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Bio year 13 content > Topic 6: Immunity > Flashcards

Topic 6: Immunity Flashcards

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Biology 101 flashcards
1
Q

What is an antigen?

A

A surface protein which triggers an immune response

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2
Q

What are the 3 different bacteria shapes?

A

Cocci - Spheres
Bacilli - Rods e.g. salmonella and E.coli
Spirilla - Twisted or comma shape

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3
Q

Outline 3 physical barriers in response to infection

A

Skin - Contains keratin which makes it effective at protecting against microorganisms

Cillia - The respiratory tract is lined with cilia which are hairs that can catch dust and bacteria before they reach the lungs. Cillia push gunk-filled mucus away from the lungs. Mucus is produced by goblet cells

Mucus - Trap pathogens and prevent them from entering the respiratory system

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4
Q

Outline chemical barriers in response to infection

A

Hairs on the skin produce sebum. This kills microorganisms and keeps skin supple and waterproof

Hydrochloric acid - HCL in the stomach kills bacteria which has been swallowed in food

Eyes produce tears which contain lysozyme which kills bacteria on the surface of the eye. Blinking spreads this enzyme over the eye surface

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5
Q

Definition of the immune system

A

A group of cells, tissues, organs and mechanisms that defends an organism against pathogens and other foreign substances

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6
Q

What is a phagocyte?

A

A cell that engulfs bacteria
E.g. Macrophages and neutrophils

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7
Q

Outline the steps in phagocytosis

A

-The phagocyte recognises a foreign marker on the pathogen’s outer membrane called the antigen
-Small non-specific protein opsonin attaches to antigen receptors
-Phagocyte engulfs pathogen and the pathogen is then enclosed in a vacuole
-This phagosome then fuses with a lysosome which contains digestive enzymes called lysozymes to form a phagolysosome
-The digestive enzymes in the phagolysosome break down the pathogen and this is excreted via exocytosis. However, the antigens are preserved and presented on cell membrane of macrophage

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8
Q

Using the fluid mosaic model of cell membranes, explain how a macrophage carries out phagocytosis (4 marks)

A

-Membrane proteins interact with bacteria
-Pseudopodia formed around bacteria
-Membranes of pseudopodia fuse/pinch off to form a vacuole which contains bacteria
-Change in shape of the membrane is due to fluidity caused by movement of phospholipids in the presence of cholesterol

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9
Q

Outline the role of interferons in the immune system

A

-Cells infected by viruses produce anti-viral proteins called interferons
-Interferons prevent viruses from spreading to uninfected cells
-They inhibit the production of viral proteins, preventing the virus from replicating
-They activate white blood cells involved with the specific immune response to destroy infected cells
-They increase the non-specific immune response e.g. by promoting inflammation

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10
Q

Explain the importance of interferons in the body’s response to infection by viruses (2)

A

Interferons prevent the virus from attaching to host cells by binding to receptors preventing the virus from entering cells, so the virus can’t replicate and infect more cells

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11
Q

Outline the process of inflammation

A

-Histamine is secreted by mast cells
-Histamine causes vasodilation which increases blood flow through capillaries
-Capillary walls become ‘leaky’ as they are more permeable allowing fluid to enter the tissue
-Phagocytes leave the blood and enter the tissue to engulf foreign particles

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12
Q

What are the 2 types of specific immune responses?

A

-B cells mature in the bone marrow and are involved in the humoral response.
-T cells move from the bone marrow to the thymus gland where they mature, they are involved in both the humoral and cell-mediated response.

