AP BIOLOGY

Detailed explanation-1: -Answer and Explanation: The correct answer is C, glycoproteins. Glycoproteins in the cell membrane are integral proteins with N-glycans and O-glycans attached to face the extracellular environment. These carbohydrate moieties can serve various functions, including signaling and self-recognition.

Detailed explanation-2: -In addition to lipids, membranes are loaded with proteins. In fact, proteins account for roughly half the mass of most cellular membranes. Many of these proteins are embedded into the membrane and stick out on both sides; these are called transmembrane proteins.

Detailed explanation-3: -Integral membrane proteins(also called intrinsic proteins)have one or more segments that are permanently embedded within the phospholipid bilayer and have their domains on both sides of the membrane.

Detailed explanation-4: -Integral proteins are those that are permanently attached to the membrane via stabilizing hydrophobic interactions. Remember that the membrane core consists of hydrocarbon tails and therefore non-polar interactions will stabilize the attachment of the protein within the membrane.

Detailed explanation-5: -Carbohydrates. Carbohydrates are the third major component of plasma membranes. They are always found on the exterior surface of cells and are bound either to proteins (forming glycoproteins) or to lipids (forming glycolipids) (Figure 5.1. 1).