Lipids and Membranes Flashcards
How does cholesterol affect a membrane?
Since it is amphipathic it can fit between the phospholipids and it makes it harder to move things across (less permeable)
Are lipids soluble?
No
Are lipids polymers?
No
They are not made of monomers
What do phospholipids and fats have in common?
A glycerol backbone
Steroid structure
Four hydrophobic rings
addition of a hydrophilic hydroxyl group
What is cholesterol?
A steroid
What aspect of phospholipids is the most important to formation of bilayers?
Amphipatheic
What is the most permeable type of bilayer?
short and unsaturated
the kinks in unsaturated create more space
What is the least permeable type of bilary?
long and saturated
the long tail increases the force of Van der Waals interactions between the hydrophobic tails
What crosses lipid bilayers the fastest?
Small, nonpolar molecule (O2)
What crosses bilayers the slowest?
ions
What do you want more of in the bilayer when it is cold?
Unsaturated phospholipids
more kinks=more space=less van der waals force=more permeability
Is facilitated diffusion passive?
Yes
If water rushes into the cell, what does that make the solution on the outside of the cell?
Hypotonic
lower in solute so water moves into hypertonic cell
If water rushes out of the cell, what does that make the solution on the outside of the cell?
Hypertonic
higher in solute so water moves out of the hypotonic cell
If water rushes into the cell, what does that make the solution on the inside of the cell?
Hypertonic
higher in solute so water rushes in
Fats structure
Composed of 3 fatty acids linked to glycerol
What do fatty acids have?
A carboxyl group attached to the hydrocarbon chain
What is glycerol?
An alcohol
How are fats formed?
Dehydration reaction between carboxyl group of fatty acid and hydroxyl group of glycerol
Are fats amphipathic?
No since oxygen is buried within molecule
What are fats good for?
Long term energy storage due to all the energy stored in the nonpolar bonds
Are steriods amphipathic?
They normally have a polar group attached to the four ring structure
Why do steroids need to be polar?
In order to move in and out of cells if they are going to be used as a hormone
uses of sterioids
- hormones
- constituents of cell membrane
- starting point for synthesis of molecules
Fluid mosaic model
the membrane is not a solid barrier, molecules are free to move around like buoys
Channel Proteins
facilitate diffusion
help ions diffuse in a directional manner through electrochemical gradient
Integral membrane proteins
proteins that have segments facing both the interior and the exterior of the cell
Peripheral membrane proteins
bind to membrane without passing through it
Detergent
small, amphipathic molecule that can form miscelles
water soluble
aquaporins
channels that allow water to cross the plasma membrane 10x faster than by diffusion alone
Gated channels
open and close in response to a signal
Carrier proteins
carrier proteins undergo shape changes that selectively pick up a solute on one side of the membrane and then drop it off on the otherside
still works by diffusion
Pumps
perform active transport and go against the concentration gradient
Ex: sodium-potassium pump
What do all forms of facilitated diffusion require?
A carrier protein
Secondary transport
uses another molecule’s concentration gradient to pump uphill
Primary transport
pumping solutes from an area of lower concentration to higher concentration using energy
How does sodium potassium pump work?
three sodium cations are pumped out
two potassium cations are pumped in
What does the sodium potassium pump make the inside of the cell?
Net negative
