Topic Two - Chapter Five

Question 1

Definition: Pathogen

Answer 1

Microorganisms that cause disease and produce an immune response

Question 2

Definition: Antigens

Answer 2

Foreign protein that causes an immune response

Question 3

Definition: Antigenic Variability

Answer 3

All previous immunity is lost so previous vaccine is now ineffective
Happens when pathogens mutate frequently

Question 4

Definition: phagocytosis

Answer 4

Non-specific response, particles can be engulfed by cells in vesicles formed by cell surface membrane

Question 5

Process: Phagocytosis (5)

Answer 5

1. Chemical products released by pathogens attract the phagocyte
2. Phagocytes have receptors that attach to the pathogens
3. They engulf the pathogen, = forms a phagosome
4. Lysosomes move towards phagosome + fuse with it, they release lysozomes into the phagosome. Lysosomes destroy the bacteria by hydrolysing their cell walls
5. Soluble products from the breakdown are absorbed into the cytoplasm of the phagocyte

Question 6

T cells

Answer 6

• Cellular respond to foreign antigens
• mature in thymus gland
• respond to APC

Question 7

B cells

Answer 7

• Humoral response to foreign antigens
• matures in bone marrow

Question 8

Process: T cells (5)

Answer 8

1. Pathogens invade body cells or are taken in by phagocytes
2. Phagocytes/infected cells place the antigens on their cell surface (APC)
3. T helper cells come + attach to the antigens that have been placed on the cell-surface (A-A complex)
4. Cytotoxic t cell will divide by mitosis + form genetically identical clones
5. They differentiate into:
   - Memory T cells: stay in blood and tissue fluid, waiting for re infection
   - T helper cells: stimulates cells to divide
   - Cytotoxic T cells: kills infected cells by producing perforin
   - cells that stimulate phagocytosis

Question 9

Definition: Perforin

Answer 9

Protein that makes holes in infected cell’s cell membrane which causes them to die

Question 10

Process: B cells

Answer 10

1. B cells will take in antigens from the pathogens via endocytosis
2. B cells process these antigens and present them on their surface
3. Complimentary helper t cells come and binds to the antigens that the B cells have presented on their surface, this activates B cells
4. B cells divide by mitosis to produce memory or plasma cells

Question 11

Plasma cells

Answer 11

• Primary immune response
• produce + secrete the specific antibody

Question 12

Memory cells

Answer 12

• Secondary immune response
• remain dormant, when body comes in contact with pathogen again they divide to form plasma cells

Question 13

Definition: vaccination

Answer 13

Process of introducing an antigen into the body

Question 14

HIV structure

Answer 14

• outside= lipid envelope, has attachment proteins
• inside = protein layer, capsid, contains RNA + enzymes
• reverse transcriptase - catalyses the production of DNA from RNA

Question 15

HIV replication

Answer 15

1. Attachment proteins attach to CD4 receptors on T helper cell
2. Nucleic acid RNA enters the cell
3. Reverse transcriptase converts RNA to DNA
4. Viral proteins are created (HIV DNA in nucleus makes mRNA)
5. Virus is assembled + released

Question 16

Process: Elisa test

Answer 16

1. Sample is applied to a surface, to which all the antigens in the sample will attach
2. Surface is washed to remove unattached antigens
3. Add the antibody that is specific to the antigen you’re looking for + leave them to bind
4. Wash the surface to remove excess antibody
5. Add 2nd antibody that binds to first, this 2nd antibody has an enzyme attached to it
6. Add colourless substrate of the enzyme, enzyme forms a e-s complex and changes colour
7. Intensity of colour is relative to the amount of antigen present