Lesson 45 - Phagocytosis

Question 1

Name some physical defenses of the human body to pathogens.

Answer 1

Skin, membrane lining, cilia

Question 2

Name some chemical defenses of the human body to pathogens.

Answer 2

Sweat and oils, saliva, stomach acid, urine, tears, mucus

Question 3

What is an antigen?

Answer 3

A foreign protein that stimulates an immune response/production of an antibody

Question 4

What is an antibody?

Answer 4

A protein/immunoglobulin specific to an antigen produced by B cells/secreted by plasma cells

Question 5

What is the difference between a specific and non-specific immune response?

Answer 5

Non-specific - Response is immediate and the same for all pathogens, e.g. phagocytosis and physical barrier (skin)
Specific - Response is slower and specific to each pathogen, e.g. cell mediated response (T lymphocytes) and humoral response (B lymphocytes)

Question 6

What types of ‘non-self’ cells can be detected?

Answer 6

• Pathogens (bacteria, fungi, viruses)
• Cells from other organisms of the same species (when you receive cells from another person, such as a blood transfusion/organ transplant)
• Abnormal body cells (cancerous or pathogen infected cells with abnormal antigens on their surface, which trigger an immune response)
• Toxins (‘poisonous’ molecules produced by bacteria, e.g. chlamydia, which the immune system can respond to.)

Question 7

What is antigen variability?

Answer 7

Pathogen’s DNA can mutate frequently. If a mutation occurs in the gene which codes for the antigen, the shape of an antigen will change.
Any previous immunity to this pathogen is no longer effective, as all the memory cells in the blood will have a memory of the old antigen shape. E.g. new flu vaccines have to be created each year due to the influenza virus mutating and changing its antigens very quickly

Question 8

What is the composition of your blood?

Answer 8

Plasma: 52-62% of your blood. It’s a straw colored fluid which transports: RBC’s, WBC’s, proteins, and other substances
White Blood Cells: Leukocytes constitute less than 1% of your blood. They attack/destroy potentially harmful matter.
Platelets: Thrombocytes constitute less than 1% of your blood. They form clots, blocking blood from exiting wounds.
Red Blood Cells: Erythrocytes constitute 38-48% of your blood. They keep tissue alive by bringing O2 to it and removing CO2.

Question 9

What is a phagocyte?

Answer 9

A macrophage that carries out phagocytosis

Question 10

Describe phagocytosis? (4marks)

Answer 10

1. Phagocyte attracted by a substance/ recognises (foreign) antigen;
2. (Pathogen) engulfed/ingested;
3. Enclosed in vesicle/phagosome;
4. (phagosome) fuses/joins with lysosome;
5. Lysosome contains lysozymes;
6. Pathogen digested/molecules hydrolysed by lysozymes;
7. The phagocyte displays the important antigens on it’s self surface membrane