B 2.1 Membranes Flashcards
phospholipid structure
amphipathic molecule
head = phosphate group + glycerol
2 tails = fatty acids
be able to draw a phospholipid
+ phospholipid bilayer
circle for phosphate head + 2 tails for fatty acid tails
+ two rows of phospholipids, tails within the bilayer
how does the lipid bilayer act as a barrier between (aq) solutions?
hydrophobic hydrocarbon chains that form at the center have low permeability to
- large molecules
- hydrophilic particles (ex.ions)
simple diffusion
+ example
passive transport
high concentration → low concentration
+ O2 & CO2 exchange across alveoli (lungs) membrane
integral proteins
- penetrate phospholipid bilayer
- hydrophobic center, hydrophilic top and bottom (to anchor protein)
(glycoproteins, channels, protein pumps)
peripheral proteins
- temporarily attached (electrostatic interactions) to one side of membrane
- hydrophilic
(receptors, enzymes)
osmosis
passive transport
low solute concentration → high solute concentration through semipermeable membrane
polar but small => passes through phospholipid bilayer
solutes = polar => not pass bilayer
Facilitated diffusion example
Aquaporins!
integral channel proteins
faster than osmosis
increase membrane permeability to water
Facilitated diffusion
the passive transport of molecules from a region of high concentration to a region of low concentration through channel proteins
channel proteins
central pore: lined with hydrophilic R-groups allowing ONLY specific molecule
can be gated: only open in response to stimulus (ex. Na & K pumps in neuron)
Active transport definition
movement of particles from a region of low concentration to a region of high concentration using protein pumps and ATP energy
Active transport how?
- A specific particle binds to a binding site on a specific protein pump.
- ATP binds to the protein pump and performs hydrolysis
- phosphate attached causes protein pump to change shape
- particle moves against concentration gradient
- phosphate released, protein back to original shape
membrane selectivity & transport types
Facilitated diffusion = selective
Active transport = selective
Simple diffusion = not selective
glycoproteins & glycolipids
(function)
carbohydrate chain attached to protein/lipid billayer
1. receptors (antigens)
2. cell to cell communication
3. immune response
4. cell to cell adhesion
temp effects on membrane fluidity
high temp = more fluid
(+low viscosity, doesn’t hold shape, too permeable)
low temp = more solid
(+high viscosity, dense, rigid, not permeable)
fatty acids and membrane fluidity
longer tail = more interaction between tails = less fluid
saturated = higher viscosity = high melting point (better 4 high temp)
unsaturated = lower viscosity = low melting point (better 4 low temp)
membrane composition adaptations
chickpea = increases unsaturation of fatty acids at low temp
reindeer = different fatty acid compositions within organism
hooves → more unsaturated
cholesterol in membrane (animal cells)
amphipathic
fluidity modulator
↑ temp → it stabilizes membrane
↓ temp → it prevents phospholipids from interfering
membrane fluidity affected by:
- temperature
- fatty acid length
- fatty acid saturation
- presence of cholesterol
formation of vesicles
+examples
exocytosis (out of cell)
+ macrophages engulf pathogens
endocytosis (into cell)
+ secretion of hormones (ex.insulin)
missing?
B.2.1.14
B.2.1.15
B.2.1.16
B.2.1.17 (this one she didn’t miss but i dont understand it :(
