Protozoa Flashcards
Category 7 (18 cards)
Briefly contrast protozoans with bacteria, highlighting key differences in cellular structure and size.
Protozoans: Eukaryotic, unicellular organisms that can range in size from 1 µm to several cm.
Bacteria: Prokaryotic, unicellular organisms, and are typically much smaller, averaging around 2 μm in length.
Explain the significance of sexual reproduction in protozoa, even if the process is complex or not fully understood in all species.
Sexual reproduction enhances ability of protozoa to adapt to changing environmental conditions.
This is crucial for survival, especially when facing immune responses or drug treatments.
Describe the four major classes of protozoa based on motility, and provide an example of a disease-causing organism from each class.
except class D
A: Flagellates (Giardia lamblia cause diarrhoea),
B: Amoebae (Entamoeba histolytica cause amoebic dysentery).
C: Sporozoans (Plasmodium, malaria).
D: Ciliates.
How do amoebae move, and what is their primary method of reproduction?
Using pseudopods (temporary projections of the cell membrane).
Binary Fission
What is unique about sporozoans compared to other protozoan classes in terms of motility?
Sporozoans generally lack cilia or flagella for movement, except in their sexual phase. They are often capable of gliding movements.
Describe two unique features of ciliates in terms of physical characteristics or survival.
- Presence of cilia (small hair-like structures surrounding their body) which beat in a synchronised pattern to cause movement.
- Contractile vacuoles to regulate water balance.
Name the primary and secondary hosts of Toxoplasma gondii.
Primary Hosts: Members of the family Felidae (cats).
Secondary Hosts Most species of warm-blooded animals, including humans.
Outline the three forms that Toxoplasma gondii exists in nature, and briefly describe each one.
- Oocyst (which releases sporozoites).
- Tachyzoite (a rapidly dividing form).
- Tissue Cyst (containing bradyzoites).
Describe, in general terms, how toxoplasmosis is diagnosed and treated.
Diagnosis: Serological tests, such as ELISA, which detect Toxoplasma-specific antibodies in the blood.
Treatment: Primarily targets the tachyzoite stage, combination of drugs, such as pyrimethamine, sulfadiazine, and folinic acid. Treatment priority for immunocompromised individuals or pregnant women.
Describe the key differences between uncomplicated and severe malaria, focusing on the symptoms and organ involvement.
Uncomplicated Malaria
Cyclical fever, chills, sweats, headache, and muscle aches.
Severe Malaria
Involves organ failure / abnormalities in blood, such as cerebral malaria (neurological symptoms), severe anaemia, respiratory distress, or kidney failure.
A medical emergency requiring immediate, aggressive treatment due to the risk of death.
Outline the two hosts involved in the malaria parasite life cycle, specifying the stage of the parasite present in each.
Humans: Sporozoites are injected by the mosquito and infect the liver, developing into merozoites that then infect red blood cells.
Female Anopheles Mosquitoes: Gametocytes ingested from an infected human undergo sexual reproduction, eventually producing sporozoites in the salivary glands.
Explain why Plasmodium parasites favour erythrocytes as host cells.
Erythrocytes lack MHC molecules on their surface. Infected erythrocytes are less easily detected and destroyed by the host’s immune system, providing a safe haven for parasite replication.
What is the significance of antigenic variation in the context of Plasmodium falciparum infection, and how is Pf-EMP1 involved?
Crucial for Plasmodium falciparum to evade the host’s immune system. Pf-EMP1 (Plasmodium falciparum Erythrocyte Membrane Protein 1) is a variant surface antigen displayed on infected red blood cells, allowing them to adhere to blood vessel walls. This cytoadherence prevents splenic clearance, and because Pf-EMP1 structure varies, the parasite can escape detection by pre-existing antibodies.
Detail the symptoms of malaria in 16th-18th Century England.
Characterised by high infant mortality. Common symptoms were fever, chills, and sweats.
How do artemisinin-based combination therapies (ACTs) work to combat malaria, and what is a major challenge in their implementation?
Artemisinin reduces parasite biomass.
It is combined with another antimalarial drug that has a longer half-life to eliminate remaining parasites.
Major Challenge: High cost, limiting access in resource-poor settings.
Explain how sickle-cell anaemia provides resistance to malaria.
Altered red blood cells are less conducive to parasite development. The premature destruction of infected sickle cells by the spleen reduces the parasite load and severity of the infection.
Outline the steps in the erythrocytic stage of the malaria life cycle within a human host.
Merozoites released from the liver infect red blood cells. Merozoites develop into ring-stage trophozoites in human erythrocytes, which then mature into schizonts. The schizonts rupture, releasing more merozoites to infect additional red blood cells, continuing the cycle. Some parasites differentiate into gametocytes, the sexual stage that can be ingested by mosquitoes.
Name the different stages of the malaria parasite that infect the human liver and red blood cells.
The sporozoites infect the liver, where they develop into merozoites. Once released from the liver, merozoites infect red blood cells and differentiate into trophozoites.
