Module 4

Question 1

Name 2 properties of bacteria and 3 examples (5)

Answer 1

PROPERTIES
• Can rapidly multiply in the right conditions
• Cause disease by damaging cells or producing toxins that are harmful

EXAMPLES
• TB, BACTERIAL MENINGITIS, RING ROT(plants)

Question 2

Name 3 properties of a virus and state 3 examples (5)

Answer 2

PROPERTIES
• They INVADE cells and take over protein-synthesising organelles

• Infect the cells with new DNA
• Host cell’s eventually burst and release new copies of the viral DNA

EXAMPLES
• HIV/AIDS
• INFLUENZA
• TOBACCO MOSAIC VIRUS (plants)

Question 3

State 2 properties of fungi and 3 examples (5)

Answer 3

PROPERTIES
• Cause REDNESS and IRRITATION in ANIMALS

• This is due to HYPHAE releases from the fungus

EXAMPLES
• BLACK SIGATOKA (bananas)
• RINGWORM (cattle)
• ATHLETES FOOT

Question 4

Outline what type of transmission droplet transmission is and how it occurs

Answer 4

DIRECT TRANSMISSION

E.g. through sneezing - pathogen is contained within mucus

Question 5

Outline what type of transmission physical contact is and how it occurs

Answer 5

DIRECT TRANSMISSION

Common for skin diseases like ringworm, a fungal disease in cattle, which is spread by an infected animal brushing against an uninfected animal

Question 6

Outline what type of transmission faecal-oral transmission is and how it occurs

Answer 6

DIRECT TRANSMISSION

E.g. E. coli
Transmitted by consumption of food or water with traces of faeces from infected animal

Question 7

Outline transmission by spores and what type of transmission it is

Answer 7

DIRECT TRANSMISSION

Spores are a resistant form of the pathogen and can resist extremes of temperature, pH, and even strong disinfectants
E.g. anthrax

Question 8

Outline vector transmission and how it occurs

Answer 8

INDIRECT TRANSMISSION

E.g. malaria where the vector is a female mosquito

The pathogen is carried from one host to another via a vector

The pathogen cannot be spread directly from one host to another

Question 9

Outline how the climate can contribute to the spread of disease

Answer 9

CLIMATE
> Some vectors only live in hot climates, e.g. mosquitos carrying malaria

> Many viruses, protoctists and bacteria survive better in warm climates

> Very cold climates can kill pathogens

Question 10

Outline how cramped and crowded environments are conducive to spread of disease

Answer 10

> Droplet infection rate likely to be higher

> Contact infection also much higher

Question 11

State 3 and outline the function of 3 physical barrier plant defenses

Answer 11

> Lignin thickening of cell walls
Waxy cuticles
Closed stomata - to prevent entry to leaves

Callose
> Deposits between cell wall and cell membrane near the site of infection to strengthen the cell wall.
» Block movement of pathogens up and down plants to avoid infection of the entire plant

Tylose
> Balloon-like swelling in xylem
» Blocks xylem and stops pathogens from travelling this way around the plant

Question 12

State 3 chemicals that act as plant defenses

Answer 12

> Terpenoids
these are essential oils with antibacterial properties.

> ALKALOIDS
such as CAFFIENE and MORPHINE which have a BITTER flavour- preventing
herbivores from feeding on the plant.

> HYDROLYTIC ENZYMES
such as CHITANASES which are released with the purpose of BREAKING DOWN the CELL WALL of an invading organism.

Question 13

Outline active defenses in plants

Answer 13

> Leaves sense presence of pathogens and begin to prioritise use of energy in secreting harmful chemicals

> > Cellulose produced to further fortify the cell walls

Question 14

Outline the mucus-cough reflex

Answer 14

Goblet cells in trachea secrete mucus and the mucus traps pathogens and irritants that are inhaled

Cilia cells lining respiratory tract waft mucus towards the back of the throat ans the cough reflex expels mucus and clears the airway

Question 15

Outline the physical primary non specific defenses in animals

Answer 15

Skin is a tough physical barrier consisting of keratin and secretes sebum to waterproof skin

• Stomach acid (HYDROCHLORICH ACID) which kills bacteria
• GUT and skin flora – natural bacterial flora compete with pathogens for food and space

Question 16

Outline inflammation as a non specific defense in animals

Answer 16

HISTAMINES released by MAST CELLS in injured tissue cause VASODILATION
which INCREASES BLOOD FLOW TO THE INFECTED AREA and INCREASES PERMEABILITY of BLOOD VESSELS.

