AS Biology Module 1 Find a seat I

AS Biology Module 1 Find a seat, I will be here soon!

Bits and Bobs • Text books • Information booklets • What to expect from AS biology. • HOMEWORK 1: read through the 2 booklets.

Cells and the microscope. What do animal and plant cells look like and how can we work out their size? Starter: Draw and fully label an animal cell and a plant cell. State what each organelle (part) is for.

Glossary Organelle Microscope

How do we know what they look like?

History of cells

Keywords Resolution – the degree to which it is possible to distinguish clearly between 2 objects. Magnification – how many times bigger an object appears in relation to real life.

Light microscopes and resolving power. • The maximum resolving power of a light microscope is 200 nm. • Particles can be seen as separate if they are over 0. 5 the wavelength of light, apart. • We can use it to observe microorganisms such as Euglena and Daphnia, thin sections of other organisms and samples of cells. • Wait … what the hell is a nm? !

Complete “magnification and resolution”

Scientific measurements Text book page 6. μm = micrometer = 1/1000 of a meter. or 1/1000 of a mm nm = nano meter = 1/1000 000 of a meter or 1/1000 of a μm Nano is smaller than micro. Q: if the human eye an resolve 100 μm and the light microscope can resolve 200 nm , which can see smaller things and why?

Complete “units of measurement” • http: //www. youtube. com/watch? v=NFVSWO a. U 0 f 0 • First half

Cells and the microscope. How can I work out the size of a microscopic sample? Starter: 1) Label your light microscope diagram. 2) work out the overall magnification when using an objective lens of x 40 and an eye piece lens of x 10.

Working out the size of microscopic samples. • A quick Recap • http: //www. youtube. com/watch? v=NFVSWO a. U 0 f 0

To work out the size of a microscopic sample, you use a graticule Glossary word- a small ruler etched onto an eye piece lens.

Amoeba under microscopes X 10 objective x 40 objective

Calibrating the graticule The eye piece graticule will always stay the same. The stage micrometer has been zoomed in on (magnified) The micrometer is 1 mm long and has 100 divisions. Each division is 10 μm.

Converting eye piece units to μm Q: if you are using a x 4 objective lens and a x 10 eye piece lens, what is the overall magnification?

Converting eye piece units to μm at x 40 1 mm = 40 epu. Each division on the micrometer = 0. 01 mm or 10 μm. The whole micrometer = 1000 μm So 1 epu is = to 1000/40 = 25 μm 40 epu 1 mm

At x 100 1 mm = ____ epu 100 epu Each division on the micrometer = 0. 01 mm or 10 μm. The whole micrometer = 1000 μm So 1 epu is = to _____/____ = ___ μm 1 mm

Magnification and micrographs • When given a drawing/micrograph, you can work out how big things are in real life, using the following relationship. All measurements need to be in μm

Complete the questions on magnification.

Using a light microscope How can I draw what I see under a microscope? Starter:

Label your diagram of the light microscope. 1) What are the 2 lenses in a light microscope? 2) Describe the journey of light through the microscope.

The light microscope • Has a maximum resolution of 200 nm – half the wave length of light.

Observing and drawing cells. • Follow the schedule for the plant cell so you have a sample on your microscope. STOP BEFORE DRAWING. Read the information on biological drawings. Repeat with animal cells.

Staining Stains are coloured chemicals that are used to bind to certain parts of cells that might be clear, in order for them to be visualised. Stain Use Colours produced Methylene Blue Stains acidic cell parts blue Acetic orcein stains chromosomes and connective tissue Dark red Stains alkaline parts of the cell Pink Gentian Violet Stains bacterial cell walls Violet Iodine solution Stains carbohydrates Brown / black Eosin Light green

Sectioning Thin samples are needed for microscopy. This is so that the light can get through. TO see inside larger specimens, sections must be cut – a bit like with one of those ham slicers on the deli counter. The sample is embedded in wax to stop it from distorting, set and then sliced.

Microscopes What are the differences and uses of the 3 main types of microscope? Starter: How many parts of an animal cell can you name. There at least 11 you need to know!

Did your animal cell look like this?

Modern Microscopes • Light microscope – useful for basic microscopy and in schools, but low resolution. • Electron microscopes – use beams of electrons so the resolution is as good as 0. 2 nm. • What is that in mm?

Transmission Electron Microscope – TEM Max magnification x 500’ 000 Electron beam passed through a very thin sample. Electrons pass through thick bits less easily so give contrast. Final image black and white.

What do you notice about these, compared to light microscope images?

Scanning Electron Microscope – SEM Max magnification x 100’ 000 Electron beam directed onto a sample. Electrons bounce off and produce a 3 D image of the surface. Final image black and white.