18 Questions
What is the reason behind lipid bilayers being asymmetric?
Cellular energy is used to maintain the asymmetry
Which type of integral membrane protein has a hydrophilic interior and hydrophobic exterior?
Beta-barrel proteins
What is the minimum number of hydrophobic residues required for an alpha-helical protein to cross the membrane once?
20-30
What is the main difference between peripheral membrane proteins and lipid-linked membrane proteins?
Their interaction with the lipid bilayer
Which type of lipid is usually found on the outer leaflet of the lipid bilayer?
Glycosphingolipids
What is the characteristic of the 1st strand of a beta-barrel protein?
It H-bonds to the last strand
What is the primary function of TAGs in most organisms?
Energy storage
What is the difference between phospholipids and TAGs?
One fatty acid is replaced by a phosphate group
What is the characteristic of the head group of phospholipids?
Polar and charged
What is the function of phospholipases?
Hydrolyze phospholipids at specific ester bonds
What is the main difference between phospholipids and sphingolipids?
Phospholipids have a glycerol backbone, while sphingolipids have a sphingosine backbone
What are the main components of biological membranes?
Phospholipids, sphingolipids, and cholesterol
What is the main factor that determines the fluidity of a lipid bilayer?
The length of the hydrophobic acyl chains
How does cholesterol influence membrane fluidity?
It has a dual effect, decreasing fluidity by being rigid and increasing fluidity by preventing close packing
What is the main reason why lipids rarely flip from one leaflet to the other in a membrane?
It is energetically unfavorable
What is the typical distribution of lipids in a cell membrane?
Asymmetrical distribution between the inner and outer leaflets
Why do polar head groups of lipids face outward in a membrane?
To H-bond with water
What is the result of having lots of long and saturated lipids in a membrane?
Higher melting temperature, less fluid
Test your understanding of cell membrane structure, including lipid bilayers, asymmetry, and integral membrane proteins. Learn how lipids are distributed and maintained in the cell membrane.
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