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A Level Biology Paper 1 > Section 2 - Chapter 5: Cell recognition and the immune system > Flashcards

Section 2 - Chapter 5: Cell recognition and the immune system Flashcards

1
Q

What are Antigens

A
  • Are molecules (usually proteins) on the surface of cells that can generate an immune response when detected by the body
  • Antigens not found on the body are known as foreign antigens and allow the immune system to identify
    • Pathogens
    • Abnormal body cells
    • Toxins
    • Cells from other individuals of the same species
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2
Q

What are Pathogens

A
  • Are organisms that cause disease
  • All pathogens have antigens on their surface and are foreign by the immune system which respond
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3
Q

What are Abnormal body cells

A
  • Cancerous or pathogen-infected cells that have abnormal antigens on its surface which trigger an immune response
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4
Q

What are Toxins

A
  • These are poisons
  • Some toxins are produced by bacteria. The immone system can respond to toxins and their releasers.
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5
Q

What are cells from other individuals of the same species

A
  • Organ transplant/ blood transfusion
  • Those cells will have some antigens different from your own
  • The foreign anigens will trigger an immune response - leads to rejection of transplanted organ if drugs aren’t taken to suppress the system
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6
Q

What is Antigenic Variation

A
  • Antigens activate primary response so when infected again with same pathogen (same antigens on surface) they activate secondary response
  • However antigens may change their surface antigens - Antigenic Variation (Formed due to changes in the genes of a pathogen)
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7
Q

What is the effect of Antigenic Variation

A
  • This means that when you are infected for a second time, the memory cells produced from the first infection will not recognise the different antigen
  • So immune system has to start again mounting primary response
  • Also makes it harder to develop vaccines against some pathogens
  • Examples: HIV, Influenza virus
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8
Q

What is the main stages of the immune response

A
  1. Phagocytosis
  2. T-Cells - Phagocytes activate T-cells
  3. B-Cells - T-cells activate B-cells which divide into plasma cells
  4. Antibody production - plasma cells make antibodies for a specific antigen
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9
Q

What happens in Phagocytosis

A
  • A phagocyte is a type of WBC that carries out phagocytosis
  1. A phagocyte recognises foreign antigens
  2. These acts as attractants causing phagocyte to move towards pathogen
  3. Phagocytes have receptors on their cell-surface membrane that attach to chemicals on pathogen
  4. They engulf pathogen to form a vesicle - phagosome/phagocytic vacuole
  5. Lysosomes move towards the vesicle and fuse with it
  6. Enzymes called lysozymes destroy ingested bacteria by hydrolysis of cell walls
  7. The soluble products of the breakdown are absorbed by cytoplasm of phagocyte
  8. The phagocyte presents pathogen’s antigens on its cell surface membrane to activate other immune system cells (antigen-presenting cell)
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10
Q

What are Lymphocytes and what are the 2 types

A
  • Phagocytosis is non-specific and a lymphocyte is a type of White blood cell that has specific responses and provide longer term immunity
  • Are produced by Stem cells in the bone marrow
    • B-Lymphocytes
    • T-Lymphocytes
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11
Q

What are T-Cells and what do they do

A
  • Mature in the Thymus Gland
  • It has receptor proteins on its surface that bind to complementary antigens presented to it by phagocytes that activate the helper T-Cell and causes it to divide by mitosis to produce clones.
  • It can stimulate and activate other cells
  • Known as cell-mediated immunity
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12
Q

What are the types of cells that a T-Helper cell can activate and stimulate

A
  • Activate Cytotoxic cells - which kills abnormal and foreign cells
  • Stimulate B-Cells - to divide and secrete antibody
  • Stimulate phagocytes - engulf pathogens in phasgocytosis
  • Develop into memory cells to enable rapid response to future infection
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13
Q

What is a B-cell and what does it do

A
  • Type of WBC that has antibodies that bind with antigen to form antigen-antibody complex
  • When the antibody on the surface of a B-cell meets a complementary shaped antigen it binds to it. and the antigens are presented on the surface.
  • T helper cell binds to the antigen and stimulate it to divide by mitosis
  • This process is called clonal selection and the activated B-cell divides into plasma cells
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14
Q

What are plasma cells and what are memory cells

A
  • Are identical to B-cells and secrete lots of antibodies specific to the antigen - monoclonal antibodies and form lots of antigen-antibody complexes - primary immune response
  • Are responsible for secondary immune response - when the encounter antigen they rapidly divide into plasma and more memory cells. Longer tem immunity
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15
Q

What does Agglutination mean

A
  • An antibody has 2 binding sites so can bind to 2 pathogens at the same time
  • This means pathogens become clumped together this is called agglutination
  • Phagocytes can phagocytose many pathogens at once
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16
Q

What is the structure of an antibody

A
  • Antibodies are proteins and made of chains of amino acids
  • The specificity of an antibody depends on its variable regions - form antigen binding sites that has a unique tertiary structure that is complementary to 1 antigen
  • All antibodies have the same constant regions
17
Q

What are the Primary and Secondary responses

A
  • Primary Response
    • When the antigen enters the body for the first time it activates the immune system
    • This is slow - there aren’t many B-cells that make antibody needed.
    • After exposure both T and B cells produce memory cells and these remain in the body
  • Secondary Response
    • When antigen enters again - the immune system will produce a quicker, stronger response
    • Memory B-cells activated and divide into plasma cells that produce right antibody
18
Q

What are the differences between Non-specific and Specific responses

A
  • Non-specific
    • Is immediate (faster) and same for all pathogens
    • Not long lasting
    • No antigens involved
  • Specific
    • Response is slower and specific to each pathogen
    • B and T cells
    • Longer lasting effects
19
Q

