Cell Structure Flashcards
What is resolution
Distinguish between 2 points
What is the formula for magnification
Drawn size
_____________
Actually size
Cell fractionation
What does cold do
To reduce enzyme activity that might break down organelles
Cell fractionation
What does isotonic do
Same water potential
So water doesn’t come In or out and prevents organelle from bursting or shrinking through osmosis
Cell fractionation
What does buffered do
Maintains pH levels so it doesn’t fluctuate so proteins don’t denature
What are the 2 stages of cell fractionation
Homogenised
Ultracentrifugation
What does homogenised do
organelles placed into blender and is filtered as while cells or cell debris is removed
What happens in a ultracentrifugation
Fragment is placed into a centrifuge and is spun slowly at a LOW SPEED, so that the HEAVIEST organelles will be forced to the bottom ( nucleus first)
The SUPERNATANT (fluid at top) is removed and then spun at the HIGHER SPEED for LONGER so then the NEXT HEAVIEST organelles forced to the bottom ( MITOCHONDRIA)
Process is repeated at increases SPEED AND TIME
Optical microscope
Uses beams of light through specimen and uses 2 lenses: eyepiece lens and objective lens
Limitation= not much detail produced with low magnification and resolution
Transmission electron microscope (TEM)
Electrons are fired from an electrogun and pass through a thin section of the specimen
Gives high resolution, the electron beam focused using electromagnets and denser parts of the specimen to absorb more electrons (darker parts)
Image produced on a florescent screen
Magnification can be increased up to 500,000 X
Limitation= must be in a vacuum, specimen must be rally thin and the specimen are killed (complex process) and only 2D images are formed and method can have artefacts ( alterations to the specimen)
Scanning electron microscope (SEM)
Electrons are passed across the surface of the specimen
Scattered electrons form and image on the screen
Depressions appear darker and extensions appear lighter
Produces 3D image
Limitations= resolving power is lover then TEM and is less complex than TEM so less chance of an artefact
Cell surface membrane role
Responsible for controlling what goes in and out and sending and receiving chemical signals
Role of the nucleus
2 membranes, nuclear pores that allows stiff to go in and out and contains chromosomes & the chromatin which is everything inside the nucleus and the nucleus - RNA (were ribosomes are made)
Role of the mitochondria
Aerobic respiration = produces ATP
Cristae increases the surface area and ATP synthase the matrix which is the filling in the mitochondria, contains DNA and has its own ribosomes to make its own protein and cells can’t survive without them
Role of the chloroplast (in plants and algae )
Double membrane and stacks of chloroplast is known as granum and chlorophyl embedded in, the stacks can be joined together and thylakoid membranes (covers little rings in the stacks) has own ribosomes and DNA, this is where photosynthesis takes place and has a large surface area
