Biology Topic 7 Communicable Diseases

Question 1

Pathogens definition

Answer 1

Pathogens are microorganisms that cause infectious disease: viruses, bacteria, protists or fungi.

Question 2

Pathogens how there spread and what they infect

Answer 2

Pathogens may infect plants or animals and can be spread by direct contact, water or air.

Question 3

Summary of what bacteria do to the body

Answer 3

Bacteria reproduce rapidly inside the body and may produce poisons (toxins) that damage tissues and make us feel ill.

Question 4

Summary of what viruses do to the body

Answer 4

Viruses reproduce inside cells, causing cell damage. (Viruses are not living and are not made of cells).

Question 5

Measles

Answer 5

Spread by inhalation of droplets from sneezes and coughs. Symptoms of fever and red skin rash. Can be fatal if complications arise. Most young children are vaccinated against measles.

Question 6

HIV

Answer 6

HIV - Spread by sexual contact or exchange of bodily fluids such as blood, which can occur when drug users share needles. Initially causes flu-like symptoms. Unless successfully controlled with antiretroviral drugs the virus attacks the body’s immune cells. Late stage HIV, or AIDS, occurs when the body’s immune system becomes so badly damaged it can no longer deal with other infections or cancers.

Question 7

TMV

Answer 7

Tobacco Mosaic Virus - Gives a distinctive ‘mosaic’ pattern of discolouration on the leaves, which affects the growth of the plant due to lack of photosynthesis. Widespread plant pathogen affecting many species of plant eg. tomatoes

Question 8

Salmonella

Answer 8

Salmonella - food poisoning spread by bacteria ingested in food, or on food prepared in unhygienic conditions. Symptoms of fever, abdominal cramps, vomiting and diarrhoea are caused by the toxins secreted by the bacteria. In the UK, poultry are vaccinated against Salmonella to control spread.

Question 9

Gonorrhoea

Answer 9

Gonorrhoea - STD causing symptoms of thick yellow or green discharge from the vagina or penis and pain when urinating. Easily treated with the antibiotic penicillin. Spread can be controlled by using barriers methods of contraception eg. condoms

Question 10

Rose black spot

Answer 10

Rose black spot - purple or black spots develop on leaves. Leaves often turn yellow and drop early. Affects the growth of plants as photosynthesis is reduced. Fungal spores are spread by water or wind. Can be treated using fungicides and / or removing and destroying infected leaves.

Question 11

Malaria

Answer 11

Malaria - Symptoms of recurrent episodes of fever, which can be fatal. Spread is controlled by preventing the mosquito vectors from breeding and by using mosquito nets to avoid being bitten.

Question 12

The spread of diseases can be reduced or prevented by:

Answer 12

simple hygiene measures eg. hand washing
destroying vectors eg. insects
isolation of infected individuals
vaccination.

Question 13

triple only definition of how bacteria multiply

Answer 13

Bacteria multiply by simple cell division (binary fission) as often as once every 20 minutes if they have enough nutrients and a suitable temperature.

Question 14

How can bacteria be grown and why

Answer 14

Bacteria can be grown in a nutrient broth solution or as colonies on an agar plate. Uncontaminated cultures of microorganisms are required for investigating the action of disinfectants and antibiotics.

Question 15

Describe how to prepare an uncontaminated culture using aseptic technique and why :

Answer 15

first sterlise all Petri dishes and culture media bacteria broth and agar before use must be sterilised before use this kills any unwanted microrganisms and it prevents contamination.
then clean bench with disinfectant solution this kills microorganism that could contaminate our culture .
Inoculating loops used to transfer microorganisms to the media must be sterilised by passing them through a flame.
open a sterile agar plate near a bunsen burner flame , the flame kills bacteria in the air
now use the loop to spread the bacteria that had been chosen evenly over the plate.
place sterile paper discs containing antibiotics onto the plate.
The lid of the petri dish should be secured with adhesive tape( stops lid from falling off and any unwanted microorganisms from entering) and stored upside down to prevent condensation damaging the agar.
In school labs, cultures should generally be incubated at a maximum of 25℃ which reduces the chances that harmful bacteria will grow

Question 16

Describe non-specific defence systems of the human body against pathogens:

Answer 16

Skin - Barrier, produces antimicrobial secretions
Nose - hairs and mucus to trap particles that may contain pathogens
Trachea & bronchi - secrete mucus which traps pathogens, cilia waft mucus to back of throat
Stomach - produces acid which kill the majority of pathogens

Question 17

Explain the role of the immune system in the defence against disease.

