Final answer:
In human plasma membranes, the lipids primarily found are b. phospholipids and c. steroids such as cholesterol. These lipids are vital to the membrane's structure and function, with phospholipids forming the bilayer and cholesterol maintaining the membrane's fluidity.
Step-by-step explanation:
In human plasma membranes, you would mainly find phospholipids and steroids, such as cholesterol, which are crucial components. Phospholipids are made up of a glycerol or sphingosine backbone, two fatty acid chains, and a modified phosphate group, which forms a bilateral layer that constitutes the membrane's matrix. They are amphipathic, meaning they contain both hydrophilic (water-attracting) and hydrophobic (water-repelling) parts, which is essential for the membrane's function. Cholesterol is a steroid with a basic structure of four fused carbon rings, and it plays a vital role in maintaining the fluid nature of the plasma membrane and is also a precursor of steroid hormones like testosterone.
The lipids that you would find in human plasma membranes are phospholipids. Phospholipids are major components of the plasma membrane and are composed of a glycerol or sphingosine backbone attached to two fatty acids and a phosphate-containing group. The phosphate group is modified by an alcohol. Phospholipids, such as phosphatidylcholine and phosphatidylserine, play a crucial role in maintaining the fluid nature of the plasma membrane and regulating the passage of substances into and out of the cell.