Biology Chapter 2: Cell Structure and Organisation

Study Notes

Cytoplasm: jelly-like substance containing particles and organelles, surrounded by the cell membrane, where chemical reactions take place
Cell membrane: partially permeable, forms a boundary around the cytoplasm, prevents cell contents from escaping, controls what substances enter and leave the cell
Nucleus: circular or oval structure containing DNA in the form of chromosomes, controls cell division, development, and cell activities
Mitochondria: circular, oval, or slipper-shaped organelles, responsible for aerobic respiration
Ribosomes: small, circular structures attached to the membrane or lying free, responsible for protein synthesis

Cell wall: tough, non-living layer made of cellulose, surrounding the cell membrane, prevents plant cells from bursting, allows water and salts to pass through (freely permeable)
Vacuole: fluid-filled space surrounded by a membrane, contains salt and sugars, helps to keep plant cells firm
Chloroplast: organelle containing chlorophyll, traps light energy for photosynthesis

Cytoplasm: jelly-like substance containing particles and organelles, surrounded by the cell membrane
Cell membrane: partially permeable, forms a boundary around the cytoplasm, prevents cell contents from escaping, controls what substances enter and leave the cell
Circular DNA: single circular chromosome, controls cell division, development, and cell activities
Plasmids: small, circular pieces of DNA, contain genes that carry genetic information for survival and reproduction
Ribosomes: small, circular structures, responsible for protein synthesis
Cell wall: tough, non-living layer (not made of cellulose), prevents cell from bursting, allows water and salts to pass through (freely permeable)

When cells finish dividing and growing, they become specialised and have specific functions
Specialised cells perform one special job, develop a distinct shape, and undergo special kinds of chemical changes in their cytoplasm
Examples of specialised cells:
- Ciliated cells: form the lining of the nose and windpipe, with cilia that create a stream of fluid carrying dust and bacteria away from the lungs
- Root hair cells: absorb water and minerals salts from the soil
- Palisade mesophyll cells: found in plant leaves, columnar and packed with chloroplasts for photosynthesis
- Nerve cells: conduct electrical impulses along the fibre, connecting distant parts of the body to the CNS