As a result of that ANTIBODIES, WHITE BLOOD cells and plasma LEAK OUT INTO the INFECTED TISSUE and DESTROY the PATHOGEN

Question 17

Outline lysosomal action as a non specific defense in animals

Answer 17

Lysosomes are ENZYMES FOUND IN SECRETIONS such as tears and

mucus which KILLS BACTERIAL CELLS BY DAMAGING THEIR CELL WALL

Question 18

Outline interferons as a non specific defense in animals

Answer 18

Interferons PREVENT VIRUSES SPREADING TO UNINFECTED CELLS BY STOPPING PROTEIN SYNTHESIS IN VIRUSES

Question 19

Outline phagotysosis as a non specific defense in animals

Answer 19

Phagocytosis is a process in which WHITE BLOOD CELLS ENGULF PATHOGENS thus
destroying them. It’s chemical markers called ANTIGENS are then PRESENTED ON THE SURFACE OF THE PHAGOCYTE. The phagocyte then becomes an ANTIGEN PRESENTING CELLS which ACTIVATES an IMMUNE RESPONSE to be stimulated IF the ANTIGEN is RECOGNISED AS FOREIGN.

Question 20

Outline blood clotting as a non specific defense in animals

Answer 20

Reduces the blood loss by temporarily sealing the opening thus preventing entry of pathogens

Question 21

Outline neutrophils as a phagocyte

Answer 21

Are manufactured in BONE MARROW and have a MULTIBLOBED NUCLEUS which enhances the flexibility of the cell

Neutrophils are released in large numbers and are short lived

Question 22

Outline B cells (B Lymphocytes) as plasma cells

Answer 22

They circulate in the blood and produce and secrete antibodies into circulation

Question 23

Outline B cells as memory cells

Answer 23

They remain in the body for many years after the initial infection and serve to ‘remember’ the antigen

Question 24

Outline T helper cells

Answer 24

They release cytokines which stimulate B cell maturation and promote phagocytosis

Question 25

Outline T killer cells

Answer 25

They identify and kill infected host cells and are especially important during viral infections

Question 26

Outline T memory cells

Answer 26

They provide long-term immunity

Question 27

Outline T regulatory cells

Answer 27

They recognise when the pathogen has been removed and is no longer a threat and subsequently alerts the rest of the immune system that it no longer needs to be active, resulting in the immune response ending

Question 28

Outline the structure of antibodies

Answer 28

4 polypeptide chains held together by disulphide bridges

> Constant regions, which remains the same
> Variable region which changes
» Hinge regions, which allow for flexibility

Question 29

Outline how antibodies carry out their role and functions

Answer 29

Antibodies are GLOBULAR PROTEIN molecules PRODUCED BY LYMPHOCYTES. Antibodies are COMPLEMENTARY in shape TO a SPECIFIC ANTIGEN, to which they attach and subsequently inhibit its action. This process is known as neutralisation and can occur in a number of ways, such as facilitating binding of phagocyte to pathogen, agglutination which is where several antibodies bind together as well as neutralisation of toxins released by the pathogen

Question 30

Outline natural passive and active immunity

Answer 30

Natural active immunity arises from being exposed to an antigen/getting the disease
whereas natural passive immunity is the result of crossing of mother’s antibodies
through the placenta and their presence in breast milk.

Question 31

Outline artificial passive and active immunity

Answer 31

Active artificial immunity is acquired through vaccinations which stimulate the
immune system and lead to production of antibodies whereas passive artificial
immunity is where antibodies are injected into the body.

Question 32

Outline auto immune diseases

Answer 32

Autoimmune diseases are diseases that evolve when a person or animal’s immune system attacks a part of the host body, in absence of pathogenic infection.
During clonal selection, lymphocytes that are programmed to attack ‘self’ are normally destroyed before entering the bloodstream.

Question 33

Outline vaccinations as a mode of immunisation

Answer 33

Vaccination provides a way of artificially stimulating primary immune response without the risk of illness
This occurs through exposing the immune system to the antigen which allows the body to produce adapted memory cells and allows for demonstration of secondary response when next exposed to the virus

Question 34

Outline antibiotics and explain what the 2 types are

Answer 34

Antibiotics can also be used to fight infection by killing the bacteria and stopping their
growth. There are two types of antibiotics:
• Bactericidal antibiotics kill bacteria by destroying their cell wall thus causing them
to burst
• Bacteriostatic antibiotics which inhibit the growth of bacteria by stopping protein
synthesis and production of nucleic acids so the bacteria can’t grow and divide

Question 35

Outline bacterial resistance

Answer 35

some bacteria become resistant to antibiotics as a result of natural selection. The
bacteria which are not killed by the antibiotic possess a selective advantage – resistance
which enables them to survive and reproduce. Therefore, the allele for antibiotic resistance
is passed onto their offspring thus creating a resistant strain.