Cells
C8:  Cells arise from pre-existing cells, and cell division leads to an increase in cell number

Learning Objective

1. Understand that cell division is the basis of growth, reproduction and repair
2. Explain why chromosomes must be replicated by semi-conservative replication before a cell divides to ensure that daughter cells are identical to the parent cell
3. Describe how prokaryotes divide by binary fission
4. Describe the cell cycle
5. Illustrate the process of mitosis in eukaryotic cells.

• Cell division is the basis of: Growth, Repair, Reproduction
• The ratio of cell membrane Surface Area: Volume Ratio is a factor that limits cell size
• When a cell reaches its OPTIMUM size the NUCLEUS initiates cell divisioin

• All cells contain Deoxyribose Nucleic Acid (DNA)
• In prokaryotes the DNA is found in the cytoplasm in the form of a circular chromosome
• In eukaryotes the DNA is found in chromosomes located in the nucleus as linear DNA. When a cell divides to form 2 identical daughter cells, then the amount of DNA in a cell must be doubled before the cell divides to maker sure that both daughter cells receive a copy of the DNA.
• This process is called semi-conservative replication of DNA

• Chromosomes around found with the nucleus of cells
• When NOT dividing chromosomes are in the form of chromatin granules
• When the cell is preparing to divide these thread like chromatin granules become shorter and fatter and we refer to them as chromosomes.
• Chromosomes contain GENES. Genes determine an individuals characteristics such as eye colour, nose shape etc.