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Biology Revision > Cells And Immunology > Flashcards

Cells And Immunology Flashcards

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1
Q

State 2 ways that pathogens cause harm/disease?

A

Damage host cells
Produce toxins

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2
Q

Each type of cell has…

A

…specific molecules on its plasma cell surface membrane that identify it

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3
Q

The proteins on the cell surface membrane enable the immune system to identify….

A

Pathogens
Cells from other organisms of the same species
Abnormal body cells
Toxins

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4
Q

Define antigen

A

An antigen is a molecule / protein that stimulates an immune response that results in the production of a specific antibody

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5
Q

If the antigens on the surface of the cell are not recognised what does the body do

A

The body will treat that cell/pathogen as a non self and initiate an immune response which will lead to the destruction o the cell / pathogens / protein

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6
Q

The innate immune response is….

A

….NON SPECIFIC and is the first line of defence such as skin, blood clotting, tears, saliva

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7
Q

The adaptive immune reponse is….

A

…SPECIFIC to a certain antigen. Involves T-cells and B-cells

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8
Q

Phagocytes are a group of…

A

…white blood cells

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9
Q

Whats wrong with non specific immunity?

A

Although it works the same for any cell that displays a non self antigen,
It would take far too log to destroy ALL the pathogens which may result in damage to tissues and organs.
As a result we also have more efficient systems which involve specific immunity.

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10
Q

What happens in the non specific response (phagocytosis)

A

Pathogen is engulfed by the phagocyte
Engulfed pathogen enters the cytoplasm of the phagocyte in a vesicle which is now called a phagosome
Lysosomes fuse with phagosome releasing hydrolytic digestive enzymes called lysozymes
Lysosome enzymes hydrolyse the pathogen
Waste materials are released from the cell by exocytosis
Antigens are presented on the cell surface membrane and the phagocyte becomes an antigen presenting cell (APC)

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11
Q

What are the two types of specific immunity

A

Cell mediated immunity (T cells)
Humoral response (B cells)

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12
Q

Define specific immunity

A

A specific response to a specific antigen on the surface of a cell or pathogen that has been recognised as non self

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13
Q

T cells are responsible for the stage of an immune response called the cellular response.

The cellular response occurs in the following stages:

A
  1. Antigen presenting
  2. Clonal selection
  3. The role of T cells
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14
Q

Explain the Cellular response - specific immunity - cell mediated immunity

A

Phagocyte engulfs and hydrolyses the pathogen and presents the antigen on cell surface membrane
T-H cell with specific receptor molecule binds to presented antigen
One the T-H cell binds to the presented antigen it is activated and rapidly clones by mitosis.

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15
Q

What happens in clonal selection of the cell mediated response

A

A specific T-H cell binds to presented antigen via its complementary receptor
T-H cell is activated and clones to produce many T-H cells with complementary receptors to the antigen.

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16
Q

Why is clonal selection required

A

Because there is not enough room in the body to have lots of T- cells for every antigen you may encounter. Increasing number of cells would increase the total energy demands of the organism

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17
Q

What is the role of a T helper cell

A

Specific TH cell binds to the antigen presenting cell
Release cytokines that attract phagocytes to the area of infection
Release cytokines that activate cytotoxic killer T cell
Activates a specifically complementary B Cell
Form memory T helper cells

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18
Q

What is the role of a TC cell (cytotoxic killer cell)

A

Locate and destroys infected body cells that present the correct antigen
Binds to antigen presenting cells
Releases perforin (protein) which creates holes in the cell surface membrane which destroys the APC.

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19
Q

The humoral response involves

A

…the activation of B cells to produce antibodies.

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20
Q

B cells must be…

A

…stimulated by their complementary T helper cell by the release of cytokines

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21
Q

What is the process of the humoral response

A

Specific T helper cell with correct receptor binds to presented antigen and then locates and activates a specifically complementary B cell
The specific T helper releases cytokine chemicals that signal the specific B cell to clone by mitosis (clonal selection)
The B cell then differentiates into two types of cell:
-Plasma cells - produce an secrete vast quantities of specific antibodies into the blood plasma
-memory B cells - remain in the body to respond to pathogen rapidly and extensively should there be a future re-infection

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22
Q

Define antibody

A

A protein made in response to foreign antigen - has binding sites which bind specifically to an antigen. A specific antibody is produced by a specific plasma cell.

