Higher Biology | Key Area 1.4: Cellular Differentiation

Cellular differentiation

The process by which a cell expresses certain genes to produce the proteins characteristic for that cell.

Cellular differentiation allows a cell to:

Adapt and carry out a specialised function as part of a permanent tissue. This happens as different proteins are synthesised based on what genes are expressed, resulting in different cell types.

Multicellular organisms tend to retain stem cells. Why?

Differentiated cells often lose the ability to divide or make new copies of themselves.

Meristem

A region of unspecialised cells in plants capable of self-division (self-renewal), ie. the place where differentiation occurs in. These are the only places a plant may grow.

What is the function of a meristem?

- Groups of unspecialised plant cells are capable of dividing throughout a plant’s entire lifespan, unlike animals.

- Some meristematic cells continue to divide to form more meristematic cells, while others become differentiated, eg. a meristematic cell specialising into a xylem cell.

What are the two types of meristems?

- Apical meristems, found at the tips of roots and shoots

- Lateral meristems, found within the stem, in the cambium

Apical meristems

- Meristems found at the tips of a plant’s roots and shoots.

- Source of primary growth, ie. the lengthening of a plant, and produces new leaves and flowers.

Lateral meristems

- Meristems found within the stem, in the cambium (between xylem and phloem cells) of vascular bundles

- Source of secondary growth, ie. the widening of a plant, and produces bark in trees

Stem cell

Unspecialised cells in animals that can divide (self-renew) and differentiate.

What are the two types of stem cells in animals?

Embryonic stem cells, and tissue stem cells

Embryonic stem cells

- Pluripotent stem cells that can differentiate into all cell types that make up an organism, as all genes can be switched on.

- Found in early embryos, and can divide continuously.

- Use is ethically concerned as it requires the destruction of an embryo.

Tissue stem cells

- Multipotent adult stem cells that can differentiate into all types of cells found in a particular tissue type, ie. they can only give rise to the limited range of cells within their particular tissue type.

- Involved in the growth and renewal of cells, and repair of damaged tissue found in their particular tissue, by the replacement of dead/damaged cells, eg. red bone marrow stem cells produce various types of blood cells.

What are some uses of stem cells?

Research; therapeutic use

Stem cells in research

- Stem cells can be used as model cells to study how disease develops, eg. taking stem cells from a person with Parkinson’s disease and studying how it develops.

- Can be used as an alternative for drug testing.

- They provide information on cell processes such as cell growth, differentiation and gene regulation.

Stem cells in therapeutic use

- Assists in the repair of damaged or diseased organs or tissues by replacing dead/damaged cells within them, eg. cornea repair and regeneration of damaged skin.

- Stem cells taken from an embryo can self-renew in vitro under the right conditions in a lab, and be manipulated into specialising into required cells.