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Biology OCR A A-Level > Disease > Flashcards

Disease Flashcards

(71 cards)

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1
Q

what are communicable disease caused by

A

pathogens

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2
Q

what is a communicable disease

A

a disease that can be passed from organism to another

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3
Q

what are vectors

A

things can carry pathogens from one organism to another

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4
Q

what are the 2 main ways that bacteria can be classified

A

by their basic shapes
by their cell walls

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5
Q

what are the different shapes of bacteria

A

rod shaped
spherical
comma shaped
spiralled
corkscrew

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6
Q

what are the 2 different main types of bacterial cell walls and how do they look under a microscope when stained

A

gram positive (blue-purple under a microscope when stained

gram negative (red under a microscope when stained)

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7
Q

what are the size of viruses

A

0.02-0.3 micrometers in diameter

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8
Q

what is the basic structure of a virus

A

genetic material (dna or rna) surrounded by protein

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9
Q

how do viruses work

A

takes over cellular metabolism.

viral genetic material is inserted into the genetic material of the host cell.

the host cell then makes more viruses which then burst out of the cell destroying it.

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10
Q

what are bacteriophages

A

viruses that attack bacteria

they take over bacterial cells and use them to replicate, destroying the bacteria at the same time

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11
Q

what kind of celled organisms are protists

A

eukaryotes

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12
Q

what kind of celled organisms are bacteria

A

prokaryotes

they do not have a membrane bound nucleus nor organelles

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13
Q

are viruses prokaryotes or eukaryotes

A

neither because they are not living

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14
Q

how do protists work

A

they take over a cell, digest the insides and use this as a medium to reproduce, before bursting out.

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15
Q

how do fungi work

A

digest and destroy living cells

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16
Q

why can fungi spread rapidly

A

when they reproduce they produce millions of tiny spores which can spread over long distances

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17
Q

which pathogens damage the host tissues directly

A

viruses
fungi
protists

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18
Q

which pathogens produce toxins which damage host tissues

A

bacteria
fungi

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19
Q

how does secreted bacterial toxins damage tissues

A

secreted toxins damages the cells of the host organism by breaking down the plasma membrane or inactivating enzymes and some interfere with genetic material so the cell cannot divide

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20
Q

what is ring rot and how is it spread

A

a bacterial disease of potatoes, tomatoes and aubergines

caused by bacterium spread by direct contact, or indirect contact, via infected water, machinery etc.

creates ring shaped damage to vascular tissue in plants including potatoes and tomatoes

there are some resistant strains

good hygiene practice and quarantine to avoid spread

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21
Q

what is tmv and how is it spread

A

a virus that affects tomatoes, tobacco and peppers

spread by direct contact, including human handling. it also persists in dead plant matter

causes leaf discolouration that leads to stunted growth and reduced yields

minimise spread by sanitation (remove affected material, washing hands) and crop rotation

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22
Q

what is potato blight and how is it spread

A

a protist that acts like a fungus that affects species including as potatoes and tomatoes

spread by wind-borne pores

hyphae penetrates and kills cells in leaves / tubers / fruits massively affecting yields

no cure - careful management and chemical treatment reduces spread and impacts

resistant strains exist

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23
Q

what is black sigatoka and how is it spread

A

a fungus that affects banana plants - hyphae penetrate leaves, killing cells and turning leaves black

spread by wind and water borne spores

significantly reduces yields

good husbandry to reduce effects - rotation, intercropping, good drainage, remove leaves with infection

