The actual site of gas exchange in the mammalian respiratory system is:
A. Bronchi
B. Larynx
C. Trachea
D. Alveoli
Answer: Option D
Solution (By JKSSB Mock Tests)
The alveoli are the terminal, microscopic, thin-walled, highly vascularized air sacs in the lungs. They are the primary and actual sites of gas exchange, where oxygen diffuses from the inhaled air into the blood, and carbon dioxide diffuses from the blood into the alveolar air to be exhaled. Their large surface area and thin walls facilitate this diffusion.
Explanation:
Restriction endonucleases cut DNA at specific palindrome sequences, generating sticky or blunt ends, which can be ligated to vector DNA. This is the basis of genetic engineering. R explains A.
Explanation:
Trypsinogen, secreted by the pancreas, is activated to trypsin by enterokinase (intestinal enzyme). Trypsin then activates other zymogens. Pepsin is active in the stomach, rennin in infants, amylase digests starch. This cascade prevents premature protein digestion in the pancreas.
Explanation:
Hans Fischer determined the structure of chlorophyll in the 1930s and synthesized hemin. Willstätter studied its composition, Calvin elucidated the carbon fixation pathway, Woodward synthesized chlorophyll.
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