Sec 3 biology

• A cell takes in raw materials
• A cell processes raw materials to make new molecules.
• Molecules can either be used by the cell itself or transported to other parts of the body
• Most cells are too small to be seen with the naked eye.
• We can use light and electron microscopes to see the structure of cells and their parts.
• Light microscopes magnify objects up to 1000x.
• Electron microscopes magnify objects to more than 200 000x
• A camera can be fitted to either types of the microscopes to take pictures. These pictures are called micrographs.
• Light microscopes can come out as coloured images.
• Electron micrographs are black and white images but they can be artificially colourised.
• A cell is a unit of life. It consists of a mass of living matter called protoplasm.
• Protoplasm is a complex jelly like substance
• Many chemical activities that allow the cell to survive and grow are carried out in the protoplasm
• The protoplasm of cells consists of the cell membrane, cytoplasm, vacuole and nucleus
• The cell membrane surrounds the cytoplasm of the cell
• The cell membrane is made out of lipids and proteins
• The cell membrane is a partially permeable membrane that controls what enters and leaves the cell
• A plant cell also has a cell wall that encloses the entire plant cell, surrounding the cell membrane
• The cell wall is made of cellulose.
• The cell wall protects the cell from injury and gives the plant cell a fixed shape.
• The cell wall is fully permeable
• The cell wall is absent in animal cells