Proteins are the most common constituents in the cell membrane (plasma membrane). Transmembrane/ Integral proteins and peripheral proteins are the two types.

1. Cell membrane proteins
Structure and functions
Dr. GT Wijesinghe, MBBS
@ www.simplyphysiology.com

2. Key features
• 55% of total membrane constitutes are proteins 😮😮
• Transmembrane (intergral) or peripheral; two types
• Part of membrane structure
• Facilitate the diffusion of water and water soluble molecules
• Facilitate active transport

3. Integral protein
• Transmembrane protein
• Often carbohydrate molecule is bound and called glycoprotein

4. Integral protein cont.
• Act as channels; allow to diffuse water and water soluble molecules
• Act as carriers; carry special molecules in and out through the
membrane

5. Integral protein functions
• Part of cell membrane structure
• Allow substance transport across the membrane
• Act as enzymes
• Act as receptors for water soluble Chemicals

6. Carrier protein
• A type of integral protein
• Carry special molecules in or out of intracellular compartment
Ex: Glucose transporter, Urea transporter
• Sometimes carry molecules against the concentration gradient; Active
transport
Ex: Sodium-Pottasium ATPase pump

7. Peripheral proteins
• peripheral proteins are attached only to one surface of the membrane
and do not penetrate all the way through
• Often attached to integral proteins
• Almost all act as enzymes
• Act as controllers of transporters across cell membrane

8. Thank you
• Visit for more details
www.simplyphysiology.com