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A-level Biology > Cell Recognition And The Immune System > Flashcards

Cell Recognition And The Immune System Flashcards

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1
Q

What is a primary defence?

A

A defence which prevents pathogens from entering the body

Eg skin

Blood clotting and skin repair

Mucous membranes

Inflammation

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2
Q

What is the non specific immune system?

A

All pathogens are treated in the same way by the same cells and is immediate

Uses physical barriers and phagocytosis

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3
Q

How is a scab formed?

A
  1. Damage to skin exposed collagen
  2. This activates platelets to trap RBC’s around the wound.
  3. This forms a clot
  4. The clot dries leaving a scab over the wound
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4
Q

How do mucous membranes act as a primary barrier?

A

Goblet cells release mucous which is transported around by cilia on the epithelium.

This music is then traps invading pathogens from entering into the body

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5
Q

What is a secondary defence?

A

A defence which combats pathogens which have entered the body.

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6
Q

What is an antigen?

A

Protein found on the surface of a cell membrane which are specific to that particular cell and recognised as non self to an immune system to trigger an immune response

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7
Q

What are opsonins?

A

Type of antibody which binds to the surface of a pathogen and enhances the ability of phagocytise cells to identify and engulf pathogens.

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8
Q

What are the two types of phagocytes and what does a phagocyte do?

A

Neutrophils:
Made in bone marrow
Short lived

Macrophages:
Larger
Monocytes in the blood
Found in lymph nodes
Ability to present pathogen antigen on own cell membrane (antigen presenting cell)
Initiated specific immune response

Phagocytes engulf an invading pathogen and destroy them to prevent further harm to the body

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9
Q

How does the body identify its own cells from others?

A

The antigens on the surface membrane (proteins) are a specific shape and so enable the lymphocytes of the immune system to identify:
Pathogens
Cells from other organism of same species
Abnormal body cells
Toxins

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10
Q

What is the specific immune system?

A

A response which is specific to each pathogen, but this is a much slower response

Uses a cell mediated response (T lymphocyte)

Or humoral response (B lymphocytes)

Kick started by phagocytosis

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11
Q

What are the different types of white blood cell?

A

Phagocytes - destroy pathogen before it causes harm

Lymphocytes - involved in an immune response

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12
Q

What is the process of phagocytosis?

A
  1. The phagocyte is attracted to the pathogen by chemical products (chemotaxis) and moves toward the pathogen along a concentration gradient.
  2. The phagocyte binds to the pathogen via receptors (complementary) on the cell surface membrane
  3. Lysosomes within the phagocyte migrate towards the phagosome (formed by engulfing the bacterium)
  4. The lysosomes release their lysozymes into the phagosome where they hydrolyse the bacterium
  5. The hydrolysis products of the bacterium are absorbed by the phagocyte.
  6. If a macrophage, the phagocyte will present the bacterium’s antigens on it’s own cell surface membrane
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13
Q

What are the two types of lymphocytes?

A

B lymphocytes (B-cells):
Made in the bone marrow
Associated with the humoral immune response

T lymphocytes (T-cells):
Made in the thymus gland
Associated with the cell mediated immune response

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14
Q

What is a cell mediated immune response?

A

Where T lymphocytes respond to an organisms own cells that have been infected by non self material (virus). These invading cells have different antigens to the organisms own cells and so enable the T lymphocytes to distinguish between invader cells and normal cells.

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15
Q

What is an antigen presenting cell?

A

A cell that displaced a foreign antigen on their surface cell membrane.

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16
Q

How does the cell mediated immune response occur? (Process)

A
  1. Pathogen invades body cells or are taken in by phagocytes
  2. The phagocyte places antigens from the pathogen on its cell surface membrane
  3. Receptors on specific T-cells (T helper cell) fit exactly into these pathogens
  4. This attachment activates the T cell to divide by mitosis and form a clone of genetically identical T cells.
  5. The T cells divide into Cytotoxic T cells, T helper cells, T suppressor cells and T & B memory cells.
  6. Cytotoxic T cells kill abnormal cells and body cells infected by pathogens.
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17
Q

How do cytotoxic T cells kill infected cells or pathogens?

A

Produce a protein which makes holes in the cell surface membrane of the pathogen making the cell permeable to substances which kills it as a result.

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18
Q

What are the functions of the 4 types of T lymphocytes?

A

T helper cells:
Bind to antigens to initiate cell mediated response
Binds to B cells to make them divide

T killer (cytotoxic) cells:
Kill abnormal body cells or pathogens

T suppressor cells:
Regulate the immune system

T memory cells:
Remember the specific pathogens antigen

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19
Q

What is humoral immunity?

A

Immunity which involves antibodies in the blood and other body fluids (humour)

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20
Q

What are the different populations B lymphocytes divide into?

A

Plasma cells:
Secrete antibodies into the blood plasma

Memory cells:
Responsible for remembering the antigen of pathogen for a secondary immune response at a later date

21
Q

How does the humoral immune response occur? (Process)

A
  1. The surface antigens of the invading pathogen are taken up by a B cell
  2. The B cell processes the antigens and presents them on its surface
  3. T helper cells attach to the B cell activating it
  4. The B cell divides by mitosis to give a clone of plasma cells
  5. The cloned plasma cells produce and secrete antibodies specific to the pathogens antigen
  6. Antibody attaches to the antigen on the pathogen and destroys them
  7. Some B cells develop into memory cells for a secondary immune response in the future.
22
Q

What are antibodies?

A

Quaternary proteins produced by B plasma cells which have a specific binding site complementary to that of an antigen of a pathogen and hence bind to it.

23
Q

What is the structure of an antibody?

