6.3 disease defense

Question 1

2 components of first line of defense (keep pathogens out)

Answer 1

skin and mucosa

Question 2

how does skin keep pathogens out?

Answer 2

Protects the outer body. Has a thick, dry layer of cells that are mostly dead.
Contains sebaceous glands which secrete sebum, a liquid that contains fatty acids, and acids that help protect the body from microbes.

Question 3

how does mucosa (mucous membrane) keep pathogens out?

Answer 3

Protects the inner body. Living cells that secrete fluids (mucous, saliva, tears) to wash away pathogens. Some cells are also ciliated to sweep away pathogens.

Cells may also secrete an enzyme/acids to protect from microbial growth

Question 4

how do clots protect cuts?

Answer 4

Blood clots help seal broken skin to prevent access into the body by pathogens.

Question 5

how are blood clots formed?

Answer 5

Platelets
Fibrin strands
Red blood cells

Blood clots are formed through a series of reactions known as the coagulation cascade.

Question 6

coagulation cascade

Answer 6

1. When blood vessel is cut, platelets in circulating blood bind to the exposed collagen and become active. They release a variety of chemicals called “clotting factors”
2. The clotting factors signal the activation of more platelets as well as cause blood vessels to constrict, reducing blood flow to the area.
3. Clotting factors also activates prothrombin. It becomes the active enzyme thrombin.
4. Thrombin catalyzes the conversion of water soluble fibrinogen into water insoluble fibrin.
5. Fibrin meshes around the platelets plugging the cut and form a blood clot.

Question 7

Coronary thrombosis

Answer 7

The formation of a blood clot in the coronary artery as a result of atherosclerosis

Question 8

examples of pathogens

Answer 8

bacteria, virus, fungi, parasite

Question 9

toxin

Answer 9

disrupts metabolic processes

Question 10

antigen

Answer 10

An antigen is a molecule (peptide, polysaccharide, lipid) that the body recognises as foreign and that will elicit an immune response

Question 11

antibody

Answer 11

An antibody is a protein that is specific to a given antigen. One side of the antibody binds to the antigen.
The other side of the antibody serves as a recognition site for immune cells so they can destroy the pathogen.

Question 12

pathogen

Answer 12

an infectious agent

Question 13

Leukocyte/Leucocyte

Answer 13

A white blood cell. 5 broad types: monocytes & neutrophils (which are phagocytes), eosinophils, basophils, lymphocytes (B cells, T cells, NK cells)

Question 14

2 key immune systems

Answer 14

innate immune system and adaptive immune system

Question 15

phagocytosis

Answer 15

the ingestion of pathogens by a cell via endocytosis

Question 16

innate immune system

Answer 16

• Phagocytes (ex: macrophages, neutrophils) circulate throughout the blood
• During chemical infection, chemical signals (ex: histamine), signal phagocytes to a certain location (chemotaxis).
• Pathogens are engulfed by the phagocyte and enter the cell in a vesicle.
• A lysosome fuses with the vesicle and the lysozyme enzymes digest the cell.
• Antigens from the pathogen may be sent to the cell surface to trigger the adaptive immune system.

Question 17

lines of defense

Answer 17

1: skin and mucosa
2: innate immune system
3: adaptive immune system

Question 18

adaptive immune system

Answer 18

Involves the production of antibodies that are pathogen (antigen) specific (immune response).
Involves immunological memory - upon re-exposure to a pathogen it can respond rapidly.
There are two types of lymphocytes:
* B-cells - produce antibodies
* T-cells

Question 19

describe adaptive immune system response

Answer 19

1. phagocyte engulfs a pathogen & presents its antigen on its surface
2. the phagocyte presents the antigen to a helper T cell at the lymph node
3. the helper T cell activates a B cell (it releases cytokines)
4. activated B cells clone themselves, clones are plasma cells & they create+secrete specific antibodies
5. antibodies in blood bind to antigens on pathogens to mark them for phagocytosis
6. some plasma cells are converted to memory B cells to provide a faster adaptive response upon re-infection

Question 20

antibiotics

Answer 20

Target prokaryotic cells (bacteria) and structures that are unique to them.
Antibiotics either kill the bacteria or prevent its ability to reproduce (binary fission)
Block processes such as:
- DNA replication
- Transcription
- Translation
- Cell wall formation
As viruses do not have a metabolism, antibiotics do not work on viruses.

Question 21

penicillin

Answer 21

Derived from the saprotrophic fungus Penicillium which compete with saprotrophic bacteria for food.
Discovered accidentally by Alexander Fleming in 1928.

Question 22

what did Florey and Chain do for penicillin

Answer 22

Florey and Chain developed a method to grow the fungus so that it would secrete penicillin. They then infected 8 mice with the Streptococcus bacterium.
After successful results with the mice, they tested on humans subjects.

Question 23

HIV

Answer 23

Human Immunodeficiency Virus
HIV infect T-cells. It replicates inside the cell and destroys it. It then goes on to infect other T-cells.
This leads to immunodeficiency (the inability to fight infection from pathogens) and can result in acquired immunodeficiency syndrome (AIDS).
HIV is transmitted through specific bodily fluids: blood, semen, vaginal fluids, and breast milk.

Question 24

antibody structure

Answer 24

Antibodies are made up of four polypeptide chains, two heavy and two light chains.

Question 25

order of coagulation cascade events

Answer 25

clotting factors released from platelets – clotting factors convert prothrombin to thrombin – thrombin converts fibrinogen to fibrin

Clotting factors are released from platelets when a blood vessel is injured. Clotting factors cause inactive prothrombin to be converted to thrombin. Thrombin converts soluble fibrinogen to insoluble fibrin, which forms a mesh over the site of injury.

Question 26

Which clotting factor is missing in people suffering from hemophilia?

Answer 26

Clotting factor VIII

Hemophiliacs have a mutation which means that clotting factor VIII is not produced correctly by the body, therefore the blood cannot clot correctly.