Which feature of a membrane desrcibes whether molecules can cross the membrane

Which of the following describes a negative feedback loop? when the heart rate is too high, the body sends hormones that continually increase the heart rate higher. when a pregnant woman is in labor, the body sends hormones that increase the intensity of contractions, which then increases the secretion of the same hormones. when blood sugar is too low, the body sends hormones that raise blood sugar until it reaches a typical level and hormone secretion slows. when a person is jogging, the body sends hormones that continually decrease the rate of oxygen supply to the legs.

Ihave a question. diplontic animals usually produce both eggs or sperm which are :

Why do you suppose the structural polysaccharide cellulose does not contain branches?