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Yr 12 Biology > Immunity > Flashcards

Immunity Flashcards

1
Q

What is the function of a lymphocyte?

A

Identifies the presence of pathogens and potentially harmful substances

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2
Q

How do lymphocytes identify the presence of pathogen and harmful foreign substances?

A

-each type of cell has specific molecules on its surface that identifies it

-these molecules are useualy proteins

  • as their 3D structures enable lots of unique and identifiable shapes to be made- which lymphocytes recognise
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3
Q

What types of substances does surface molecules allow lymphocytes to recognise?

A
  1. Pathogens
  2. Cell from other organisms of the same species
  3. Abnormal body cells
  4. Toxins
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4
Q

What happens when foreign substances are identified?

A

Once the cells are discovered they’ll trigger a response to destroy them- the immune system is triggered

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5
Q

Why do lymphocytes not attack self cells?

A

-lymphocytes are made when your a foetus

-lymphocytes complementary to self cells die

-This prevents your lymphocytes from attacking your own cells

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6
Q

What are antigens?

A

These are molecules that generate an immune response by lymphocytes cells when detected in the body

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7
Q

What type of molecule are antigens usually?

A

They are usually proteins

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8
Q

What is antigen variability?

A

Pathogens DNA can mutate frequently. If a mutation occurs in the gene which codes for the antigen, then the shape of the antigen will change

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9
Q

Why does antigen variability cause people to get re-vaccinated?

A

-any previous immunity to the pathogen (either naturally through prior infection or artificially through vaccination)

-is no longer effective, as all the memory cells in the blood will only have a memory of the old antigen shape

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10
Q

When will white blood cells be the line of defence?

A

If a pathogen gets past:

  • the chemical

-physical barrier

And enters the blood, then the white blood cells are the second line of defence.

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11
Q

Which white blood cells have a specific and non-specific response?

A

Phagocytes- non-specific response

Lymphocytes- specific response

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12
Q

What is a phagocyte?

A

A macrophage (type of white blood cell) that carries out phagocytosis

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13
Q

What does it mean if a phagocyte carries out a non-specific response?

A

-they non-specific meaning that any non-self cell (e.g.pathogen) that is detected will trigger the same response to destroy it- isn’t specific to antigens

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14
Q

What are the steps to phagocytosis?

A
  1. Phagocytes are in the blood and tissues, any chemical and debris released by the pathogen or abnormal cells attract the phagocytes and they will move towards the cells
  2. The receptors on the surface of phagocytes allow the phagocyte to bind to the chemicals or antigens on the pathogen
  3. The phagocyte will then change shape and move around and engulf the pathogen
  4. Once engulfed the pathogen is contained within a phagosome vesicle
  5. A lysosome will fuse with the phagosome and release its contents
  6. Lysosomes contain enzymes called lysozymes, which are released into the phagosome where it hydrolyses the pathogen
  7. This destroys the pathogen
  8. The antigens are then placed on the cell surface membrane and the phagocyte then becomes an antigen presenting cell.
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15
Q

Where do t-lymphocytes mature?

A

In the thymus

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16
Q

What is a cell mediated response?

A

The response involving t-cells and body cells

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17
Q

What are antigen presenting cells (APC)?

A

Any cell that presents a non-self antigen on its surface

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18
Q

How do antigen presenting cells develop?

A

-if a body cell becomes infected with a virus inside

  • a phagocyte which has engulfed and destroyed a pathogen will present the antigens on the surface
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19
Q

What triggers a cell mediated response?

A

Antigen presenting cells

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20
Q

Why is it called a cell-mediated response?

A

Because t-cells only respond to antigens which are present on antigen presenting cells

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21
Q

What are the steps to a cell-mediated response?

A
  1. Once a pathogen has been engulfed and destroy by a phagocyte, the antigens are then positioned on the cell surface. This is now called an antigen presenting cell.
  2. Helper t-cells have receptors on their surface which can attach to the antigen on the antigen presenting cell.

