Infections And Disease

Question 1

Describe the three basic shapes bacteria can have.

Answer 1

Bacteria can have a round, rod and spiral shape.
• round shaped bacterium is called a coccus
• rod shaped bacterium is called a bacillus
• spiral shaped bacterium is called spirochaete

Question 2

What structures can bacteria have?

Answer 2

Spore- a reproductive structure formed within a bacterial cell, they’re particularly resistant to heating and drying out. There’s usually one spore formed per cell.
Cell wall- a firm, flexible layer that maintains the shape of the cell and protects the underlying protoplasm.

Question 3

What is the gram stain?

Answer 3

A Danish bacteriologist Joachim Gram developed the Gram stain, which distinguishes two main groups of bacteria by the chemical and physical properties of their cell walls.
Gram-positive bacteria take up the violet colour of the stain due to having a thicker cell wall that contains peptidoglycan.
Gram-negative bacteria fail to take up the stain due to having a thinner cell wall and default staining pink.

Question 4

What are some metabolic characteristics for bacteria?

Answer 4

Gaseous requirements and nutritional patterns

Question 5

What is bacteria?

Answer 5

Bacteria are typically single-celled organisms that do not have a membrane bound nucleus and other cell organelles. These types would be prokaryotic cells.

Question 6

What is the metabolic characteristic gaseous requirements?

Answer 6

Some bacteria are aerobic (grow in presence of oxygen e.g. Pseudomonas aeruginosa aka external ear infections)
Anaerobic bacteria (grow only in the absence of bacteria e.g. Clostridium botulinum aka food poisoning)
Facultative anaerobic bacteria (grows wether there is oxygen present or not e.g. Streptococcus pyogenes aka tonsillitis)

Question 7

What is the metabolic characteristic nutritional patterns?

Answer 7

Some bacteria are photosynthetic- they use light as their energy source (some may be able to use carbon dioxide as their carbon source).
Chemosynthetic- they’re organisms that obtain their energy from oxidation reactions, some bacteria can only oxidise from organic compounds for their carbon source although some others can oxidise inorganic substances such as ammonia.

Question 8

What is flagella and what does its presence indicate?

Answer 8

Flagella are thin appendages that original just below the bacterial wall, their presence indicates that the bacterium is able to move.

Question 9

Name two diseases caused by protozoans. How are they transmitted from host to host?

Answer 9

• Fungi- fungi can transfer from petting a dog or touching an individual that’s infected.
• Malaria- malaria an be transferred through an infected anopheles mosquito biting an individual to continue its reproductive process.

Question 10

If the Anopheles mosquito could be eliminated, explain the impact this may have in the incidence of malaria.

Answer 10

The incidence rate of malaria would dramatically decrease because there wouldn’t be any anopheles mosquitos to continue infecting individuals with the disease.

Question 11

Explain why most fungal infections are not serious infections.

Answer 11

Most fungal infections are superficial because they only infect the skin, hair and nails.

Question 12

Describe two common fungal diseases.

Answer 12

Tinea of the nails- thickened, discoloured nails.

Thrush- white coating of the tongue.

Question 13

What is an ectoparasite? Give three examples.

Answer 13

Ectoparasites are parasites that live on the surface of their host. Examples would be most fungi, head lice and body louse.

Question 14

What factors lead to the spread of threadworm from one host to another?

Answer 14

Clothes, bed sheets, linen and by hand.

Question 15

What are ways that diseases can be transferred?

Answer 15

• Contact transmission
• Indirect contact
• Direct contact
• Vehicle transmission
• Animal Vectors

Question 16

What are the four portals of entry for diseases? And give two examples for each.

Answer 16

• Respiratory tract (whooping cough and meningococcal)
• Gastrointestinal tract (cholera and salmonellosis)
• Urinogenital openings (gonorrhoea and HIV)
• Breaking the skins surface (tetanus and malaria)

Question 17

State how pathogens benefit from invading a host.

Answer 17

They can benefit from invading a host because they can use them for their food supply and also to continue reproduction.

Question 18

List two personal hygiene practises that would minimalist the risk of transmitting an infectious disease.

Answer 18

a) washing your hands

b) cover your mouth whilst coughing or sneezing

Question 19

Outline the main components of a typical virion.

Answer 19

They contain either a double or single stranded type of nucleic acid (either DNA or RNA) that is encased in a capsid.

Question 20

Explain why viruses are such a difficult group to classify conventionally.

Answer 20

Because they cannot be defined by the five kingdoms (plantae, Animalia, fungi, protists and monera)

Question 21

Are viruses living or non living? Explain your response.

Answer 21

Non-living because they require a host to survive.

Question 22

Explain why viruses are classified as obligate intracellular parasites.

