ch 6: lipids and membranes Flashcards
lipid
organic substance that does not dissolve in water, but dissolves well in nonpolar organic solvents
what are the kinds of lipids
fatty acids, fats, oils, waxes, steroids and phospholipids
what are the monomers of lipids?
fatty acids
what are characteristics of lipids?
hydrophobic and nonpolar
why are lipids insoluble?
high proportion of nonpolar C-C and C-H bonds relative to polar functional groups
saturated lipids
hydrocarbon chains that consist of only single bonds between carbons
unsaturated lipids
one or more double bonds exist in the hydrocarbon chains
what happens if lipids are in a straight chain?
they pack tightly together and form a solid through van der Waals
what happens if lipids are bent?
they have fewer interactions and form a liquid
3 types of lipids
steroids, fats, and phospholipids
fats (aka triglycerides)
3 fatty acids joined by ester linkages to a glycerol molecule
are fats polar or nonpolar?
NONPOLAR
how do fats form?
through condensation reaction between hydroxyl group of gylcerol and carboxyl group of a free fatty acid
phospholipids
consists of glycerol that is linked to a phosphate group and two hydrocarbon chains of either isprenoids or fatty acids
phospholipids are ________
amphipathic: contains hydrophilic and hydrophobic regions
what are the regions of a phospholipid?
phosphate hydrophilic head and fatty acid hydrophobic tail
function of fats
energy storage
function of phospholipids
cell membrane
what are the phosphate heads stabilized by?
stabilized by hydrogen bonds with water and each other
what are the fatty acid tails stabilized by?
van der Waal interactions with each other
unsaturated hydrocarbon tails are _____
more fluid because they are not tightly packed together
- liquid
saturated hydrocarbon tails are ____
less fluid because they are tightly packed
- solid
how does cholestrol stabilize membrane?
keeps lipid bilayer more stable and less fluid at high temps and more fluid at low temps
micelles
spherical aggregates that have hydrophobic tails and hydrophilic heads formed by FATTY ACIDS (single hydrocarbon chains)
lipid bilayers
created when a lipid molecule aligns in paired sheets and form in water
- has hydrophilic heads on top and bottom and hydrophobic tails in center
selective permeability
some substances cross a membrane more easily than other substances do
what crosses the bilayer quicker?
small, nonpolar molecules such as gases
what crosses the bilayer a little slower?
small polar and uncharged polar molecules
what cannot cross the bilayer?
large, uncharged polar molecules and ions
short and unsaturated hydrocarbon tails have ______ permeability
higher
long and saturated hydrocarbon tails have ______ permeability
lower
what happens as temps drop in a bilayer?
molecules move slower and become less fluid and solidfy
diffusion
substances on one side move to other side of bilayer, with no energy
what does diffusion require?
concentration gradient: high concentration to low
- molecules move down the CG
osmosis
water molecules move from low solute/high water to high solute/low water
hypertonic solution
solution outside vesicle has a high solute concentration, so water moves out of vesicle to establish equilibrium
- causes vesicle to shrink
hypotonic solution
solution outside has lower concentration of solutes, so water moves inside vesicle
- vesicle swells and can burst
isotonic solution
solute concentrations are equal so there is no change to vesicle
what type of structures are plasma membranes?
fluid mosaic: components move laterally and can be changed based on needs of cell and are made up of more than one type of biomolecule
what biomolecule is important part of plasma membranes?
integral and peripherial proteins
integral proteins
inside the cell membrane, spanning the phospholipid bilayer
peripheral proteins
loosely attached to surface of cell membrane, outside phospholipid bilayer
4 critical functions of plasma membranes
- allow some things to enter and others to leave
- recognizes signals and responds
- barrier: keeps inside in and outside out
- attaches to other things
what type of proteins change permeability of plasma membranes?
integral membranes
facilitated diffusion
movement of molecules from high to low concentration through a protein tunnel (passive transport)
channel proteins
only allows specific molecules through
- many of specific molecule enters when it changes shape to open
- either open or closed
- works like a bridge
carrier proteins
only allow specific molecules through and usually 1-3 for each change in shape
- changes shape to open
- picks up solute and drops it off to other
aquaporin
channel protein for water
- allows up to 100 milion
- direction depends on concentration gradient
passive transport
high to low concentration
- no energy needed
- type of facilitated diffusion
what does active transport require?
- input of energy
- carrier protein to move it across membrane (protein pump)
active transport moves molecules ________
against their concentration gradient