3.once attached this activates the helper t-cells to divide by mitosis to replicate and make larger number of clones

  1. Cloned helper t-cells differentiate into different cells: some remain as helped t-cells and activate B lymphocytes, some stimulate macrophages to perform phagocytosis, some become memory cells for that shaped antigen and some become cytotoxic T-cells= killer t-cells
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22
Q

What is the function of cytotoxic T-cells?

A

Destroy abnormal or infected cells

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23
Q

How do cytotoxic T-cells destroy abnormal or infected cells?

A

-The release a protein

-perforin

  • which embeds in the cell surface membrane and makes a pore (a hole) so that substances can leave or enter the cell- leading to cell death
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24
Q

When is it most common for cytotoxic t-cells to form pores in cells?

A

-It’s most common in viral infections because viruses infect body cells

-this prevents the virus from replicating

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25
Q

Where do lymphocytes and b cells mature?

A

In the bone marrow

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26
Q

What is a humoral response?

A

A response involving b cells and antibodies

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27
Q

Give the function of antibodies?

A

They are soluble and transport in bodily fluids

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28
Q

What do b cells have on their surface & what are they complementary to?

A

They have antibodies on their surface which are complementary to many different antigens

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29
Q

What is the process of b cell activation?

A
  1. If you have a pathogen in your blood, the antigen in the blood from the pathogen will collide with their complementary antibody on a B cell. The B cell then takes in the antigen by endocytosis and then presents it on its cell surface membrane.
  2. When the B-cell collides with a helper T-cell receptor, this activates the B cell to go through clonal selection.
  3. B cells then undergo mitosis to make large numbers of cells, these differentiate into plasma cells or memory b cells
  4. Plasma cells make antibodies
  5. B memory cells can divide rapidly into plasma cells, so if ever re infected with the same pathogen a large number of antibodies can be made rapidly.
30
Q

What is a positive of memory b cells?

A

They can live for decades in your body

31
Q

Can memory cells make antibodies?

A

No but they can divide by mitosis and make plasma cells rapidly if they collide with a pathogen they’ve encountered before

32
Q

What structure do antibodies have?

A

A quaternary protein structure (4 polypeptide bonds)

33
Q

What does an antibody consist of?

A

2 long,heavy chains

2 short, light chains

34
Q

What part of the antibody changes?

A

The variable regions

35
Q

Where do the antigen bind on the antibody and why?

A

-the variable region

  • because it has a complementary shape to the antigen
36
Q

What part of the antigen never changes?

A

The constant region

37
Q

What is an antigen- antibody complex?

A

What’s formed when antibodies binds to antigens

38
Q

What’s an advantage of antibodies being flexible?

A

It’s means that they can bind to one antigen then slightly twist and flex to attach to another antigen and them clump them together

39
Q

What’s good about antibodies forming clumps of antigens?

A

It’s makes it easier for phagocytes to locate them and destroy pathogens

  • because is there’s a big clump of antibodies binded to the antigen and therefore the pathogen it makes it easier for the phagocyte to engulf it
40
Q

What is passive immunity?

A

Antibodies which are introduced into the body and aren’t made in it

41
Q

What are the characteristics of passive immunity?

A

-Pathogen doesn’t enter body, so plasma cells and memory cells aren’t created.

-no long term immunity

42
Q

What is an example of passive immunity?

A

Antibodies passed onto a foetus through the placenta or through breast milk to a baby

43
Q

What is active immunity?

A

This is immunity created by your own immune system following exposure to the pathogen or it’s antigen

44
Q

What is natural active and artificial active immunity?

A

Natural active- following infection and the creation of the bodies own antibodies and memory cells

Artificial active- following the introduction of a weakened version of the pathogen or antigen via a vaccine

45
Q

What is a vaccine?

A

It’s when small amounts of weakened or dead pathogens or antigens are introduced in the mouth or by injection

46
Q

Describe the steps of a vaccine?

A
  1. Exposure of the antigens activates the b-cells to go through clonal selection
  2. B cells undergo mitosis to make more large numbers of cells, these then differentiate into plasma cells or memory b- cells
  3. Plasma cells make correct antibodies
  4. B- memory cells can divide rapidly into plasma cells when re-infected with the same pathogen to make large numbers of antibodies quickly
47
Q

What is the primary response?

A

When the pathogen enters the body for the first time.