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13
Q

Explain the differences between bacteria and viruses
(3)

A
  • Bacteria are prokaryotes but viruses just consist of nucleic acid (DNA or RNA) enclosed in the protein coat
  • Viruses are significantly smaller than bacteria

-Bacteria don’t require a host to survive whereas viruses are completely dependent on them for them to carry out their processes, consequently, they are not considered living organisms

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14
Q

Explain how changes in the blood vessels result in the redness and swelling seen at the site of inflammation (4)

A

-Mast cells secrete histamine
-Histamine causes vasodilation
-Which increases blood flow to the site (causing redness)
-Histamine also causes the permeability of capillaries to increase, allowing blood plasma to leave the capillary causing swelling

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15
Q

Outline T cell and B cell response after phagocytosis

A

T helper cells bind to the antigen. This causes them to activate and release cytokines which activate B cells and T killer cells.
B cells are activated by cytokines as well as antigens binding to the antibody receptors on its cell membrane. This activation causes mitosis to occur and the cloned B cells differentiate to form either plasma cells or B memory cells.

The plasma cells produce specific antibodies that are complementary to antigens on the pathogen. These are released into the bloodstream so they can bind to pathogen

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16
Q

Features of antigens

A
  • Antigens are found on cell surface membranes, bacterial cell walls, or the surfaces of viruses
  • Antigens can be either self antigens or non-self antigens. Antigens produced by the organism’s body cells are known as self-antigens. Self-antigens do not stimulate an immune response
  • After pathogens are engulfed by phagocytosis, phagocytes transfer the antigens of the digested pathogen to their cell surface membrane, becoming antigen-presenting cells
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17
Q

Outline the function of an antibody

A
  • Antibodies bind to specific antigens that trigger the specific immune response
  • Pathogens enter host cells by binding to them using receptors on their surface; antibodies can bind to these receptors, preventing pathogens from infecting host cells
  • Antibodies cause pathogens to clump together, a process known as agglutination; this reduces the chance that the pathogens will spread through the body and makes it possible for phagocytes to engulf many pathogens at one time
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18
Q

What is meant by a bacteriocidal antibiotic?

A

Inhibit enzymes needed to make chemical bonds in bacteria cell walls - leads to cell death due to the pressure of water moving in as the cell isn’t strong enough

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19
Q

What is a bacteriostatic antibiotic?

A

Inhibit enzymes, antibiotic binds to bacterial ribosome meaning no metabolic process occur

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20
Q

Codes of practice in a hospital

A

-Wash hands before and after visiting patient
-Disinfect hospital beds and surfaces quicker
-Move patients to certain isolation wards specific for these infections

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21
Q

Methods which should be used to prevent antibiotic drug resistance

A

-Doctors shouldn’t prescribe medicine for minor bacterial or viral infections
-Dont prescribe to prevent infection
-Should use a narrow spectrum of antibiotics so it only targets the specific bacteria
-Should rotate the use of antibiotics
-Patients should complete their cycle of antibiotics

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22
Q

Give two differences between the genetic material of bacteria and viruses (2)

A
  • Bacteria have plasmids, viruses have linear genetic material
  • Bacteria have double-stranded genetic material whereas viruses have single or double-stranded genetic material
23
Q

Explain the importance of interferon in the body’s response to infection by viruses (2)

A

Interferons prevent the virus from binding to the uninfected host cell as interferon binds to receptors of the host cell, meaning the virus can’t replicate

24
Q

State two ways in which the skin flora can help protect a person from infection by pathogenic bacteria (2)

A
  • Compete with bacteria for nutrients
  • Secrete lysozymes which affect the PH of the skin, killing the bacteria
25
Q

Give two examples of places where non-self antigens might occur inside an organism (2)

A
  • Found in tumour cell
  • Found in toxins
26
Q

State 3 roles of T helper cells

A
  • Activation of phagocytes
  • Activate B cells
  • Formation of B memory cells
27
Q

Explain why the presence of microorganisms on the skin and in the gut helps to prevent pathogenic organisms from multiplying In the body (3)

A
  • Flora in the gut and skin are better adapted to the conditions
  • Therefore they can outcompete pathogenic organisms
  • Bacteria in the gut secrete chemicals which help to destroy pathogens
28
Q

