A characteristic of a is that they do not separate in water. * carbohydrates
sugars
lipids
cellulose

I believe the answer is sugars.

Explanation:

A characteristic of sugars is that they do not separate in water. Sugars is the only answer in the options that makes since because you can dissolve sugar in water, however, you can't separate the sugars in water.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.

blood enters the heart through two large veins, the inferior and superior vena cava, emptying oxygen-poor blood from the body into the right atrium of the heart. as the ventricle contracts, blood leaves the heart through the pulmonic valve, into the pulmonary artery and to the lungs where it is oxygenated.