Immunity and Vaccination

Question 1

What are the physical and chemical barriers against disease in our bodies?

Answer 1

eyes - enzymes in tears

nose - nosal hair, mucus, sneezing refles

mouth - enzymes in saliva, coughing reflex

stomach - stomach acid, pepsin

vagina - acidic secretions

skin - waterproof, impermeable

respiratory system - mucus, ciliated epithelial cells

Question 2

How does our immune system defend against disease?

Answer 2

platelets - blood clotting

white blood cells:

phagocytes - phagocytosis

lymphocytes - antibodies

lympochytes - antitoxins

Question 3

What are platelets?

Answer 3

platelets are small cells in the blood, the function of which is blod clotting

Question 4

How do platelets and blood clotting defend against disease?

Answer 4

When the skin is injured (e.g. through a cut), the most important thing is to seal the wound quickly, so the microbes cannot enter and blood loss is limited

Platelets are tiny cells in the blood which help close a wound. When a blood vessel is cut or broken, platelets stick together and activate the formation of a mesh made of a protein called fibrin

More platelets and red blood cells are trapped in this mesh. This leads to the formation of a clot/scab which seals the cut

Question 5

Label this diagram of a phagocyte

Answer 5

Question 6

Why is a lobed nucleus necessary in a phagocyte?

Answer 6

the lobed nucleus is necessary because cells need to change shape to squeeze through, e.g. ciliaped epithelial cells

Question 7

How does phagocytosis defend against disease?

Answer 7

phagocytes can easily pass through blood vessel walls into the surrounding tissue and move towards pathogens

they engulf the pathogen

once the pathogen is engulfed they release enzymes to digest and destroy the pathogen

Question 8

Phagocytes are specific/non-specific

Answer 8

Phagocytes are non-specific - they attack anything that’s not meant to be there

Question 9

What are antibodies?

Answer 9

antibodies are proteins that recognise and bind to antigens

Question 10

What are antigens?

Answer 10

antigens are substances on the surface of a pathogen that can be recognised by an antibody

Question 11

Different pathogens carry the same/different antigens (the same/different shape)

Answer 11

Different pathogens carry different antigens (different​ shape)

Question 12

Different lymphocytes produce the same/different type of antibody which is specific/non-specific for a particular antigen (i.e. can bind to one/multiple types of antigen)

Answer 12

Different lymphocytes produce a different type of antibody which is specific for a particular antigen (i.e. can bind to only one types of antigen)

Question 13

Explain lymphocyte and antibody action

Answer 13

when a lymphocyte meets a pathogen with an antigen that is recognised by its antibodies, it reproduces quickly and releases man ycopies of the antibody which bind to the pathogen

binding of antibodies to the antigens on the pathogen can directly destroy the pathogen or help phagocytes to engulf and digest pathogens more easily

Question 14

What can bacteria (and some viruses) release?

Answer 14

bacteria (and some viruses) can release toxins that make us ill

Question 15

What are antitoxins?

Answer 15

a chemical produced by a lymphocyte that can neutralise toxins

Question 16

What is blood clotting?

Answer 16

the formation of a scab to prevent infection and blood loss

Question 17

What are phagocytes?

Answer 17

a white blood cell that can engluf and digest pathogens

Question 18

What is phagocytosis?

Answer 18

the process of engulfing and digesting pathogens

Question 19

What are lymphocyte?

Answer 19

a white blood cell that can produce antibodies or antitoxins

Question 20

What is a toxin?

Answer 20

a chemical produced by a pathogen which can make you ill

Question 21

What happens during your first infection with a virus?

Answer 21

The person feels unwell

Lymphocytes are stimulated by the antigens on the surface of the virus and release antibodies

They also make memory cells which stay in the blood

Antibodies attach to the antigens - agglutination (microbes stick together so they can’t reproduce)

The person recovers

Question 22

What is agglutination?

Answer 22

microbes stick together so they can’t reproduce

Question 23

What happens during your second infection?

Answer 23

Memory cells, made by the lymphocytes in the first infection, can repridcue very quickly if the same antigen enters the body a second time

the memory cells are stimulated by the same antigens on the surface of the virus

Antibodies are released and attach to the antigens - agglutination

The person recovers

Question 24

What do vaccines contain?

Answer 24

antigens of the pathogen

Question 25

What can vaccines be?

Answer 25

parts of the pathogen

dead pathogens

similar but less infectious pathogen

Question 26

What do vaccines trigger?

Answer 26

lymphocyte activation (antibody prdocution and memory cell formation)

Question 27

How do vaccines work?

Answer 27

When you’re infected with a new pathogen it can take your lymphocytes a while to produce the antibodies to deal with it. In that time you can get very ill, or maybe even die

To avoid this you can be vaccinated against some diseases, e.g. polio or measeles

Vaccination involved injecting dead or inactive pathogens into the body. These carry antigens, so even though they’re harmless they still trigger an immune repsonse - your lymphocytes produce antibodies to attack them

Some of these lymphocytes will remain in the blood as memory cells so if live pathogens of the same type ever appear, the antibodies to kill them will be producd much faster and in greater numbers

Question 28

What is the consequence of having too few platelets in the blood?

Answer 28

the blood would not clot; you would loose too much blood

Question 29

Phagocytes … antigens

Lymphocytes … antibodies and antitoxins

Answer 29

Phagocytes engulf antigens

Lymphocytes produce antibodies and antitoxins

Question 30

Describe the advantages to the human body by producing memory cells

Answer 30

antibodies produced faster

faster repsonse to the infection

Question 31

How do antibiotics work (2 ways) ?

Answer 31

destruction of bacterial cell walls

inhibition of protein synthesis (and thus cell division)

Question 32

What antibiotic is used in the destruction of bacterial cell walls?

Answer 32

penicillin

Question 33

What antibiotic is used in the inhibition of protein synthesis (and thus cell division)?

Answer 33

tetracycline

Question 34

Can human c

Question 35

Can the immune system fight weak infections?

Answer 35

yes

the infection will be cleared

Question 36

Can the immune system fight severe infections?

Answer 36

no

immune system cannot cope

infection not cleared

Question 37

What happens if you treat a severe infection with antibiotics?

Answer 37

severe infection → antibiotics → infection reduced but not cleared → immune system → infection cleared

Question 38

What happens if you treat a severe infection with antibiotics but do not finish the course of antibiotics?

Answer 38

severe infection → antibiotics not finished → infection reduced but not cleared → immune system → infection not cleared

Question 39

What causes antibiotic resistance?

Answer 39

a mutation (change in DNA) in the bacteria making a resistant bacterium that cannot be treated by antibiotics

Question 40

What happens if you treat antibiotic resistant-bacteria with antibiotics?

Answer 40

severe infection → antibiotics → infection reduced but not cleared → immune system → infection cleared

Question 41

What happens if you treat antibiotic resistant-bacteria with antibiotics but do not finish the course of antibiotics?

Answer 41

severe infection → antibiotics not finished → infection not cleared → immune system cannot cope→ infection not cleared → bacteria multiply → many resistant bacteria → antiniotics and immune system cannot cope → infection not cleared