Physiology Lec 2 Flashcards
4 functions of a membrane
- physical isolation 2. regulation of exchange 3. communication 4. structural support
How does a membrane provide phyical isolation
surrounds cytoplasm and separates intracellular from extracellular
How does a membrane regulate exchange?
controls exchange of ions, nutrients, watse and products between membrane
How does a membrane facilitate communication
membrane proteins enable the cell to recognize and respond to molecules in environment
How does a membrane provide structural support?
contains membrane bound proteins that attach to the cytoskeleton, adjacent cells, and extracellular matrix
What’s the most common type of glycolipid in the outermembrane?
antigens
2 categories membrane proteins?
- peripheral 2. imtegral
Define peripheral proteins
- loosely bound to surface of membrane, cell surface identiy marker (like antigens)
Define integral proteins
penetrate lipid bilayer (across whole membrane), transmembrane protein, transport proteins (channels, permeasse (pumps)
What are the 6 major functions of membrane proteins
- transport 2. enzymatic activity 3. signal tranduction 4. cell-cell recognition 5. intercellular joining 6. attachment to the ECM
What bond holds the membrane together?
non-covelent
Where is the hydrophillic structure of the membrane lipid?
head
Where is the hydrophobic end of a phospholipid?
tail
What’s the total mass of a membrane to a whole cell?
50%
Structures found in the membrane (3)
phosphlipids, cholesterol, glycolipids
Bacteria (prokaryotes) lack which common component in their bilayer?
cholesterol
How does cholesterol affect the membrane?
helps stiffen and stabilize the bilayer. Less fluid. Less permeable.
What replaces the effect of cholesterol in prokaryotes?
cell wall
Which direction can phospholipids move (and not move)?
horizontally, not usually transversely (flip).
Which 2 factors determine membrane fluidity
- temperature 2. composition
Cholesterol blurs the distinctin between which two states of the membrane?
gel and fluid state
Which 2 phospholipids are confined to the outer membrane?
- phospatidylcholine and sphingomyelin
Which 2 phospholipids are confined to the inner monolayer?
phosphatidyethanolamine and phosphatidylserine
Which layer are glycolipids found in?
outer monolayer
What are the functions of glycolipids
- protection 2. cell recognition 3. electrical impulses
Example of enzymatic activity function (of membrane)?
hydrolase
Example of signal transduction
vasopressin receptor
Example of cell-cell recognition?
major histocompatibility complex proteins.
Example of intercellular joining?
desmocollin
What do desmosomes do?
hold neighboring cells together and transmit force from cell to cell.
Example of desmosome?
epithelia, heart muscle
What are tight junctions?
Prevent lateral diffusion of proteins in the bilayer and regulate pericellular permeability. They maintain cell polarity.
Example of tight junction?
epithelia
What are gap junctions?
intercellular membrane that connects cytoplasm of cells and allows ion and molecule exchange.
Examples of cells with gap junctions?
heart muscle, smooth muscle, epithelia
The membrane is ______ permeable
selectively
Which molecules cannot cross the membrane?
Na, K, Ca2+, Cl-, Aminos, Sugar
Which molecules can cross the membrane?
Water, CO2, fatty acids, small nonpolar molecules, steroid hormones
Define passive transport
no energy required. Diffusion. Flows down concetration gradient
What is the difference between the unidirectional movements in the two directions?
net flux
Which factors increase the rate of diffusion
^ concentration gradient, ^ surface area of membrane ^ membrane permeability, ^ temperature
Which factors decrease the rate of diffusion
^ molecular weight, ^ distance of two concentrations
What’s the name of the law that determines diffusion properties?
Flick’s Law
What is the Van Hoff Equation?
all non-permeable solutes in a solution exert osmotic pressure, which depends on molecular concetration ,and temperature
What is the van Hoff Equation (actual equation)?
pie=RCT (r is gas constant, C is molar concentration)
When concentration difference and temperature are high, osmotic pressure is ….
higher
What is osmolarity?
concetration of solutes in a solution.
What happens to a cell whose plasma membrane is weak and not expandable?
^ in extracellular osmolarity, v cell size …. v extracellular osmolarity ^ cell size.
Isotonic?
2 solutions haveequal solutes
Hypertonic?
one with higher solute and one with a lower solvent
Hypotonic?
One has a lower solute, and one has a higher solvent.
