Higher Human Biology SQA

Division and Differentiation in Human Cells

Cell Division and Specialisation

• The life cycle of a cell is called the cell cycle, composed of interphase and mitosis.
• Interphase includes subphases G1 (growth), S (DNA replication), and G2 (preparation for mitosis).
• Mitosis is the process by which a single cell divides into two identical daughter cells, having the same number of chromosomes as the parent cell.
• The phases of mitosis include prophase, metaphase, anaphase, telophase, and cytokinesis.

Cell Differentiation

• Cell differentiation takes place in multicellular organisms allowing the development of specialised cell types.
• Stem cells can differentiate into various cell types due to the presence of pluripotent genes.
• During differentiation, cells undergo changes in shape, function, and metabolic activity controlled by the activation and deactivation of genes.

Stem Cells

• Stem cells are undifferentiated cells with the potential to differentiate into different cell types.
• Embryonic stem cells are pluripotent, capable of differentiating into nearly all cell types.
• Adult stem cells, also known as somatic stem cells, have a lesser potential for differentiation but play a key role in growth, healing, and replacing cells lost through daily wear and tear.

Cellular Differentiation and Organism Development

• Cellular differentiation initiates during the early stages of embryonic development.
• The initial cell division leads to the formation of blastocyst, composed of an inner cell mass that becomes the embryo.
• Cells of the embryo keep dividing and differentiating guided by various biological signals, resulting in formation of various organs and systems.
• The development of functionally different cells, organs, and systems from the same zygote is a result of genetic signals and the local environment.

Tissues, Organs, and Systems

• Differentiated cells with similar structure and function group together to form tissues.
• Several tissues work together to form an organ, each contributing to the organ's specific function.
• Organs work in a coordinated manner to form a system.
• Examples include the circulatory, respiratory, and digestive systems.

Implications of Cell Differentiation

• Understanding the process of cell differentiation can lead to advances in regenerative medicine and treatment of various diseases.
• Manipulating the differentiation of stem cells in laboratories can potentially help in organ transplantation, treating neurodegenerative diseases, and heart disease. -The study of cell differentiation helps understand the process of development, ageing, and the basis of biological diversity.