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Biology A Level > Communicable Diseases > Flashcards

Communicable Diseases Flashcards

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1
Q

Describe Bacteria (3 points)

Where are they normally found in plants?

A

reproduce rapidly
damage cells
releases waste products (toxins)

vascular tissues (cause blackening and death)

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2
Q

Describe Fungi (3 points)

Where is it normally found in plants?
What does it do?

A

lives under skin of animal
hyphae which form mycelium, grow under skin surface
send out reproductive hyphae that grow to skin’s surface and release spores

in vascular tissues where it gains nutrients
the hyphae release enzymes to digest the tissue which causes decay

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3
Q

Describe Viruses (3 points)

A

invade cells and take over genetic machinery and organelles
cause cell to make copies of virus
host cell bursts releasing them

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4
Q

Examples of bacteria

A

tuberculosis
bacterial meningitis
ring rot

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5
Q

Examples of fungi

A 
black sigatoka (leaf spots on banana plant
ring worm (cattle)
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6
Q

Examples of viruses

A

HIV/AIDS
influenza
tobacco mosaic virus

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7
Q

Describe Protoctista (2 points)

A

enter host cell

feed on contents

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8
Q

Examples of protoctista

A

blight

Malaria (plasmodium) - feed on haemoglobin in RBC

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9
Q

What is the transmission of pathogens?

A

when they travel from one host to another

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10
Q

What is DIRECT TRANSMISSION?

A

passing a pathogen between hosts without intermediary

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11
Q

What are 4 types of direct transmission

A

1) physical contact - HIV, meningitis, athlete’s foot
2) faecal (oral - food/water) - cholera, food poisoning
3) droplet infection - tuberculosis, influenza (sneeze)
4) spores (in air, surfaces, soil) - tetanus

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12
Q

What is INDIRECT TRANSMISSION?

A

passing on pathogens with a vector (organism that carries pathogen between hosts)
e.g. plasmodium enters via bite from female mosquito

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13
Q

Direct transmission in plants?

Indirect transmission?

A

pathogens in soil
fungi produce spores by reproduction then carried in wind
pathogen in leaves return to soil when shed
enter fruit or seed so offspring infected

insect attach and spores/bacteria attach to insect which carries pathogen away

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14
Q

What is a PASSIVE DEFENCE against pathogens?

A

present before infection, prevents entry or spread of pathogen

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15
Q

What are 7 physical passive defenses of plants?

A

1) cellulose cell wall (contains chemicals)
2) lignin thickening of cell walls (waterproof indigestible)
3) waxy cuticle (pathogens need water)
4) bark (chemicals)
5) stomatal closure (stop entry)
6) callose (blocks flow, deposited in sieve tubes)
7) tylose (swelling fills xylem to prevent spread in water, also contains chemicals that toxic to pathogens)

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16
Q

What are 2 chemical passive defences of plants?

Why are there not many chemicals present before infection?

A

chemicals have anti-pathogenic properties

1) terpenes in tyloses
2) tannins in bark

producing them takes energy

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17
Q

What are 6 active defences on plants?

A

1) fortify defences present
2) thicken/strengthen walls (cellulose)
3) callose between wall and membrane near pathogen - prevent entry
4) oxidative bursts (oxygen damage pathogen)
5) necroses (cell suicide near infection, stop spread)
6) canker (sunken necrotic lesion in woody tissues that causes death of cambium tissue in bark)

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18
Q

How does the skin act as a primary defence mechanism against disease?

A

the epidermis (outer surface) consists of keratinocytes which are produced by mitosis at the base of the epidermis then move up to the surface. They dry out and the cytoplasm is replaced by keratin. This is keratinisation which creates dead cells on the surface that act as a barrier.

19
Q

What does blood clotting require?

A

calcium ions and at least 12 clotting factors which are released from platelets and damaged tissue. They activate the enzyme cascade.

20
Q

Describe the process of how a blood clot forms.

A

1) damage to blood vessel exposes collagen fibres
2) platelets are activated and create temporary plug
3) platelets and damaged cells produce thrombokinase (protein)
4) this activates an enzyme which converts prothrombin (protein) to thrombin (enzyme)
5) thrombin catalyses soluble fibrinogen to insoluble fibrin
6) fibrin combines and forms mesh
7) mesh traps platelets and RBC
8) CLOT

21
Q

What happens after a clot is formed?

A

it dries out into a scab, shrinks and draws sides of the cut together and skin is repaired underneath

stem cells in epidermis divide and migrate to edges of cut
new blood vessels grow to supply oxygen and nutrients to the new tissue

22
Q

Where are mucous membranes needed?

