L13 Flashcards
What is the definition of a parasite?
A parasite is an organism that lives on or in another species (host) and relies on the host for nutrition and reproduction.
How does chloroquine act as an antimalarial drug?
Chloroquine becomes protonated in the parasite’s lysosome, preventing hemoglobin digestion. Resistance arises from mutations in transporter proteins.
What is the mechanism of action of quinine?
Quinine inhibits haem polymerase, causing toxic free haem accumulation in parasites.
How do benzimidazoles work as anthelmintics?
Benzimidazoles bind to β-tubulin, inhibiting its polymerization and interfering with glucose uptake in worms.
What is the mechanism of action of ivermectin?
Ivermectin opens glutamate-gated chloride channels, increasing Cl⁻ influx, causing paralysis of the parasite.
What is praziquantel used for, and how does it work?
Praziquantel treats schistosomiasis by activating calcium channels, causing paralysis, and enhancing immune recognition of the parasite.
What are the three main types of helminths?
Cestodes (tapeworms), nematodes (roundworms), and trematodes (flukes).
How does pyrimethamine work as an antimalarial drug?
Pyrimethamine inhibits folate metabolism by targeting dihydrofolate reductase in parasites.
What is piperazine’s mechanism of action as an anthelmintic?
Piperazine is a GABA receptor agonist that paralyzes worms, allowing them to be expelled alive.
Why is resistance a common issue in antiparasitic drugs?
Resistance arises from genetic mutations in parasite enzymes or transport proteins, reducing drug efficacy.
Discuss the life cycle of malaria and how antimalarial drugs target different stages of the parasite.
Malaria parasites (e.g., Plasmodium falciparum) infect liver cells and red blood cells (RBCs). Drugs like chloroquine act on parasites in RBCs by preventing hemoglobin digestion. Quinine inhibits haem polymerase, while pyrimethamine disrupts folate synthesis, essential for parasite DNA replication. Resistance remains a major challenge due to mutations in transporters and enzymes.
Describe the various mechanisms by which anthelmintic drugs act against parasitic worms.
Anthelmintics work by:
Paralysis: Piperazine activates GABA receptors, and ivermectin opens glutamate-gated chloride channels.
Cuticle damage: Drugs like praziquantel enhance immune recognition.
Metabolic interference: Benzimidazoles inhibit glucose uptake by binding β-tubulin. Each mechanism targets specific parasitic processes, causing their expulsion or death.
How do quinine and pyrimethamine differ in their mechanisms of action and resistance issues?
Quinine inhibits haem polymerase, leading to toxic haem buildup, while pyrimethamine inhibits dihydrofolate reductase, blocking DNA synthesis. Resistance to quinine involves efflux mechanisms, while pyrimethamine resistance arises from single-point mutations in the target enzyme.
What is the role of ivermectin in treating river blindness, and how does it work at the molecular level?
Ivermectin treats onchocerciasis (river blindness) by opening glutamate-gated chloride channels, increasing Cl⁻ influx, leading to paralysis of the nematode. Its specificity for invertebrates minimizes human toxicity. Resistance may occur through mutations in chloride channels.
Compare the actions of praziquantel and piperazine in treating parasitic infections.
Praziquantel treats flukes by activating calcium channels, causing paralysis and enhanced immune detection. Piperazine targets roundworms by acting as a GABA receptor agonist, causing muscle relaxation and expulsion. Both drugs are effective but have specific parasite targets and mechanisms.
