Ib Biology Sl Topic 2 Revision Notes

* Topic 2: Cells * 2.1 Cell theory * 2.1.1 * Outline Cell Theory 1. All living organism are composed of cells 2. Cells come from pre-existing cells 3. Cells are the smallest unit of life * * 2.1.2 * Discuss the reasons for cell theory 1. When organism are looked at under a microscope, they are consistently made up of cells 2. Cells carry out asexual reproduction – called Mitosis 3. Cells are the smallest unit of organisms that can carry out all process of life * * 2.1.3 * State Unicellular organisms can carry out all functions of life * G – Growth = size and volume increase * H - Homeostasis = Maintenance of internal cell conditions * M – Metabolism = chemical reactions e.g. respiration * N – Nutrition = synthesis of organic materials * R – Reproduction = asexual (cell division) * R – Response = to change (environmental) * * 2.1.4 * Compare relative sizes * 1 nm = molecule * 10nm = Membrane * 100nm = Virus * 1 um = Bacteria * 10um (or less) = organelle * 100um (or less) = cell * * 2.1.5 * Calculating Linear Magnification (answer = magnification) 1. Measure scale bar on page e.g. 15mm 2. Convert answer into same units on scale bar e.g. 15mm = 15000um (as 1000um = 1 mm) 3. Divide answer by number on scale bar e.g. 15000um / 5um = 3000 * Magnification is 3000x

* If magnification given (answer = actual size) 1. Measure object given e.g. 41mm 2. Divide answer by Magnification e.g. 41mm/750 = 0.055mm 3. Convert to sensible unit 0.055 x 1000 = 55um * * 2.1.6 * Explain the importance of Surface area to volume ratio * Mathematical rule- as an object increases in volume, the ratio of its total surface area to its volume decreases, i.e. the larger an object, the smaller its surface-volume ratio. The rate of metabolism of a cell is a function of its mass/volume, whereas the rate