Exam 1 Import Flashcards
What do membranes do? (5)
- define life forms as distinct entities,
- separates cell from outside world,
- necessary to perform internal chem. rxns,
- maintain diff. environment w/i eukaryotic cell,
- important role in formation of life/evolution
Membrane composition
-Lipids and proteins
Phospholipids arranged as lipid bilayer
Proteins can span across both layers or may be attached to 1
Proteins and lipids modified w/ carbs
What are Phospholipids?
a lipid consisting of a glycerol bound to two fatty acids and a phosphate group
Define amphipathic.
having both a hydrophilic region and a hydrophobic region; can spontaneously form a bilayer in H2O
What is Fluidity?
behave like crystals (liquid) b/c they form ordered arrays (proteins also fluid); controlled by degree fatty acid saturation (not too fluid or too rigid)
What is Fluidity Regulation?
Animal cells insert cholesterol in between lipid bilayer
Low temp = cholesterol acts as spacer (Increase fluidity)
High temp = cholesterol prevents weakening of membrane (hydrophilic heads together)
Plants use other sterols
Compartmentalization
Membrane-bound organelles allow different parts of the cell to perform different functions at the same time (ORGANELLES)
Concentration Gradients
results from an unequal distribution of ions inside and outside of the the cell
electrochemical gradient
The diffusion gradient of an ion, which is affected by both the concentration difference of an ion across a membrane (a chemical force) and the ion’s tendency to move relative to the membrane potential (an electrical force).
voltage gated channels
Electrical charge caused by an imbalance in ions; open and close in response to changes in membrane potential
ligand-gated channels
respond to chemical messengers
Vesicles
small membrane sacs that specialize in moving products into, out of, and within a cell
selective permeability
Keep inside in and outside out
Must allow nutrients and molecules in
Must allow waster and molec out
Entrance=size and charge of particle (also comp of membrane)
Biological membrane: some things in but not others
Transport proteins
A transmembrane protein that helps a certain substance or class of closely related substances to cross the membrane.
Diffusion
Particles move high to low
Equilibrium reached when equal
Particles can still move back and forth but no net change
Osmosis
Diffusion of H2O across membrane
H2O=high to low
Dissolved solute lowers H2O by interacting with H2O molec and preventing movement across
H2O moves toward area of high solute
Facilitated Diffusion
Particle binds to protein in membrane
Binding causes protein to change shape and allow cell in
Enter cell following concentration gradient
Ex: Glucose uniporter in red blood cells
Vasoconstriction
nervous system restricts blood flow to fingers and toes (grip)
isotonic
equal (.9% NaCl)
hypotonic
less inside than outside (0.4% NaCl) less H2O inside
hypertonic
more H2O inside (1.3% NaCl)
Active transport
move particles against the concentration gradient (energy required)
uniporter, symporter, antiporter
carries one solute
carries two solutes in same direction
carries two solutes in opposite direction