Response to infection (6.7–6.9, 6.12–6.13)

Question 1

lysis

Answer 1

the bursting of a cell

Question 2

antigens

Answer 2

Foreign material that invades the body

Question 3

What are the 4 non specific immune system responses?

Answer 3

Lysozyme, inflammation, phagocytosis and antimicrobial proteins

Question 4

How do lysozymes protect against pathogens?

Answer 4

found in tears they kill bacteria by breaking down their cell walls. Also found in saliva and nasal secretion.

Question 5

How does inflammation occur?

Answer 5

The damaged white blood cells release special chemicals eg histamine. Causing the arterioles in the area to dilate and increasing the permeability of the capillaries. Plasma fluid, white blood cells and antibodies leak from the blood into the tissue causing oedema.

Question 6

Phagocytes

Answer 6

white blood cells that engulf antigens. Inc neutrophils and macrophages.

Question 7

phagocytosis

Answer 7

when phagocytes engulf and destroy antigens.

Question 8

How do antimicrobial proteins provide a defence against pathogens?

Answer 8

They diffuse into the surrounding cells where it prevents microbes from multiplying. It inhibits microbial protein synthesis.

Question 9

What are the two main types of lymphocytes?

Answer 9

T cells and B cells

Question 10

Where are B cells produced?

Answer 10

bone marrow

Question 11

Where are T cells produced?

Answer 11

thymus

Question 12

What are immunoglobulins?

Answer 12

antibodies

Question 13

What bonds hold the peptide chains of a T cell?

Answer 13

Disulphide bonds

Question 14

Explain what happens in the activation of T helper cells

Answer 14

Bacterium with antigen on surface is engulfed by macrophage. Macrophage presents antigens on its surface and becomes an APC. The APC eventually find the T helper cell with the complimentary CD4 receptor. Clonal expansion occurs and the T helper cell activates and divides into more T memory cells and T helper cells.

Question 15

Explain what happens in clonal selection

Answer 15

Bacterium binds to B cell with complimentary receptor. The B cell becomes an APC. The activated T helper cell with a complimentary receptor binds to the APC (B cell) and produces cytokines that stimulate the B cell. The B cell divides to give B memory and B effector cells. The B effector cells differentiate into plasma cells. The plasma cells secrete antibodies which bind to the antigens.

Question 16

Explain what happens once the antibodies are produced by the B cell

Answer 16

Antibodies bind to the bacteria with antigens on the surface and label them. Antibodies bind to the antibody receptors on a macrophage. The macrophage engulfs the antibodies and bacterium. Lysosomes fuse with the vacuole releasing the digestive enzymes that destroy the bacterium.

Question 17

Explain the role of T killer cells

Answer 17

A bacterium infects cell of host.
The cell presents the antigen and becomes an APC.
T killer cell with a complimentary receptor binds to the APC.
Cytokines stimulate the differentiation of the T killer cell into T killer memory cells and active T killer cells.
The clones of the active T killer cells bind to infected cells presenting antigens.
T killer cell release chemicals that cause pores to form in the infected cell, causing lysis.
The infected cell dies.

Question 18

How can one gene give rise to more than one protein?

Answer 18

Through post transcriptional changes to mRNA. The introns are removed leaving only the exons. This is mRNA. Before this it is called pre-mRNA when introns were still present. Once the introns are removed the exons can be spliced in many different ways leading to more than one protein.

Question 19

What are the 3 ways the body is protected from infection?

Answer 19

Skin, stomach acid, and gut and skin flora.

Question 20

How does the skin protect the body?

Answer 20

tough physical barrier consisting of keratin

Question 21

How does stomach acid protect the body?

Answer 21

kills bacteria ingested

Question 22

How does gut and skin flora protect the body?

Answer 22

natural bacterial flora competes with pathogens for food and space.

Question 23

What is an example of natural passive immunity?

Answer 23

the crossing of mother’s antibodies through the placenta and/or breast milk

Question 24

What is an example of natural active immunity?

Answer 24

Being exposed to or getting the disease

Question 25

What is an example of artificial passive immunity?

Answer 25

When antibodies are injected into the body

Question 26

What is an example of artificial active immunity?

Answer 26

when vaccinations stimulate the immune system leading to production of antibodies

Question 27

What is the theory of the evolutionary race?

Answer 27

pathogens evolve adaptations that enable them to survive and reproduce.

Question 28

How do hospitals minimise the selection pressure on bacteria?

Answer 28

New patients screened on arrival antibiotics only used when needed and must complete the full course. Strict hygiene regimens