OCR AS F211 Cell Structure 1.1.1

a) State the resolution and magnification that can be achieved by a light microscope, a transmission electron microscope and a scanning electron microscope

• light microscope = 200nm , x1500
• transmission electron microscope = 0.1nm, x500,000
• scanning elctron microscope = 0.1nm, x100,000, produces a 3D image

b) Explain the difference between magnification and resolution

Magnification = the number of times larger an image is compared to the object itself

Resolution = the ability to distinguish between two objects that are very close together

c)Explain the need for staining samples for use in light and electron microscopy

staining for light microscopy involves using coloured chemicals or fluorescent dyes

salts of heavy metal ions are used for electron microscopy

it is necessary because most biological cell structures are colourless and otherwise invisible. Stains bind to chemicals in or on specimens, giving contrast and allowing you to distinguish between different parts of the cell

d) calculate the linear magnification of an image

actual size = image size / magnification

e) describe and interpret drawings and photographs of eukaryotic cells as seen under an electron microscope and be able to recognise the following structures: nucleus, nucleolus, nuclear envelope, rough and smooth endoplasmic reticulum, golgi apparatus, ribosomes, mitochondria, lysosomes, chloroplasts, plasma cell surface membrane, centrioles, flagella and cilia

f) outline the functions of the structures listed in e)

• nucleus - controls activities of the cell
• nucleolus - makes ribosomes and RNA
• nuclear envelope - contains pores to allow materials into or out of the nucleus
• rough ER - transports protein
• smooth ER - makes lipids
• golgi apparatus - makes secretory vesicles and lysosomes & modifies and packages proteins
• ribosome - makes proteins
• mitochondria - aerobic respiration
• lysosome - contains enzymes for destroying worn-out organelles and food particles
• chloroplast - photosynthesis
• plasma cell surface membrane - regulates passage of substances into and out of cells
• centriole…