All Free Biology MCQs with Answers

2471. Interferons are synthesized in response to :

• A. Mycoplasma
• B. Bacteria
• C. Viruses
• D. Fungi

Explanation: Interferons are proteins that increase a cell's resistance to viral attacks by unmasking genes that synthesize antiviral proteins. In humans, three groups of interferons have been discovered: a) interferons from white blood cells; b) interferons from connective tissue fibroblasts; and c) interferons from lymphocytes.

2472. Reason of lung cancer is :

• A. Coal mining
• B. Calcium fluoride
• C. Cement factory
• D. Bauxite mining

Explanation: Lung cancer is a disease where lung tissue grows out of control. This may lead to metastasis, invasion of adjacent tissue, and infiltration beyond the lungs. The vast majority of primary lung cancers are carcinomas of the lung, resulting from epithelial cells. One of the causes of lung cancer is exposure to coal dust. Exposure to coal dust can cause some coal mine workers to develop pneumoconiosis, or "black lung." This occurs when inhaled coal dust becomes embedded in the lungs, causing them to harden and making breathing difficult.

2473. Which is showing accurate pairing?

• A. Syphilis, Treponema pallidum
• B. AIDS, Bacillus conjugalis
• C. Gonorrhoea, Leishmania donovani
• D. Typhoid, Mycobacterium leprae

Explanation: Syphilis is caused by a spirochete (spiral bacterium) called Treponema pallidum. The symptoms of syphilis occur in three stages. The first stage usually consists of a painless lesion called a chancre at the organism's site of entry. The second stage begins when the organism enters the bloodstream. Symptoms such as fever, flu-like illness, a skin rash, hair loss, and swollen joints may come and go over a period of several years. In the third stage, permanent brain damage, heart disease, and blindness often occur. AIDS is a viral disease caused by the Human Immunodeficiency Virus (HIV). Gonorrhea is a sexually transmitted disease, and its causative organism is Neisseria gonorrhoeae. Typhoid is caused by the bacillus bacterium Salmonella typhi.

2474. Which disease of man is similar with cattle's, bovine spongiform encephalopathy?

• A. Encephalitis
• B. Jakob Cruetzfeldt disease
• C. Spongiocitis of cerebrum
• D. Spondylitis

Explanation: The common term for bovine spongiform encephalopathy is mad cow disease, which is a progressive neurological disorder in cattle. In humans, it is called Creutzfeldt-Jakob disease, named after the two doctors who first described its symptoms. It is caused by prions (proteinaceous infectious particles) and is characterized by rapidly progressive dementia associated with myoclonic jerks. The brains of affected individuals show characteristic cystic degeneration.

2475. Saline solution is given to patients of cholera because :

• A. Na+ prevents water loss from body
• B. NaCl function as regulatory material
• C. NaCl produces energy
• D. NaCl is antibacterial

Explanation: Cholera is an acute infection of the small intestine caused by the bacterium Vibrio cholerae, resulting in severe vomiting and diarrhea (known as rice-water stools) that leads to dehydration. The disease is contracted through the consumption of contaminated food or drinking water containing feces from an infected individual. The resulting dehydration and imbalance in the body's fluid concentration can lead to death within 24 hours. Since a significant amount of fluids and salts are rapidly lost through stools and vomiting, the most critical treatment involves rapidly replacing the lost fluids and salts. Rapid fluid and electrolyte replacement is achieved through oral rehydration therapy, with electrolytes comprising Na+ ions that help prevent water loss from the body.

2476. The antibodies are :

• A. Proteins
• B. Carbohydrates
• C. Lipids
• D. Germs

Explanation: Antibodies are members of a class of proteins known as immunoglobulins. Immunoglobulins are glycoproteins in the immunoglobulin superfamily. The terms 'antibody' and 'immunoglobulin' are often used interchangeably. They are found in blood and tissue fluids, as well as in many secretions. In terms of structure, they are globulins (in the region of protein electrophoresis). They are synthesized and secreted by plasma cells derived from the B cells of the immune system.

2477. The term 'active immunity' means :

• A. Increasing rate of heart beat
• B. Increasing quantity of blood
• C. Resistance developed after disease
• D. Resistance developed before disease

Explanation: Active immunity is the immune response generated in an individual due to contact with an infectious pathogen or vaccination. In many cases, it can last a lifetime.

2478. Typhoid fever is caused by :

• A. Shigella
• B. Escherichia
• C. Giardia
• D. Salmonella

Explanation: Typhoid is caused by Salmonella typhi. The organisms of the disease are present in the stool, and they may also be found in urine. Therefore, they can be carried by water and contaminated food, which can lead to severe epidemics. Polio is caused by Enterovirus. TB is caused by Mycobacterium tuberculosis. Tetanus is caused by Clostridium tetani.

2479. Botulism caused by Clostridium botulinum affects the :

• A. Lymph glands
• B. Central nervous system
• C. Spleen
• D. Intestine

Explanation: Clostridium is a genus of gram-positive bacteria. They are obligate anaerobes capable of producing endospores. Individual cells are rod-shaped. Foodborne disease caused by C. botulinum is referred to as botulism (a muscle-paralyzing disease). It is caused by the ingestion of a neurotoxin (botulinum) produced by the microorganism in the food. Botulinum blocks nerve function, leading to respiratory and musculoskeletal paralysis. Symptoms of botulism include weakness, fatigue, and dizziness, followed by blurred vision and progressive difficulty in speaking and swallowing. Weakening of the respiratory muscles is also observed, and death may occur due to respiratory failure.

2480. Which of the following is an opiate narcotic?

• A. Amphetamines
• B. LSD
• C. Barbiturates
• D. Morphine

Explanation: Opiates are derived from opium along with their synthetic relatives. Opiates have narcotic, analgesic, sedative, and astringent effects. A narcotic is a drug that induces stupor and relieves pain. Morphine is the main opium alkaloid, which is a strong analgesic and also has a sedative and calming effect. It depresses the respiratory center and contributes to the fall in blood pressure. It can cause the release of ADH, reduction in urine output, constipation, and mild hyperglycemia, among other effects. It also leads to addiction.Barbiturates are substituted derivatives of barbituric acid. They reduce anxiety and induce sleep. Amphetamines are synthetic drugs that act as strong stimulants. LSD (Lysergic acid diethylamide) is one of the most powerful hallucinogens, causing severe damage to the central nervous system.