AQA GCSE Specialised cells in animals (Biology)
Specialised cells in animals
A specialised cell is one that is adapted to carry out a particular function.
Specialised animal cells include:
1.Sperm cells
2. Nerve cells
3. Muscle cells
These adaptations could include certain cell structures, or the shape of the cell.
Unspecialised cells, such as stem cells undergo differentiation to form specialised cells.
Sperm Cells.
The role of a sperm cell is to fertilise the egg cell, in order to form a zygote.
Adaptations include:
1. Acrosome within the head which contains digestive enzymes to break down the outer layers of the egg cell.
2.Nucleus within the head will contain the haploid (half) number of chromsomes. When the sperm fuses with the egg, the diploid (normal) number of chromosomes will be restored.
3. Mitochondria in the middle section carry out aerobic respiration to release energy so that the tail can propel the sperm forward.
4. Tail (flagellum) will move side to side to propel the sperm forward.
In the tissue (testes tissue), sperm cells are produced through a process called spermatogenesis.
As part of the reproductive system (organ system), sperm are transported through the sperm ducts and delivered to the egg during ejaculation.
For the whole organism, this specialised structure helps ensure successful reproduction, passing on genetic material to offspring.
Nerve cells
Nerve cells form part of the nervous system, which is used for communication within the body.
The nerve cells, or neurones transmit electrical impulses.
Adaptations include:
1.Dendrites (branched endings) allow connections to many other neurones, allowing nerve signals to be passed between cells and across networks.
2.Myelin sheath (insulating layer) electrically insulates the axon and speeds up impulse transmission, like insulation on a wire.
3.Nucleus and cytoplasm keeps the cell alive and maintain function by controlling activities and supporting energy needs.
4.Long axon (nerve fibre) carries electrical impulses over long distances (e.g., from spinal cord to limbs). This links different parts of the body.
In tissues, neurones are found in nervous tissue, often grouped in bundles (nerves).
As part of an organ system — the nervous system — they work with the brain, spinal cord, and sense organs to send and receive signals.
For the whole organism, this allows movement, thinking, sensing, and reacting — essential for survival.
Muscle cells
There are 3 types of muscle in the human body, we will look at skeletal muscle.
Skeletal muscle cells are specialised to contract and cause movement. They are found in skeletal muscle tissue, which moves bones and allows voluntary movements in the muscular system of the whole organism.
Adaptations include:
Long cylindrical shape which allows cells to contract over long distances and work together in bundles for strength.
Striped or striated appearance caused by organised proteins (actin and myosin) that slide past each other during contraction
Multiple nuclei (blue ovals), each muscle fibre has many nuclei to control protein production along its long length.
Packed in bundles, muscle fibres work together in tissue to create powerful, coordinated contractions.
Tissue: Muscle cells work together in muscle tissue to produce force.
Organ: Skeletal muscles (like biceps, triceps) are organs made of muscle tissue, connective tissue, blood vessels, and nerves.
Organ system: Part of the muscular system, working closely with the skeletal system to allow movement.
Whole organism: Enables walking, running, speaking, breathing, posture — all essential activities in humans and other animals.
Practice Question
1.Define the term specialised cell
2. State the name of the process that cells undergo in order to form a specialised cell
3. Explain how a sperm cell is adapted to carry out its function.