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Biology A-level > Immunity > Flashcards

Immunity Flashcards

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1
Q

What is the function of a lysosome?

A

Contains hydrolytic enzymes to digest waste materials.

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2
Q

Explain why the cell membrane is considered to be ‘fluid-mosaic’ (2 points).

A
  1. Mosaic represents the different molecules that are arranged randomly.
  2. Fluid refers to the movement of the membrane due to the phospholipids.
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3
Q

Definition of hydrolysis

A

A water molecule that is added to a polymer to produce the monomers.

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4
Q

What is the function of a glycoprotein?

A

Cell recognition

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5
Q

Definition of pathogen

A

A micro-organism that causes disease.

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6
Q

Definition of an antigen

A

A non-self protein that stimulates an immune response causing production of antibodies.

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7
Q

Definition of an antibody

A

A protein, produced by the lymphocytes, in response to the presence of the appropriate antigen. Antibody is complementary in shape to the antigen.

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8
Q

Decsribe the immune system

A

A system of biological structures and processes that identifies and kills pathogens (and tumor cells).

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9
Q

The 3 stages fo defense

A
  1. Prevent invasion.
  2. Non-specific: phagocytosis.
  3. Specific: lymphocytes.
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10
Q

Describe phagocytosis (6 points)

A
  1. Phagocyte attached to pathogen by chemicals / recognises antigens on pathogen as non-self.
  2. Phagocyte englufs the pathogen.
  3. The pathogen in membrane bound pocket called a phagosome.
  4. Lysosomes fuse with the phagosome and release hydrolytic (digestive) enzymes into the phagosome.
  5. The enzymes hydrolyse the pathogen destroying it.
  6. Antigens from the pathogen are displayed on the surface membrane (antigen-presenting cell).
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11
Q

Where are T-lymphocytes made and matured?

A

Made in the bone marrow and matured in the thymus gland.

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12
Q

Where are B-lymphocytes made and matured?

A

Made in the bone marrow and matured in the bone marrow.

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13
Q

4 Examples of antigen-presenting cells

A
  1. Phagocytes
  2. Body cells invaded by viruses.
  3. Cancer cells.
  4. Transplanted cells
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14
Q

Which type of immunity involves T-lymphocytes?

A

Cell-mediated immunity

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15
Q

The 3 roles of cloned T-cells

A
  1. T-helper cell
  2. T-memory cell
  3. Suppressor T-cell
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16
Q

Describe and explain the function of a T-helper cell (2 points).

A
  1. Secrete cytotoxins (hydrogen peroxide) which stimulates phagocytosis (B-lymphocytes to divide via mitosis).
  2. These are the only cells that are able to detect pathogens hiding in the body cells.
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17
Q

Describe and explain the function of T-memory cells

A

Remains in the body for many years.

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18
Q

Describe and explain the function of suppressor T-cells

A

Inhibit T and B-cells.

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19
Q

Describe the process of clonal selection in T lymphocytes (2 points).

A
  1. Antigen presenting cell / infected cells presents antigen.
  2. Antigen binds to complementary receptor on cell surface of T-helper.
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20
Q

Describe the process of clonal expansion in T lymphocytes (2 points).

A
  1. T-lymphocyte reproduces by mitosis.
  2. Produces T-lymphocyte clones.
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21
Q

Describe the function of T-cytotoxin cells

A

Secretes hydrogen peroxide to destroy the body’s infected cells.

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22
Q

Explain immunological memory (4 points).

A
  1. Large number of clones (memory cells) of T-lymphocytes with specific receptor to antigen.
  2. Quicker clonal expansion.
  3. More clones differentiate.
  4. More T helper cells to stimuate mitosis / more T-cytotoxic cells to destroy infected cells.
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23
Q

Which pathogen are T-cells most effective against?

A

Viral pathogens as they produce cytotoxins that destroy the cells infected with the virus.

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24
Q

Explain the role of T-lymphocytes in the defence of the body against a virus infection (7 points).

