Consider statements about human immunity: 1. Innate immunity is non-specific. 2. Acquired immunity is specific. 3. Secondary immune response is weaker than primary. Which are correct? MCQ with Answer and Explanation

Question

Consider statements about human immunity: 1. Innate immunity is non-specific. 2. Acquired immunity is specific. 3. Secondary immune response is weaker than primary. Which are correct?

A. 1 and 2 only

B. 1, 2 and 3

C. 1 and 3 only

D. 2 and 3 only

Answer: Option A

Solution (By JKExamLibrary)

Innate immunity is the non-specific, inborn defense mechanism present from birth, providing immediate but general protection against pathogens. Acquired (adaptive) immunity is highly specific, targeting particular antigens and developing memory. The secondary immune response, occurring upon re-exposure to the same antigen, is much faster, stronger, and more prolonged than the primary response due to the presence of memory cells. Thus, statements 1 and 2 are correct.

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Question #1

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Typhoid fever is caused by which bacterium?

A. Mycobacterium leprae

B. Salmonella typhi

C. Vibrio cholerae

D. Streptococcus pneumoniae

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Correct Answer: Option B

Explanation:
Typhoid fever is a life-threatening systemic infection caused by the bacterium Salmonella typhi. It is transmitted through contaminated food and water. Symptoms include sustained high fever, headache, abdominal pain, and sometimes a rash. The Widal test is a common diagnostic test for typhoid. S. pneumoniae causes pneumonia, and V. cholerae causes cholera.

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Question #2

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Which of the following is a defining feature of prokaryotic cells?

A. Presence of 70S ribosomes only

B. Linear chromosomes

C. Absence of cell wall

D. Presence of membrane-bound nucleus

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Correct Answer: Option A

Explanation:
Prokaryotic cells lack a true nucleus; their genetic material is located in a nucleoid region. They possess 70S ribosomes (50S+30S subunits), whereas eukaryotic cells have 80S ribosomes. Prokaryotes generally have a cell wall (except Mycoplasma) and circular DNA, not linear. Membrane-bound organelles like mitochondria, ER are absent. Examples: bacteria and blue-green algae. This distinction is fundamental in cell biology.

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Question #3

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Which part of the brain regulates body temperature, hunger, and thirst?

A. Hypothalamus

B. Medulla oblongata

C. Pons

D. Cerebellum

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Correct Answer: Option A

Explanation:
The hypothalamus is a small region in the forebrain that maintains homeostasis by regulating body temperature, hunger, thirst, sleep, and emotions. It also controls pituitary gland secretions. The cerebellum coordinates movement, medulla controls respiration and heart rate, pons relays signals. Hypothalamus acts as the body's thermostat and the link between nervous and endocrine systems.

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