Question

2. A protein spans the nuclear membrane, with a small extranuclear domain, a substantial segment crossing the nuclear membrane, and a domain within the nucleus. It is

(a) a peripheral membrane protein

(b) an integral membrane protein

(c) a lipid-anchored protein

(d) impossible

Answer 1

Answer) Integral membrane protein

• A membrane protein is a protein molecule that associated with the membrane of the cells

Integral membrane protein

• The protein molecule which permanently attache to the membrane is termed as integral membrane protein, They classified as polytopic proteins and monotopic proteins. The polytopic protein also known as transmembrane protein which can span across the membrane. But monotopic protein which can not span across the membrane. The polytopic proteins again classified as single pass membrane protein which pass once across the membrane where as multi pass
• The main functions of Integral membrane proteins are transport, receptors, linker, enzymes etc
• Example : Glycophorin A

Peripheral membrane protein:

• which are temporarily attached to the membrane or to the integral membrane protein.
• They are attached to either outer side or inner side of the membrane by ionic interaction

Lipid anchored protein

• Lipid anchored protein found to surface of the membrane linked to the lipid  embedded in the membrane