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23
Q

The overall shape of an antibody is…

A

Y shaped

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24
Q

Structure of the antibody

A

Complex protein with a quaternary structure
Made up of 4 polypeptide chains
The main part of the antibody is the CONSTANT REGION (same across all antibodies)
The VARIABLE REGIONS have a different primary structure and therefore a different tertiary structure
Variable region and therefore binding site is specific which is different for each antibody
Specific antibodies are only complementary to one antigen

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25
Q

How do antibodies assist in the destruction of pathogens

A

Agglutination
Opsonisation

26
Q

What is agglutination

A

Specific antibodies bind to the antigens on the pathogen and clump them together

27
Q

What is opsonisation

A

Marking pathogens so phagocytes recognise and destroy the pathogen more efficiently

28
Q

Memory cells

A

Not involved directly in destroying the invading pathogen
Remains in the circulate in case of future re infection by same pathogen
The plasma cells produce lots of antibodies in a short period of time

29
Q

Define secondary response

A
  • The activation of memory cells to produce antibodies
  • It’s rapid and extensive
  • Antigen can be eliminated before it can cause the disease or any symptoms develop
  • In secondary response more antibodies are produced more rapidly
30
Q

The secondary immune response is effective as..

A

…most pathogens have the same antigens on their surface and so are recognised by memory cells when re infection occurs

31
Q

What happens when the antigens on the pathogen mutate or change shape

A

Will not be recognised by memory cells from previous infection as it is not complementary to receptors
Secondary response cannot be initiated

32
Q

Change in the antigen is known as

A

Antigenic variability and makes it difficult to develop vaccines against these pathogens

33
Q

What is passive immunity

A

No exposure to antigen
Antibodies received from elsewhere - not produced by individual (mothers milk or injection)
No production of memory cells

34
Q

What is active immunity

A

Antibodies produced in response to exposure to an antigen.
Memory cells are produced

35
Q

Vaccines are not effective when…

A

..when the pathogen shows antigenic variability (mutation or change of shape of antigen)

36
Q

How do vaccinations work

A

Vaccines contain antigens from dead, weakened pathogens
Pathogen is engulfed by phagocyte and displayed on APC
A specific T helper cell finds to the antigen on the APC
The specific T helper cell stimulates a specific B cell by releasing cytokines
B cell divides by mitosis to produce plasma cells and memory cells
Plasma cells produce and release antibodies
Memory cells recognise antigen on second reinfection

37
Q

What is herd immunity

A

If enough individuals in the population are vaccinated then there is less chance of the disease spreading

38
Q

What are monoclonal antibodies

A

Antibodies are specific protein molecules that bind specifically to one antigen type.

39
Q

Uses of monoclonal antibodies

A

Research
Pregnancy testing kits and ELISA
Diagnosis
Targeting drugs
Killing specific cells
Isolating specific chemicals

40
Q

Explain the process of the ELISA test

A

Test uses monoclonal antibodies which are fixed to the surface of test wall
Sample containing the molecule to be detected is added and binds to antibody due to complementary shape
Second monoclonal antibodies with enzyme attached added and al;so bind to molecule
Washed so unbound antibodies are removed
Substrate is added
Colour change = positive result and confirms presence of the molecule

41
Q

What is the process of HIV replication using T helper cell

A

Protein on HIV binds to protein on T helper cell
Capsid fuses with the cell surface membrane and releases viral mRNA and enzymes into the T helper cell
The HIV reverse transcriptase converts viral mRNA into cDNA using host nucleotides
Viral cDNA moves into nucleus of T helper cell and is inserted into the host cell. The person is now infected
Viral DNA is transcribed into viral mRNA which is then translated to produce HIV proteins
Overtime there is a reduction in the number of T helper cells

42
Q

More HIV means

A

MORE destruction of MORE T helper cells
LESS activation of specific Tc and B cell
LESS able to destroy other pathogen/ cancerous/ infected cell

43
Q

How do antibiotics work

A

Antibiotics work by preventing bacteria making a normal cell wall (murein)
This means bacteria are unable to resist osmotic pressure and the cells burst due to increase in water by osmosis

44
Q

Why can you NOT use antibiotics for viruses

A

Viruses have a capsid (protein coat) rather than a murein cell wall. This does not allow antibiotics to act on viruses as they do for bacteria.
Viruses also spend time within a host cell so are out of reach of antibiotics.

