Question

Sketch out a cross section of a cell membrane showing a proposed transporter involved in either facilitated diffusion or active transport. Include and label the following: Phospholipid bilayer(show head group and tails), hydrophilic and hydrophobic regions of transporter including possible amino acids, concentration gradient and direction of transport and whether transport is passive or active.

Answer 1

Biological membranes are lipid bilayers composed of phospholipids and proteins.
Transmembrane receptors contain hydrophobic membrane-spanning regions (represented by the red rectangle) composed of Leu, Val, Ile, and Phe.

The peripheral regions (represented by yellow circles) contain hydrophilic amino acids such as His, Lys, Arg, Asp, and Glu.

1. Facilitated diffusion occurs along the concentration gradient without the expense of energy (Passive).
See the image

2. Active transport occurs against the concentration gradient at the expense of energy (Active).
See the image