Our study partner has drawn four models of membrane-bound vesicles to try to show what a vesicle would look like with water both inside and outside of the membrane. Help him to select the most accurate model.

The answer (Image 1) is attached. Since the options weren't provided, I've attached the image of the options, too.

Explanation:

The plasma membrane is composed of phospholipids, a special form of lipids with a hydrophilic head and hydrophobic tail. According to the fluid mosaic model, the hydrophilic heads are positioned towards the outside where they freely interact with the extracellular matrix and cytosol. Whereas, the hydrophobic tails are positioned towards the inside so they aren't exposed to water.

Liposomes are lipid bases particles used for drug and vector delivery. The picture shows a typical liposome.

In the current case, for water to move both outside and inside, hydrophilic heads should be present inside as well as outside the tails.

cells use diffusion to get substances in and out of themselves. that diffusion will occur across the cell membrane or the outer covering of the cell. because we are talking about the surface of the cell, surface area and volume are  important factors here. as a cell increases in size, its surface area and volume increase as well.  we call that the surface area to volume ratio (sa: vol).  but the catch is that  volume increases at a greater rate than surface  area. in other words, as a cell gets bigger, the sa: vol gets smaller. so a really small cell like bacteria is mostly cell membrane (surface) with very little contents (volume). a really big cell like an egg, is mostly insides with a super thin membrane. so what ends up happening is that the cell cannot efficiently diffuse all of the stuff it needs in/out to survive. therefore cell size is limited to about 100mm. so how do we make organisms bigger than 100mm? cells divide! by dividing and becoming multicellular, organisms are able to grow!   check out the diagrams i attached to see the effect of sa: vol. i hope this ! good luck!