ch.5 proteins: multifunctional components

Question 1

although cells interact with their environment through their plasma membranes in many ways, we will focus on 7 key classes of membrane proteins:

Answer 1

1. transporters
2. enzymes
3. cell-surface receptors
4. cell-surface identity markers
5. cell-to-cell adhesion proteins
6. attachments to the cytoskeleton
7. proteins that affect membrane structure

Question 2

some membrane proteins are attached to the surface of the membrane by molecules that associate strongly with phospholipids. The anchoring molecules are modified lipids that have:

Answer 2

1. nonpolar regions that insert into the internal portion of the lipid bilayer
2. chemical bonding domains that link directly to proteins.

Question 3

other proteins (____________) actually span the lipid bilayer.

Answer 3

transmembrane proteins

Question 4

The part of the protein that extends through the lipid bilayer and that is in contact with the nonpolar interior are __________ or _________ that consist of nonpolar amino acids.

Answer 4

alpha helices or Beta pleated sheets

Question 5

transmembrane domains

Answer 5

-cell membranes have a variety of different transmembrane proteins, which differ in the way they travel across the lipid bilayer.
-the difference lies in the number of times the protein crosses the membrane.
-each membrane-spanning region is called a transmembrane domain.

Question 6

transmembrane domains are composed of

Answer 6

hydrophobic amino acids are usually arranged into alpha helices.

Question 7

proteins need only a single transmembrane domain to be anchored in the membrane, but they often have more than one such domain. true or false?

Answer 7

true!

Question 8

some transmembrane proteins have extensive nonpolar regions with secondary configurations of ________ instead of _______.

Answer 8

Beta pleated sheets instead of a helices