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Questions and Answers
What is the primary function of the apicoplast in Plasmodium?
What is the primary function of the apicoplast in Plasmodium?
Plasmodium species are exclusively found in humans.
Plasmodium species are exclusively found in humans.
False
Name one of the five secretory/structural organelles that make up the apical complex in Plasmodium.
Name one of the five secretory/structural organelles that make up the apical complex in Plasmodium.
Rhoptries
The life cycle of Plasmodium involves three distinct processes: sporogony, merogony, and __________.
The life cycle of Plasmodium involves three distinct processes: sporogony, merogony, and __________.
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Match the following Plasmodium species with their associated characteristics:
Match the following Plasmodium species with their associated characteristics:
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Which of the following structures contributes to the attachment and invasion of host cells by Plasmodium?
Which of the following structures contributes to the attachment and invasion of host cells by Plasmodium?
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The rhoptries and micronemes are expelled into the host cytoplasm during the invasion process.
The rhoptries and micronemes are expelled into the host cytoplasm during the invasion process.
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The __________ network of microtubules is involved in the motility of the Plasmodium parasite.
The __________ network of microtubules is involved in the motility of the Plasmodium parasite.
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What is the process by which sporozoites reproduce in liver cells?
What is the process by which sporozoites reproduce in liver cells?
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Hypnozoites are only formed in P. malariae and P. vivax.
Hypnozoites are only formed in P. malariae and P. vivax.
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What causes the cyclic pattern of fever and chills known as malarial paroxysms?
What causes the cyclic pattern of fever and chills known as malarial paroxysms?
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The ___________________ stage occurs when the hypnozoites are reactivated, leading to a recurrence of disease symptoms.
The ___________________ stage occurs when the hypnozoites are reactivated, leading to a recurrence of disease symptoms.
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Match the following malaria stages with their characteristics:
Match the following malaria stages with their characteristics:
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Which of the following symptoms is NOT associated with malaria?
Which of the following symptoms is NOT associated with malaria?
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Merozoites are present in the blood for an extended period before infecting red blood cells.
Merozoites are present in the blood for an extended period before infecting red blood cells.
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What type of macrophages are Kupffer cells?
What type of macrophages are Kupffer cells?
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The __________________ phase begins when microgametes and macrogametes fuse in the mosquito.
The __________________ phase begins when microgametes and macrogametes fuse in the mosquito.
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What enhances the attraction of Anopheles mosquitoes to infected hosts?
What enhances the attraction of Anopheles mosquitoes to infected hosts?
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What is one of the consequences of renal failure caused by infected RBCs?
What is one of the consequences of renal failure caused by infected RBCs?
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Premunition indicates that a pre-existing infection can protect against newly arriving conspecifics.
Premunition indicates that a pre-existing infection can protect against newly arriving conspecifics.
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What is the role of heme in the action of chloroquine against malaria parasites?
What is the role of heme in the action of chloroquine against malaria parasites?
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As kidney function declines, urine output is reduced, leading to ______ or sometimes anuria.
As kidney function declines, urine output is reduced, leading to ______ or sometimes anuria.
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Match the following terms related to malaria to their definitions:
Match the following terms related to malaria to their definitions:
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Which of the following describes a method to reduce malaria transmission?
Which of the following describes a method to reduce malaria transmission?
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Older individuals are more likely to exhibit high parasitemia.
Older individuals are more likely to exhibit high parasitemia.
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What mutation allows malaria parasites to develop resistance to chloroquine?
What mutation allows malaria parasites to develop resistance to chloroquine?
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Hemoglobin released from destructed RBCs appears in the urine, as kidneys cannot filter urine, leading to ______.
Hemoglobin released from destructed RBCs appears in the urine, as kidneys cannot filter urine, leading to ______.
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What is the main action of artemisinin in the treatment of malaria?
What is the main action of artemisinin in the treatment of malaria?
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What is the typical duration of the hot stage in malaria symptoms?
What is the typical duration of the hot stage in malaria symptoms?
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TNF-alpha is considered an anti-inflammatory cytokine.
TNF-alpha is considered an anti-inflammatory cytokine.
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What are the symptoms of severe malaria?
What are the symptoms of severe malaria?
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Malarial paroxysm cycles for Vivax and Ovale occur every ____ hours.
Malarial paroxysm cycles for Vivax and Ovale occur every ____ hours.
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Match the following complications of malaria with their descriptions:
Match the following complications of malaria with their descriptions:
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Which species of malaria is considered the most pathogenic?
Which species of malaria is considered the most pathogenic?
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PfEMP1 proteins allow infected red blood cells to bind to endothelial walls.
PfEMP1 proteins allow infected red blood cells to bind to endothelial walls.
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What do merozoites produce to evade the host's immune response?
What do merozoites produce to evade the host's immune response?
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The enzyme ______ neutralizes toxic heme into harmless hemozoin crystals during the digestion of hemoglobin.
The enzyme ______ neutralizes toxic heme into harmless hemozoin crystals during the digestion of hemoglobin.
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Which process leads to the increased metabolic demand of infected erythrocytes?
Which process leads to the increased metabolic demand of infected erythrocytes?
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Rosetting refers to the binding of infected RBCs to each other.
Rosetting refers to the binding of infected RBCs to each other.
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What is the role of PTEX in Plasmodium-infected erythrocytes?
What is the role of PTEX in Plasmodium-infected erythrocytes?
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The cycle of malaria infection typically manifests every ____ hours for the malaria species Plasmodium malariae.
The cycle of malaria infection typically manifests every ____ hours for the malaria species Plasmodium malariae.