application of fungicides

GM species

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24
Q

what is TB and how does it spread

A

a bacteria that is
caused by the airborne bacteria mycobacterium tuberculosis

it is a widespread disease that affects the respiratory system

it can be treated with antibiotics but resistant strains of TB have emerged

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25
what is HIV/AIDS and how does it spread
caused by retrovirus that affects and kills t-helper cells, compromising the immune system and leading to secondary infections such as pneumonia, TB and some forms of cancer spread by the exchange of bodily fluid anti-retroviral drugs slow the progress of disease no current cure due to lifecycle of virus and mutation rate
26
what is influenza and how is it spread
a virus that is spread by droplet infection and direct contact affects and kills ciliated epithelial cells in gas exchange system leading to fever, aching, headaches. can cause death (often from secondary respiratory system) short term vaccines produced but rapid mutation rates means that the production of a complete vaccine is not possible
27
what is malaria and how is it spread
caused by a protist life cycle: a person with malaria → gametes of plasmodium in blood → female mosquito sucks blood → plasmodium develops and migrates to a mosquito’s salivary gland → an uninfected person is bitten → plasmodium migrates to liver → plasmodium migrates to blood malaria is transported via the vector of a mosquito treated with anti malarial drugs - they are mixed together due to resistance
28
what is ring worm and how is it spread
a fungus that affects many mammals - causing unsightly, itchy, round areas of skin that can cause further infection spread by direct contact treated with fungicidal creams
29
what is athlete's foot and how is it spread
a fungus that digests skin between toes - causing cracking and scaling spreads through direct contact with spores treated with fungicidal creams
30
how are pathogens identified
traditionally, pathogens were identified using a microscope monoclonal antibodies DNA sequencing
31
how does TB work
when a person becomes infected with TB, an immune response is triggered in healthy people, white blood cells called macrophages engulf the bacteria by phagocytosis, controlling the infection a tissue mass called a tubercle forms around the infected site, and after 3-8 weeks, the infected region heals. however, the bacteria can survive inside the macrophages for years until the immune system becomes weak
32
symptoms of TB
coughing shortness of breath loss of appetite weight loss fever night sweats fever and night sweats occur due to neutrophils and macrophages releasing fever-causing substances, as part of the inflammatory response. these chemicals affect the hypothalamus and increase core body temperature.
33
How can pathogens be directly transmitted in animals
Direct transmission: - Bodily fluids - Skin to skin contact - Droplet infections Inoculation: - Break in the skin - Animal bite - Puncture wound Ingestion: - Taking in contaminated food / drink - Transferring pathogens from hand to mouth
34
How can pathogens be indirectly transmitted in animals
Fromites: Inanimate objects that are likely to carry pathogens - e.g socks Vectors: - Mosquitos - Water
35
Factors that increase the rate of transmission of communicable disease in animals
- population density - travel - being immune compromised - climate change - damp living conditions - waste disposal - infrastructure - poverty - culture - homelessness - poor nutrition
36
Factors that prevent the spread of communicable diseases in animals
- hand washing - improving living conditions - disposal of both bodily and household waste effectively
37
How can pathogens be directly transmitted in plants
Direct contact of a healthy plant with an infected plant Pathogen entering fruits, affecting offspring
38
How can pathogens be indirectly transmitted in plants
Soil contamination: Affected plants leaving pathogens in the soil which can infect nearby plants
39
How might wind act as a vector for pathogens
Spores may be carried in the wind
40
Factors affecting the transmission of communicable diseases in plants
- susceptibility of disease - overcrowding - density of planting - resistance - poor mineral content of the soil reduces resistance of plants - climatic conditions - damper, warmer conditions increase the spread of disease - climate change
41
Factors that prevent the transmission of disease in plants
- space out the plants - clear fields as thoroughly as possible - rotate crops - follow strict hygiene practises
42
What is a passive defence
One that is present before any infection, their aim is to prevent entry and spread of pathogens
43
what is an active defence
occur, or are enhanced, when pathogens are present
44
how do plants respond to an attack
receptors in the cell respond to molecules from the pathogens stimulates release of signalling molecules that switch on genes in the nucleus triggering cellular responses
45
examples of physical (passive) plant defences
- cellulose cell wall - physical barrier - lignin thickening of cell walls - waterproof and indigestible - waxy cuticle - prevents water from collecting on the surface - guard cells - can close the stomata when pathogens are detected - callose - large polysaccharide that is deposited in sieve tubes at the end of the growing season. blocks the flow so that pathogens can’t spread - tylose formation - balloon-like swelling that fills the xylem-vessels. xylem can no longer carry water which limits pathogen spread
46
examples of physical (active) defences
canker - a sunken necrotic lesion in the woody tissue such as the main stem or branch. it causes the death of the cambium tissue in the bark
47
examples of chemical (passive) defences
tannins in bark: deactivate salivary enzymes
48
examples of chemical (active) defences
