Membrane Structure and Transport Flashcards
1
Q
semi-permeable membrane
A
- allows certain things in and out
- Used to organize internal organelles and spaces
2
Q
railroad tracks
A
- how the membrane looks
- intercellular space in between
- phospholipid heads facing in and out, tails face in
3
Q
3 most common lipids in membranes
A
- Phosphatidylethanolamine (PE)- biggest (fatty acids, glycerol)
- Phosphatidylcholine (PC)
- Phosphatidylserine (PS)
4
Q
Galactocerebroside (glycolipic)
A
- found in membrane of brain
- 2 fatty acid tails, head
Ga1 attached
5
Q
cholesterol
A
- steroid arrangement of rings, OH at one end (ampipathic), fit into phospholipid bilaryers and arrange so OH sticks out to fact water side, and embedded in bilayer
6
Q
distribution of membrane lipids
A
- nonrandom
- asymmetric distribution
(ex. brain has unique distribution, different from other tissues)
7
Q
Glycolipids
A
- sugars attached to nonpolar tails of fatty acids
- sugar is always facing out–> types of sugars facing out represents signal for the types of cell it is
- arrangement and types of sugars–> give information important for cell communication
ex. liver cell near other liver cells can detect that, might act differently next to a non-liver cell
8
Q
fluidity
A
- types of lipid affects fluidity
- phospholipid can move around in membrane
1. unsaturated- more fluid b/c not tightly packed
2. cholesterol- the more cholesterol, the more fluid, but if too much then becomes gooey (less fluid- NOT a linear relationship)
3. length of fatty acid tails- longer tend to stick together and are less fluid
9
Q
protein fluidity (human and mouse cells)
A
put marker on mouse and humans antibodies and fuse cells together–> after 40 min, proteins from both mice and humans are mixed
10
Q
fluid mosaic model
A
- complex relationship- proteins embedded in the membrane, some in the inner leaf some in just outer leaf
- supported by freeze fracture- showed that proteins were embedded in membrane
4 layers- inner spectrin cortex, phospholipids, proteins, sugars (face out)
**just AS MANY proteins as phospholipids
11
Q
integral proteins
A
- when proteins go through bilayer
- usually an alpha helix
12
Q
peripheral proteins
A
- just associated with inner and outer membrane
13
Q
linker (channel)
A
- hooked up to something inside and outside (ex. integrin/spectrin when attached, structures cannot move freely)
14
Q
receptors
A
- integral protein that goes through bilayer and has a binding site that faces out
- has a signal tool for ligands to bind to
- ligand not brought in, but sends message to cell
- ex. growth hormone
15
Q
enzyme
A
- recognizes ligand, changes shape, converts something into something else
- ex. phosphorylation- often will put a phosphate on X which becomes Y
16
Q
transmembrane
A
- alpha helices sometimes arrange in a way to create a pore
- beta barrel- sometimes sheets in opening
- have hydrophobic regions (alpha helix)
hydrophilic parts (R groups) anchor protein to membrane
17
Q
aqueous pores
A
- some transmembrane proteins create pores–> that allow water to flow though
- side chains (R groups) face into pore
- nonpolar (hydrophobic) parts face out
18
Q
cortex
A
- area beneath the outside surface of a cell or organ
19
Q
spectrin
A
- Network of protein molecules inside of the cell to help support the plasma membrane
- also attachment proteins
20
Q
glycocalyx
A
- (sugar halo) acts as a distinctive covering of the cell and is composed of oligosaccharides linked to membrane components
- important for cells during recognition of neighbors
21
Q
Not all proteins can move freely
A
- spectrin- in cortex w/ transmembranes anchored
- proteins attached to extracellular matrix
- junction proteins holding one cell to another
- polarized cell (epithelial cell with 2 jobs)- proteins on top can’t get to bottom and vv
22
Q
selective permeability
A
- transport across membrane is selective
- small hydrophobic, or nonpolar uncharged molecules get through
- larger ones get through w/ channels
23
Q
aquaporin
A
- H2O channel
- important in tissues that move a lot of water (kidneys)
- also glycerol and ethanol (drinking- alcohol reached stomach)
24
Q
facilitated diffusion
A
- passive transport
- specific protein acts as a carrier or channel to facilitate movement across the membrane
- no energy requirement
- specific recognition
- saturable–> each protein has a finite capacity (rate) that it can allow things to pass
- direction- only works w/ concentration gradient
1. carrier transport
2. channel protein
25
Q
saturation in facilitated diffusion
A
- curve shows a plateau
