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National 4/5 Biology

National 4/5 Biology. Unit 1: Cell Biology Section a: Cell Structure and Function. We are learning to:. Work out the size of cells using two calculations: Total magnification Conversion of millimetres to micrometres. Total Magnification. Total magnification =

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National 4/5 Biology

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  1. National 4/5 Biology Unit 1: Cell Biology Section a: Cell Structure and Function

  2. We are learning to: • Work out the size of cells using two calculations: • Total magnification • Conversion of millimetres to micrometres

  3. Total Magnification • Total magnification = magnification of x magnification of objective lens eye piece • Example - if eyepiece has a magnification of x5 and objective lens has magnification of x40. Total magnification is 200x (5 x 40)

  4. Total magnification calculations • Calculate the total magnification for the following: • Eyepiece is 5x and objective lens is 25x • Eyepiece is 5x and objective lens is 50x • Eyepiece is 5x and objective lens is 250x

  5. Cell size • 1 millimetre (mm) = 1000 micrometres (um) • Therefore a field of view of 2mm diameter = 2000 micrometres • So if 10 cells are going across the diameter • each cell will be 200 micrometres (2000/10 = 200)

  6. Calculations • How wide are the cells in micrometres? 2mm = 2000um 3 cells across field of view 2000/3 = 666.67um 2mm

  7. Calculations 2 • How long are the onions cells in micrometres? 5mm = 5000um 5 cells across the field of view 5000/5 = 1000um 5mm

  8. Calculations 3 • The following slide has been magnified 100x. How long is one cell? 5mm = 5000um 5 cells in field of view 5000/5 = 1000um 1000/100 = 10um

  9. Your turn! • In pairs come up with two examples for your class mates to work out • Remember you are the teacher you have to know the answer • If you want to make it more difficult show the working with an error that they have to spot!

  10. For fun • Using plasticine • Build models of a plant or animal cell • Label the structures and state their functions • Extra: • State how the cell you have chosen is similar or different to the three other types of cell you have studied

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