A

at exchange surfaces where the surface is thin and less protected

23
Q

What layer is involved with mucus and what does it do?

What cells are involved?

A

epithelial layer contains goblet cells which secrete mucus which traps pathogens
ciliated cells move mucus to the top of the trachea to be swallowed (pathogen killed by stomach acidity)

24
Q

Describe Inflammation:

which cells detect MO?
what effects does the chemical they release have?
what happens to excess tissue fluid?

A

Mast cells detect presence of MO in tissue, they release histamine (cell signalling substance)

Histamine causes vasodilation and make capillary walls more permeable to WBCs. Blood plasma and phagocytic WBCs leave blood and enter tissue fluid. This causes increased production of tissue fluid which causes swelling (oedema)

Excess tissue fluid is drained to lymphatic system where lymphocytes. Lead to pathogens coming into contact with lymphocytes and causing specific immune response

25
Q

Opsonins

A

type of antibody
proteins that attach/bind to antigen on pathogen, allow phagocytes to bind and engulf pathogen

some not very specific, some produced as part of specific immune response

26
Q

What is neutralisation?

A

opsonins bind to antigen of pathogen that is a binding site used for attachment to host cells
opsonin renders antigen useless
opsonin assists in phagocytosis but also prevents pathogen entering host cell

27
Q

What are neutrophils?

A 
phagocyte
multi-lobed nucleus
manufactured in bone marrow
travel in blood and squeeze out into tissue fluid
short lived
released in large numbers when infection
contain large number of lysosomes 
engulf digest pathogens
28
Q

Macrophages

A 
larger cells manufactured in bone marrow
travel in blood as monocytes
many found in lymph nodes where mature into macrophages
engulfs pathogens
becomes antigen-presenting cell
29
Q

Antigen-presenting cell

A

antigen moved to surface of cell after digesting pathogen
special protein complex on surface makes sure not mistaken for foreign cell and attacked
cell moves around body to come in contact with specific T or B lymphocytes

30
Q

Clonal selection

A

activation of specific T and B cells

leads to production of antibodies

31
Q

cytokines

A

stimulates differentiation and activity of macrophages, B cells, T cells
used in cell signalling

32
Q

T lymphocytes differentiate into…

A

T helper cells release cytokines that stimulate B cells (to develop) and phagocytosis

T memory cells provide long-term immunity

T killer cells kill host body cells that display antigen

T regulator cells shut down immune response after success and prevent autoimmunity

33
Q

B lymphocytes develop into 2 cells

A

plasma cells in the blood make and release antibodies

B memory cells remain for years and act as immunological memory

34
Q

Examples of communication using cytokines

A

macrophages release monokines which attract neutrophils by chemotaxis and stimulate B cells

T cells and macrophages release interleukins which stimulate clonal expansion (proliferation) and differentiation (of B+T)

many release interferon which inhibits virus replication and stimulates T killer cells

35
Q

The specific immune response consists of 3 stages

A

activation - clonal selection

clonal expansion - proliferation

differentiation

36
Q

Activation - clonal selection

A

to trigger immune response, T + B lymphocytes (with receptor molecules on plasma membrane complementary to antigen) need to detect antigen (in lymph nodes or antigen-presenting cell) then this is correct lymphocyte with correct receptor so replicates

37
Q

Clonal expansion - proliferation

A

correct lymphocytes activated and increase in numbers to be effective (by mitotic cell division)

38
Q

Differentiation

A

lymphocytes don’t manufacture antibodies directly

clones of lymphocytes develop into range of useful cells

39
Q

antigens are usually…

A

proteins or glycoproteins in plasma membrane of pathogen

40
Q

antibodies are ____________ which are…..

A

immunoglobins

complex proteins produced by plasma cells
have region with shape complementary to particular antigen

41
Q

structure of antigen

A

Y-shaped
2 distinct regions
4 polypeptide chains
disulfide bridges to hold polypeptides (s-s)
hinge region allows flexibility and grips more than one antigen
light polypeptide chain is the variable region with the specific shape
heavy polypeptide chain is the constant region and the same in all antibodies, may have site for easy binding of phagocytic cells

42
Q

Agglutinins

A

cross-link pathogens
antibody has 2 binding sites so bind to 2 antigens , clump together (agglutinate) and prevent pathogen from carrying out some functions, can easily be engulfed by phagocytes

43
Q

Anti-toxins

A

bind to toxins released by pathogens and render harmless

Biology A Level (28 decks)

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