What are Active and Passive Immunity

A
  • Active Immunity - Your immune system makes its own antibodies when stimulated by an antigen
    • Natural - Catching a disease
    • Artificial - Vaccination
  • Passive Immunity - You get given antibodies made by a different organism
    • Natural - Baby becomes immune through antibodies recieved by placenta/breast milk
    • Artificial - After being injected with antibodies from someone else
20
Q

What are the differences between active and passive immunity

A
  • Active requires exposure to antigen, passive doesn’t require exposure
  • Active takes a while for protection ro develop, passive the protection is immediate
  • Active - memory cells are produced, Passive no memory cells produced
  • Active - protection is long term as antibody is produced in response to complementary antibody. Passive is short term because antibosies get broken down
21
Q

What do vaccines do and what do they contain and what is Herd Immunity

A
  • Vaccines contain dead or weakened antigens that cause the body to produce memory cells against a particular pathogen
  • Vaccines protect individuals because they reduce the occurence of the diseases.
  • Herd Immunity is when most of the population is vaccinated and there are few people to catch it from.
22
Q

What are the Ethical issues surrounding the use of vaccines and monoclonal antibodies

A
  • Vaccines are tested on animals before tested on humans - some people disagree with animal testing
  • Testing vaccines on humans is risky
  • Some people dont take vaccine for side effects but are still protected by herd immunity - can be unfair
  • If there was an epidemic - rush to get vaccine. Have to decide who gets vaccine first.
  • Monoclonal Antibodies - Animal rights
23
Q

What are the different uses of antibodies in medicine

A
  • Pregnancy Testing
  • Medical Diagnosis
  • Medical Treatment - e.g Cancer
24
Q

How are Monoclonal Antibodies used in Anti Cancer drugs targeted to cancer cells

A
  • Different cells in the body have different surface antigens
  • Cancer cells have antigens called tumour markers not found on normal cells
  • Monoclonal antibodies can be made that will bind to tumour markers and can attach anti-cancer drug to antibody.
  • Therefore antibody bind to tumour marker. Accumulate near specific cells
25
Q

How are Monoclonal Antibodies used in Pregnancy Tests

A

Pregnancy tests detect HCG, a hormone that is found in the urine of pregnant women

  • Application area contains antibodies complementary to HCG bound to a coloured bead
  • Urine is applied if preganant HCG binds with antibody to form antigen-antibody complex and moves up stick carrying the beads
  • The test strip contains immoblised antibodies to HCG and HCG binds to immoblised antibody creating a blue line.
  • If negative nothing binds and passes through
26
Q

What are HIV and AIDS

A
  • HIV (Human immunodeficiency virus) that affects the human immune system
  • It leads to AIDS (Acquired Immune Deficiency Syndrome) - Immune system deterioates and fails
27
Q

What are the symptoms of AIDS

A
  • Initial symptoms of AIDS include mino infections of mucous membranes (nose, ear and genitals) and recurring respiratory infections
  • As AIDs progresses the number of immune system cells decreases and become susceptible more infections
  • During the late stages - patients have low number of immune system cells and get serious infections which kill them.
28
Q

What is the structure of HIV

A
  • Made of core containing genetic material (RNA) and some proteins (enzyme: reverse transcriptase)
  • Has an outer coating called capsid and outer envelope
  • Sticking out of envelope are copies of attachment proteins that help HIV attach to host helper T-cell
29
Q

How does HIV replicate

A

HIV can replicate inside cells of the organism. HIV replicates inside helper T-cells

  1. The attachment protein attaches to receptor molecule on the cell membrane of Helper T-cell
  2. The capsid releases the genetic material (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 is made and inserted into the human DNA
  5. Host cell enzymes are used to make viral proteins from the viral DNA
  6. The viral proteins are assembled into new viruses which bud from the cell and go on to infect other cells
30
Q

Why do antibiotics not kill viruses

A
  • Antibiotics kill bacteria by interfering with their metabolic reactions.
  • Viruses dont have their own enzymes and ribosomes they use the host cell’s. Antibiotics don’t inhibit human processes. Don’t kill human cells.
  • Most anti-viral drugs are designed to target virus -specific enzymes
31
Q

What is an ELISA test

A
  • The enzyme-linked immunosorbent assay (ELISA) allows you to see if a patient has antibiotics to a certain antigen or any antigen to a certain antibody.
  • Used in medical diagnosis
  • In an ELISA test, an antibody is used which has an enzyme attached to it. The enzyme can react with the substrate to produce coloured product.
  • In some types of ELISA, the quantity can be worked out by intensity of colour
  • There are 2 types need to know: Direct and Indirect
32
Q

How does Direct ELISA test work

A
  • Uses a single antibody complementary to teh antigen
  1. Antigen from patient sample are bound to the inside of the well.
  2. A detection antibody with an attached enzyme complemntary to antigen is added.
  3. If the antigen is present it will be immoblised on the inside and antibody will bind to it
  4. The well is washed to remove unbound antibody
  5. A substrate solution is added. If detection antibody is present, the enzyme reacts with substrate. Substrate binds to enzyme to produce colour change
33
Q

How does an Indirect ELISA test work

A
  • Uses 2 different antibodies
  1. HIV antigen is bound to the bottom of the well
  2. A sample of patient blood is added. If there are any HIV specific antibodies in the plasma these will bind to antigen. The well is then washed to remove unbound antibodies
  3. A secondary antibody is added that has a specific enzyme attached is added. This binds to first antibody. The well is washed again to remove unbound secondary antibody.
  4. A solution is added that contains substrate specific to enzyme on secondary antibody to produce colourec product. If solution changes colour = positive

A Level Biology Paper 1 (15 decks)

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