A
  1. T-lymphocytes invloved in cell-mediated immunity.
  2. Antigen-presenting cell.
  3. Antigen binds to complementary receptor on cell surface membrane of T-helper cell.
  4. T-cells reproduce by mitosis forming clones.
  5. Cytotoxic T-cells destroy infected cells.
  6. Other T-cells stimulate phagocytes to engulf the virus.
  7. Other T-cells stimulate B-cells to divide by mitosis.
25
Q

Describe the process of clonal selection of B-lymphocytes (2 points).

A
  1. Pathogen’s antigen presented to B-lymphocyte.
  2. Antigen binds to complementary receptor on cell surface of B-lymphocyte.
26
Q

Describe the process of clonal expansion of B-lymphocytes

A

B-lymphocyte reproduces by mitosis. Produces B-lymphocyte clones.

27
Q

Explain the process of differentiation in B-lymphocytes

A

B-lymphocytes differentiate into plasma cells which secrete antibodies specific to the pathogen’s antigen and B-memory cells which remain in the body for many years.

28
Q

Describe immunological memory for B-lymphocytes (5 points).

A
  1. Large number of clones of B-lymphocytes with specific receptor to antigen.
  2. Quicker clonal expansion.
  3. More clones differentiate.
  4. More plasma cells.
  5. More antibodies secreted into blood.
29
Q

Which pathogen do B-lymphocytes respond to?

A

Bacterial pathogens.

30
Q

4 similarities between B and T-cells

A
  1. Antigen binds to complementary receptors surface on T/B-cells.
  2. Reproduces by mitosis to form clones.
  3. Memory cells produced which remain in the body for many years.
  4. Large number of clones produced with specific antigen receptor.
31
Q

3 differences between B and T-cells

A
  1. Plasma B-cells lead to antibody production / T-cells cannot produce antibodies.
  2. B-lymphocytes respond to bacterial and viral infections / T-lymphocytes on;y respond to viruses.
  3. B-lymphocytes differentiate into plasma cells / T-lymphocytes can differentiate into cytotoxic T-cells and T-helper cells.
32
Q

*Definition of antibody

A

A protein that is specific to an antigen that is produced by B-cells.

33
Q

Defintion of a monoclonal antibody

A

Antibodies made from a hybridoma which all the antibodies are the same. A single type of antibody produced from one type of plasma cell is called a monoclonal antibody.

34
Q

The structure of antibodies

A

Made up of 4 polypeptide chains and 2 long, heacy chains. The variable region is specific to an antigen.

35
Q

Describe how antigens prepare pathogens for destruction

A
  1. Antibodies cause agglugation.
  2. Acts as markers for pathogens.
36
Q

Definition of agglugation

A

Antibodies that cause microbes to stick together, making it easier for phagoctes to engulf them.

37
Q

Definition of markers

A

Having antibodies attached also stimulates phagocytes to engulf the pathogens.

38
Q

Draw a diagram of an antibody

A

*Refer to immunity notes

39
Q

Draw an antigen-antibody complex diagram

A

*Refer to immunity notes

40
Q

Describe how monoclonal antibodies are used for the direct treatment of cancer

A

Monoclonal antibodies specific to antigens on a cancer cell and blocks the chemical signal that stimulates growth.

41
Q

Describe how monoclonal antibodies are used for the indirect treatment of cancer

A

A radioactive or cytotoxic drug is attached to the antibody. When the antibody binds to the receptor on the cancer cell is killed.

42
Q

Describe how monoclonal antibodies are used in medical diagnosis

A

Using antibodies that are complementary in shape to specific pathogens or toxins in the blood, to detect their presence. For example: influenza, hepatitis, chlamydia, prostate cancer.

43
Q

Describe how monoclonal antibodies are used for pregnancy tests

A
  1. Potential mother urinates on chromatography paper- contains free HCG antibodies with attached coloured particles.
  2. If HCG is present, it will bind to the complementary antibodies and move up the paper.
  3. HCG antibody complexes with the dye bind to the fixed HCG antibodies.
  4. They build up in the test area, causing a coloured band to appear.
  5. No HCG present, then the free HCG antibodies flow past the fixed HCG antibodies. No build up of dye, so no colour appears.
44
Q

Definition of vaccine

A

Contains an antigen that stimulates the production of antibodies.

45
Q

Definition of attenuated microorganism

A

A microorganism that is alive but doesn’t cause any symptoms.

46
Q

Definition of herd immunity

A

Vaccination of majority of the population to prevent infection spreading.

