The highlighted questions

first answer

Explanation:

Transport of material across the plasma membrane of cell is essential for life of a cell. Certain substances must move into the cell for metabolic activities; while some substances which are produced by the cell or are waste products should move out of the cell. Majorly, there are two transport processes

a great strategy for moving molecules into or out of a cell. It's cheap, it's easy, and all the cell has to do is sit there and let the molecules diffuse in. But...it also doesn't work in every situation. For instance, suppose the sugar glucose is more concentrated inside of a cell than outside. If the cell needs more sugar in to meet its metabolic needs, how can it get that sugar in?

Here, the cell can't import glucose for free using diffusion, because the natural tendency of the glucose will be to diffuse out rather than flowing in. Instead, the cell must bring in more glucose molecules via active transport. In active transport, unlike passive transport, the cell expends energy (for example, in the form of ATP) to move a substance against its concentration gradient.

it is second answer

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answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation:

answer: c

explanation: