Week 102 - Swollen finger

Question 1

What are the three functions of the complement system?

Answer 1

1) Destroys pathogens through membrane-attack-complexes.
2) Inflammatory mediation (C3a and C5a attract immune cells)
3) Opsonise pathogens (C3b)

Question 2

What are the three pathways of the complement cascade?

Answer 2

1) Classical pathway
2) Lectin pathway
3) Alternative pathway

Question 3

What is the classical pathway of the complement system?

Answer 3

• C1 binds to antibodies on the pathogen surface

* C1 catalyses breakdown of C2 and C4 to form C3 convertase.

Question 4

What is the lectin pathway of the complement system?

Answer 4

• ‘Mannose binding lectin’-MASP protein complex binds to mannose on the pathogen surface.
• This complex acts as C3 convertase.

Question 5

What is the alternative pathway of the complement system?

Answer 5

• This is spontaneous cleaving of C3 in the circulation.

* C3b then binds to the pathogen and acts as a C3 convertase.

Question 6

What are the three main stages of the complement cascade?

Answer 6

• C3 splits 
- C3a Inflammatory mediator
- C3b opsonises and acts as C5 convertase and C3 convertase.
• C5 splits
- C5a Inflammatory mediator
- C5b - Catalyst of further cascade
• Membrane attack complex forms
- C6, C7, C8 and 5xC9

Question 7

What are the three safeguards of the complement system to prevent self-attack?

Answer 7

• C3 inactivated by blood proteins unless bound to a pathogen.
• C3 convertase inactivation is accelerated by human cell surface proteins.
• MAC is kicked off human cell surfaces by surface proteins.

Question 8

What are the two methods of chemokine action?

Answer 8

• Autocrine - Feedback loop, to amplify response.

* Paracrine - Act on other cells, communication.

Question 9

Which interleukin is responsible for activation of T-cells?

Answer 9

IL-12

Question 10

What are the four main mechanisms of action of antibiotics?

Answer 10

• Disruption of the cell wall.
• Inhibition of nucleic acid synthesis.
• Inhibition of protein synthesis.
• Antimetabolite activity.

Question 11

What is the difference in the structure of the bacterial wall between gram +ve / -ve?

Answer 11

Gram -ve have a membrane on the outside of the peptidoglycan, whilst in gram +ve the peptidoglycan is the most outerly layer.

Question 12

Give some examples of Beta-lactams and describe their mechanism of action.

Answer 12

• Penicillins, cephalosporins, carbapenems.

* Form covalent bonds with proteins in the cell wall preventing final cross-linking, thus disrupting the wall.

Question 13

Give some examples of Glycopeptides and describe their mechanism of action.

Answer 13

• Vancomycin, Teicoplanin
• They inhibit the release of the building block part of the membrane, they prevent addition to the growing end of the peptidoglycan.

Question 14

Give three antibiotics that work by inhibiting the production of nucleic acids in antibiotics.

Answer 14

• Quinolones.
• Metronidazole
• Rifampicin

Question 15

Give some examples of Quinolones, and describe their mechanism of action.

Answer 15

• Ciprofloxacin, levofloxacin.

* They inhibit the DNA gyrase enzyme, which stops supercoiling of bacterial DNA.

Question 16

What is the mechanism of action of metronidazole?

Answer 16

Damages DNA, which prevents DNA synthesis.

Question 17

What is the mechanism of action of Rifampicin?

Answer 17

Inhibits the action of RNA polymerase.

Question 18

Which three families of antibiotics work by inhibiting protein synthesis? Give the stand-alone antibiotic which also acts in this way.

Answer 18

• Tetracyclines
• Aminoglycosides
• Chloramphenicol
• Macrolides

Question 19

What is the mechanism of Tetracyclines? Give some examples.

Answer 19

• Inhibits protein synthesis by binding to the 30s subunit of the ribosome.

Question 20

Give some examples of Aminoglycosides, and describe their mechanism of action.

Answer 20

• Gentamicin, Amikacin.

* Binds to the 30s subunit of the ribosome, leading to misreading of codon on mRNA.

Question 21

Give some examples of macrolides, and describe their mechanism of action.

Answer 21

• Clarithromycin, Erythromycin.

* Binds to the 50s subunit of the ribosome and prevents translocation. (Where tRNA is moved along ribosome).

Question 22

What are the two most likely bacteria found on the skin? Give an antibiotic for the treatment of each.

Answer 22

• Steptococcus - Penicillin V

* Staphylococcus - Flucloxacillin

Question 23

What type of bacteria is most likely to be found within an abscess? Give an antibiotic that will treat it.

Answer 23

Anaerobes - Metronidazole

Question 24

How do anti-Beta-lactamases work?

Answer 24

• They widen the spectrum of the drug, by adding to the molecule a subunit that will irreversibly bind to the beta-lactamases.

Question 25

Give two examples of what can be added to an anti-biotic to add beta-lactamase resistance, give an example antibiotic for each.

Answer 25

* Clavulanic Acid - Co-Amoxiclav (Augmentin) | * Tazobactam - Tazocin

Question 26

Week 102 - Swollen Finger: Which cytokine is responsible for T-cell activation?

Answer 26

IL-12

Question 27

Week 102 - Swollen Finger: Which cytokines (four) are responsible for vasodilation, vascular permeability, fever, macrophage and lymphocyte activation?

Answer 27

* Il-1ß * TNF-å * IL-6 * IL-8

Question 28

Week 102 - Swollen Finger: What are the four main mechanisms through which antibiotics work?

Answer 28

* Disruption of cell wall * Inhibition of nucleic acid synthesis * Inhibition of protein synthesis * Antimetabolite activity

Question 29

Week 102 - Swollen Finger: What is the difference between gram-negative and gram-positive bacteria in terms of cell wall composition?

Answer 29

The gram -ve bacteria have an outer membrane that covers the peptidoglycan layer, whilst gram +ve bacteria have the peptidoglycan layer exposed.

Question 30

Week 102 - Swollen Finger: Give examples of some Beta-lactams and describe their mechanism of action.

Answer 30

* Penicillins, cephalosporins, carbapenems. | * Form covalent bonds with penicillin-binding proteins to inhibit final formation of cross-links.

Question 31

Week 102 - Swollen Finger: Give examples of glycopeptides and describe their mechanism of action.

Answer 31

* Vancomycin, Teicoplanin. * Inhibits the release of the building block unit from the cell membrane. Prevent addition to growing end of peptidoglycan.