The enzyme that seals nicks in the sugar-phosphate backbone of DNA is: MCQ with Answer and Explanation

Explanation:
Louis Pasteur proved that fermentation is caused by living yeast cells, not spontaneous chemical reactions. Buchner later showed that cell-free extracts could ferment sugar, discovering enzymes. Fleming discovered penicillin, Leeuwenhoek observed microbes.

Explanation:
The pancreas is a mixed gland: exocrine acini secrete digestive enzymes (trypsin, lipase, amylase) into the duodenum, while endocrine islets secrete insulin and glucagon into the blood. The liver produces bile, not digestive enzymes. Spleen filters blood, gall bladder stores bile.

Explanation:
Veins carry blood back to the heart under low pressure and have one-way valves that prevent backflow. Skeletal muscle contractions also assist venous return.