45
Q

Describe the non-specific defence mechanisms the body may launch against pathogens (5 marks)

A

The process is called phagocytosis – No Mark
1. Pathogen is engulfed by the phagocyte.
2. Engulfed pathogen enters the cytoplasm of
the phagocyte in a vesicle;
3. Lysosomes fuse with vesicle releasing
digestive enzymes;
4. Lysosome enzymes break down the pathogen.
5. Waste materials are ejected from the cell by exocytosis;

46
Q

Describe how a phagocyte destroys a pathogen present in the blood.

A
  1. Engulfs;
  2. Forming vesicle/phagosome and fuses with lysosome;
  3. Enzymes digest/hydrolyse;
47
Q

Give two types of cell, other than pathogens, that can stimulate an immune response.

A
  1. (Cells from) other organisms/transplants;
  2. Abnormal/cancer/tumour (cells);
  3. (Cells) infected by virus;
48
Q

When a vaccine is given to a person, it leads to the production of antibodies against a disease-causing organism. Describe how

A
  1. Vaccine contains antigen from pathogen;
  2. Macrophage presents antigen on its surface;
  3. T (helper) cell with complementary receptor protein binds to antigen;
  4. T cell stimulates B cell;
  5. (With) complementary antibody on its surface;
  6. B cell divides to form clone secreting / producing same antibody;
  7. B cell secretes large amounts of antibody;
49
Q

Explain how the humoral response leads to immunity.

A
  1. B cells specific to the antigen reproduce by mitosis.
  2. B cells produce plasma and memory cells
  3. Second infection produces antibodies in larger quantities AND quicker.
50
Q

Describe and explain the role of antibodies in stimulating phagocytosis.

A

• Bind to antigen OR Are markers;
• (Antibodies) cause clumping/agglutination OR Attract phagocytes

51
Q

Describe the difference between active and passive immunity.

A
  1. Active involves memory cells, passive does not;
  2. Active involves production of antibody by plasma cells/memory cells;
  3. Passive involves antibody introduced into body from outside/named source;
  4. Active long term, because antibody produced in response to antigen;
  5. Passive short term, because antibody (given) is broken down;
  6. Active (can) take time to develop/work, passive fast acting;
52
Q

State why some antibodies are referred to as monoclonal

A

(Antibodies) produced from a single clone of B cells / plasma cells;
OR

(Antibodies) produced from the same B cell / plasma cell;

53
Q

Tests using monoclonal antibodies are specific. Use your knowledge of protein structure to explain why.

A

• Specific) primary structure / order of amino acids;
• (Specific) tertiary / 3D structure / shape;
• (So) Only binds to / fits / complementary to one antigen;

54
Q

Describe the structure of the human immunodeficiency virus (HIV).

A
  1. RNA (as genetic material);
  2. Reverse transcriptase;
  3. (Protein) capsomeres/capsid;
  4. (Phospho)lipid (viral) envelope OR Envelope made of membrane;
  5. Attachment proteins;
55
Q

Describe how a person infected with HIV will develop AIDS (if untreated) and die of secondary infections.

A

• High viral load leads to increased destruction of helper T/CD4 cells;
• Less activation of B cells/cytotoxic T cells/phagocytes;
• Less production of plasma cells/antibodies OR (With cytotoxic T cells) less able to kill virus infected cells;
• (More able to) destroy other microbes/pathogens OR (More able to) destroy mutated/cancer cells;

56
Q

Describe the role of antibodies in producing a positive result in an ELISA test.

A
  1. (First) antibody binds/attaches /complementary (in shape) to antigen; 2. (Second) antibody with enzyme attached is added;
  2. (Second) antibody attaches to antigen;
  3. (Substrate/solution added) and colour changes;
57
Q

What is the role of the disulphide bridge in forming the quaternary structure of an antibody?

A

Joins two different polypeptides

58
Q

Explain how HIV affects the production of antibodies when AIDS develops in a person

A

Less/ no antibody produced
Because HIV destroys/ reduces the number of T helper cells
So few / no B cells are activated

59
Q

Describe how HIV is replicated once inside the T helper cells

A

RNA converted into DNA usuing reverse transcriptase
DNA inserted into T helper cell
DNA transcribed into HIV mRNA
Translated into HIV proteins

60
Q

Name two features of HIV particles that are not found in bacteria (don’t include attachment protein)

A

Capsid
Reverse trabscriptase
RNA genome
Envelope

Biology Revision (22 decks)

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