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Which of the following processes describes the destruction of erythrocytes leading to jaundice in severe malaria?
Which of the following processes describes the destruction of erythrocytes leading to jaundice in severe malaria?
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Study Notes
Plasmodium and Malaria
- Phylum Apicomplexa: Includes Plasmodium, Cryptosporidium, Toxoplasma, Babesia, among others. Majority are obligate intracellular parasites, except Cryptosporidium.
- Likely evolved from predatory flagellates/dinoflagellates. Retained apicoplast (chloroplast remnant) acquired by secondary endosymbiosis.
- Apicoplast is crucial for parasite survival; involved in host cell invasion and nutrient synthesis.
- Apical complex (apical organelles): used for attachment and invasion of host cells.
- Apical complex structure: Polar ring (unknown function), Conoid (spiral microtubules), Rhoptries (secretory, anterior), Micronemes (small, connect to rhoptries), Subpellicular microtubule network.
- Rhoptries and micronemes are involved in host RBC invasion; other organelles' functions less well understood.
- Plasmodium life cycle: Sporogony, Merogony, Gametogony.
Plasmodium Life Cycle
- Sporogony (in mosquito): Development of sporozoites in mosquito's gut.
- Merogony (in liver and red blood cells): Asexual reproduction involving schizonts (multinucleated cells). Formation of merozoites (infectious forms).
- Gametogony (in red blood cells): Some merozoites differentiate into sexual forms: microgametes (flagellated) and macrogametes (larger).
Host Cell Invasion Mechanism
- Apical end attaches to host cell; rhoptries, micronemes, and dense granules are expelled into host cytoplasm.
- Micronemal adhesins (TRAP, EGF-like, APPLE domains, lectin) facilitate attachment. Examples: Plasmodium vivax - Duffy binding protein, Plasmodium falciparum - erythrocyte binding antigen (EBA).
- Subpellicular microtubule network involved in parasite motility, active invasion.
- Parasitophorous vacuole (PVM) encapsulates parasite, derived from parasite and host cell membrane. PVM ruptures before merozoite release.
Human Malaria
- Caused by 6 Plasmodium species infecting humans: P. falciparum, P. vivax, P. malariae, P. ovale curtisi, P. wallikeri, P. knowlesi.
- Four main stages of the Plasmodium life cycle in humans:
- Liver stage: Sporozoites enter liver cells (hepatocytes), undergo asexual reproduction (exoerythrocytic schizogony). Merozoites enter bloodstream.
- Blood stage: Merozoites infect red blood cells (RBCs); develop into ring stages and trophozoites, ingest Hb. Produces hemozoin. Asexual reproduction (schizogony) until merozoites release into blood, inducing paroxysms
- Sexual stage: Some merozoites differentiate into gametocytes (micro and macro). Travel in blood until consumed by mosquito.
- Sporogony (in mosquito): Zygotes develop into ookinetes, penetrate mosquito gut wall to form oocysts. Sporozoites develop and migrate to the mosquito's salivary glands.
- Vector transmission: Anopheles mosquitoes. Infected hosts attract anopheles by releasing HMBPP and increased CO2, aldehydes and monoterpenes from erythrocytes.
- Hypnozoite stage: Dormant forms in liver (P. vivax, P. ovale); can cause relapses.
- Recrudescence: Recurrence of disease in an existing infection due to immune inadequacy or suboptimal drug treatment.
- Clinical manifestations: Flu-like symptoms, fever, muscle pain, anorexia, nausea, malarial paroxysms (chills, fever, sweats). Severe cases include anemia, respiratory stress, hypoglycemia, renal failure, and coma.
Plasmodium falciparum: Pathogenesis
- Invades all RBC stages, particularly reticulocytes.
- Sequestration of infected RBCs (to blood vessel walls) limits immune system response.
- Produces PfEMP1 proteins with variable (antigenic variation) structures binding diverse host receptors, enabling sequestration and rosetting of red blood cells.
- Knob formation (PfEMP1) on infected RBC surface for enhanced cytoadherence to blood vessels. This can lead to severe disease like cerebral malaria.
Plasmodium Pathogenesis: Mechanisms
- Severe malarial anemia: Destruction of erythrocytes, bilirubin formation, jaundice, hemozoin accumulation, impaired immunity, decreased iron recycling.
- Host inflammatory response: Sequestration causes impaired blood flow, resulting in hypoperfusion, ischemia, and hypoxia in organs like the brain. Cytokines (e.g., TNF-α) contribute to fever and pathogenesis.
- Renal failure: Infected RBCs can block kidney capillaries, leading to acute tubular necrosis. Released Hb appears in urine (blackwater fever).
Immunity and Resistance
- Limited long-term immunity in endemic regions.
- Immune responses are slow to develop. Factors like sickle-cell anemia, ovalocytosis, Duffy-negative status, thalassemia, and G6PD deficiency can confer resistance.
Drug Resistance
- Chloroquine acts by preventing heme detoxification; resistance arises in the PfCRT protein, which pumps chloroquine out.
- Antimalarial drug targets include asexual parasites (chloroquine), hypnozoites (primaquine/tafenoquine), and gametocytes (gametocides).
Epidemiology and Control
- Malaria transmission depends on human and animal reservoirs, vectors (Anopheles species), new host populations, and environmental factors.
- Control strategies include vector control, mosquito nets, and antimalarial drugs. Mosquito control and vaccine development (Mosquirix) are also crucial.
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Description
Explore the fascinating world of Plasmodium, the parasite responsible for malaria. This quiz covers its life cycle, evolutionary background, and unique structures that facilitate host invasion. Test your knowledge on the biology and ecology of this important organism.
