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Biology > 6.3 > Flashcards

6.3 Flashcards

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1
Q

what is a pathogen

A

an organism or virus that causes disease

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2
Q

name some pathogens and their diseases

A

virus:
human immunodeficiency virus - acquired immunodeficiency syndrome

bacteria:
streptococcus- strep throat

fungi:
candida albicans-athletes foot

protozoa:
plasmodia falciparens- malaria

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3
Q

what is the body’s first line of defence

A

skin and mucous membranes

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4
Q

explain how the skin and mucous membranes prevent entry of pathogens into the body

A

skin and mucous membranes act as
physical barriers
skin:
- has several layers of tough keratinised skin cells
- skin has a low pH which inhibits growth of bacteria
- is a continuous layer

mucous membrane:
- goblet cells secrete sticky mucous which traps pathogens and prevents them from reaching cells to infect
- mucus also contains lysozyme which kills bacteria

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5
Q

why is it important that blood clots fast

A
  • to prevent entry of pathogens
  • to prevent too much blood loss
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6
Q

platelets

A
  • cell fragments which adhere to a site of damage to form a temporary platelet plug
  • they then release clotting factors
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7
Q

clotting factors

A
  • chemicals which convert plasma protein prothrombin into thrombin
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8
Q

prothrombin

A
  • the inactive form of thrombin
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9
Q

thrombin

A
  • an ‘activated’ enzyme which converts plasma protein fibrinogen into fibrin
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10
Q

fibrinogen

A
  • a soluble plasma protein
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11
Q

fibrin

A
  • an insoluble fibrous protein which forms a mesh that traps RBCs which eventually dries out to form a scab
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12
Q

describe the process of blood clotting

A
  • a cell/tissue is damaged
  • platelets adhere to site of damage and form temperature platelet plug
  • platelets then release clotting factors
  • clotting factors convert prothrombin into the activated thrombin
  • thrombin converts soluble fibrinogen into insoluble fibrin
  • fibrin forms a mesh/net that traps RBCs to form a clot
  • this prevents further blood loss
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13
Q

coronary thrombosis

A
  • fatty deposits of plaque in arteries may rupture which can trigger blood clotting that blocks an artery (coronary thrombosis)
  • an area of cardiac muscle therefore receives no oxygen and stops beating in a coordinated manner
  • can cause heart attack
  • diabetes, high blood glucose, smoking, stress may cause this
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14
Q

phagocytosis

A
  • a phagocyte detects the presence of a pathogen and adheres to it
  • the pathogen gets stuck to the receptors on the surface of the phagocyte
  • the pathogen is engulfed into a vesicle via endocytosis
  • a lysosome fuses with the vesicle and release hydrolytic/digestive enzymes
  • this breaks down the pathogen into molecules which are then dispersed in the phagocytes cytoplasm
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15
Q

what is phagocytosis and why is it called this

A

it’s is known as non-specific immunity as phagocytes will engulf any foreign body (non-specific)

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16
Q

what is specific immunity

A

production of antibodies by lymphocytes in response to particular pathogens

17
Q

what is an antigen

A
  • all non self proteins which will trigger the production of antibodies
  • all cells have proteins in their plasma membranes
  • viruses however have protein coats
18
Q

what is an antibody

A
  • a specifically shaped protein produced by lymphocytes in response to an antigen
  • they have a Y-shape with specific antigen binding sites at the top of each arm
19
Q

antibiotics

A
  • antibiotics block processes is prokaryotic cells but not in eukaryotic cells
  • viruses don’t have all the function of life (lack metabolism) thus can’t be treated with antibiotics (ineffective)
  • viruses can only reproduce inside host cells so antibiotics would also damage hosts cells
20
Q

florey and chain

A
  • infected 8 mice with streptococcus
  • injected 4 of them with penicillin and left others untreated
  • mice injected with penicillin survived, those without died
  • then went on to human testing (would not be allowed today)
21
Q

HIV

A
  • Human Immunodeficiency Virus
  • HIV infects T lymphocytes which regulate the immune system
  • HIV has a latency period of 8-10 years during which the virus replicates and divides
  • eventually the virus becomes active which decreases the hosts immune system so that no infection can be resisted because no antibodies are being produced
  • most people with AIDS die from disease
  • HIV transmitted through bodily fluids but risk can be minimised by using protection (condoms), clean needles, education
  • many social consequences associated with AIDS including grief, loneliness, guilt, stigma:
    refused employment, no partners, depression

Biology (38 decks)

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