LIFE SCIENCE

Detailed explanation-1: -The answer is D) lipid. This is because plasma membranes are composed of phospholipid bilayers that contain lipids attached to phosphate groups. They also contain proteins and carbohydrate chains, but these are less common than the lipid molecules.

Detailed explanation-2: -A eukaryotic cell is separated from the extracellular environment by a plasma membrane composed of a phospholipid bilayer containing proteins that regulate transit of molecules into and out of the cell. Loss of this barrier function can lead to compromised cellular homeostasis and death of the cell.

Detailed explanation-3: -Biological membranes consist of a continuous double layer of lipid molecules in which membrane proteins are embedded. This lipid bilayer is fluid, with individual lipid molecules able to diffuse rapidly within their own monolayer. The membrane lipid molecules are amphipathic. The most numerous are the phospholipids.

Detailed explanation-4: -Phospholipids are the most abundant type of lipid found in the membrane.

Detailed explanation-5: -Membrane lipids are principally of two types, phospholipids and sterols (generally cholesterol). Both types share the defining characteristic of lipids-they dissolve readily in organic solvents-but in addition they both have a region that is attracted to and soluble in water.