Module 1 Lecture 4: Plasma Membrane Flashcards
What is the plasma membrane also called?
Cell membrane
What does the plasma membrane separate the cell into?
Separates the extracellular and intracellular compartments/fluids
What is the plasma membrane composed of?
Mainly thin lipid bilayer with proteins and lipids (some carbohydrates)
How is the membrane a bilayer? What does that look like?
Two polar heads on each side facing the intracellular and extracellular side; tails face each other away from the water
Why are phospholipids so unique?
They have a polar head and non-polar tail
What is special about the polar head of the phospholipid?
Choline and **phosphate group along with glycerol backbone = polar and charged => **hydrophilic
What is special about the tail of the phospholipid?
Made of aliphatic hydrocarbons = non-polar, uncharged => Hydrophobic
How does the membrane have an active role in determining the composition of the cell?
Because it selectively permits the movement of various molecules (ions, nutrients, secretory and waste products)
What is the plasma membrane other than a physical barrier?
It controls movement of molecules in and out of the cell
Cell to cell communication and cell to environment communication is a role of?
Plasma membrane
Where is cholesterol found with respect to the plasma membrane?
Anchored within hydrophobic part of the membrane
Why is the plasma membrane both fluid and rigid?
It’s fluid so that it allows for the passage of the molecules but it’s rigid so that a cell doesn’t fall apart entirely
How are the phospholipids in the bilayer adding fluidity?
They are constantly twirling, spinning and vibrating; moving around and exchanging places with other phospholipids
How can you tell if a cell is dying?
1) If it lets anything through
2) If there’s a lot of phospholipid exchange going on within the membrane
What does cholesterol contribute to the plasma membrane?
Contributes to fluidity and stability of the membrane
What are proteins in the plasma membrane similar to? and why?
Proteins are like icebergs in a “sea” of lipids; they float on the plasma membrane and move along the membrane
Are proteins anchored to the cell?
Not unless something is holding it in place
Do proteins span the membrane?
Some proteins span the membrane going from the intracellular fluid to the extracellular fluid - helps with shuttling molecules in and out.
Structural characteristics of channel proteins?
Very narrow; only allows one molecule to go at a time - needs to fit criteria to go through
How was the Fluid Mosaic Model given its name?
Fluid because it is not rigid & Mosaic because there’s a bunch of things floating around spanning the membrane
Some proteins have sugar molecules called glycolipids and glycoproteins? What role do they play?
They play a role in the function, stability and shape of those proteins and lipids; overall acting as self-recognition molecules for cell to cell interactions
How many more lipid molecules are there compared to protein molecules?
50x more lipid molecules than protein molecules
What molecule accounts for most of the weight of the membrane?
Proteins account for half the mass; much larger than lipids
How do channel proteins work?
They fit small enough water-soluble molecules, such as small ions
Would charged ions be able to pass through the lipid bilayer without the channel proteins?
No; they would get repelled by the hydrocarbons
How can you have a channel protein where some of it interacts with the non-polar tails and then the other interact with the fluid?
Some proteins are hydrophobic and hydrophilic; the channel protein or protein that transports molecules is made and arranged in the membrane based on those characteristics
What are carrier molecules?
Another type of membrane protein; transfers larger specific substances - i.e. glucose
What are docking-marker acceptors
Membrane protein; specific to secretory vesicles and exocytosis process; accepts and binds the vesicles (lock and key process)
How do the secretory vesicles interact with the docking-marker acceptors?
Fuses to the protein and releases the contents
What are membrane-bound enzymes?
Membrane protein; important for signalling
What are receptors?
Membrane protein; span the membrane - go in and out the cell; recognize and bind with molecules in the environment
What are cell adhesion molecules?
Membrane protein; important for cell adhesion so that the cell is apart of the tissue - doesn’t wander off
What are peripheral proteins?
Do not cross the entire membrane; either on intracellular or extracellular
What do peripheral proteins do?
They act like enzymes and sends signals or act like a scaffold (connecting two proteins together)
