biology cell structure

Question 1

what are the two main advantage of a electron microscope over a light microscope

Answer 1

• electron beams have a shorter wavelength and there for a high reslutitution
  -electrons are charged and can be focused using electromagnets

Question 2

what are the two types of electron microscope

Answer 2

-scanning
-transmission

Question 3

how dose a TEM work
give 3 limitations

Answer 3

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

Question 4

how dose a SEM work
give 3 limitations

Answer 4

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

Question 5

what is the nucleus function and what are the parts of it called

Answer 5

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

Question 6

what are the mitocondria

Answer 6

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

Question 7

what are the structures of the mitoconria

Answer 7

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

Question 8

name a protein associated with DNA in the chromosones

Answer 8

histones

Question 9

describe the structure of the nucleus

Answer 9

-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

Question 10

what is the structure of DNA in the nucleus

Answer 10

DNA is linear and wrapped around hi stone

Question 11

what are 3 factors both mitochondria and chloroplasts share

Answer 11

-Both have a double membrane
-both contain there own circular DNA
- both contain ribosomes for protein systehsis

Question 12

what is the function of mitochondria

Answer 12

-ATP synthesis
-site of aerobic respiration
structure- folded internal membrane

Question 13

what is the function of chloroplast

Answer 13

thyroidal membrane contains pigments to absorb light and stroma contains enzymes needed for photosynthesis