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What makes up the cell membrane?
- Phospolipid bilayer
- Cholesterol (animals)
- Carbs (euk)
What kinds of proteins make up the cell membrane?
- Integral (Transmembrane)
What part of a protein is glycosylated?
The portion facing the extracellular matrix
What are the functions of the membrane?
- Selective barrier
- In eukaryotes, formation of organelles/compartments
- Localization of enzymatic reactions
- Cell-cell communication
- Transmission/reception of signals
- Receive stimuli
- Site of ECM attachment
Where does glycoslyation occur, and what is the destination?
- Cell membrane (i.e. not organelles)
What does flippase do?
It "evens out" enzymes since most are on cytosol side
What is a lipid raft?
A "microdomain" of the plasma membrane which aggregates proteins and phospholpids for transportation.
How does a lipid raft travel?
Do proteins for organelles get glycosylated? Why or why not?
- Glycosylation is for cell-cell recognition
What is an advantage of a compartment/organelle?
- Useful for specialized enzymatic reactions.
- Greater rate of collisions for reactions to occur.
What is the minimum length of a transmembrane protein?
What are some functions of transmembrane proteins on the cytoplasmic side?
- Intrinsic or associated enzymatic activity
- Provide cell with shape
What are functions of transmembrane proteins on the outside?
- Receptors for soluble ligands
- ECM attachment (e.g. integrins)
- Cell-cell attachment (e.g. cadherins)
How are gates/channels activated?
Hormones or action potentials
What are types of secondary structures for transmembrane proteins?
- Alpha helices
- Beta barrels
For alpha helices in a gate, where is the hydrophobic side?
Facing the outside surface of the gate
What transports water thru the membrane?
What is the function of membrane cholesterol?
Provides membrane fluidity
What types of molecular movement are there in the membrane?
- Rotation on axis
- Lateral (sideways)
- Flip-flopping (from one side to the other)
Describe flip-flopping movement in a membrane.
- Requires energy and is thus uncommon
- Requires the flippase enzyme
- Proteins are too large for this movement
What can cross a membrane by simple diffusion?
CO2 and O2
What happens if a cell membrane has no fluidity?
The cell dies
What are some ways to alter membrane fluidity?
- Change length of hydrocarbon tails
- Change saturation
- Change cholesterol content
- Change temperature
What does an increase in cholesterol do?
What does an increase in temp do?
What does an increase in saturation do?
What does an increase in hydrocarbon tail length do?
What is the most common phospholipid in cell membranes?
Why does the phospholipid bilayer form a sphere and not a plane?
It's more energetically favorable.
Where are membrane phosholipids synthesized?
How are phospholipds moved to the other side of a membrane?