Consider statements about human immunity: 1. Skin is a physical barrier. 2. White blood cells fight infection. 3. Antibiotics kill viruses. Which are correct? MCQ with Answer and Explanation
Consider statements about human immunity: 1. Skin is a physical barrier. 2. White blood cells fight infection. 3. Antibiotics kill viruses. Which are correct?
A. 1, 2 and 3
B. 2 and 3 only
C. 1 and 2 only
D. 1 and 3 only
Answer: Option C
Solution (By JKSSB Mock Tests)
The skin and mucous membranes form the first line of defense (innate immunity), acting as physical barriers that prevent pathogens from entering the body. White blood cells (leukocytes), including phagocytes and lymphocytes, are the cellular components of the immune system that identify, attack, and destroy pathogens. Antibiotics are drugs specifically designed to kill or inhibit the growth of bacteria by targeting their unique structures or metabolic pathways; they are completely ineffective against viruses. Thus, statements 1 and 2 are correct.
Explanation:
Vitamin C is chemically L-ascorbic acid. It is water-soluble, an antioxidant, and required for collagen synthesis. Deficiency causes scurvy. It is found in citrus fruits, amla, and green vegetables.
Explanation:
Solanum tuberosum is the scientific name of potato, a member of the Solanaceae family. Solanum melongena is brinjal (eggplant), Capsicum annuum is chili, and Lycopersicon esculentum is tomato. Potato is a tuber (modified stem) rich in starch, and is one of the world's major food crops.
Explanation:
DNA contains the pentose sugar 2'-deoxyribose, which lacks an oxygen atom on the 2' carbon compared to ribose in RNA. This structural difference makes DNA more chemically stable and suitable for long-term genetic storage. Nucleotides consist of a nitrogenous base, a pentose sugar, and a phosphate group. Ribose is present in RNA.
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