2.1 - Cell Structure Flashcards
What is magnification
How much bigger an image appears compared with the original object
What is resolution
The ability of an optical image to see or produce an image that shows fine detail clearly
Light microscopes
They are cheap, easy to use, portable and used to study living specimens
Has a magnification up to x2000 but has a low resolution
Use visible light
Magnification calculation
Magnification = image size/ actual size
Laser scanning microscopes
Use laser light to scan object by point to point and is assembled by a computer
High resolution
Use living organisms
Transmission electron microscopes
Specimen has to be chemically fixed by being dehydrated and stained
Electrons pass through the specimen and forms a 2D image
Has a high magnification and resolution
Large and expensive and need a large amount of skill
Scanning electron microscopes
Electrons do not pass through the specimen which cause a 3D image
High magnification less than transmission
Non-living organisms has to vacuumed and stained
Are large and expensive and need a great deal of training to be used
Preparation of microscopes slides
Staining specimens binds to molecules in the specimen making it easier to see
Methylene blue is an all purpose stain
Differential staining
Acetic orcein binds to DNA and stain chromosomes dark red
Eosin stains cytoplasm; Sudan red stains lipids
Iodine in potassium iodine stains cellulose yellow and starch granular blue/black
Observing specimens
Unstained some use a dark background which the illuminated specimen will show up
Prepared specimens are prepared by dehydrating,embedding them in wax to prevent distortion and cutting them into thin sections
Stage graticule
It is a small scale that is placed on a microscope stage and used to calibrate the value of eyepiece divisions at different magnification
Eyepiece graticule
It is placed on the eyepiece of a microscope and acts as a ruler when you view an object under the microscope
Nucleus, nucleolus and nuclear envelope
Nuclear envelope - large organelle surrounded by double membrane
Nuclear pore - allows movement of substances between nucleus and cytoplasm
Chromatin - genetic material
Makes ribosomes for protein synthesis
Control centre of the cell
Store organisms genome
Contain genetic information
Plasma membrane
Made out of lipids and proteins
Has receptor which allows response to chemicals
Regulates the movements of substances into and out of the cell
Rough endoplasmic reticulum
Contains fluid filled cavities (cisternae)
Coated with ribosomes
Forms channels to transport substances from one area to another
Ribosomes produce proteins that can be secreted out of the cell
Smooth endoplasmic reticulum
Contains fluid filled cisternae continuous with nuclear membrane
Contain enzymes that catalyse reactions
Involved with absorption and synthesis of lipids
