D2 Aspirin and Penicillin

Question 1

who was penicillin discovered by and how

Answer 1

alexander fleming, noticed that a fungus that contaminated some of his cultures generated a clear region w/o bacterial growth

Question 2

structure of penicillin

Answer 2

dipeptide formed from two amino acids: cysteine + valine.

molecule consists of a Sulfur atom,

attached to a four-membered ring containing a cyclic amide group known as beta-lactam.

The ring consists of 1 nitrogen and 3 carbon atoms – these parts are responsible for antibacterial properties.

Question 3

structure of penicillin: unusual structure of beta-lactam

Answer 3

bond angles are reduced to 90-degrees, and despite having sp2 and sp3 hybridised atomic orbitals the angles seek to form bonds with angles of 120-degrees and 109.5-degrees

Question 4

disadvantages of penicillin 2

Answer 4

• broken down by stomach acid = has to be injected into bloodstream
• use is limited bc sig. no. of ppl have allergic responses

Question 5

areas of body for action of penicillin

Answer 5

infections in
- ear
- nose
- throat
- mouth
- wound infections

Question 6

whats up with some bacteria having antibiotic resistance? like how

Answer 6

-beta-lactam ring – crucial to penicillin’s antibacterial action = ring broken = no activity
- shown in some bacteria: produce an enzyme, penicillinase – can open the ring = inactive.

Question 7

responses to antibiotic resistance

Answer 7

• discourage over prescription: make it prescription only
• synthesis of different forms of penicillin to withstand the action of penicillinase eg methicillin
• education of patients of the importance of completing the full course of treatment with an antibiotic = patient compliance

Question 8

describe the process of penicillin action 4

Answer 8

1. disrupt formation of cell walls of bacteria by inhibiting bacterial enzyme transpeptidase.
2. High reactivity of amide group in ring causes it to bind irreversibly near the active site of the enzyme as the ring breaks.
3. Inactivation of enzyme blocks cell wall construction within the bacterium.
4. Cell walls unable to support the bacterium = bursts and dies.

Question 9

how to describe the action of penicillin in a structural equation type beat

Answer 9

the enzyme –> corner of square connected to =O, arrows from the corner to O and N

becomes N-, breaks that bond.
corner becomes C, enzyme (E) is connected to it

Question 10

brefily describe penicillin and aspirin

Answer 10

penicillin: an early antibiotic
aspirin: a mild analgesic (pain relief)

Question 11

how does pain work

Answer 11

nerve messages sent from various pain receptors – stimulated by Prostaglandins

Question 12

what are prostaglandins and what do they do

Answer 12

• released from cells damaged thermally/mechanically/chemically
• mediates inflammatory response – causes dilation of blood vessels near injury
• leads to swelling and incr pain
• affects temp regulation = can cause Fever

Question 13

describe action of aspirin

Answer 13

• prevents stimulation of nerve endings at site of pain
• inhibits release of prostaglandins from injury site

= intercepts/blocks pathway between source and receptors of pain

Question 14

does aspirin interfere with brain function?

Answer 14

no = known as non-narcotics

Question 15

development of aspirin

Answer 15

• 400BCE –> chewing willow bark for pain/fever relief
• early 1800s –> active ingredient in bark is salicin, salicylic acid for treatment
• 1890 –> bayer company in germany: made ester derivative – aspirin

Question 16

how is aspirin synthesised

Answer 16

Salicylic acid is converted into aspirin through esterification (condensation reaction). Process usually uses ethanoic anhydride, (CH3CO)2O.

conc sulfuric acid / phosphoric acid added –> mixture is warmed gently –> cooled to form crystals –> suction filtered and washed with chilled water.
= prevents loss of product (low solubility of aspirin at low temp)

Question 17

word equation for synthesis of aspirin bc i cant add the chem one withot pics

Answer 17

salicylic acid + ethanoic anhydride –> aspirin + ethanoic acid

Question 18

how has aspirin been modified for absorption and distribtion

Answer 18

• avail in many formations: various coatings, buffer components
  = delay activity until its in small intestine = alleviates some side effects

Question 19

how is aspirin purified

Answer 19

• recrystallisation –> dissolving impure crystals in min. vol. of hot ethanol (better solvent for impurities)
  = forms saturated aspirin –> cooled slowly –> aspirin crystalises out first –> seperated by filtration

Question 20

how is purity of aspirin determined

Answer 20

melting point determination
- pure substance: aspirin 138-140 degC, salicylic 159 degC
- mixture: lower, less defined melting point

Question 21

infrared spectrascopy (IR) of aspirin

Answer 21

• used to characterise – absorption of particular wavenumbers of IR radiation – helps identify presence of certain functional grps
• early on OH trough: for –OH in acid
• 2 large spikes starting at around 1800, left: ester grp, right: C=O in acid

Question 22

synergistic effects of ethanol and aspirin

Answer 22

more acute physiological effects – synergy (care advised when consm. alcohol w meds)
- can cause incr bleeding of stomach lining, incr risk of ulcers

Question 23

positive physiological effects of aspirin 2

Answer 23

1. anticoagulant – reduces bloods ability to clot
   - useful for patients at risk of heart disease, stroke
   - potentially dangerous for ppl whose blood does not clot easily
2. regular intake of low doses – may reduce risk of colon cancer

Question 24

negative physiological effects of aspirin 3

Answer 24

1. irritation, even dev of ulcers in stomach, duodenum – possible bleeding
2. large no. of ppl esp. asthma – allergic to aspirin
3. linked to Reye’s syndrome in children under 12 (liver + brain disorder, po. fatal)