Characteristics of the Membrane Flashcards
Major functions of memebrane
- Separates outside environment fro inside of the cell
- allows certain things to cross into the cell
- compartmentalizes cells
Selective Permeability
makes sure that what goes into the cell is good
Compartmentalization
keeps the cell organized
Homeostasis
the way things are supposed to be, this is maintained by the membrane even if crazy stuff is happening outside the cell
What is the biological membrane made up of?
phospholipid bilayer that has a hydrophobic head and hydrophilic tail…..the head and the membrane proteins interact to form a insoluble barrier
What is carbohydrates role in the membrane?
cell recognition
Integral membrane proteins
span or penetrate the cell, causing them to have transmembrane, cytoplasm and extracellular domains. Allow things to enter cell and determine functional properties of cell.
Peripheral membrane proteins
proteins located outside of cell. Allow things to enter the cell and determine functional properties of cell.
Glycoproteins
allow cells to recognize each other- transfers communication between the cell
Glycolipids
determine person’s blood type
Why is the phospholipid bilayer responsible for preventing the free passage of most materials across the membrane?
the bilayer has a hydrophobic head which DOES NOT allow hydrogen ions to cross of big molecules to cross unless proteins are involved.
-It has a hydrophobic tail which keeps ions and other molecules from entering the membrane
Explain why membranes are described as fluid structures..
"Fluid Mosaics" fluid assume shape easily moved changing position
Fluid Mosaic Model
“Proteins and substances such as cholesterol become embedded in the bilayer, giving the membrane the look of a mosaic. Because the plasma membrane has the consistency of vegetable oil at body temperature, the proteins and other substances are able to move across it. That’s why the plasma membrane is described using the fluid-mosaic model.”
How do saturated vs unsaturated fatty acids differ structurally?
SATURATED: STRAIGHT. all carbons have single covalent bonds w/ other carbons and hydrogens.
UNSATURATED: KINKED. contain 1 or more double C-C bonds
How does that (unsat. vs sat.) affect fluidity?
Fatty acid tails are very hydrophobic and interact tightly w/ each other to avoid water = saturated= membrane rigid and viscous
Double bonds in unsaturated fatty acid tails put kinks (can’t pack tightly) = unsaturated = membranes more fluid
How does the ratios of different types of lipids effect the fluidity of the membrane?
- Some types of phospholipids make the membrane more fluid than others
- Cells can alter the rations quickly
- Different organelles have diff. ratios of lipids
How does cholesterol have the ability to both increase and decrease membrane fluidity?
It inserts itself in between the fatty acid tails of the bilayer.
- At high concentrations, cholesterol blocks phospholipids from moving laterally (decreases fluidity)
- At low concentrations, prevents phospholipid tails from packing in tightly (increases fluidity)
T/F: A increase in temp. would cause an increase in membrane fluidity
true
T/F: An increase in saturation of the fatty acid chain would decrease the membrane fluidity
true
T/F: An increase in the number of double bonds present in the phosolipid side chains would cause an increase in membrane fluidity
true
T/F: An increase in the average length of the phospholipid fatty acid side chain would cause an increase in fluidity.
true
