Chapter 3 Flashcards
Describe the structure of the cell membrane (3)
1) 75% Phospholipid bilayer and proteins in a fluid mosaic
- separates ICF from ECF
- polar, hydrophilic head & nonpolar, hydrophobic tail with kinks (unsaturated fatty acids)
2) 5% glycolipids: lipids with sugar molec on the outer membrane surface
3) 20% cholesterol: increases membrane stability and fluidity
interstitial fluid (IF): ECF that surrounds cells
What is the membrane potential (3)?
- more Na+ in the ECF, more K+ in the ICF
- resting membrane potential: voltage measured in resting state
- due to movement K+ and large anions trapped inside cell
What does it mean to say that the cell membrane is selectively permeable?
- allows specific substances to pass through
- passive: small/fat-soluble/nonpolar molecules
- requires channel proteins to let polar/water-soluble substances into cell
How does the arrangement of the phospholipids help make it selectively permeable?
-the small kinks in the phospholipid bilayer due to unsaturated bonds allows small/fat-soluble/nonpolar molecules throgh
Give several functions of the 2 types of proteins in the cell membrane.
- integral proteins: inserted into the membrane
- most transmembrane but some protrude from one side only
- functions: transport proteins (channels and carriers), enzymes, receptors - Peripheral proteins: loosely attached to integral proteins
- functions: enzymes, cell to cell links
What is glycocalyx (5)
- sugar covering at the cell surface (cell surface markers)
- lipids and proteins attached with carbs
- every cell type have different pattern of sugars (ID tag - specific biological markers for cell to cell recognition)
- allows immune system to recognize self and non self
- cancerous cells change it continuously
Describe these membrane junctions and where each might be found in the body.
- Tight junction
- Desmosome
- Gap junctions
Tight junction: impermeable
-line the digestive tract to prevent digestive organisms and enzymes from seeping through into the blood stream
Desmosome: anchor junctions, reduces chances of cell being torn apart due to force
-abundant in tissues subjected to great mechanical stress such as in the skin & heart muslce
Gap junctions: communicating junctions: allows small molec to pass through
-in electrically excitable tissues such as heart and smooth muscle
What is the function of microvilli? Where are they found?
- increase SA
- found on absorptive cells such as kidney and intestinal cells
What factors determine whether a substance can cross the cell membrane?
-whether it is hydrophobic, small, or existence of energy & receptors for active transport
4 types of passive transport
diffusion, osmosis, facilitated diffusion (glucose), filtration
4 kinds of diffusion
- simple diffusion: molecules move from high to low concentration
- channel-mediated facilitated diffusion: diffusion of large molecules
- carrier-mediated facilitated diffusion: molecules attach onto carriers and changes its shape (ex glucose)
- osmosis: movement of H2O
Rate increases or decreases:
- higher temperature
- large SA
- larger diffusion molecule
- larger diffusion distance
- larger steepness of gradient
- temperature: higher temp = faster
- SA: high SA = faster
- large diffusion distance: slower
- size of substance: slower
- steepness of gradient: faster
Osmosis (5)
-specific kind of diffusion for water
-tonicity: percentage of salt
(9% salt = 9g salt, 91g water)
-isotonic: when the concentration of water is same and no movement; same concentration of molecules in both ECF and ICF
-either wiggle through bilayer or move through aquaporins
-osmolarity: measure of total concentration of solute particles
What happens to cells in a hypertonic environment? What happens in a hypotonic environment?
- hypertonic: more salt on the outside of the cell
- water diffuses out, causing the cell to shrivle. water follows salt!
- hypotonic: water moves into the cell, causing it to swell and lyse
2 active processes
-active transport, vesicular transport
2 types of channel/carrier proteins
- Ligand channel proteins (substances/ligands attach to receptors)
Ex. H2O binds to receptor, which then becomes a 2nd messanger used for chemical reactions - voltage channel proteins: electrical gradient
Active transport (6)
- ATP required
- transport against the gradient
- primary: energy comes from ATP hydrolysis
- secondary: energy comes from the energy stored in ionic gradients created by primary transport
- ATP energy changes the shape of transport protein to pump ions across the membrane
- symporters in same directions, antiporters opposite
3 types of endocytosis
- pinocytosis: transport of water into cell
- receptor-mediated pinocytosis
- phagocytosis: engulfs large molecules, later fuses with the lysosome to make a phagosome
exocytosis (1) examples (5)
- transport out of cell
- hormone secretion, neurotransmitter release, ejection waste, oil secretion from sebaceous glands, sweat production
In diffusion, osmosis and facilitated diffusion, is the movement “down” the gradient or “uphill” against the gradient? Do each of the above processes depend on a concentration or pressure gradient?
down, yes
the sodium-potassium exchange pump is an example of what kind of transport? Why must ATP be used
- active transport
- used because pumping Na and K from a low to higher concentration
- 3 Na out. 2K in
why would the sodium potassium exchange pump be shut down in poisoning that damage the cells mitochondria? What would happen to the cell
-there is not ATP to draw the energy to drive the Na/K pump. The cell’s electrical gradient would disappear
Compared to the inside of the cell what is isotonic? hypertonic and hypotonic solutions? what happens to a cell red blood cell placed in each
- isotonic: same solute concentration as outside
- hypertonic sol: higher concentration of solute outside the cell; water from cell leaves and shrivels
- hypotonic: solute concentration inside cell higher; water enters and cell lyse
what is hydrostatic pressure and what is osmotic pressure
- Osmotic pressure (OP): force of water due to solute concentration (hi solute = hi OP); sucks
- hydrostatic pressure (HP): force driving filtration; pushes