Suggest why the protein structure of lysozyme is important to the way in which it acts against pathogens (3)

A

-Lysozyme is an enzyme
- Proteins/ active site/ enzymes have different shapes
-Lysozyme acts on the cell wall of bacteria

29
Q

Why does the destruction of T helper cells cause the symptoms of AIDS? (4)

A

-Lack of T helper cells means less cytokines are produced

-This means that the cloning of B cells is also reduced

-Therefore the production of antibodies are reduced

  • Increasing risk of infection
30
Q

Explain why there are relatively few species of bacteria in the stomach (2)

A
  • The PH inside the stomach is too low for the enzymes of most bacteria to function
  • Bacteria in the stomach have adaptations that enable them to survive
31
Q

Explain the role of conditions in the gut in preventing infection by microorganisms (2)

A
  • Acidic conditions in the stomach
  • Because the acidic conditions denature the enzymes of microorganisms
32
Q

Compare and contrast the structure of Ebola virus with that of the human immunodeficiency virus (HIV). (4)

A

Similarities:
- Both contain RNA
- Both have glycoprotein/protein capsid

Differences:
-Ebola contains one strand of RNA but HIV contains two strands of RNA
-HIV is spherical but Ebola is elongated

33
Q

Describe how HIV particles enter T helper cells (3)

A

-HIV particles have GP120 on the surface of its virus

-T helper cells have CD4 receptors that the GP120 bind to

-Viral envelope fuses with cell membrane of T helper cell

-Viral RNA enters the cell

34
Q

Which cells produce antibodies?

A

Plasma cells

35
Q

Stem cell therapy can be used to treat patients infected with HIV.

The bone marrow of these patients can be destroyed using radiotherapy.

The patients can then be given stem cells from the bone marrow of a donor with this mutation.

Explain why these stem cells may prevent HIV causing AIDS. (4)

A

-Stem cells in the bone marrow can differentiate into specialised cells

-These cells can differentiate into T helper cells that are resistant to HIV

-T helper cells are destroyed by HIV so a patient cannot produce an immune response

-Mutated CD4 receptor prevents HIV from entering the replacement T helper cells

-T helper cells are not destroyed therefore AIDS don’t develop/HIV is not in the blood.

36
Q

Explain the effect of using antiviral drugs to treat HIV on the number of deaths from TB (6)

A
  • TB is more likely to develop in patients with HIV
  • Antiviral drugs reduce the incidence of TB in patients with HIV
  • HIV binds to CD4 receptors on T helper cells
  • HIV replicates inside T helper cells and then destroys the cells as it bursts out
  • This reduces the number of T-helper cells
  • When TB enters the body, reduction in T helper cells means there is no immune response so the patient develops TB
  • Drugs that prevent viral replication mean that T-helper cells are not destroyed so the immune system can prevent TB from developing
    -Therefore deaths from TB will decrease in patients with HIV
37
Q

M.tuberculosis bacteria can remain dormant in the body after infection

Explain why these dormant bacteria are not destroyed the immune system (3)

A
  • The bacteria are inside the phagocyte, TB has a thick waxy cell wall so lysosomes cant fuse with the phagocytic vacuole so bacteria within tubercles can’t be destroyed
38
Q

Explain why, following a measles infection, it may be advisable for children to repeat other vaccinations they have had (3)

A
  • Due to a loss of memory cells there is no secondary immune response
  • Therefore antibodies cannot be produced quickly
  • Therefore there is less immunity to diseases previously vaccinated against
  • Need to repeat vaccinations to produce more memory cells
39
Q

Explain why antibiotics cannot be used to treat influenza (2)

A
  • Antibiotics work by breaking down the cell wall of the pathogen
  • Viruses don’t have cell walls which can be attacked, rather they have a protective protein coat
40
Q

Describe how Tuberculosis bacteria evade the immune system (2)

A
  • TB survives in macrophages
  • Remains dormant in tubercles
  • M tuberculosis inhibits T helper cells
41
Q