- terpenoids - oils with antibacterial and antimicrobial properties. they may also create deterring scents - phenols - these also have antibiotic and anti fungal properties. tannins found in bark inhibit attack by insects. these compounds bind to salivary proteins and digestive enzymes such as trypsin, deactivating the enzymes. - alkaloids - nitrogen containing compounds with a bitter tase like caffeine, nicotine, cocaine and morphine. this stops herbivores feeding on them. less grazing means less exposure to pathogens - defensins - cystein rich proteins that have broad anti-microbial activity. they appear to inhibit the action of ion transport channels - hydrolytic enzymes - found in the spaces between cells. chitinases break down fungal cell walls, lysozymes break down bacterial cell walls
49
Actions that plants take when producing an active chemical response
- cell walls become thickened with additional cellulose - callose deposited between plant cell wall and cell membrane near invading pathogen - oxidative bursts - produce highly reactive oxygen molecules capable of damaging invading organisms - necrosis - deliberate cell suicide. limits pathogen access to water and nutrients. brought about by injury that allowed pathogens in
50
what are the 2 types of immunity
inate adaptive
51
examples of barriers (inate immunity) (first barrier)
skin mucous membranes
52
examples of non-specific defences (inate immunity) (second barrier)
- phagocytic leukocytes - antimicrobial proteins - inflammatory response - fever
53
examples of specific defences (adaptive immunity)
- lymphocytes - antibodies - memory cells
54
How does the skin work as a non-specific defence
Secretes cebum (oily substance) that inhibits the growth of pathogens Shedding of skin: When the cell reaches the surface it has keratinised and acts as a barrier
55
How do expulsive reflexes work as a non-specific defence
Coughing and sneezing expel foreign objects and happen automatically
56
How do mucous membranes work as non-specific defences, and where are they most commonly found
Most commonly found in airways and lungs Mucus (produced by goblet cells in epithelial layer) traps microbes and ciliated epithelial cells waft it to the back of your throat, then you swallow it.
57
How does the nose act as a non-specific defence
Full of hairs and mucus which trap microbes and then you blow it out or sniff it to the back of your throat and swallow it. The mucus contains lysozymes which destroy bacterial cell walls
58
How does the eye act as a non-specific defence
REM pushes microbes to the front of your eye Tears contain water, salts and lysozymes
59
How does the ear act as a non-specific defence
Yellow sticky ear wax which traps pathogens
60
How does the stomach act as a non-specific defence
Microbes ingested in food enter the stomach which contain stomach acid at approx pH 2
61
How does the penis act as a non-specific defence
Microbes can't usually live in urea Urine also contains lysozymes
62
How does the vagina act as a non-specific defence
Moderately acidic pH (3.8-4.5) The menstrual cycle ensures that most microbes are ejected from the vagina every 28 days with the uterine wall
63
How does blood clotting work
When platelets come into contact with the collagen in skin or the wall of the damage blood vessel they secrete: thromboplastin and serotonin Thromboplastin is an enzyme that triggers a cascade of reactions. The cascade produces fibrin, this creates a mesh/network of fibres which trap platelets and blood cells to form a clot. Calcium (Ca2+) is needed alongside this. Serotonin makes the muscle in the walls of the blood vessels contract, reducing the supply of blood to that area The clot then dries to form a tough, hard scab that keeps pathogens out Fibrous collagen under the scab is formed which helps to hold the sides of the cut together Stem cells in epidermis divide to form new skin cells across the cut​ New blood vessels form (angiogenesis)​ Scab is released ​ ​
64
What are lysozomes
Enzymes that disrupt the cell wall of gram-positive bacteria by digesting the peptidoglycan
65
What are interferons
Proteins produced by virus-infected cells in response to the virus. Interferons trigger the production of a second protein that inhibits viral replication by binding to mRNA coded for by the virus.​
66
What is the inflammatory response and what is it characterised by
A localised response to pathogens resulting in inflammation at the site of the wound Characterised by redness, heat, pain, and swelling of tissue
67
What is inflammation
The swelling of skin immediately around the rupture
68
How does the inflammatory response work (non-specific response)
Mast cells are activated when skin is ruptured. They release histamines and cytokines Histamines make the blood vessels dilate, causing localised heat and redness. The raised temperature helps prevent pathogens from spreading Histamines also make the permeability of the capillary wall increase, causing more tissue fluid (blood plasm) to be forced out of the blood - this is what causes swelling and pain Excess tissue fluid drains into the lymphatic system – where pathogens and antigen presenting cells will come into contact with lymphocytes.​ Cytokines attract phagocytes to the site which dispose of pathogens through phagocytosis
69
What are cytokines
Small soluble proteins that act as cell signals, particularly in the immune response
70
How do fevers work (non-specific response)
Normal core body temperature is 37 degrees which is controlled by the hypothalamus in the brain​ During infection the large presents of white blood cells causes the hypothalamus to reset, increasing temperature​ This is because pathogens cannot reproduce as quickly at temperatures above 37 degrees, and the specific immune system can work faster​ above 37 degrees
71

Biology OCR A A-Level (3 decks)

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