Parasite Biochemistry Flashcards
State the significance of the Duffy antigen in relation to malaria.
The Duffy antigen is a protein found on the surface of red blood cells, endothelial cells, and epithelial cells. It serves as a receptor for the malaria parasites Plasmodium vivax and Plasmodium knowlesi.
What is the essence of hemozoin formation in plasmodium?
◾ Plasmodium breaks down haemoglobin in red blood cells for nutrients.
◾ Haemoglobin breaks down into heme, a toxic molecule.
◾ To detoxify heme, the parasite converts it to hemozoin, an inert crystalline substance.
enzyme that converts haem to haemozoin in plasmodium
haem polymerase
Explain the mechanism of action of chloroquine.
Chloroquine inhibits the enzyme haem polymerase, which is responsible for converting haeme to haemozoin. This leads to accumulation of toxic haeme within the parasite.
All the following are parasitic protozoa except ________.
(a) Trypanosoma cruzi
(b) Ascaris lumbricoides
(c) Leishmania donovani
(d) Giardi intestinalis
(e) Trichomonas vaginalis
(b) Ascaris lumbricoides
Which of the following is not a protozoan parasite?
(a) Plasmodium knowlesi
(b) Trichomonas vaginalis
(c) Trypanosoma brucei
(d) Ascarissuum
(e) Leishmania donovani
(d) Ascarissuum
A product of haemoglobin catabolism in Plasmodium is ________.
(a) Hemozoin
(b) Bilirubin
(c) Biliverdin
(d) Albumin
(e) Bilirubin diglucuronide
(a) Hemozoin
The following are protozoan parasites, except ________.
(a) Trypanosoma brucei
(b) Fasciola hepatica
(c) Plasmodium falciparum
(d) Leishmania donovani
(e) Trichomonas vaginalis
(b) Fasciola hepatica
Explanation:
Fasciola hepatica, commonly known as the common liver fluke or sheep liver fluke, is a parasitic flatworm that primarily infects the livers of various mammals, including humans.
Which one of the following is an infective stage of the Plasmodium life cycle?
(a) Ring
(b) Gametocyte
(c) Merozoite
(d) Trophozoite
(e) Schizont
(c) Merozoite
The following are some of the end products of carbon dioxide fixation in Plasmodium except ________.
(a) alanine
(b) proline
(c) glutamate
(d) aspartate
(e) citrate
(b) proline
Which of the following is the major product of the pentose phosphate pathway in plasmodium?
(a) lactate
(b) proline
(c) pyruvate
(d) ribose-5-phosphate
(e) 3-Phosphoglycerate
(d) ribose-5-phosphate
Which of the following is not a protozoan parasite?
(a) Schistosoma mansoni
(b) Trichomonas
(c) Trypanosoma brucei
(d) Leishmania donovani
(e) Plasmodium falciparum
(a) Schistosoma mansoni
Plasmodium cannot grow and reproduce in individuals with sickle cell disease because,
(a) Erythrocytes have a low oxygen binding capacity.
(b) Haemoglobin S is only one amino acid different from haemoglobin A.
(c) The parasite has a very active aerobic metabolism.
(d) The parasite does not like the blood of sickle cell individuals.
(e) The parasite relies squarely on anaerobic metabolism.
(f) Pyrimidine synthesis by the parasite does not require the presence of folates.
(a) Erythrocytes have a low oxygen binding capacity.
Which one of the following statements is true regarding haemoglobin degradation in plasmodium food vacuole?
(a) Haemozoin is a soluble product of haem degradation.
(b) Chloroquine inhibits haemozoin formation.
(c) Haemozoin formation occurs in the food vacuoles of both parasites and the human host.
(d) The parasite can utilize the haem released from the host haemoglobin degradation for its biosynthetic functions.
(e) The products of haemoglobin digestion in the parasites’ food vacuoles are generally non-toxic to the parasites.
(b) Chloroquine inhibits hemozoin formation.
Which one of the following represents the form of plasmodium that is released from the erythrocyte by lysis?
(a) Trophozoites
(b) Schizont
(c) Merozoite
(d) Macrogametocyte
(e) Microgametocyte
(c) Merozoite
[Diagram]
Presence of Duffy antigen on host RBCs
(a) Provides resistance against Plasmodium vivax
(b) Provides resistance against Plasmodium falciparum
(c) Allows infection with Plasmodium vivax
(d) Allows infection with Plasmodium falciparum
(e) None of the above
(c) Allows infection with Plasmodium vivax
The major role of variant surface glycoprotein (VSG) in trypanosomes is to ________.
