Polvi Lec #3 Flashcards
What are the seven membrane functions?
compartmentalization, scaffold for biochemical activities, selectively permeable barrier, solute transport, response to external stimuli, cell-cell communication, energy transduction
What’s an example of compartmentalization?
When organelles are sectioned off in the cell
What is the example of the membrane function: scaffold for biochemical activity
proteins and enzymes embedded in the membrane itself so the right reactions can take place
What is an example of the selectively permeable membrane barrier?
water enters the cell and membrane selectively choose what ions go in and out of the
What is an example of the membrane function solute transport?
channels, proteins, and other cell machinery pushes the import and export of stuff
What determines the physical state of the membrane?
viscosity
What is viscosity influenced by?
It’s influenced by temperature, specifically the transition temperature (melting temp)
What is the state of the membrane below the transition temperature?
It’s a crystalline gel, which is more fluid at higher temps but stiffer at lower temps.
What’s the state of the membrane above transition temperature?
it’s in a liquid crystalline phase (in a relatively fluid state)
What are the three factors that affect membrane fluidity?
fatty acid chain saturation
(saturated fatty acids vs cis-unsaturated fatty acids (which increase membrane fluidity)
cholesterol content- the flat rigid hydrophobic tails rings impair the movement of the phospholipid fatty acid tails, this also eliminates a sharp transition temp which creates intermediate fluidity and stops tails from coming too close to eachother
fatty acid chain length- shorter fatty acid chains lead to fewer van der waal interactions and therefore less energy is required to break them apart.
Why does cholesterol increase membrane fluidity?
It increases membrane fluidity by eliminating a sharp transition temperature, this also leads to it having a higher membrane fluidity at lower temps and a lower membrane fluidity at higher temps
How do double bonds effect melting points?
The lower amount of double bonds the higher the melting point
A balance of membrane fluidity and rigidity is important for?
Maintaining structural organization & mechanical support
Enabling interactions (clusters of proteins)
membrane assembly/cell growth/ cell division
cell movement, secretion, and endocytosis
How do cells change their membrane fluidity in response to colder temps?
They make single bonds in fatty acid chains to double bonds using the enzyme desaturase
They reshuffle chains between phospholipids to create those with two unsaturated fatty acids
They change the type of phospholipids that it synthesizes by having fatty acids with more unsaturated bonds and shorter chain lengths
How do cells change their membrane fluidity in response to warmer temps?
they become more rigid
