Cell immunity and recognition

Question 1

Describe how HIV is replicated.

Answer 1

• Attachment proteins attach to receptors on helper T cells
• RNA enters cell
• Reverse transcriptase converts RNA to DNA
• Viral protein produced
• Virus particles assembled and released from cell

Question 2

Describe how the human immunodeficiency virus (HIV) is replicated once
inside helper T cells (TH cells).

Answer 2

• RNA converted to DNA using reverse transcriptase
• DNA inserted into nucleus
• DNA is transcribed to mRNA
• mRNA is translated into viral proteins

Question 3

Describe how a phagocyte destroys a pathogen present in the blood.

Answer 3

• Engulfs
• Forming phagosome and fuses with lysosomes
• Enzymes/lysozymes digest/hydrolyse

Question 4

What is the role of the disulfide bridge in forming the quaternary structure
of an antibody?

Answer 4

Joins two polpeptides

Question 5

Explain how HIV affects the production of antibodies when AIDS develops in a person.

Answer 5

• Less/no antibody produced
• because HIV destroys helper T cells
• So few/no B cells activated

Question 6

Determining the genome of the viruses could allow scientists to develop a
vaccine.
Explain how.

Answer 6

• (The scientists) could identify proteins (that derive from the genetic
  code)
  OR
  (The scientists) could identify the proteome;
• (They) could (then) identify potential antigens (to use in the vaccine)

Question 7

Describe the role of antibodies in producing a positive result in an ELISA
test.

Answer 7

(First) antibody binds/attaches /complementary (in shape) to antigen;
2. (Second) antibody with enzyme attached is added;
3. (Second) antibody attaches to antigen;
Accept (second) antibody attaches to (first) antibody
(indirect ELISA test).
4. (Substrate/solution added) and colour changes;
Only award if enzyme mentioned.

Question 8

Describe and explain the role of antibodies in stimulating phagocytosis.

Answer 8

• bind to antigen
• causes agglutination