1. National 5 Biology Course Notes Unit 1 : Cell Biology Part 1 : Cell Structure

2. Organelles Cells of animals, plants and fungi contain specialised structures called organelles. Bacteria are unicellular (exist as single cells) and do not have organelles in the same way as other cells. Looking at Organelles The diagram shows organelles in a cell Nucleus ribosomes mitochondrion Chloroplast (only in plant cells) Cell wall (not found in animal cells) Cell membrane

3. Function of cell organelles Nucleus Controls all the activities of the cell. Contains the genetic material (DNA) Cell membrane Controls which substances enter and leave the cell. The membrane is made of protein and lipid. Mitochondrion The part of the cell where aerobic respiration takes place. Ribosomes Part of the cell where protein synthesis takes place Chloroplasts Part of the cell where photosynthesis occurs (Found only in plant cells) Part of cellFunction Nucleus Controls cell activities Contains genetic material Cell membrane Controls entry and exit of substances (Made of protein and lipid) MitochondriaSite of aerobic respiration RibosomesProtein synthesis Chloroplasts (only in plant cells) Photosynthesis Cell wall Prevents cell from bursting when it absorbs water by osmosis

4. Bacteria Bacteria are single celled micro-organisms. They come in a variety of shapes such as rod shaped, spherical and spiral shaped. They have a cell wall and ribosomes, but lack other organelle s. A bacterial cell wall has a different structure to the cell wall of a plant or a fungus The diagram represents the structures found in a bacterial cell: Bacteria have a circular chromosome which contains all the genetic information needed to control all the activities of the bacterial cell. Some bacteria have plasmids – these are small, circular pieces of DNA in addition to the normal chromosomal material. Plasmids are not found in all bacteria. Plasmids can be transferred from one bacterial cell to another. They give bacteria extra properties such as the ability to resist antibiotics. Cell wall Cell membrane Single circular chromosome Ribosomes Plasmid

5. Organelles found in different types of cell Organelle Is the organelle found in: Animal cellPlant cellFungus cell (e.g. yeast) Bacterial cell NucleusYES NO Cell membrane YES Cell wallNOYES Ribosomes YES Chloroplasts NOYESNO Other organelles, e.g. mitochondria YES NO PlasmidsNO YES