- Transport by specific proteins demonstrates “saturation” because each protein molecule has a finite capacity (rate) at which it can allow molecules to pass
26
Q
Ion concentrations inside/outside cell
A
- Na+ 10X more concentrated outside cell
- K+ much higher inside
- Ca2+ more outside
- -> difference represent potential energy
27
Q
Fixed anions
A
- usually organic molecules- proteins that are generally negative charge
28
Q
Active Transport
A
- requires energy
- against concentration gradient
- saturable and specific
1. coupled transporter
2. ATP-driven pump
3. light-driven (bacteria)
29
Q
ATP driven pump
A
- ATP binds to substance–> causes to change shape
- Pump for moving H+ into lysosomes
30
Q
coupled transporter
A
- allows things to bind that DO follow the concentration gradient, and another substance AGAINST the concentration gradient will couple with it
- this will change the confirmation and allow the one against gradient to move in
- source of E is gradient
31
Q
light-driven pump
A
- absorbed energy from light
- ex. beta barrel absorbs light and can change confirmation that will allow things in
32
Q
electrochemical gradient
A
- if things in concentration gradient are charged
33
Q
types of transport carriers
A
- uniport- single thing brought across in one direction, ATP driven
- symport- bringing two things in, in the same direction (coupled)
- antiport- one thing in, one thing out (coupled)
34
Q
Hydrolysis of ATP
A
- phosphate is removed- breaking high energy bond
- releases energy, ADP
- exergonic, 7.3 kcal/mol
- Equilibrium lies very far towards ADP + Pi because they are lower in energy than ATP
35
Q
The Na+/K+ ATPase Pump
A
- Complex protein–> ATPase
- enzyme that acts upon ATP (bind and breaks in ADP + Pi)
- With each cycle, 3K+ go out, 2 Na+ go in
- Energy from ATP hydrolysis drives movement of 3 Na+ out, and 2 K+ in, both against their concentration gradients
- Binding sites for Na+, K+ & ATP
- Covalent attachment of phosphate to the protein (and subsequent removal) cause conformational changes that drive the process
36
Q
Na+/glucose Symport
A
- facilitiative diffusion (NOT active)
- Na+ concentration is higher outside cell than inside–> movement into cytoplasm is favorable
- Carrier is designed to only allow Na+ to enter if glucose goes along too–> coupled
- so glucose is pumped out AGAINST its gradient
37
Q
gut glucose (symport)
A
- symport example
- epithelial cell with microvilli in intestinal lumen, and other side is blood/body tissue
- use coupled symporter (w/ Na+) to bring glucose into epithelial cell, and then into the blood
- Use Na+/K+ pump to balance [Na+] in epithelial cell
- use uniport (passive) when enough glucose is in cell to pass to blood
38
Q
ion channels (3)
A
- voltage gated- charges on both sides and as membrane voltage changes, gate will open at a certain voltage
- ligand gated (intracellular)- substances bind form inside to open channel
- ligand gated (extracellular)- substances bind from outside to open channel - stress activated- open when stressed (temp, UV)
39
Q
bulk transport/endocytosis/exocytosis
A
- final step in secration- secretory vessel w/ lipid bilayer and “cargo”
- fuses with membrane, open up–> everything what was inside goes outside
- lipid bilayer fusion
- vesicle inversion- phospholipids on interior of vesicle because exterior when fused
endocytosis- vesicle comes into cell
exocytosis- vesicle leaves cell
40
Q
endocytosis (opposite of secretion)
A
- put membrane around matter outside the cell and bring inside
- the area of membrane is often lines with protein called clathrin (involved in infolding and production of the endosome)
1. phagocytosis (cell eating)- food/ old cell parts are brought in and vesicle fuses with lysosome
2. pinocytosis (cell drinking)- cell brings in extracellular fluid for nutrients
3. receptor-mediated endocytosis- receptors bind to molecules, which helps with the infolding of vesicle, Clathrin lines the membrane where receptors are, when receptors are full, clathrin held with the infolding (coated pit), clathrin leaves, receptors are recycled (move to one side of endosome and break off), ligands go to golgi and then lysosome–> facilitated diffusion
41
Q
LDL receptor-mediated endocytosis
A
- LDL- core is nonpolar, particles circulate through the blood
- RME is how LDL is taken out of the blood–>
- receptors recognize LDL an when full, folds inwards–> brought in and lysosome breaks it down
42
Q
cell membrane function
A
- boundary and permeability barrier for protection
- organization
- transport process
- signal detection
- cell to cel lcommunication
43
Q
endosome
A
- membrane bound compartment
