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

Question 13

during certification what type of fluid do the organelles have to be put into

Answer 13

• buffered neutral pH
• iostonic same water potential prevent osmotic effect
• cold prevent enzyme activation and break down

Question 14

what is homogenasation

Answer 14

blending cells- breaking open cell membrane and realseasing the orgnaelles

Question 15

what type of material gose to the bottom of the center during certification

Answer 15

denser material (eg neucleus at the bottlom forms pellet first

Question 16

what results from mitosis

Answer 16

two genetically identical daughter cells

Question 17

what results from meiosis

Answer 17

4 daughter haploid cells

Question 18

what are the name of the process in mitosis

Answer 18

PMAT
-prophase
-metaphase
-anaphase
-telophase

Question 19

what happens in interphase

Answer 19

the cell grows in size and increases

Question 20

prophase events

Answer 20

• chromosomes becomes very thick and visible
• centrioles move to the opposite ends of the cell and produce spindle fibres( centroles not in plant cells but spindle apparatus is)
• nucleolus disappear and nuclei envelope breaks down

Question 21

meta phase

Answer 21

• centro mere
• chromosomes aline themself along the equator with the spindle fibres attache

Question 22

anaphase

Answer 22

• the centro mere divide into 2 and chromstids are pulled in opposite directions to the other ends of the cell

Question 23

telophase

Answer 23

chromatids at opposite ends un coil and a new nuclear envelope forms

Question 24

cystokenisis

Answer 24

cell membrane and cytoplasm divides - and new cell membrane forms

Question 25

name 3 factors that increase the risk of cancer

Answer 25

- exposure to ionzing radiation mutation in the DNA base sequences exposure to chemicals

Question 26

how do tumors form

Answer 26

cell passes check point in cell cycle with damaged DNA which can lead to uncontrollable cell division

Question 27

what are channel proteins

Answer 27

proteins tta allow movement of large polar molecules through facilitated diffusion and active transport

Question 28

what is ATP useful for

Answer 28

- breaking down and regenerating -soulable and small can move easily - relase the right amount of energy at once

Question 29

what factors effects facilitated diffusion

Answer 29

-concentration gradient - surface area (folding) -higher temprature( more energy) membernae thickness (shorter ddiffusion pathway

Question 30

what happens during co transport

Answer 30

na+ is pumped out of the the cell into the capillaries therefore the concentration gradient gose down glucose binds with the co transporter and a co transport proteins allows glucose to move against the concentration gradient into the cell