Which feature of modern plant cell is not found in modern algal cells

What are some possible short and long term medical concerns for crew members on longer space exploration trips

What is the difference between a scientific hypotheses and a scientific theory?

Lactase is essential for digesting lactose in milk. this enzyme is specific for this sugar. why? molecules and active sites vary in size; only properly sized molecules can fit.there is a precise compatibility between the active site and the lactose molecule.specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.