(a) help escape the host’s immune system
(b) provide a surface for attachment to host antibodies
(c) increase the permeability of nutrients required by the parasite
(d) reduce the duration of infection
(e) make them more susceptible to antibody mediated lysis
(a) help escape the host’s immune system
African trypanosomes evade the immune system through ________.
(a) cleavage of antibodies by proteolytic enzymes
(b) intracellular sequestration
(c) antigen mimicry
(d) antigen variation
(e) none of the above.
(d) antigen variation
The following are true regarding energy metabolism in trypanosomatides, except
(a) glycolysis occurs in specialized organelles known as glycosomes
(b) glycolytic enzymes are not subject to allosteric regulation
(c) NADH produced in the glycosomes is used to reduce dehydoxyacetone phosphate to glycerol-3-phosphate
(d) A net of 8 ATPs are produced by the oxidation of glucose via glycolysis
(e) The parasite species and stage influences energy metabolism in trypanosomatidae
(d) A net of 8 ATPs are produced by the oxidation of glucose via glycolysis
Which of the following is true about visceral leishmaniasis?
(a) affects internal organs
(b) is also called kala azar
(c) is transmitted by the bite of infected female sandflies
(d) all of the above
(e) none of the above
(d) all of the above
Which of the following compounds is not a precursor of de novo pyrimidine synthesis in parasitic protozoa?
(a) aspartate
(b) carbon dioxide
(c) formate
(d) pyruvate
(e) glutamine
(d) pyruvate
The following statements are true regarding folate metabolism in parasitic protozoans and human beings except
(a) Folate and its derivatives mediate methyl group transfer reactions.
(b) Mammalian cells do not synthesize folate moiety de novo.
(c) Folate and its derivatives are required in high demands for nucleotide biosynthesis in actively dividing cells of humans.
(d) The precursor for folate biosynthesis include GTP, para-aminobenzoic acid and glutamate.
(e) The presence of sulfur based drugs like sulfodoxine increase the activity of dihydrofolate reductase enzymes.
(e) The presence of sulfur based drugs like sulfodoxine increase the activity of dihydrofolate reductase enzymes.
Explanation:
Sulfur-based drugs like sulfadoxine are a type of antimicrobial agent known as sulfonamides. These drugs interfere with bacterial growth by targeting the folate synthesis pathway. They act by inhibiting an enzyme in the folate pathway called dihydropteroate synthase, which is necessary for the synthesis of dihydrofolic acid.
Regarding plasmodial metabolism
(a) The parasite depends on both salvage and de novo pathways for purine nucleotide metabolism.
(b) The parasite can utilize preformed pyrimidines for nucleic acid synthesis.
(c) The parasite uses different types of purine and pyrimidine bases compared to those used by the mammalian host.
(d) Hypoxanthine is the primary purine salvaged by the parasite.
(e) Pyrimidine synthesis by the parasite does not require the presence of folates.
(d) Hypoxanthine is the primary purine salvaged by the parasite.
The following statements are true regarding carbohydrate metabolism in malarial parasite, except;
(a) The bloodstream parasite depends on anaerobic metabolism for energy generation.
(b) Lactate is the end product of glucose catabolism.
(c) Malarial parasite infected RBCs have a large requirement for glucose than uninfected RBCs.
(d) The bloodstream parasites depend on the pentose phosphate pathway for energy generation.
(e) The TCA cycle and the electron transport chain are non-functional in the blood stream stages.
(d) The bloodstream parasites depend on the pentose phosphate pathway for energy generation.
Explanation:
While malarial parasites do have a pentose phosphate pathway (PPP), it’s not their primary source of energy generation in the bloodstream stages. The PPP is crucial for producing NADPH (for antioxidant defense) and ribose-5-phosphate (for nucleotide synthesis), but the bloodstream forms of the parasite rely heavily on anaerobic glycolysis for their ATP production.
The following statements are true regarding parasite metabolism, except
(a) Enzymes and their metabolites are highly conserved.
(b) Possess most metabolic pathways that are present in the mammalian host.
(c) Generally rely on the metabolism of the host both for supply of preformed components.
(d) Can possess genetic capacity to induce many pathways when needed.
(e) Have developed complex mechanisms for their survival in the host.
(b) Possess most metabolic pathways that are present in the mammalian host.
In the hydrogenosome, pyruvate is converted to the following compounds except ________.
