2.1.3 Specialisation of Eukaryotic Cells

Key Features of Cell Specialisation:

1. Structure and Function:

• The shape, size, and organelles within a cell are adapted to its specific function.
• Example: Muscle cells contain many mitochondria to provide energy for contraction, while red blood cells are specialised for carrying oxygen due to their lack of nucleus and presence of haemoglobin.

2. Differentiation:

• Differentiation is the process through which unspecialised cells (e.g., stem cells) become specialised.
• During differentiation, certain genes are activated or deactivated, allowing the cell to produce specific proteins required for its function.

Examples of Specialised Eukaryotic Cells:

1. Red Blood Cells (Erythrocytes):

• Function: Transport oxygen around the body.
• Adaptations:
• Biconcave shape increases surface area for oxygen diffusion.
• No nucleus or organelles, leaving more space for haemoglobin.
• Flexible membrane allows passage through narrow capillaries.

2. Muscle Cells:

• Function: Contraction to enable movement.
• Adaptations:
• Contain many mitochondria to supply ATP for energy.
• Packed with contractile proteins (actin and myosin).

3. Nerve Cells (Neurones):

• Function: Transmit electrical signals throughout the body.
• Adaptations:
• Long axon to carry impulses over long distances.
• Myelin sheath insulates the axon, speeding up signal transmission.
• Many dendrites to connect with other neurones.

4. Epithelial Cells:

• Function: Form protective layers or aid absorption.
• Adaptations:
• Cells in the intestine have microvilli, which increase surface area for nutrient absorption.
• Some have cilia to move mucus (e.g., in the respiratory tract).

5. Sperm Cells:

• Function: Fertilise an egg.
• Adaptations:
• Tail (flagellum) for mobility.
• Many mitochondria to provide energy for swimming.
• Acrosome contains enzymes to penetrate the egg cell membrane.

Tissues, Organs, and Systems:

• Specialised cells group together to form tissues (e.g., muscle tissue).
• Tissues combine to form organs (e.g., heart, lungs).
• Organs work together in organ systems (e.g., circulatory system).