Cell Biology
Cells and Organisms
- All living things are made up of cells, and these cells arise from other cells.
- Organisms may be unicellular (consist of one cell) or multicellular (consist of many cells).
Cell Components
- Plant, animal and bacteria cells have common components like cell membrane, cytoplasm and genetic material (DNA or RNA).
- Plant and animal cells also have a nucleus which houses the DNA.
- Bacteria cells don’t have a true nucleus. Their genetic material floats in the cytoplasm in an area called the nucleoid.
- Plant cells have additional structures: a rigid cell wall, large central vacuole and chloroplasts.
Cell Specialisation
- In many multicellular organisms, cells are specialised to perform different functions.
- Specialisation allows cells to be incredibly efficient at performing their specific role.
Cell Division
- Cell division in eukaryotes takes place through a process called mitosis.
- Mitosis involves replication of the cell’s DNA, division of the nucleus, followed by cytoplasmic division to produce two identical daughter cells.
- In prokaryotes such as bacteria, cell division takes place through a process called binary fission.
Cell Nutrition
- Cells need nutrients to perform their functions.
- Animal cells get nutrients from food via digestion.
- Plant cells can make their own food through photosynthesis.
Exchange of Substances
- Substances move in and out of cells through the cell membrane.
- This can occur through several processes such as diffusion, active transport or osmosis.
- The movement of substances across membranes depends on the properties of those substances and the permeability of the membrane.
Culturing Microorganisms
- Bacteria and fungi can be grown in culture in a laboratory.
- Cultures must be sterilised to prevent contamination by unwanted microorganisms.
- Aseptic techniques must be used to safely handle cultures.
Role of Enzymes
- Enzymes are proteins that speed up the rate of chemical reactions in biological systems.
- They provide an alternative reaction pathway with a lower activation energy.
- Each enzyme is specific to one type of substrate due to the unique shape of its active site.