Cell Processes: Structure and Function of the Cell Flashcards
Width of the cell membrane
8nm
Are proteins free moving in the plasma membrane
Yes
Composition of lipids and proteins in membrane
50 % lipid & 50 % protein
with hydrogen bonds
What are the three lipids in the plasma membrane
cholesterol, phospholipids, glycolipids
Arrangement of lipids in plasma membrane
Cholesterol and glycolipids scattered among a double row of phospholipid molecules
How many membrane lipids are phospholipids?
75%
How many layers are in a phospholipid bilayer
2 parallel layers
Are phospholipids polar or non polar?
They are amphipathic (have both a polar & nonpolar region)
What do phospholipids do when put in water?
they will orientate themselves to make the lowest energy structure (nonpolar tails will spontaneously face away from water)
What is a membrane leaflet
One side of the phospholipid bilayer
Are membranes fluid
Yes
How can lipids move in the membrane?
They can move around within the plane of the membrane leaflet
Can lipids change between leaflets
Lipids rarely flip flop between membrane leaflets therefore the lipid composition of the leaflets can be asymmetric
What effect does the a longer lipid tail have on fluidity of the membrane
It makes the membrane less fluid
What do more double bonds do to the fluidity of the membrane
It makes it more fluid
What forms in the membrane due to double bonds
Double bonds make kinks, making them pack less tightly giving more fluidity (membrane less stable)
What are integral proteins
Membrane proteins that extend into or completely cross the cell membrane (they are embedded in the hydrophobic core)
What is a transmembrane protein
An integral membrane protein that goes completely across the plasma membrane
What are peripheral proteins
Membrane proteins attached to either inner or outer surface of cell membrane and are easily removed from it
How can you remove a peripheral protein from a plasma membrane
Easily removed by changing in ionic strength as you breaking an ionic bond
Are integral proteins polar or nonpolar?
They are amphipathic
What do the hydrophobic regions of integral proteins contain?
non polar amino acids coiled into helices
How to get membrane protein out of the membrane
break interactions between hydrophobic lipids and hydrophobic amino acids
What is an ion channel protein?
An integral membrane protein that allows specific substances to move through a water-filled pore
What is a transporter protein?
An integral membrane protein that changes its shape to move molecules across the membrane
What is the membrane permeable too?
nonpolar uncharged molecules, small polar uncharged molecules, lipid soluble molecules
What is the membrane NOT permeable too?
large uncharged polar molecules, ions
How do lipid soluble molecules get across plasma membrane?
Lipid soluble molecules can interact with hydrophobic core and pass through the lipid bilayer
How can ions and glucose cross the plasma membrane?
Through transmembrane proteins: Membrane proteins mediate the transport of substances across the membrane that can not permeate the hydrophobic core of the lipid bilayer
What is the principal of diffusion
the random mixing of particles in a solution as a result of the particle’s kinetic energy
How to molecules move across the concentration gradient?
molecules move away from an area of high concentration to an area of low concentration
What does a grater distance in concentration between two side of the membrane do to diffusion rate?
it will increase the rate of diffusion
What does increasing the temperature do to the rate of diffusion
increase the rate of diffusion
What do increasing the size of a diffusing substance do to diffusion rate?
slows the rate of diffusion
What does increasing surface area do to the rate of diffusion?
It will increase the rate of diffusion
What do increasing the diffusion distance do to the rate of diffusion
it slows the rate of diffusion
Physical limit to cell size, due to diffusion
20 µm
What does a thick membrane do to the rate of diffusion
it slows the rate of diffusion
What is a concentration gradient?
non charged molecules will diffuse down their concentration gradients
(passive transport)
What is an electrical gradient?
ions will be influenced by membrane potential in addition to their concentration gradient (Movement of ions will be influenced by the electrochemical gradient)
Concentration of Na+ outside of the cell
150mM
Concentration of K+ outside of the cell
5mM
Concentration of Cl- outside of the cell
150mM
Amount of resting energy that a cell uses to maintain a separation of charge between the cytoplasm and extracellular fluid
30%
What does a gradient represent?
Stored energy
Where do Na+ ions diffuse to
Into cell
Where do K+ ions diffuse to
out of cell
Where do Cl- cells diffuse to
in and out cell
What is osmosis
The net movement of water through a selectively permeable membrane from a high [water] to a low [water].
When will osmosis occur?
When there is a solute difference
What feature does a membrane need to have to carry out osmosis?
Water permeable
