biology cell structure Flashcards
what are the two main advantage of a electron microscope over a light microscope
- electron beams have a shorter wavelength and there for a high reslutitution
-electrons are charged and can be focused using electromagnets
what are the two types of electron microscope
-scanning
-transmission
how dose a TEM work
give 3 limitations
an electron gun produces a beam of electrons focused onto a thin specimen by condenser electron magnets. the denser parts of the specimen absorb the electrons and appear darker
the resolving power of a TEM is 0.1 nanometres
higher energy beam required may damage specimen
there is a complex staining method
it has to be in a vacuum which means living specimens cant be observed
artefacts- may appear in the photomicrograph but are nt actually part of the cell
how dose a SEM work
give 3 limitations
SEM directs beams of electrons onto the surface of the specimen from above. the beam is passed back amd fourth across the portions of the specimen in a pattern. electrons are scattered by the specimen we can build up a 3d image by computer anylsis of the patterns of electrons.
has a resolving power of 20nm so lower than the TEM
has all the same limtations of a TEM appart from the specimen dosnt need to be thin as a result of it not needing to penitrate the specimen
what is the nucleus function and what are the parts of it called
the nucleus contains the organisms hereditary material and controls the centre of control of the cell
- nuclear envelope a double membrane out side of the nucleus
-nuclear pores allows the passage of large molecules out of the nucleus
chromosomes
what are the mitocondria
mitocondria are the sight in which areobic resperation takes place. they are responsible for the production of atp a energy carrier molecule. it also realses energy for the cell. they are high in cells with a high metabolic rate
- conatins matrix and has a folded structure
what are the structures of the mitoconria
it has a double outside membrane that controls materials entering and exiting the cell.
an inner membrane is folded to form a cristea which provides a large surface area for the attachment of enzymes
name a protein associated with DNA in the chromosones
histones
describe the structure of the nucleus
-contains a nuclear envelope which is a double membrane
-nuclear pours for exit of mRNA
-dense area which is called the nucleolus which produces ribosomes
what is the structure of DNA in the nucleus
DNA is linear and wrapped around hi stone
what are 3 factors both mitochondria and chloroplasts share
-Both have a double membrane
-both contain there own circular DNA
- both contain ribosomes for protein systehsis
what is the function of mitochondria
-ATP synthesis
-site of aerobic respiration
structure- folded internal membrane
what is the function of chloroplast
thyroidal membrane contains pigments to absorb light and stroma contains enzymes needed for photosynthesis
during certification what type of fluid do the organelles have to be put into
- buffered neutral pH
- iostonic same water potential prevent osmotic effect
- cold prevent enzyme activation and break down
what is homogenasation
blending cells- breaking open cell membrane and realseasing the orgnaelles