biology past paper questions

Question 1

explain why a tree might die if the roots are damages?

Answer 1

less water absorption
-lower rate of photosynthesis
-less glucose produced for respiration
damage to the phloem
-less transport of sugars to the root cells for respiration
damage to the xylem
-less water transported
-fewer nitrates and magnesium

Question 2

explain how mitosis produces two genetically identical cells

Answer 2

-first DNA replication occurs which produces two identical chromosomes
-the replicated chromosomes are pulled apart
-the set of chromosomes are identical to each other

Question 3

what are the two differences between the transpiration steam and translocation

Answer 3

-transpiration involves the xylem and translocation involves the phloem
-translocation transports sugars and transportation transports water

Question 4

Explain how a vaccine could work to prevent a person from developing HIV infection?

Answer 4

-a vaccine which is an inactive form of a antigen is injected to the person
-white blood cells produce antibodies
-if infected, specific antibodies are produces
-antibodies destroy the active site of the antigen

Question 5

describe how monoclonal antibodies for HIV can be produced

Answer 5

-inject the HIV into an animal such as a mouse
-the animal’s immune system would produce white blood cells call b-lymphocytes that make a specific antibody to the antigen
-isolate these antibodies and combine them with fast diving tumour cells to form a hybridoma
-hybridoma cloned to create many cells that produce cells that produce the antibody