Cell structure Flashcards
describe the function and structure of the cell-surface membrane
function is to regulate movement of substances into and out of cell
- a bilayer of lipids (phospholipid)
- large surface area
describe the function and structure of the nucleus
function is to control reactions within the cell
- has a double membrane
- contains genetic material
- has pores so substances can move in and out
- nucleolus which manufactures rRNA and assembles ribosomes
- nucleoplasm - jelly-like material
describe the function and structure of the mitochondrion
function is to release energy during aerobic respiration
- has a double membrane
- has a folded inner membrane
- folds are called cristae
- inner fluid is called matrix
- high surface area for more efficient respiration
describe the function and structure of the chloroplast
function is to absorb light energy during photosynthesis
- has a double membrane
- folded inner membrane
- folds are called thylakoid
- chlorophyll within thylakoid
- liquid is called stroma
- high surface area for more efficient photosynthesis
describe the function and structure of the Golgi apparatus
function is to process and package polypeptides for exocytosis, and makes lysosomes
- a stack of fluid-filled membrane-bound sacs
- have a high surface area
describe the function and structure of the lysosomes
function is to hydrolyse unwanted material using hydrolytic enzymes
- a vesicle containing enzymes
- lots in one cell for faster breakdown
describe the function and structure of the ribosomes
function is for protein synthesis during translation
- made up of 2 sub-units
- consist of proteins and rRNA
- no membrane so sub-units can move
- 80s in plant cells and 70s in prokaryotic cells
describe the function and structure of the RER
function is to transport polypeptides
- a fluid-filled membrane
- covered in ribosomes
- large surface area
describe the function and structure of the SER
function is to process and synthesise lipids
- fluid-filled membranes
- large surface area
describe the function and structure of the cell wall
function is to support and maintain shape of cell
- made from cellulose - condensation of beta glucose molecules form fibrils - fibrils joined by hydrogen bonds which collectively provide strength
- found on the surface of plant, algal and fungal cells
- arrangement of fibres gives strength
describe the function and structure of the cell vacuole
function is to maintain the shape and pressure of the cell, and to move chemicals
- membrane-bound (tonoplast)
- within the cytoplasm
- contains cell sap
- membrane separates sap from cytoplasm
describe how a lysosome can break down eg. proteins
- the lysosome will fuse with the faulty protein and the phospholipid biolayers will join together to become 1
- the hydrolytic enzymes within the lysosome are released which will break down the protein into amino acids
- exocytosis then occurs (when the waste molecules leave the cell)
name the structures found within prokaryotic cells
- cell wall made from murein
- cell membrane
- slime capsule (for protection)
- DNA loop
- ribosomes (70s)
- flagellum for mobility
- plasmid which can transfer DNA to other cells
describe how light microscopes work
- light from a mirror is reflected up through the object into the objective lens
- the image produced is magnified by the eyepiece lens
describe how an SEM microscope works
- a beam of electrons is produced at the top of the microscope by an electron gun
- the electron beam follows a vertical path through the microscope held within a vacuum
describe how a TEM microscope works
- electrons are emitted which travel through a vacuum
- electromagnetic lenses are used to focus the electrons into a thin beam which is directed into the object
why can electron microscopes give a higher resolution?
electrons have a shorter wavelength than visible light so produce higher resolution images
what are the advantages and disadvantages of light microscopes?
advantages:
- cheap to purchase and operate
- simple and easy sample preparation
disadvantages:
- low magnification
- lower resolution than electron microscopes
what are the advantages and disadvantages of SEM microscopes?
advantages:
- higher magnification and resolution than light microscopes
- can look at 3D structures
disadvantages:
- very expensive
- cannot look at live specimens
- produces only black and white images
- lower resolution than TEM’s
what are the advantages and disadvantages of TEM microscopes?
advantages:
- high magnification and resolution
- can see internal structures
disadvantages:
- very expensive
- cannot look at live specimens
- produces only black and white images
- can only be used with very thin objects
what are artefacts in microscopy and give some examples
they are things that can be seen under the microscope which are not meant to be there
eg. foreign bodies such as eyelashes, clumps of stain/dye
what is the formula for magnification
magnification = image size divided by actual size
how do you convert from nm to mm
divide by 1,000,000
how do you convert from micrometers to mm
divide by 1000
what is cell fractionation?
the process of separating different organelles of a cell, so they can be studied in detail
what are the steps involved in cell fractionation and give reasons
- tissue is cut up and kept in a cold (to stop enzymes breaking down cells), isotonic (to stop osmosis), buffered solution (to stop a pH change).
- cut-up tissues are further broken up in a homogeniser to make the tissue as small as possible and to break open the cells to release organelles
- mixture is filtered to remove cell debris
- homogenised tissue is spun in an ultracentrifuge at a low speed to force the heaviest organelles to sink to the bottom, to form a pellet
- the supernatant is transferred to another tube and spun at a different speed to form pellets of different organelles
