1.1 introduction to cells -Cell theory There are multicellular and unicellular cells.
1. All cells come from pre-existing cells.
2. All living organisms are composed of cells
3. Cells are the smallest unit of life

-Functions of life. These indicate life existing in a structure. There are 7/8 functions that organisms need to stay alive:
1. Growth
2. Response/defense
3. Homeostasis
4. Reproduction
5. Metabolism
6. Nutrition

-Cell size is proportional to its rate of reaction. The effect of larger surface area in a cell will result in heat loss.

-Multicellular organisms have certain properties that emerge from cell interaction.

-Cellular differentiation is when a simple cell becomes specialized. Differentiation forms complex tissues and cell types in multicellular organisms. A Tissue is a group of cells that develop the same way with the same functions

-Differentiation takes place in multicellular cells by cells expressing a selection of genes, but not others. This means switching the pattern of gene expression and thus changes the shape and size of a cell.

-Stem cells are undifferentiated cells. They can differentiate and divide (by mitosis). Stem cells are found in multicellular organisms. They can be used therapeutically as a tissue repair system in the body.

	Created by Elisabeth Morell over 11 years ago

Revision of Topic 1.1 Introduction to Cells for IB Biology