## Core Concept
Transport proteins, also known as carrier proteins or transmembrane proteins, facilitate the movement of molecules across cell membranes. They can be involved in various processes, including nutrient uptake, waste removal, and maintaining cellular homeostasis. These proteins can be specific to certain molecules or types of molecules.

## Why the Correct Answer is Right
The correct answer involves identifying which option does not function as a transport protein. Transport proteins typically have specific characteristics, such as binding sites for their substrates and conformational changes that allow for the translocation of molecules across the membrane.
- **Albumin** is a plasma protein that primarily binds and transports various substances, such as hormones, vitamins, and drugs, but it does not facilitate transport across cell membranes in the same way transmembrane proteins do; rather, it is involved in maintaining osmotic pressure and acting as a carrier in the bloodstream.
- Without specific details on the other options, we focus on the nature of transport proteins being embedded within cell membranes and directly facilitating the movement of substances across these membranes.

## Why Each Wrong Option is Incorrect
- **Option A:** Assuming it refers to a known transport protein, its role in transporting specific molecules across cell membranes makes it a transport protein.
- **Option B:** Similarly, if this option is a recognized transport protein, it participates in the transport of substances across membranes, categorizing it as a transport protein.
- **Option D:** If this option is also a transport protein, it would be directly involved in the transport of molecules across cell membranes.

## Clinical Pearl / High-Yield Fact
A key point to remember is that transport proteins are crucial for the uptake of essential nutrients and the removal of waste products from cells. **Albumin**, while not a transport protein in the traditional sense of facilitating membrane transport, plays a critical role in the transport of substances in the blood.

## Correct Answer: B. Albumin.