endings have many mitochondria, which supply energy to make transmitter chemicals called neurotransmitters. These allow the impulse to be passed from one cell to another.

Muscle cell function

Specialised to contract quickly to move bones (striated muscle) or simply to squeeze (smooth muscle, e.g. found in blood vessels so blood pressure can be varied) therefore causing movement

Muscle cell adaptation

Special proteins (myosin and actin) slide over each other, causing the muscles to contract and can change the length

lots of mitochondria to provide energy from respiration for contraction.

They can store a chemical called glycogen that is used in respiration by mitochondria.

\

Root hair cells function

Specialised to take up water by osmosis and mineral ions by active transport from the soil, as they are found in the tips of the root

Root hair cell adaptation

Have a large surface area due to root hairs, meaning more water can move in and dissolve minerals more easily

No chloroplast because they are underground so they cannot perform photosynthesis

The large permanent vacuole affects the speed of movement of water from the soil to the cell

Mitochondria to provide energy for from respiration for the active transport of mineral ions into the root hair cells

Xylem cells function

Specialised to transport water and mineral irons up from a plant from the roots to the shoots

Xylem cell adaptation

Upon formation, a chemical called lignin is deposited which causes the cell to die.

The end walls between the cells are dead. They become hollow and a joined from end to end to form a continuous tube so water and mineral irons can move through easily

Thick walls containing lignin, this provides support to the plant

Lignin is deposited in spirals, which helps the cells, withstand the pressure from the movement of water

No internal structures so easier for eater and minerals to flow

Phloem cells function

Specialised to carry the products of photosynthesis (food/ dissolved sugars)to all parts of the plants

Phloem cells adaptation

Cell walls of each cell form structures called sieve plates, when they break down, allowing the movement of substances from cell to cell

Despite losing many sub-cellular structures, the energy these cells need to be alive is supplied by the mitochondria of companion cells

Phloem cells have companion cells connected by pores mitochondria in the companion cell provide energy to the phloem vessel cell