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Question 1

explain how a diverging lens helps short sighted ness

Answer 1

distant objects are over refracted normally (forms an image before retina)
need diverging lens refract light outwards and counteracts the over refraction so now light hits on retina

Question 3

wyhy r stage 1 and stage 3 needed

Answer 3

stage 1
to break open cells

stage 3
to precipiate dna from solution

Question 4

Explain how a bacterial cell can be genetically modified to glow in the dark.

Answer 4

phospherent gene needs to be isolated from the dna of phospherent organism using enzyme to expose sticky ends

plasmid is removed from bacterial cell and cut open using same enzymes to expose complementary sticky ends

the phopherent gene inserted into backterial cell matching the sticky ends using enzyme ligase

plasmid inserted back into bacterial cell and grown on a petri dish bacterial cell will express the gene and glow in dark

Question 5

explain how plasmid can be used to genetically modify a bacterial cell to contain a human gene

Answer 5

removal of human gene
plasmid is cut and removed from bacteria using enzymes
gene added to plasmid
plasmid inserted into bacterium

Question 6

BALANCE NH3

Answer 6

N2+3H2—->2NH3

Question 7

explain why graphene good conductor of elecrical current

Answer 7

4 electrons in outer shell
graphene each carbon atom covalently bonded to three others
the delocalised electrons in graphene to carry the charge

Question 8

Explain why oxygen has a low melting point

Answer 8

The force of attraction between molecules
is weak so…
a small amount of heat energy needed to overcome the force of attraction

Question 9

explain why x high melting point

Answer 9

The force of attraction between molecules
is strong so…
a large amount of heat energy needed to overcome the force of attraction

Question 10

Suggest an explanation for the extinction of Homo habilis.

Answer 10

out competed by homo erectus