MICROANATOMY

Detailed explanation-1: -Steroids are overall hydrophobic because of their common tetracyclic hydrocarbon core (Figure 1G).

Detailed explanation-2: -The carrier proteins involved in facilitated diffusion simply provide hydrophilic molecules with a way to move down an existing concentration gradient (rather than acting as pumps).

Detailed explanation-3: -Steroid hormones have similar chemical structures to their precursor, cholesterol. Because these molecules are small and hydrophobic, they can diffuse directly across the plasma membrane into the cell, where they interact with internal receptors.

Detailed explanation-4: -A transport protein completely spans the membrane, and allows certain molecules or ions to diffuse across the membrane. Channel proteins, gated channel proteins, and carrier proteins are three types of transport proteins that are involved in facilitated diffusion.