8. Microorganisms
· General Science/Everyday Science
50 MCQs
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of 50 MCQs
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1
Tuberculosis (TB) is a contagious infection that usually attacks the lungs. It is caused by which type of pathogen?
Answer:
Bacterium
Tuberculosis is caused by the bacterium Mycobacterium tuberculosis. It is primarily an airborne disease spread through respiratory droplets. Unlike viral infections, TB can be treated with a specific course of antibiotics over several months to eradicate the bacterial population.
2
What happens during the 'Lytic Cycle' of a virus?
Answer:
The virus replicates and causes the host cell to burst
In the lytic cycle, a virus infects a host cell, immediately hijacks its machinery to mass-produce new viral components, assembles them into new viruses, and then causes the host cell to rupture (lyse) to release the offspring. This is contrasted with the lysogenic cycle, where the virus remains dormant.
3
Which microorganism is considered a 'biological bridge' between living and non-living things?
Answer:
Virus
Viruses are considered to be at the edge of life because they exhibit living characteristics only when they are inside a host cell (like replication and evolution). Outside a host, they are inert crystalline structures with no metabolism, making them seem non-living.
4
What is the primary method of locomotion for the protozoan 'Euglena'?
Answer:
Flagellum
Euglena is a flagellated protozoan that possesses a long, whip-like tail called a flagellum. By whipping the flagellum back and forth, the Euglena can pull itself through its aquatic environment. Interestingly, Euglena also contains chloroplasts and can perform photosynthesis.
5
What is the genetic material found inside a virus?
Answer:
Either DNA or RNA, but never both
Viruses are unique because their genome can consist of either DNA or RNA, which can be single-stranded or double-stranded. However, a single virus particle (virion) will only contain one type of nucleic acid. This is one of the primary criteria used to classify different families of viruses.
6
Which of the following protozoa causes 'Sleeping Sickness' and is transmitted by the tsetse fly?
Answer:
Trypanosoma
African Sleeping Sickness (Trypanosomiasis) is caused by the protozoan parasite Trypanosoma brucei. It is transmitted to humans through the bite of the tsetse fly. The parasite eventually enters the central nervous system, causing neurological symptoms and disrupted sleep patterns.
7
Which group of microorganisms is considered 'non-living' outside of a host cell because they cannot reproduce or carry out metabolism independently?
Answer:
Viruses
Viruses are often described as obligate intracellular parasites because they lack the machinery for independent metabolism and reproduction. They consist of genetic material (DNA or RNA) wrapped in a protein coat called a capsid and must infect a living host cell to replicate themselves.
8
Which protozoan is responsible for causing 'Malaria'?
Answer:
Plasmodium
Plasmodium is the genus of unicellular parasites that cause malaria. There are several species, with Plasmodium falciparum being the most deadly. They are transmitted by mosquitoes and spend part of their life cycle in the liver and red blood cells of humans.
9
Which type of bacteria are shaped like spirals or coils?
Answer:
Spirilla
Spirilla are bacteria with a rigid spiral shape. Another type of spiral bacteria, known as spirochetes, are more flexible. Bacilli are rods, and Cocci are spheres. Understanding these shapes helps scientists identify and classify bacteria during clinical diagnosis.
10
What is the extra-chromosomal, small circular DNA found in many bacteria that often carries genes for antibiotic resistance?
Answer:
Plasmid
Plasmids are small, circular, double-stranded DNA molecules that are distinct from a cell's chromosomal DNA. They can replicate independently and often carry 'advantageous' genes, such as those providing resistance to antibiotics, which can be transferred between bacteria through a process called conjugation.
11
Which of the following is NOT a viral disease?
Answer:
Tetanus
Tetanus is a bacterial disease caused by Clostridium tetani, which enters the body through wounds. It produces a toxin that causes painful muscle contractions (lockjaw). Mumps, Chickenpox, and Measles are all caused by different types of viruses.
12
In protozoa like Paramecium, what is the function of the contractile vacuole?
Answer:
Osmoregulation (expelling excess water)
Because many protozoa live in freshwater environments that are hypotonic to their cytoplasm, water constantly enters the cell via osmosis. The contractile vacuole acts as a pump, collecting this excess water and periodically contracting to expel it from the cell, preventing the organism from bursting.
13
Which microorganism is unicellular, eukaryotic, and widely used in the food industry for the fermentation of bread and alcoholic beverages?
Answer:
Yeast
Yeast is a unicellular fungus that carries out fermentation, a process that converts sugars into ethanol and carbon dioxide. In bread making, the carbon dioxide gas produced causes the dough to rise, while in brewing, the ethanol produced is the desired product for alcoholic drinks.
14
Which microorganism is responsible for the 'spoiling' of milk into curd through the production of lactic acid?
Answer:
Lactobacillus
Lactobacillus is a genus of Gram-positive, rod-shaped bacteria. They convert lactose (milk sugar) into lactic acid during fermentation. The increase in acidity causes milk proteins to coagulate, turning the liquid milk into solid curd or yogurt.
15
Which of the following structures is used by Amoeba for locomotion and capturing food?
Answer:
Pseudopodia
Amoeba move and feed using pseudopodia, or 'false feet,' which are temporary projections of the cytoplasm. By extending these projections, the organism can crawl along surfaces and surround food particles to engulf them through a process known as phagocytosis.
16
What is the defining characteristic of 'Eukaryotic' microorganisms like fungi and protozoa compared to 'Prokaryotic' bacteria?
Answer:
They have a membrane-bound nucleus
The fundamental difference between eukaryotes and prokaryotes is the presence of a membrane-bound nucleus. Eukaryotic cells (found in fungi, protozoa, plants, and animals) protect their DNA inside a nucleus and contain other specialized compartments like mitochondria, whereas prokaryotic cells (bacteria) do not.
17
The organism 'Paramecium' moves through water using tiny hair-like projections called:
Answer:
Cilia
Paramecium is a ciliated protozoan. Its cell surface is covered with thousands of short, hair-like structures called cilia. The coordinated beating of these cilia allows the Paramecium to swim rapidly through aquatic environments and also helps sweep food particles into its oral groove.
18
Which of the following is a symptom or disease caused by a fungal infection in humans?
Answer:
Ringworm
Ringworm is a common fungal skin infection characterized by a red, itchy, circular rash. Despite its name, it is not caused by a worm but by various types of fungi known as dermatophytes. Common cold and Polio are viral, while Typhoid is a bacterial infection.
19
Malaria is a life-threatening disease caused by parasites that are transmitted to people through the bites of infected female Anopheles mosquitoes. What type of microorganism causes Malaria?
Answer:
Protozoa
Malaria is caused by Plasmodium, which is a genus of unicellular eukaryotes belonging to the group Protozoa. These protozoans have complex life cycles involving both humans and mosquito hosts. They primarily attack red blood cells, leading to symptoms like fever, chills, and anemia.
20
Which of the following microorganisms is used to produce the antibiotic Penicillin?
Answer:
Penicillium (Fungus)
Penicillin, the first true antibiotic, was discovered by Alexander Fleming from a mold (fungus) named Penicillium notatum. This fungus produces the chemical as a defense mechanism to kill competing bacteria by preventing them from forming stable cell walls.