47
Q

Definition of ring immunity

A

Vaccinate all people around victim- contains spread within ring.

48
Q

Describe how a vaccination can lead to the production of antibodies against a specific pathogen

A
  1. Vaccine contains antigen from specific pathogen.
  2. Displayed on antigen-presenting cell.
  3. Specific T-helper cell detects antigen and stimulates specific B-cell.
  4. B-cell divides and forms clones to give plasma cells.
  5. Plasma cells produce antibodies.
49
Q

Definition of active immunity and examples of natural/artificial methods

A

The immune system makes its own antibodies after being stimulated by antigens (this can be achieved naturally or artificially).
Natural- immune response to pathogens.
Artificial- vaccination.

50
Q

Definition of passive immunity

A

Antibodies are made by another organism and then given to others.

51
Q

4 Differences between active and passive immunity

A
  1. Active involves memory cells / passive doesn’t involve memory cells.
  2. Active involves production of antibody by plasma cells / passive involves antibody introduced into the body from outside.
  3. Active is long term because antibody produced in response to antigen (B-memory cells) / passive is short term because antibody given is broken down.
  4. Active takes time to develop / passive is fast acting.
52
Q

4 Ethical issues with vaccines

A
  1. All vaccines are tested on animals before being used on humans.
  2. Testing vaccines on humans can be risky.
  3. Some people don’t want to take the risks or side effects of using vaccines.
  4. If an epidemic occurred from a new disease… who would get the vaccine first?
53
Q

3 Ethical issues of monoclonal antibody therapy

A
  1. Animals are used to produce the cells from which monoclonal antibodies are produced.
  2. Animals are used to produce the tumour cells- involving inducing cancer is mice.
  3. Testing humans could result in problems/death.
54
Q

Draw and label HIV

A

*Refer to immunity notes

55
Q

How does HIV replicate?

A
  1. HIV enters the bloodstream.
  2. A protein on the HIV readily binds to a protein, called CD4, on T-helper cells.
  3. The capsid fuses with the T cell membrane. RNA and enzymes from HIV enter the ‘helper’ T-cell.
  4. Reverse transcriptase converts RNA into cDNA.
  5. The DNA is moved into the T-helper cell’s nucleus and is inserted into the cell’s DNA.
  6. The new DNA creates mRNA using the cell’s enzymes. This contains the instruction for making new viral proteins.
  7. mRNA passes out of the nucleus and uses the cell’s ribosomes to make HIV proteins.
  8. HIV breaks away from the T-cell with a peice of its cell membrane, forming its own lipid membrane.
  9. This process continues for a few weeks, before the HIV virus goes into dormancy in the T-helper cells.
  10. Antibodies against the virus will ciruclate, and this is how somoene can be said to be HIV positive.
56
Q

What are the consequences of HIV killing and interfering with the normal functioning of T-cells?

A
  1. Cytotoxic T-cells cannot be made to destroy infected cells.
  2. Without enoughT-cells, B-cells are not activated.
  3. B-cells, therefore don’t produce antibodies.
  4. Menory cells can also be destroyed by HIV.
  5. The body becomes susceptible to infections.
57
Q

Why are the antibiotics ineffective against viruses?

A

Antibiotics work by inhibiting enzymes that catalyse the formation of murien (peptidoglycan) cross linakges in bacterial cell walls. These cells walls prevent bacterial cells undergoing osmotic lysis. Viruses don’t have cell walls- therefore antibiotics are ineffective. Also, once a virus has entered a body cell, antibiotics can not reach it.

58
Q

What does ELISA stand for?

A

Enzyme-Linked Immunosorbent Assay

59
Q

The ELISA method

A
  1. The sample is applied to a surface, to which the HIV antigen would stick to.
  2. Surface is washed to remove any unattached antigens.
  3. An antibody specific to the antigen is added and given time to bind.
  4. Surface is washed to remove any unattached antibodies.
  5. A second antibody (with an enzyme attached) is added, which is complementary to the first antibody. These bind.
  6. Surface is washed to remove any unattached second antibodies.
  7. A colourless substrate to the enzyme is added.
  8. The amount of antigen present is related to the colour intensity.

Biology A-level (27 decks)

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