microscopes and cell structure 2.1.1

how does a light microscope work

-slide is illuminated by light source beneath slide -objective lens produces a magnified image which is magnified again by eyepiece lens -produces magnified colour image 

how does a transmission electron microscope work

-beam of electrons transmitted through a specimen and focused to produce an image

-2d black and white images are produced

how does a scanning electron microscope work

-beam of electrons sent across the surface of a specimen and reflected electrons are collected

-3d images are produced

3 positives of light microscopes

-inexpensive to buy and operate 

-small and portable

-simple sample preparation

3 positives of electron micorscopes

-over x500000 magnification -can produce 3d images -have much higher resolution

size of each division of stage micrometre

1 division = 10 micrometers

how do you work out magnification when calibrating

stage micrometre divided by eye piece graticule 50 micrometres divided by 87 graticule divisions = 5.75 micrometres

how do you then work out length of an object

Graticule divisions covered by object x magnification factor = length of object (µm)

why do we stain specimens

coloured stains bind to chemicals which allows specimen to become visible , to see certain organelles and to improve the contrast

what is an artefact

a visible structural detail caused by processing the specimen and is not a feature of the specimen

definition of magnification

the number of times larger the image is in comparison to the object

resolution defiention

the ability to distinguish between very small structures that are close together in detail

what does the nucleus do

-controls cells activities -contains genetic materiaal

what does the nucleolus do 

-makes RNA and ribosomes

what does mitochondria do

-site of ATP production during aerobic respiration -double membrane

what does the rough ER do

-involved in assembling and transporting proteins -consists of flattened membrane sacs called cisternae with ribosomes attached.

what does smooth ER do

-involved in lipid synthesis -consists of flattened membrane sacs called cisternae

what does golgi apparatus do

-involved in modifying proteins -packages proteins into vesicles for storage or transport

-stack of membrane bound sacs (pita bread)

what do vesices do

-membrane sacs used to  transport materials around the cell

what do chloroplasts do

-double membrane -site of photosynthesis -contains chlorophyll

what does a lysosome do

-spherical sac containing powerful digestive enzyme- used to break down foreign materials -causes programmed cell death

what does a vacuole do

-for storage eg sap and to maintain shape of cell by pushing cytoplasm against wall -surrounded by membrane called tonoplast

what do ribosomes do

-site of protein synthesis -not membrane bound

what do centrioles do 

-made of 2 bundles of tubular protein -form spindle fibres during cell division -involved in formation of cilia and flagella

what does cell wall do

-made of cellulose -provides strength and prevents cell bursting -fully permeable membrane

what organelles are in a animal cell (13)

nucleus, nucleolus, mitochondria, rough ER, smooth ER, Golgi apparatus , vesicles, lysosome, ribosomes, centrioles, microtubules, cell surface membrane, cytoplasm

what organelles are in a plant cell (14)

nucleus, nucleolus, mitochondria, rough ER, smooth ER, Golgi apparatus , vesicles, chloroplast, vacuole, ribosomes, amyloplast, cell wall, cell surface membrane , cytoplasm

what does amyloplast do

stores starch

what does the nuclear membrane do

separates the contents of the nucleus from the rest of the cell

what organelles are found in a prokaryotic cell

slime capsule (not always), pili, chromosone, plasmid DNA, flagella, cell wall (made of peptidoglycan), cytoplasm, ribosome

function of flagella

allows cell to move

function of cilia

can aid cell movement

organelles involved in the production and secretion of proteins

nucelus, rough er, vesicles

production and secretion of proteins steps

1. mRna is made in nucleus 2.mRNA leaves through nuclear pore 3. mRNA is then translated into a protein by ribosomes bound to the rough ER 4.the proteins pass into the rough er cisternae and are packaged into transport vesicles 5. proteins in the vesicles then enter the Golgi apparatus and are structurally modified 6. some vesicles go to cell surface membrane, fuse and excrete contents whereas others just stay in cell.

what is and makes up cytoskeleton

-network of fibres necessary for shape and stability of a eukaryotic cell. -has three main components: microfilaments, microtubules and intermediate fibres

what is the importance of the cytoskeleton

provides mechanical strength to cells, aids transport within cell and enables cell movement