Answer 17

Phagocytosis (phagocytes engulf and digest pathogens)
Lymphocytes release antibodies which attach to antigens on a pathogen / cell
Antitoxin production
Memory cells divide and release antibodies quickly in response to a second infection by the same pathogen

Question 18

what is vaccination

Answer 18

Vaccination involves introducing small quantities of dead or inactive forms of a pathogen into the body to stimulate the white blood cells to produce antibodies.

Question 19

herd immunity definition

Answer 19

If a large proportion of the population is immune to a pathogen, the spread of the pathogen is very much reduced.

Question 20

Antibiotics summary

Answer 20

Antibiotics, such as penicillin, are medicines that help to cure bacterial disease by killing infective bacteria inside the body. Antibiotics cannot kill viral pathogens. Specific bacteria should be treated by specific antibiotics. The emergence of strains resistant to antibiotics is of great concern.

Question 21

Painkillers and other medicines are used to

Answer 21

treat the symptoms of disease but do not kill pathogens.

Question 22

why can’t viruses be easily killed ?

Answer 22

It is difficult to develop drugs that kill viruses as they reproduce inside body cells. Drugs would therefore also damage the body’s tissues.

Question 23

Plant diseases can be detected by these symptoms:

Answer 23

Stunted growth
Spots on leaves
Areas of decay
Growths
Malformed stems or leaves
Discolouration
Presence of pests

Question 24

Identification of plant diseases can be made by:

Answer 24

Reference to a gardening manual or website
Taking infected plants to a laboratory to identify the pathogen
Using testing kits that contain monoclonal antibodies

Question 25

Plants can be infected by a range of pathogens:

Answer 25

: viral (tobacco mosaic virus), bacterial and fungal (black spot) as well as by insects (aphids).

Question 26

Plants can be damaged by a range of ion deficiency conditions:

Answer 26

Nitrate deficiency - stunted growth as nitrate ions are needed for protein synthesis and therefore growth
Magnesium deficiency - chlorosis as magnesium ions are needed to make chlorophyll

Question 27

Physical defence responses resist invasion from microorganisms in plants

Answer 27

Cellulose cell walls
Tough waxy cuticle on leaves
Layers of dead cells around stems (bark on trees) which fall off

Question 28

Mechanical adaptations defend against animals in plants

Answer 28

Thorns and hairs deter animals
Leaves which droop or curl when touched
Mimicry to trick animals

Question 29

Chemical defence responses in plants

Answer 29

Antibacterial chemicals eg. mint and witch hazel
Poisons to deter herbivores eg. tobacco plants, foxgloves, deadly nightshade

Question 30

broth is cloudy because it contains

Answer 30

a very large amount of bacteria

Question 31

Two examples of bacteria cultures

Answer 31

agar gel plate
nutrient broth solution

Question 32

how do agar gel plates work

Answer 32

they contain nutrient broth which has been set into a jelly using a chemical called agar this is then poured into a petri dish and left to set

Question 33

on an agar plate bacteria grow in

Answer 33

bacterial colonies

Question 34

It is really important when concerning an agar plate that we avoid contamination because there are lots of ———————————

Answer 34

microorganisms such as bacteria and fungi naturally in the environment and these could easily contaminate our cultures

Question 35

After a few days the plate :

Answer 35

around the antibiotics we have a region where the bacteria have not grown this is called the zone of inhibition

Question 36

to find the zone of inhibition we use the equation

Answer 36

pie r squared