L5 Membranes Flashcards
What are the five macromolecules that make up the plasma membrane and describe their function
Carbohydrates - cell identity
Proteins - transport
Cholesterol - fluidity
Phospholipids - form selectively permeable barrior
What are the functions of the plasma membrane
Transport - protein channels, pumps, carriers
Communication - protein receptors
Metabolism - protein enzymes
Structure - cytoskeleton proteins ( create cell junction)
Self identify markers - proteins that protect ( prevents autoimmunity)
Concentration gradient
Drives molecules down/ with concentration
(Passive process)
High ➡️ low
What is a passive process? Active?
Passive process = no energy required
Active = requires energy (ATP)
What are the 2 membrane transports?
Driving force and ATP
————— powers protein pumps ( driving molecule up concentration)
ATP
What 2 things effect a molecules pathway through a membrane?
- Molecule size
- small molecules =pass
- large molecules = not pass w/o transporter (pore, channel) - Molecule polarity
- Nonpolar = pass
- polar = transporter
Simple diffusion
Random movement of molecules
Net diffusion
Directional movement of molecules ( driven by concentration gradient)
Channel- mediated facilitated diffusion
- “facilitated” by proteins that form channels/ pores
Each channel has specificity
Ex. Ion channels
What are the 4 types of ion channels.
- Always open
- Voltage gated - switch in membrane charge
- Ligand gated - need neurotransmitter to open
- Mechanically gated - gated ion channels
Carrier- mediated facilitated diffusion
Molecules cross plasma membrane by protein carriers
Mechanism for : Carrier- mediated facilitated diffusion
- Molecule blinds w/ specificity to protein carriers (glucose, amino acids)
- Binding = shape change of carrier protein ➡️ molecule transported and released
- Released molecule = shape change back to original shape of protein carrier
What mechanism of water is used when cells need to move lots of water quickly?
Aquaporins - channel specifically for water
Primary active transport (pumps)
Uses ATP to phosphorylate transport protein
3 types : Na+/K+ pump , ca+ pump & protein pump
List the steps of the mechanism for Na+ / k+ pump
- 3 Sodium bind w/ specificity
- Activation of ATPase site
- Pump is phosphorocated
- Protein changes shape & sodium ions released
- Potassium binds
- Phosphate is released (@ ATPase site)
- Shape change back to original shape & potassium ions released
Secondary active transport and 2 sub parts
Energy is stored in Na+ concentration gradient ➡️ moving Na+ into cell &
Co-transport = same direction (down concentration)
Counter- transport = opposite direction (up concentration)
Osmosis
Net diffusion of water through a selectively permeable membrane
What molecules will promote osmosis and what will NOT promote osmosis?
Will = o2, co2, cholesterol
Not = h2o, Na+, glucose (c6H12O6)
What is Tonicity?
Comparison of solute concentration between 2 solutions
Hypertonic
One solution has more active solute than other
Hypotonic
A solution has less active solute than other solution
Isotonic
Active solute is the same on both sides
Osmolarity means
Measure of concentration of osmotically active solutes
