Membranes & transport - membrane proteins Flashcards
What is the main function of the phospholipid bilayer in the plasma membrane?
Provides a barrier to the movement of some substances into and out of the cell
What are the two categories of membrane proteins?
- Integral
- Peripheral
What characteristic do integral proteins have?
Partially hydrophobic - amphipathic
Where are integral proteins located?
Embedded in the phospholipid bilayer
What is the nature of peripheral proteins?
Hydrophilic
How are peripheral proteins attached to the plasma membrane?
Attached to either the surface of integral proteins or to the plasma membrane via a hydrocarbon chain
What can affect the protein content of membranes?
The function of the cell
Which membranes have the highest protein content?
Membranes of the mitochondria and chloroplasts
What are the main functions of membrane proteins?
- Transport
- Receptors
- Cell adhesion
- Cell-to-cell recognition
- Immobilized enzymes
What do transport proteins allow to pass across the membrane?
Ions and polar molecules
What are the two types of transport proteins?
- Channel proteins
- Carrier proteins
How do channel proteins function?
They form holes or pores through which molecules can travel
What do carrier proteins do?
Change shape to transport a substance across the membrane
What is the specificity of transport proteins?
Each transport protein is specific to a particular ion or molecule
What is the role of receptors in the membrane?
Binding of peptide hormones, neurotransmitters, or antibodies
What do immobilized enzymes have that is exposed on the surface of the membrane?
Active site
What is the function of cell adhesion?
Allows cells to attach to neighboring cells within a tissue
What role do glycoproteins play in cell-to-cell recognition?
Act as cell markers or antigens
What are the ABO blood group antigens?
Glycolipids and glycoproteins that differ slightly in their carbohydrate chains
