The site of gas exchange in the human lungs is: MCQ with Answer and Explanation

Explanation:
Mitochondria are double-membrane organelles with circular DNA (like prokaryotes) and 70S ribosomes, supporting the endosymbiotic origin. They are absent in prokaryotes. They are the site of aerobic respiration. The matrix contains enzymes for Krebs cycle. The inner membrane forms cristae, housing electron transport chain and ATP synthase.

Explanation:
Thyroid-stimulating hormone (TSH) from the anterior pituitary binds to receptors on thyroid follicular cells, stimulating synthesis and release of thyroid hormones (T₃ and T₄). ACTH targets adrenal cortex.

Explanation:
Gonorrhea is an STD caused by the bacterium Neisseria gonorrhoeae. Tuberculosis is airborne bacterial disease, malaria is vector-borne protozoan, typhoid is waterborne bacterial. Other STDs include syphilis, chlamydia, HIV/AIDS, genital herpes. STDs can be prevented by safe sex practices. Gonorrhea causes urethritis, discharge, and can lead to PID if untreated.