A

Quaternary protein
Four polypeptide chains
Two Heavy constant chains
Two lighter chains

Form a Y shape

The light chains have variable regions (different in different antibodies)

They have 2 antigen bonding sites at the top of the molecule and a receptor binding site at the bottom

24
Q

What is agglutination?

A

The clumping of pathogens together so phagocytes can ingest them more easily

(Carried out by special antibodies called agglutins)

25
Q

How does an antibody prepare an antigen for destruction?

A

An antibody binds to an antigen (specific and complementary bonding sites) and form an antigen - antibody complex. Many antibodies binding to antigens may cause the agglutination of the bacterial (pathogenic) cells so phagocytes can locate and engulf them more easily.

26
Q

What are monoclonal antibodies?

A

Antibodies which are produced and cloned which are specific to a specific antigen on a cell
(Eg antigens on cancer cells)

27
Q

Why is a secondary response much more rapid than a primary response?

A

A primary response requires the B cell to divide and form plasma cells and memory cells which takes time.

A secondary response will use the memory cells that were previously made from an earlier infection and provide a much more immediate response as the required cells are already in the blood plasma.

28
Q

What are some uses of monoclonal antibodies?

A

Specific drugs to combat illness such as cancer drugs.

Diagnosis such as prostate cancer detection or pregnancy tests

29
Q

What are the ethical issues involved in producing monoclonal antibodies?

A

Production involves mice (animal rights)

Treatment can be unsuccessful

30
Q

What is a vaccination?

A

Deliberate exposure to antigenic material that is harmless (dead/weak)

Provides immunity to a specific disease

31
Q

What kinda of antigenic material is found in a vaccine?

A

Harmless or weakened version of a pathogen

Whole live microorganism similar to the pathogen

Dead pathogen

Toxoid - harmless version of a toxin

32
Q

What is herd immunity?

A

Where a larger proportion of the population are vaccinated against a specific disease to prevent the large scale spreading

33
Q

What is ring immunity?

A

Vaccination against a particular disease around a number of reported cases

34
Q

Why do we still get epidemics?

A

Antigens change over time via mutations

And memory cells only respond to the previous antigen so new strains are not recognised and will cause disease

35
Q

What is active immunity?

A

Where the organism makes antibodies either after infection (natural) or due to a vaccination (artificial)

36
Q

What is passive immunity?

A

Antibodies are taken into the organisms via breast milk or the placenta (natural) or by injection of antibodies (artificial)

37
Q

What is personalised medicine?

A

Sequencing genes from an individual with conditions and develop specific drugs against that condition tailored to that individual

38
Q

Why is antibiotic resistance a big issue?

A

The overuse of antibiotics has lead to the growth of resistant strains of bacteria to the point where the majority of the population of bacteria have the resistant gene.

39
Q

What are some ways medicines are discovered?

A

Accident - penicillin

Old traditional remedies- morphine

Observation of wildlife - citrus oils

Plant research - tropical plants

Research into disease - how HIV infected T helper cells

40
Q

What is HIV?

A

The human immunodeficiency virus

Retro virus

41
Q

What is AIDS?

A

Acquired immune deficiency syndrome

A result of the HIV virus

42
Q

What is the structure of HIV?

A

A retro virus

2 single strands of viral RNA

Contains reverse transcriptase enzymes
(RNA ——> DNA)

43
Q

How does HIV infect cells?

A
  1. HIV infected the human and enters the blood stream which circulates around the body
  2. A protein of HIV attaches to CD4 (T helper cell)
  3. The protein capsid fuses with the T cell surface membrane
  4. HIVE reverse transcriptase converts the viral RNA to DNA
  5. DNA is moved into the T helper cells nucleus and is integrated into the host DNA
  6. This is then transcribed into mRNA
  7. Cell machined begins to translate viral proteins which assemble into new viral particles
  8. Virus “buds” from the host cell membrane taking some with it allowing to form its lipid envelop
  9. Once infected the person is HIV positive and the virus may go into dormancy
44
Q

How does HIV cause AIDS?

A

HIV specifically attacks T helper cells and therefore reduce their ability to stimulate cytotoxic cells, simulate B cells , and produce memory cells

All this leads to the increased susceptibility to infections and cancers and you immune system is deficient.

These secondary illnesses and infects are what cause death

45
Q

Why are antibiotics ineffective against viral diseases such as HIV?

A

Antibiotics work by disrupting the metabolic pathways

HIV is a virus

Viruses :
do not rely on its own metabolic pathway and hence has nothing to disrupt.

They also hide in host cells

Protein coats usually already intact once a virus is out of a cell

46
Q

What is ELISA?

And what is it used for?

A

Enzyme linked immunosorbent assay

Uses antigens or antibodies to detect the presence of the antigen or recently produced antibodies in response to an antigen.

47
Q

What is direct ELISA?

A

Where the microtitre plate is embedded with antibodies of the antigen looking to detect

Seeing if someone is infected with the pathogen

48
Q

What is indirect ELISA?

A

Where the microtitre plate is embedded with the antigen to detect for recently produced antibodies in response to that antigen

Seeing if someone has recently had the pathogen

49
Q

What are the steps in ELISA?

A
  1. Apply sample ( usually blood plasma) to the surface of the microtitre plate which sticks to antigens ( wash to remove any unattached)
  2. Add the antigen specific antibodies (and wash)
  3. Add the second enzyme linked antibody (which is a complementary shape to previous antibody) to the sample and wash
  4. Add colourless substrates for the enzymes which will change into colour substrates if bound to the enzyme
  5. Amount of antigen present is relative to the intensity of colour that develops.

A-level Biology (23 decks)

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