3 cell structure Flashcards
how do you calculate magnification?
size of image/size of real object
how do you calculate the size of the object under a microscope?
size of image/magnification
what is resolution for a microscope?
the minimum distance apart 2 objects can be in order for them to be visible as 2 different items
what does cell fractionation do?
breaks up cells so it’s different organelles are separated out
before cell fractionation can begin, what does the tissue need to be placed in?
a cold buffered solution
why is the solution that the tissue has to put in before cell fractionation cold and buffered?
cold- to reduce enzyme activity that might break down the organelles
buffered- so the pH doesn’t change and alter organelles/enzymes
what are the 2 steps of cell fractionation?
- homogenation
- ultracentrifugation
what happens during homogenation?
- cells are broken up by a homogeniser (blender) which releases the organelles
- the remaining fluid (homogenate) is filtered to remove complete cells/debris
what is magnification?
how many times bigger the image is compared to the object
explain ultracentrifugation
- filtered homogenate is spun in a centrifuge at a low speed- forcing the heaviest organelles to the bottom of the tube
- fluid at the top of the tube is removed and transferred into another tube and spun at a faster speed in the centrifuge- forcing the next heaviest organelles to the bottom of the tube
- continued at higher speeds each time
rank these 3 organelles in order of weight, heaviest first:
mitochondria, nucleus, lysosome
nucleus, mitochondria, lysosome
what is the layer of heaviest organelles called at the bottom of the tube after ultracentrifugation?
pellet
what are the two types of electron microscope?
transmission electron microscope
scanning electron microscope
compare a light microscope and an electron microscope (4)
LIGHT: can view living samples
ELECTRON: sample must be in a vacuum so cannot be living
LIGHT: lower magnification
ELECTRON: higher magnification
LIGHT: colour images
ELECTRON: black and white images
LIGHT: poorer resolution as light has a longer wavelength
ELECTRON: higher resolution as electrons have a short wavelength
what is not visible in a light microscope?
small organelles such as parts of the mitochondria
what is the difference between a TEM and SEM?
TEM: extremely thin specimens are stained and placed in a vacuum where an electron gun produces a beam of electrons that pass through producing a 2D image
SEM: specimens do not need to be thin as electrons do not pass through- electrons beamed onto the surface and scattered creating a 3D image
what 11 organelles are in eukaryotic cells?
- cell surface membrane
- nucleus
- mitochondria
- ribosomes
- lysosomes
- rough endoplasmic reticulum
- smooth endoplasmic reticulum
- golgi body and vesicles
- chloroplasts
- cell wall
- cell vacuole
what is the structure of the nucleus?
nuclear envelope (double membrane)
nuclear pores
nucleolus
chromosomes
what is the function of the nucleus?
- site of DNA replication and transcription
- contains the genetic material of the cell
what is the structure of the RER?
- folded membranes called cisternae
- ribosomes on outer surface
what is the function of the RER?
site of protein synthesis
what is the structure of the SER?
folded membranes called cisternae
what is the function of SER?
synthesise, store and transport carbs and lipids
what is the structure of the golgi apparatus?
- folded membranes making cisternae
- vesicles
