. One of the main functions of the semi-permeable cell membrane is to maintain homeostasis for the cell. Semi-permeable means that only some molecules are allowed to cross the membrane and others are not.

What molecule enables large molecules to cross the membrane?

Due to the semi-permeability of cell membrane, the molecules that allow large molecules to cross the membrane are proteins, specifically membrane integral proteins.

Explanation:

Membrane integral proteins are protein molecules that are part of the cell membrane, pass through it and cannot be separated from it. These molecules allow the passage of polar molecules and large molecules.

The channels and transporters are structures formed by integral proteins, which facilitate the passive and active transport of macromolecules, respectively.

The cell membrane is a lipid bilayer whose hydrophobic nature allows the passage of some substances and prevents the passage of others, which can pass through the membrane by using channels and protein transporters.

"menstrual cycle is a complex cycle that consists of several processes. order of occurrence of steps in menstrual cycle are as follows:

1. high progesterone levels maintain the endometrium lining of the uterus.

2. endometrium lining breaks down and low levels of estrogen stimulate the pituitary to release fsh and lh.

3. fsh and lh stimulates the follicles to develop and the oocyte to produce estrogen.

4. rising estrogen levels suppress fsh production and development of other follicles.

5. a spike in lh causes follicle to rupture.

6. a breakdown of corpus luteum causes progesterone level to drop."

correct answer is a. and d.