Biology: microscopes and preparing plant and animal cells

ultrastructure

more detailed image of cells as seen from a electron microscope

TEM

transition electron microscope, show internal structur of cell, sends beams of electrons through very thin sections

SEM

scanning electron microscope, shows surface view of cell, photographs electrons reflected from surface of the cell

advantages of electron microscope

greater magnification
greater detail

disadvantages of electron microscope

very expensiv, requires training and isnt protable

samples are dead, may not be the exact same as when theyre living

eyepiece lens

to magnify image

coars focus wheel

rough focus at low power

fine focus wheel

precise focus at high power

clip

hold slide in place

stage height adjustment

to allow the longer high power lens to fit over lside

nose piece

revolves to bring desired lens into place

objective lens

magnifies image, has low, medium and high power

stage

holds the slide

diaphram lever

controls amount of light reaching the sample

hwo to use a light microscope

switch on teh lamp

rotate nosepiece so teh low power lens is in place

place a prepared slide on the centre of teh stage and use clips to secure it

use one eye to look int the objective lens, 2 cm away

focus under low power with teh coarse focus wheel

then focus under high power with teh fine focus wheel

ensure sample is in ur field of view

adjus diaplram to control amount of light reaching the smaple

prepare an animal cell

rinse mouth with water

use cotton bud to scrape the inside og the cheeck, spread teh cells onto a drop of water on the cenre of a glass slide

use mounted needle to slowly lower the cover slip at a 45 degree angle, to avoid trapping air bubbles

add a drop of methylene blue to teh side of teh cover slipe

use filter paper to draw the stain through the sample

to eaxmine a cell

place teh slde on teh stage and secure it with clips

switch on teh lamp

examin under low power with the coarse focus wheel

examin under medium then high power using the fine focus wheel

precautions while examining the samples

use lens tissue to clean teh lens

always examine under LP then MP then HP

use a cover slip to protect lens from the stain, to keep sample in place and prevent it from drying out

how to distinguish between the nucleus and cytoplasm after staining

cytiplasm looks paler
nucelues looks darker
cell wall appears yellow

prepare a plant cell

cut an onion in half and seperate 2 leaves to locate the epidermis

use the forceps to peel off a thin layer of epidermis, use a scalpel to sut epidermis from teh onion

use paint brush to transfer one layer of tissue to a drop of water on teh slide secured with clips

use mounetd needle to slowly lower cover slip at a 45 degree angle to avoid trapping air bubbles