48
Q

What are the characteristics of the primary response?

A

-slow- aren’t many b- cells that can make the antibody needed to bind to it

  • infected person will show symptoms
49
Q

What is the secondary response?

A

It’s when the pathogen enters the body again

50
Q

What are the characteristics of a secondary response?

A

-quicker and stronger- clonal selection happens faster & memory b-cells are activated and divide into plasma cells that produce the right antibody for the right antigen

  • no symptoms- pathogen is destroyed quickly
51
Q

What is herd immunity?

A

It’s when enough of the population are vaccinated that the pathogen cannot spread easily amongst the population

52
Q

What is a positive of herd immunity?

A

It’s provides protection for those who aren’t vaccinated e.g: those who are already to I’ll

53
Q

What are the key stages of the cell cycle?

A
  • Interphase (G1,G2)
  • nuclear division (mitosis and meiosis)
  • cytokinesis
54
Q

What does interphase consist of?

A

-G-1- growth

-S- DNA synthesis

-G2- growth and preparation for mitosis

55
Q

Describe interphase?

A

The longest stage of the Cell cycle. Interphase is when the organelles double, the cell grows to replicate

56
Q

What is the purpose of nuclear division?

A

Mitosis creates cells with identical DNA for growth and repair

57
Q

Describe cytokinesis?

A

This is the final stage . It is the division of the cytoplasm to create new cells

58
Q

What are the stages of mitosis?

A

P- prophase

M-metaphase

A-anaphase

T-telophase

59
Q

What an example for when mitosis is used for growth and repair?

A

-clonal expansion of cells

60
Q

Describe prophase?

A

The chromosomes condense & become visible. The centrioles (where spindle fibres are released from) will move to opposite poles of the cell. The nucleus and nuclear envelope begins to disintegrate.

61
Q

Describe metaphase?

A

Centrioles at opposite poles release spindle fibres. Then chromosomes align along the equator of the cell. The spindle fibres now attach to the centromere (what holds the chromatids together) and the chromatids (single sticks)

62
Q

Describe anaphase?

A

Spindle fibres start to retract and pull the centromere and chromatids they are attached to towards opposite poles

  • causing centromere to divide in 2 and the individual chromatids to be pulled to each opposite poles, these are separated chromatids= chromosomes
63
Q

Describe telophase?

A

Chromosomes are now at each pole of the cell and now become longer and thinner

Spindle fibres will disintegrate and the nucleus starts to reform

64
Q

What is mitotic index?

A

The percentage of cells under going mitosis

65
Q

How is mitotic index calculated?

A

Can be calculated by counting how many cells are visible and the number of cells visible in stages of mitosis

66
Q

What is the equation for mitotic index?

A

Number of cells in mitosis
——————————-—— X100
Number of cells

67
Q

Why is it difficult to destroy viruses with medicine?

A

Because viruses replicate inside of cells so if we try destroy them the host cell will become damaged

&

They have no cell wall so they can’t be destroyed by antibodies

68
Q

What is the structure of HIV?

A

-core= genetic material (RNA) and the enzyme reverse transcriptase

-capsid= outer protein coat

  • envelope= extra outer layers, made out of membrane from the host cell

-protein attachments= on the exterior of the envelop to enable the virus to attach to the hosts helper t cell

69
Q

What are the steps to HIV replication?

A
  1. The attachment protein attaches to a receptor molecule on the cell membrane of the host helper T- cell.
  2. The capsid is released into the cell where it uncoats and releases the RNA into the cell’s cytoplasm
  3. Inside the cell, reverse transcriptase is used to make a complementary strand of DNA from the viral RNA template
  4. From this, double stranded DNA made and inserted into the human DNA
  5. Host cell enzymes are used to make viral proteins from the viral DNA found within the human DNA
  6. The proteins are assembled into new viruses, which exit the cell and go and infect others
70
Q

How is AIDS formed?

A

-Replicating viruses in T-helper cells interfere with the normal functioning of the immune system

  • due to the t-cells being destroyed because of the virus, meaning the gist can’t produce an effect immune response to pathogens being left vulnerable to infections= death

Yr 12 Biology (8 decks)

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