3.2- Cells Flashcards
What do microscopes use to produce an image
waves
what waves do the different microscopes use
optical - light waves
electron - electron beam
define magnification
the ability to produce an enlarged image of an object
define resolution
the ability to distinguish between 2 close points
why do electron microscopes have a higher resolution
an electron beam has a shorter wavelength than a light wave (more likely to be deflected by small objects)
how do transmission electron microscopes work (TEMs)
electromagnets focus beam of electrons transmitted through specimen
denser parts absorb more (look darker on image)
advantages and disadvantages of TEMs
ADV - high resolution images, can see internal structure of organelles
DIS - only used on thin specimens
how do scanning electron microscopes work (SEMs)
scan electron beam across specimen
knocks off electrons from specimen, gathered in cathode ray tube
forms an image
advantages and disadvantages of SEMs
ADV - images show surface and can be 3D
can be used on thick specimens
DIS - lower reduction images than TEMs
calculation for magnification
M = I/A
magnification = image size / real size
how do you prepare a temporary mount of a specimen on a slide
pipettes small drop off water onto slide
use tweezers to place thin section of specimen on top of water
add stain
add cover slip - stand slip upright then carefully tilt and lower so it covers the specimen without any air bubbles
what is the structure of the plasma membrane
made of lipids and protein
receptor molecules to respond to chemicals
what is the function of the plasma membrane
regulates movement of substances
what is the structure of the nucleus
surrounded by double membrane nuclear envelope - contains pores
chromosomes made from protein bound linear DNA
nucleolus
function of nucleus
controls cell activity
instructions to make proteins
pores allow substances to move between nucleus and cytoplasm
nucleolus makes ribosomes
