Which class of antibody is the most abundant in human blood plasma? MCQ with Answer and Explanation

Which class of antibody is the most abundant in human blood plasma?
A. IgM
B. IgA
C. IgG
D. IgE
Answer: Option C
Solution (By JKSSB Mock Tests)
Immunoglobulin G (IgG) is the most abundant antibody in human blood plasma, constituting about 75-80% of all antibodies. It is the only antibody that can cross the placenta, providing passive immunity to the fetus. IgG is crucial for long-term immunity, neutralizing toxins, viruses, and bacteria, and activating the complement system.

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Practice More Biology Questions

Question #1
Consider statements about human skin: 1. The epidermis is the outermost layer. 2. Sweat glands help in thermoregulation. 3. Melanin protects against UV radiation. Which are correct?
A. 2 and 3 only
B. 1 and 3 only
C. 1 and 2 only
D. 1, 2 and 3

Correct Answer: Option D


Explanation:
The skin consists of the outer epidermis and the inner dermis. The epidermis contains melanocytes that produce melanin, a pigment that absorbs harmful ultraviolet radiation, protecting deeper tissues. Sweat glands in the dermis secrete sweat onto the skin surface; its evaporation removes heat, playing a crucial role in body thermoregulation. All statements are correct.

This question belongs to: Science Biology
Question #2
The 'Widal test' is a diagnostic test used to detect the presence of antibodies against the causative agent of:
A. Dengue
B. Malaria
C. Tuberculosis
D. Typhoid fever

Correct Answer: Option D


Explanation:
The Widal test is a serological agglutination test used to diagnose enteric (typhoid) fever, caused by Salmonella enterica serotype Typhi. It detects the presence of specific antibodies (O and H antigens) in the patient's serum against the O (somatic) and H (flagellar) antigens of the Salmonella typhi bacteria. A significant rise in antibody titer indicates an active or recent infection. It is not used for TB (Mantoux test), malaria (blood smear), or dengue (NS1/IgM).

This question belongs to: Science Biology
Question #3
Which of the following is an example of a monounsaturated fatty acid?
A. Oleic acid
B. Linoleic acid
C. Linolenic acid
D. Stearic acid

Correct Answer: Option A


Explanation:
Oleic acid is a monounsaturated fatty acid (one double bond), found in olive oil. Stearic acid is saturated, linoleic acid is polyunsaturated (two double bonds), linolenic acid is polyunsaturated (three double bonds). Unsaturated fats are generally liquid at room temperature and healthier for the heart. Oleic acid is an omega-9 fatty acid.

This question belongs to: Science Biology