Microscopy

Cell Theory Living organisms either multicellular (made up of many cells) or unicellular (exist as single cells) Metabolic processes take place within cells New cells are derived from existing cells The genetic material of the organism is passed from parent cells to daughter cells A cell is the smallest unit of an organism capable of surviving independently Zooming into DNA

Parts of the microscope quiz Check that lowest power of objective lens is clicked into place Clip slide onto stage Ensure that stage is closest to the lens Look at the stage from the side and position slide so that the specimen is beneath the lens Look down the eyepiece and carefully turn coarse focus until specimen comes into view Adjust illumination Use fine focus to adjust if necessary To view with higher power make sure that the area of interest is in the centre of the field of view and then rotate objective lenses Microscopes through history Parts of the microscope quiz

Transmission electron microscope Limit of resolution for light microscope is limited by wavelength of light (red light = 400nm, therefore resolution limit is 200nm) . Tried to use x-rays (smaller wavelength e.m.r.) but can’t focus them easily. Free electrons behave like e.m.r. with a wavelength at least as short as x-rays. The negative charge means that they can be focused using electromagnets: limit of resolution is 0.5nm (cell membrane dimension is 7nm)

Electron beam Specimen Copper grid Screen Human tissue culture cell – false colour Prostate cancer cell Electron beam Specimen Copper grid Screen

Scanning electron microscope

Wellcome Institute SEM Fly foot Butterfly proboscis Wellcome Institute SEM How the SEM works SEM Images

Magnification The magnification of an object is how many times bigger the image is when compared to the original object magnification = actual size size of image M I A actual size = magnification size of image

Microscopic Units 1 millimetre = 1000 micrometres (µm) 1 micrometre = 1000 nanometres (nm) Image Actual = 2 mm = 8 mm magnification = actual size size of image = x 4

Image = 6mm ; Actual size = 20µm Magnification = ? Image = 6mm Hint: keep the units the same ! magnification = actual size size of image 6000 = = x 300 20 Image = 6mm Magnification = x 150 Actual size = ? actual size = magnification size of image 6000 = = 40 µm 150

Resolution X 6 Increasing magnification doesn’t always increase the resolution

Resolution is the ability to distinguish between two points – a lack of resolution means that the two points would appear as one The resolving power of a microscope is related to the form of radiation being used to see the specimen Using a light microscope objects 0.2µm or more apart can be seen separately

From coffee bean to carbon atom Size is everything… largest algal cell leaf (thickness) page plant cell animal cell large bacterial cell mitochondrion cell membrane 50 000 µm (50mm) 500 µm (0.5mm) 100 µm (0.1mm) 40 µm (0.04mm) 20 µm (0.02mm) 5 µm (0.005mm) 1 µm (0.001mm) 7nm (0.007µm) From coffee bean to carbon atom

=1mm =1000µm =0.5mm =500µm =0.1mm =100µm =0.04mm =40µm =0.02mm =20µm =0.005mm =5µm

Feature Light microscope Electron microscope Radiation Max. resolution Max. magnification Lenses made of Specimen Support for specimen Stains Image Cost

Light Electron Advantages: Disadvantages: Small, portable Very large Preparation of material is relatively quick and simple Lengthy preparation requiring skill and equipment Material rarely distorted by preparation Preparation of material may distort it Natural colour can be observed Images are black and white Cheap to purchase and operate Expensive to purchase and operate Maximum magnification x1500 Magnification greater than x500 000 with suitable resolution Maximum resolution 200nm Maximum resolution 0.1nm Depth of field is restricted Possible to investigate a greater depth of field

Drawing from the microscope

Drawing from the microscope

Microscope drawing Title/ Aspect(T.S. L.S ) Mag Low Power Plans of tissues Do not draw individual cells unless specifically told to do so. No shading. Ruled lines which do not cross. Medium and High Power drawings Show individual cells. Only label cell organelles that are visible e.g. Cell wall, chromosomes, cytoplasm. No shading etc. as above.

Gorgeous photomicrographs Nikon Small World Royal Microscopical Society; Biannual competition