Which organelle is known as the 'powerhouse of the cell' and is semi-autonomous? MCQ with Answer and Explanation

Explanation:
Peroxisomes are single-membrane organelles involved in oxidative reactions, not plastids. Plastids (chloroplasts, chromoplasts, leucoplasts) are double-membrane organelles found in plants and algae, involved in photosynthesis, storage, and pigmentation. Chloroplasts contain chlorophyll, chromoplasts carotenoids, leucoplasts are colorless storage plastids.

Explanation:
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 designed to kill or inhibit the growth of bacteria; they are completely ineffective against viruses, which lack the cellular machinery targeted by antibiotics. Thus, statements 1 and 2 are correct.

Explanation:
Insulin is a peptide hormone secreted by the beta cells of the Islets of Langerhans in the pancreas. Its primary function is to lower blood glucose levels (hypoglycemic effect) by promoting the cellular uptake of glucose, particularly in muscle and fat cells, and its conversion to glycogen (glycogenesis) in the liver. Glucagon has the opposite effect.