(a) hydrogen
(b) malate
(c) CO2
(d) acetate
(e) glycerol
(b) malate
(e) glycerol
Under anaerobic conditions in the hydrogenosome, ________ serves as the terminal electron acceptor of electrons.
(a) hydrogen
(b) O2
(c) acetate
(d) H+
(e) CO2
(d) H+
The glycosome ________.
(a) is an organelle in human beings
(b) is found in all parasitic protozoa
(c) plays a major role in carbohydrate metabolism
(d) contains all enzymes of glucose catabolism
(e) has no membrane
(c) plays a major role in carbohydrate metabolism
The compound preferred by P. falciparum in purine salvage pathway is ________.
(a) hypoxanthine
(b) cytosine
(c) inosine
(d) glutamine
(e) aspartate
(a) hypoxanthine
Trichomonas vaginalis oxidative decarboxylation of pyruvate to acetyl CoA is catalysed by ________.
(a) pyruvate dehydrogenase
(b) pyruvate:ferredoxin oxidoreductase
(c) pyruvate phosphate dikinase
(d) alcohol dehydrogenase
(e) pyruvate decarboxylase
(b) pyruvate:ferredoxin oxidoreductase
Which of the following statements is true about Sulfadoxine?
(a) Sulfadoxine inhibits the formation of toxic reactive oxygen species
(b) Sulfadoxine inhibits the formation of β-hematin.
(c) Resistance to Sulfadoxine is mediated by removal or inactivation of the drug.
(d) Sulfadoxine inhibits dihydropteroate synthase in de novo synthesis of tetrahydrofolate.
(e) Mechanism of resistance involves ABC type transporters.
(d) Sulfadoxine inhibits dihydropteroate synthase in de novo synthesis of tetrahydrofolate.
The following are haemoglobin catabolism products in humans except ________.
(a) biliverdin
(b) bilirubin diglucuronide
(c) β-hematin
(d) bilirubin
(e) haem
(c) β-hematin
The following statements are true about the drug chloroquine, except
(a) Resistance to Chloroquine is mediated by removal or inactivation of the drug
(b) Chloroquine inhibits the formation of toxic reactive oxygen species
(c) Chloroquine is antimalarial drug
(d) Mechanism of resistance involves ABC type transporters
(e) Chloroquine inhibits the formation of β-hematin
(b) Chloroquine inhibits the formation of toxic reactive oxygen species
Explanation:
One of the main mechanisms of chloroquine resistance involves mutations in the pfmdr1 gene, which encodes a transporter protein (P-glycoprotein). This transporter pumps chloroquine out of the parasite’s food vacuole, reducing its effectiveness. The P-glycoprotein is an ABC transporter. [The name “ABC” comes from the fact that these transporters have a specific region called the “ATP-binding cassette” that binds and hydrolyzes ATP (adenosine triphosphate), the cell’s energy currency.]
Which of the following compounds is not a precursor of de novo pyrimidine synthesis in parasitic protozoa?
(a) glutamine
(b) formate
(c) carbon dioxide
(d) lactate
(e) aspartate
(d) lactate
Niridazole is antihelminthic drug which targets the metabolism of ________.
(a) glucose
(b) amino acids
(c) lipids
(d) folic acid
(e) glycogen
(e) glycogen
Which one of the following parasites is a helminth?
(a) Trichomonas vaginalis
(b) Schistosoma mansoni
(c) Leishmania donovani
(d) Trypanosoma brucei
(e) Plasmodium knowlesi
(b) Schistosoma mansoni
Levamisole is an antihelminthic drug which targets the metabolism of ________.
(a) folic acid
(b) glucose
(c) glycogen
(d) nucleic acids
(e) amino acids
(b) glucose
Which of the following enzymes of the glycolytic pathway in Fasciola hepatica is inhibited by Clorsulon?
(a) hexokinase
(b) phosphofructokinase 1
(c) phosphoglycerate kinase
(d) glyceraldehyde-3-phosphate dehydrogenase
(e) pyruvate kinase
(b) phosphofructokinase 1
The following statements are true about glucose-6-phosphate dehydrogenase except:
(a) glucose-6-phosphate dehydrogenase is present in Plasmodium
(b) Plasmodium glucose-6-phosphate dehydrogenase has higher affinity for substrate than does the host enzyme
(c) glucose-6-phosphate dehydrogenase protects against falciparum malaria
(d) product of glucose-6-dehydrogenase reduces glutathione
(e) glucose-6-phosphate dehydrogenase is not required in the pentose phosphate pathway
(e) glucose-6-phosphate dehydrogenase is not required in the pentose phosphate pathway