Answer 22

Because they require a living host in order to reproduce and are unable to function outside a living host cell.

Question 23

Explain why viruses are difficult to culture.

Answer 23

Due to their requirements being very specific and they must be grown in living material: inside animals, embryos, or bacteria

Question 24

What are the three different structures of a virus?

Answer 24

• Bacteriophage
• Tabacco mosaic virus
• Retrivirus (HIV)

Question 25

What is narrow and broad spectrum antibiotics?

Answer 25

The term broad-spectrum antibiotic refers to disease causing bacteria. A broad spectrum antibiotic acts against both gram-positive and gram-negative bacteria. Although, narrow-spectrum antibiotics are only effective against specific families of bacteria.

Question 25

Why might a disinfectant or antibiotic work on one bacteria but not the other?

Answer 25

The reason for most resistance would most likely be due to the bacterial endospores that may be attached the specific bacteria.

Question 25

What are bacterial endospores?

Answer 25

A bacterial spore is a spore or spore-like structure produced by bacteria. Spore formation in bacteria is not the principal method of reproduction but simply a method of surviving unfavourable conditions. They can have a number of features such as being able to:
• tolerate extreme dryness
• survive subzero temperatures
For example, if you boiled a bacteria with spores for five minutes. You may kill the bacteria although the spores would survive.

Question 26

What is chemotherapy?

Answer 26

Chemotherapy is the term used when a disease is treated with chemicals, e.g. Syphilis is an infectious disease, but chemotherapy is used to treat non-infectious diseases such as cancer.

Question 27

What is an antibiotic?

Answer 27

They are naturally occurring substances that inhibit the growth of, or destroy, bacteria and other microorganisms inside a host.

Question 28

Why is penicillin effective against gram-positive bacteria in particular?

Answer 28

Because it inhibits the cell wall synthesis therefore the bacteria cannot reproduce.

Question 29

If tests show that two different antibiotics are equally effective against a particular bacterial species, why might a doctor prefer one antibiotic over the other for a patient?

Answer 29

Doctors will decide on an antibiotic based on what is best suited for their patient, having knowledge of their medical history. For example, if they’re allergic to penicillin.

Question 30

What is meant if a person is a “carrier” of an infectious disease.

Answer 30

A carrier is a person who shows no signs of the infectious disease but produces faeces and other bodily fluids containing the bacteria.

Question 31

List one difference between endotoxins and exotoxins.

Answer 31

Exotoxins are released by bacteria as they grow whereas for endotoxins to be released the cell needs to break open.

Question 32

List two ways in which exotoxins interfere with normal metabolism of their hosts cells.

Answer 32

• They inhibit protein synthesis.

* They damage cell membranes or disrupt transport of materials across cell membranes.

Question 33

What is meant by the virulence of a bacterium?

Answer 33

The degree to which it can cause disease.

Question 34

What are antiseptics used for?

Answer 34

Antiseptics are used on the skin to kill pathogens. They do this by breaking down lipids and denaturing proteins.

Question 35

What are disinfectants used for?

Answer 35

Disinfectants are used to kill pathogens on objects. For example:
• Chlorine is an oxidising agent
• Phenols denature proteins
• Ammonium compounds interact with phospholipids
• Copper sulphate precipitates proteins

Question 36

What are anti microbial agents?

Answer 36

Anti microbial agents are chemicals that inhibit microbial growth by interfering with cell walls, cell membranes, protein synthesis or nucleic synthesis. They also have the ability to damage pathogens but do not harm the host.

Question 37

What are non-cellular pathogens?

Answer 37

• Viruses
• Prions
• Viroids

Question 38

What are cellular pathogens?

Answer 38

• Bacteria
• Protozoans (single called organisms such as amoebas, giardias and malaria)
• Fungi
• Ectoparasites (such as arthropods and scabies)
• Endoparasites (such as internal worms)

Question 39

What is a prion?

Answer 39

Prions are abnormal and infectious proteins that cause degenerative neurological diseases and are non-cellular pathogens. They are also resistant to lysosomic degeneration (cannot be broken down).

Question 40

How do prions create more prions?

Answer 40

A normal protein in the cytoplasm of a nerve cell folds incorrectly therefore making it a prion which causes a chain reaction amongst other proteins due to when a prion touches a normal protein it infects it, causing the protein to change its shape also.

Question 41

What disease do prions cause and is there a cure?

Answer 41

In humans prions cause transmissible spongiform encephalopathy (TSE) which is one of the rarest diseases with 100% mortality rate and no cure.
In animals it is bovine spongiform encephalopathy (BSE) but also known as mad-cow disease because of the aggressive behaviour it caused in normally docile animals.