- Living things are made of cells
- 1 celled organisms are unicellular
- 2 or more celled organisms are multi cellular
- All multi cellular organisms are made of eukaryotic cells
- 2 types of microscope
- Light microscope and electron microscope
- Microscopes work by refracting the light that has passed through an object
- The light microscope refracts the light rays passing through an object. It has an eyepiece and objective lenses. The light microscope can see individual cells but not structural detail.
- Found in both plant and animal cells
- Surrounded by a nuclear envelope. This consists of 2 unit membranes that are perforated by nuclear pores. This allows the exchange of substances between the nucleus and cytoplasm.
- Contains chromatin which is composed of coils of DNA bound to proteins called histones.
- Contains a nucleoplasm which contains a variety of chemical substances such as ions, proteins and nucleotides.
- Contains a nucleolus which produces rRNA from which ribosomes are assembled.
- A complex network of membrane bound cavities called cisternae.
- May have vesicles, tubules, sacs and layers.
- Rough ER is covered with ribosomes. These are the sites of protein synthesis. The rough ER temporarily stores and transports the proteins that are made by the ribosomes.
- Smooth ER has no ribosomes attached. They are tubular and they synthesise lipids including steroids.
- Small, dense granules scattered through the cytoplasm and on the rough ER's surface.
- Consist of 2 sub-units each containing RNA and protein
- The two sub-units combine with each other in the presence of mRNA.
- The ribosome moves alone the mRNA in translation during which a polypeptide chain is formed
- Free ribosomes produce proteins for use in the cytoplasm whereas ribosomes bound to the rough ER synthesise proteins which are exported out of the cell
- Small, hollow cylinders
- Found in animal cells and in lower plant cells
- Occur in pairs and the two units lie at right angles to each other
- They are found in the centrosome in the cytoplasm.
- Each centriole is made up of 9 groups of microtubules arranged in triplets.
- They play a part in cells division and are involved in the formation of the nuclear…