medchem quiz corrections

what plant-derived compound was first used as an antiseptic

tannins

what property of willow extracts contributed to their use as early antipyretics and anti-inflammatory agents?

presence of salicylic acid

Which neurotransmitter's receptor does valerenic acid bind to, potentially influencing its sedative effects?

GABA

which component of valerian root is believed to have a calming effect on the nervous system?

valerenic acid

Taxol primarily affects which cellular component during cell division?

tubulin

Which compound is known to have a role in paralyzing the ciliary muscle during eye procedures?

atropine

What distinguishes alkaloids from other classes of phytochemicals?

low molecular weight and nitrogen content

What is the effect of an antagonist like atropine on the heart rate?

increases heart rate

what secondary metabolite might interfere with the neurotransmission process at GABA receptors?

valerenic acid

What secondary metabolite might interfere with the neurotransmission process at GABA receptors?

chloride channels open to allow chloride ions enter the neuron

The principle behind the separation of components using TLC is based on:

The affinity of compounds for the stationary and mobile phases

In Thin Layer Chromatography (TLC), what does a high Rf value indicate?

he compound moves rapidly with the mobile phase.

What type of information can IR spectroscopy provide?

The presence of specific functional groups

What can NMR spectroscopy reveal about a molecule?

Information about the dynamics of molecular interaction

In the chromatography process, what does the mobile phase refer to

The solvent that carries the sample through the stationary phase

what happens in TLC if the compound is soluble in the solvent

it will travel further up the TLC plate

The binding of BTX to Na⁺ channels is stabilized by

A cation-π interaction

[BTX’s protonated tertiary amine interacts with phenylalanine’s aromatic ring (cation-π)]

Which amino acid residue in Na⁺ channels interacts with BTX’s tertiary amine?

Phenylalanine

Local anesthetics (e.g., lidocaine) counteract BTX by

Competing for the same binding site

Why does BTX toxicity worsen at body temperature (37°C)?

Higher temperatures increase Na⁺ channel gating speed, exacerbating BTX effects.

The β-lactam ring in penicillin is essential for its antibiotic activity because it

Binds irreversibly to bacterial cell wall transpeptidases

Penicillin V is acid-resistant because

The amide side chain stabilizes the ring in acid

Ampicillin’s amino group enhances oral bioavailability by

Withdrawing electron density from the β-lactam ring

Atropine acts as a

Acetylcholine antagonist

(blocks muscarinic acetylcholine receptors, inhibiting parasympathetic activity)

Amides are used in drug design to

Add rigidity and hydrogen-bonding capacity

(Amides restrict rotation and participate in H-bonding)

Taxol’s mechanism of action involves

Stabilizing microtubules to block cell division

Grapefruit juice interacts with drugs by

Inhibiting intestinal CYP3A4

(Flavonoids in grapefruit juice inhibit CYP3A4, increasing drug bioavailability)

The primary site of hydrolysis by esterases in drug metabolism is

Blood plasma

The irreversible inactivation of bacterial enzymes by penicillin occurs via

Covalent bond formation with serine

Chloramphenicol’s broad-spectrum activity is due to its ability to

Target the large ribosomal subunit

Streptomycin inhibits bacterial growth by binding to

The 30S ribosomal subunit

Aminoglycoside-modifying enzymes confer resistance by

Chemically altering −OH or −NH₂ groups on the drug

Acyclovir is effective against herpes viruses because it

Inhibits viral DNA polymerase

Acyclovir’s selectivity for viral cells is due to

Activation by viral thymidine kinase

How does streptomycin differ from penicillin in its mechanism of action?

Streptomycin inhibits protein synthesis, while penicillin targets cell walls

Gram-positive bacteria retain the crystal violet stain because

Their thick peptidoglycan layer traps the dye

A mass spectrum showing a peak at m/z 180 (M⁺) and a smaller peak at m/z 182 (M+2) suggests the presence of

A chlorine atom

Aminoglycoside antibiotics are particularly effective against

Gram-negative bacteria and some anaerobes

what will gram-positive bacteria stain as

will retain primary stain and appear violet or purple

due to the thick layer of peptidoglycan

what will gram-negative bacteria stain as

will lose the primary stain and take up the counterstain

appears pink/red

what is chloramphenicol effective against

used to treat conjunctivitis

active against gram pos/neg bacteria and anaerobes

inhibits bacterial protein synthesis

Which structural feature makes cephalosporins more resistant to β-lactamases compared to penicillins

The presence of a 6-membered dihydrothiazine ring

Vancomycin inhibits bacterial cell wall synthesis by:

Binding to D-alanyl-D-alanine termini of peptidoglycan precursors

Macrolide antibiotics like erythromycin act by

Binding to the 50S ribosomal subunit