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2024 AQA A LEVEL BIOLOGY 3.2 CELLS EXAM WITH CORRECT ANSWERS
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2024 AQA A LEVEL BIOLOGY 3.2 CELLS EXAM WITH CORRECT ANSWERS
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2024 AQA A LEVEL BIOLOGY 3.2CELLS EXAM WITH CORRECT
ANSWERS
Structure of Nucleus - CORRECT-ANSWERS1. Nuclear envelope: double
membrane surrounding nucleus, outer membrane continuous with the (R)ER
of the cell.
2. Nuclear pores: allow the passage of larger molecules, such as mRNA, out
of the nucleus.
3. Nucleoplasm: granular, jelly-like material making up the bulk of the
nucleus.
4. Chromosomes: protein-bound, linear DNA.
5. Nucleolus: small spherical region(s) in nucleoplasm. Manufactures
ribosomal RNA and assembles ribosomes.
Function of the Nucleus - CORRECT-ANSWERS1. Controls cell's activities -
produces mRNA and tRNA - protein synthesis. Controls entry and exit of
materials, and contains nuclear reactions.
2. Retains genetic material in the form of DNA and chromosomes.
3. Manufactures ribosomal RNA and ribosomes.
Define Monoclonal Antibodies - CORRECT-ANSWERSAntibodies produced
from a single group of genetically identical B-cells. Monoclonal antibodies are
identical in structure.
List uses of monoclonal antibodies - CORRECT-ANSWERS1. Targeting cancer
drugs.
2. Pregnancy testing.
3. Diagnosing HIV etc.
,Outline how monoclonal antibodies are used in targeting cancer drugs. -
CORRECT-ANSWERS1. Monoclonal antibodies are made that will bind to
tumour markers (cancer cell antigens), with anti-cancer drugs attached to
antibody.
2. Antibodies bind to the tumour markers - drug will only accumulate in areas
of body where there are cancer cells.
3. Therefore, side-effects of an antibody-based drug are lower than other
drugs because they accumulate near specific cells.
Outline how monoclonal antibodies are used in pregnancy testing (Medical
Diagnosis). - CORRECT-ANSWERSApplication area contains antibodies for
hCG, bound to a blue-coloured bead.
2. When hCG present in urine, hCG will bind to the antibody on the beads,
forming an antigen-antibody complex.
3. Urine moves up the stick to test strip, carrying beads.
4. Test strip contains immobilised hCG antibodies.
5. Antibodies bind to hCG if present --> hCG-antibody complex with the blue
beads attached becomes more concentrated --> turns blue.
6. If no hCG present, beads will pass through the test area --> no visible
colour change.
Outline how monoclonal antibodies are used in the ELISA test. - CORRECT-
ANSWERSEnzyme-linked immunosorbent assay:
=> allows us to see if a patient has antibodies for a specific antigen, usually
HIV.
Indirect ELISA - used to see if a patient has HIV antibodies.
1. HIV antigen bound to bottom of a well in a well plate.
2. Patient's blood plasma sample (containing antibodies) added to the well.
Any HIV-specific antibodies will bind to the antigen in well.
3. Well washed out to remove any unbound antibodies.
4. Secondary antibody attached to a specific enzyme which can attach to
primary antibody added. Well washed out again to remove unbound
secondary antibody.
, 5. Solution containing enzyme's substrate added, which produces a coloured
product after the enzyme action.
6. Colour change of solution ---> HIV-specific antibodies present in blood --->
infected with HIV.
Explain why the ELISA test does NOT diagnose AIDS - CORRECT-
ANSWERSAIDS is a degenerative disease caused by HIV when T-cell count
has declined below a certain level.
Having HIV does not = having AIDS - takes years to develop AIDS.
Outline the ethical issues of monoclonal antibody use. - CORRECT-
ANSWERS1. Involves inducing cancer in mice to produce antibodies --->
some have reservations, despite guidelines to minimise suffering.
2. Successfully used to treat many diseases such as cancer and diabetes,
BUT some deaths have been associated with their use in MS treatments.
3. Testing for the safety of new drugs presents new dangers ---> 2006 trial,
London.
=> Society must weigh up advantages and disadvantages of their use,
combined with current scientific knowledge about them to make informed
decisions at individual to global levels about the use of drugs such as MAs.
Explain how vaccines work - CORRECT-ANSWERS1. Provide protection for
individuals and populations against disease.
2. Vaccination can help avoid suffering caused during the primary immune
response.
3. Vaccines contain antigens that cause the body to produce memory cells
against a particular pathogen, without that pathogen causing disease --->
immunity without symptoms.
4. Contain antigens, free or attached to a dead or attenuated (reduced in
virulence/weakened) pathogen.
Define Herd Immunity - CORRECT-ANSWERSGeneral immunity to a pathogen
in a population based on the acquired immunity to it over time by a high
proportion of members.
Define Active Immunity - CORRECT-ANSWERSImmune system making its own
antibodies.
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