Week 4: Membranes Flashcards
What is the primary function of cell membranes?
To keep the inside in and the outside out
What surrounds the nucleus and mitochondria in eukaryotic cells?
A double membrane
What is the structure of the plasma membrane?
A lipid bilayer made of lipids and proteins
What are the two main components of biological membranes?
- Lipids
- Proteins
What is the role of cholesterol in the lipid bilayer?
Provides structural support
Define amphipathic molecules.
Molecules that are hydrophilic (water loving) and hydrophobic (water hating)
What do lipid bilayers spontaneously form in aqueous environments?
- Micelles
- Bilayers
- Spherical structures
What is the typical behavior of lipids in membranes?
- Fluidity
- Lateral diffusion
- Rotation
- Flexion
True or False: Flip-flopping of lipids in the membrane is common.
False
What are membrane proteins responsible for?
- Transport
- Structural links
- Receptors
How many proteins are there approximately per 50 lipids in a membrane?
1 protein
What type of protein can only be separated from the membrane with detergents?
Integral membrane proteins
Fill in the blank: The carbohydrate layer on the cell surface is called the _______.
glycocalyx
What is the purpose of the glycocalyx?
Involved in cell adhesion and protection
What types of molecules are typically transported across membranes?
- Small water-soluble molecules
- Ions
What do carrier proteins do?
Bind solutes and initiate a conformational change to transport them
How do channel proteins function?
Contain a pore through the membrane that is controlled for opening
What is the permeability of the lipid bilayer to hydrophilic molecules?
Barrier to most hydrophilic molecules
What types of molecules are mostly excluded by the lipid bilayer?
- Uncharged polar molecules
- Ions
What is the difference between integral and peripheral membrane proteins?
- Integral proteins: separated with detergents
- Peripheral proteins: separated with changes in pH or salt
What is the role of membrane proteins in cellular signaling?
They allow inside things to get out and outside things to get in
What type of protein is involved in membrane curvature in the ER?
Reticulons
What type of anchor do GPI-linked proteins have?
Glycosylphosphatidylinositol (GPI) anchor
What are the examples of membrane proteins that are involved in signal transduction?
- EGFR (epidermal growth factor receptor)
- Heterotrimeric G-proteins