State two characteristic features of antibiotics (2)

A

-Have glycoproteins
-Have antigen-binding sites

42
Q

There is an evolutionary race between some viruses such as HIV and their host

Suggest how this could affect the body’s specific immune response to infection by viruses. Give an explanation for your answer (3)

A

-Mutation has occurred in nucleic acid
-Change in antigens on the virus surface
-Secondary immune response will not be possible
-Memory cells will not recognise the new antigen
-Another primary immune response is needed, a new antigen needs to be presented

43
Q

State how the genetic material in HIV differs from the genetic material in the bacterium Mycobacterium tuberculosis that causes TB (2)

A

-HIV has RNA, bacterium has DNA
-Genetic material in HIV is linear but in bacteria It is circular
-There are plasmids in bacteria but not in HIV

44
Q

What is passive immunity?

A

When ready-made antibodies, from another source, are introduced to the body

Passive immunity is:
Fast acting
Only lasts a short period of time

Breastfeeding provides a baby with natural passive immunity

45
Q

What is active immunity?

A

When the body is activated and produces the antibodies needed to fight an infection
Active immunity is
- slow acting
- provides long lasting protection

The primary response when a microorganism enters the body is described as natural active immunity

Vaccines provide artificial active immunity

46
Q

Explain how macrophages present antigens to T helper cells (2)

A

-Macrophage binds to MHC on T helper cell

47
Q

Describe how a B cell is activated (3)

A

-Antigens bind to B cells
-Antigens bind to Major histocompatibility complex (MHC)
-T helper cells bind to B cells
-Cytokines from T helper cells activate B cells which can differentiate into plasma cells to produce antibodies

48
Q

Describe the role of antigen presentation in the body’s specific immune response to infection by viruses (4)

A

-Macrophages present antigen to T helper cells
-T helper cells are needed to activate B cells
-B cells result in plasma cells which produce antibodies
-Infected host cells presents antigen to T killer cells (1) T killer cells destroy infected host cells (1)

49
Q

Describe how infection with a bacterium results in the production of plasma cells (4)

A

-Humoral response
-Phagocytosis by phagocytes
-Macrophages are antigen presenting cells
-Antigens bind to B cells
-T helper cells release cytokines for B cell activation
-B cells differentiate into plasma cells

50
Q

Explain how an immune response can take place that destroys only one type of cell (3)

A

-Different cells will have different proteins in their cell membrane
- Foreign antigens on these cells trigger an immune response
-T killer cells recognise specific cells as foreign
-T cells help B cells produce antibodies that bind to a specific cell

51
Q

Explain why insulin receptors only bind to insulin (3)

A

-The receptor has a unique primary/tertiary structure
-Tertiary structure provides cell with a specific binding site
-Which is complementary to the insulin molecule

52
Q

Explain how the bacterial molecules could trigger a specific immune response (4)

A

-Bacterial molecules are engulfed by macrophages / phagocytes / B cell
-Antigen presented on the surface of cell / antigen presenting cell produced
-T helper cells with complementary CD4 / receptor bind to APCs
-Cytokine released causes cloning of B cells / formation of B effector cells
-Plasma cells produce / release antibodies

53
Q

There are ‘trillions of microbes’ found in the gut, ‘as well as others living elsewhere in and on the body’

Describe the role of the microbes that are normally found on the skin surface of humans (2)

A

-Make environment hostile for other microbes
-Outcompetes other microbes
-Skin flora prevents /reduces colonisation by other microbes

54
Q

Compare and contrast the structure of a bacterium with the HIV (3)

A

-Bacteria have a cell wall, viruses have a protein coat / capsid
-Bacteria are cells, viruses are particles
-Bacteria have DNA, viruses have RNA
-Bacteria have circular DNA, viruses have linear RNA
-Bacteria have double stranded DNA but Viruses have single stranded RNA

Bio year 13 content (8 decks)

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