b2.1 membranes and membrane transport Flashcards
basis of cell membranes
lipid bilayers
hydrophilic
molecule is attracted to water
hydrophobic
molecule is repelled by water
amphipathic + eg
both hydrophilic and hydrophobic
eg. phospholipids
labelled diagram of the plasma membrane
ipad notes
functions of membrane proteins [6]
Transport
Receptors
Anchorage
Cell recognition
Intracellular joining
Enzyme activity
TRACIE
stucture of glycoproteins
carbohydrates structure linked to protein in membrane
glycoproteins location + reason
- on the extracellular side of the membrane
- used for cell adhesion
structure of glycolipids
carbohydrates linked to lipid in membrane
glycolipids location + reason
- on the extracellular side of the membrane
- used for cell recognition
temperature property of unsaturated fatty acids [3]
low melting point
- membranes are fluid
- flexible at temperatures experienced by a cell
temperature property of saturated fatty acids
higher melting points
- make membranes stronger at higher temperatures
definition of endocytosis + eg
cell membrane can change shape slightly to form vesicle and budded off form cell surface and enter the cytoplasm as vesicle
eg. phagocytosis
definition of exocytosis + eg
vesicles can fuse with the cell membrane to export substance out of the cell
eg. secretion of enzymes
example of a neutransmitter-gated ion channel
nicotinic acetycholine receptors
example of voltage-gated channels
- sodium and potassium channels
function of cell-adhesion molecules (CAMs)
- used for different types of cell to cell junction
what does the membrane fluidity depend on
the fatty acid composition of the phospholipids
saturated fatty acid bonds
- single bonds
- straight chain structure
straight chain structure allows for…
- more stability due to more intermolecular forces
- reduces fluidity, flexibility and permeability
unsaturated fatty acid bond
- double bonds
- results in kinks within the structure
effect of the structure of the unsaturated fatty acid
- kinks weakens the intermolecular forces -> more fluidity, flexibility and permeability in the cell membrane
homeoviscous adaptation can occur when
the cell membrane lipid composition to maintain adequate membrane fluidity
what happens to the composition of the phospholipid fatty acids when temperature decreases
- become more unsaturated in order to maintain homeoviscosity
membrane lipids in cold conditions
becomes more unsaturated during acclimatisation
- needs to maintain fluidity and permeability to allow material exchange on cell surface
- cold temperature will reduce cell membrane’s permeability
diagram of saturated fatty acid
no double bonds
diagram of unsaturated fatty acid
notes
cholesterol molecule: which parts are hydophilic and hydrophobic
OH- hydrophilic
everything else- hydrophobic
how is cholesterol imbedded in the fluid mosaic model
head to head
why is membrane’s fluidity important for endocytosis and exocytosis
- needed to transport bulk substance using a vesicle
eg. neurotransmitter - vesicle has same structure as phospholipid: vesicle can fuse with the cell membrane without breaking the cell membrane
what do endocytosis and exocytosis require
energy
endocytosis
cell membrane can change shape slightly to form vesicle and budded off form cell surface and enter the cytoplasm as vesicle
exocytosis
vesicles can fuse with the cell membrane to export substance out of the cell
annotated diagram of endocytosis
notes
annotated diagram of exocytosis
notes
nicotinic acetylcholine receptors presented at
skeletal neuromuscular junctions
acetylcholine
neurotransmitter
- act as a ligand in the ligand-gated ion channel
function of sodium potassium pump
helps maintain resting membrane potential
how does the lipid bilayer act as a barrier
hydrophobic hydrocarbon chains- low permeability to large molecules + hydrophilic particles
eg. ions, polar molecules
what can go through using simple diffusion + examples
- small molecules
- soluble molecules
- non-charged molecules
eg. oxygen, carbon dioxide
location of integral protein
embedded in one or both lipid layers of a membrane
location of peripheral proteins
attached to one or other surface of the bilayer
movement of water molecules across membranes by osmosis and role of aquaporins
- random movement of particles
- impermeability of membranes to solutes
- differences in solute concentration
how structure of channel proteins makes membranes selectively permeable
allows specific ions to diffuse through when channels are open but not when they are closed
pumps use…
energy from ATP to transfer specific particles across membranes so they can move particles against a concentration gradient
what allows selective permeability in membranes [2]
- facilitated diffusion
- active transport
why is simple diffusion not selective
depends only on the size and hydrophilic/phobic properties of particles
function of cholesterol [3]
- acts as a modulator of membrane fluidity
- stabilises membranes at higher temperatures
- maintains impermeability to hydrophilic particles
eg. sodium and hydrogen ions
how does voltage-gated sodium channels only allow sodium to go through?
- diameter
- negatively charged
what is essential for diffusion
concentration gradient
facilitated diffusion
passive movement of a particle across a cell membrane via a channel protein
processes in nerves that require a membrane protein
- active transport of sodium
- propagation of an action potential
- binding of neurotransmitter
phospholipid structure
- hydrophilic head made from phosphate and glycerol
- 2 hydrophobic tails made from fatty acids
what are phospholipids held together by
hydrophobic interactions
how are phospholipid layers stabilised
by interaction of hydrophilic heads and surrounding water
why is fluidity important in the plasma membrane
important in breaking and remaking membranes
eg. endocytosis, exocytosis
what cannot use simple diffusion [3]
- large molecules
- charged molecules
- non-soluble
eg. water, glucose
features of the fluid mosaic model [4]
- flexible, adaptable and in motion
- have freedom of movement
- individual phospholipids are attracted to each other by weak attraction
- cumulative effect: very strong membrane
how do pump proteins work
- molecule binds to the active site of the pump
- ATP transfers phosphate to the protein
- results in conformational change in the shape of the protein pump
- molecules is pushed to the other side of the membrane
voltage-gated sodium channel used + found in
used in: facilitated diffusion
found in: neurons
how does nicotinic acetylcholine receptor work + diagram
- acetylcholine binds to it
- sodium comes in: voltage to ard -50 mV
- more sodium go in
- new action potential created - impulse continues
- nicotine can also bind and open the receptor
what is the healthiest type of fatty acid
monosaturated cis fatty acid
- bends
how does cholesterol cause the membrane to be more fluid
- forces a gap between the membrane
- moves phospholipid away form each other to ensure that theyre not too closely packed
non-polar means its hydrophilic/hydrophobic?
hydrophobic
proximal convoluted tubule
how glucose goes through and comes back
1. sodium potassium pump generates low sodium concentration
2. low Na+ concentration is generated inside the cell
3. higher Na+ concentration in the lumen, this allows Na+ to diffuse into the cell using the sodium-dependent glucose co-transporter
4. since glucose is co-transported into the cell, the cell has a higher glucose concentration
5. glucose will diffuse through the glucose channel proteins and back into the blood
6. this is known as indirect active transport
what happens when an action potential reaches motor end plates
neurotransmitter is released
