Bio 3A Microscopes and levels of organisation

define tissues

groups of similar cells working togtehr to carry out a functions

define organs

groups of different tissues working togtehr to carry out a functions

what are the types of tissues

1. epithelial

2. connective

3. muscle

4. nervous

what is cell theory

all living organism are made of cells that arise from pre-existing cells

what is the need for cells

to magnify cells to see internal structures and therefore understand functions

how does a light microscope work and the limits of it and pros

lit from below, objective lens magnifies and inverts and eyepiece magnifies further

low magnification and resoltuion, produce artefacts

cheap + protable

define magbification and resolutoon

m- how much bigger compared to actual size

r- how close two points can be to be seen as seperate

what are the formulas involving microscopes

total mag= o x e

m= I/A

why must staining be done

to create contrast

how does an electron microscope work

uses a beam of electrons which is focused using EM lenses

what are the pros and cons of EM

• high reso (shorter wavelength - electrons)

• see organelles ultrastructure

• expensive, artefatcs,n dead onlyt, vaccum, complex prep

what is the difference between TEM and SEM

T- 2d, internal, high reso

S- 3d. low reso, surface image

how is a specifimen prepped before an EM

vacuum, dead, dehyrdated stained w metals (scattering electrons)

what is a graticule

scale in eyepieve used to measure cell size, calibrated depends on mag and allows accurate measurements in micrometres

how does a golgi body look in an LM and an EM

LM: dense cytoplasmic area

EM": stacks of flattened membrane sacs

define ultraturcture

sturctures only obsevered in detail using EM

how does tghe ER look in the EM

• 3d network of cavaties surrounded by a membrane

• tubular + sac like

• located in cytplasm