Lect. 8 Membrane Transport - Energy and Metabolism
No description yet. This curated deck is ready for daily study.
Card preview (24)
Definition of something that is “selectively permeable”
It allows some substances to cross it more easily than others.
Generally, biological membranes are permeable to:
small molecules (H2O, O2, CO2) and lipid-soluble substances they can penetrate the hydrophobic interior of the bilayer
A selectively permeable bilayer is permeable to:
• small uncharged molecules (O2) • very small polar molecules (H2O, CO2) • large non-polar molecules urea, glycerol
A selectively permeable bilayer is impermeable to:
• large polar molecules (glucose) • charged particles (ions: H+, Na+, Cl-, HCO-) glucose, sucrose
Molecules enter/leave cells by: (5)
• diffusion • osmosis (for water) • facilitated diffusion • active transport • bulk transport: endocytosis & exocytosis DOFAB
Water’s role in cells
• essential for survival • prevents drying • all chemicals that enter a cell can only do so if dissolved in water all cells must live in a moist env
Diffusion is a ____ process. Does the cell have to expend energy to make it happen?
Diffusion is a passive process: the cell does not have to expend energy to make it happen.
Diffusion occurs when there exists a ____ until ____ .
Diffusion occurs when there exists a concentration gradient (CG) until equilibrium is reached.
What is a concentration gradient?
The difference in concentration b/w the high concentration vs the area of low concentration. ex: - campfire: heat source; warm when close, cool when far; diff in temp represents a gradient - perfume spray at one end of room; high fragrance next to spray, low at opp side of room; diff in fragrance represents a gradient
Concentration Gradient in a Cell ex: A lipid-soluble substance moves through the lipid bilayer from ____ to ____ concentration.
A lipid-soluble substance moves through the lipid bilayer from high to low concentration.
As long as CG exists, net movement of molecules will be:
in direction of gradient.
Once equilibrium is reached, net movement stops but:
exchange still occurs on a molecule for molecule basis.
Diffusion: a physical process based on random motion All atoms and molecules possess ____ above absolute 0.
All atoms and molecules possess kinetic energy above absolute 0. This is why there is random molecular motion in diffusion.
Factors that influence diffusion rate: (3)
• Concentration gradient • Size and shape (small=more free mov, globular moves easier) • Temp (kinetic E of the particles)
What are the 2 general principles that apply to diffusion and osmosis?
• concentration gradient • equilibrium
Osmosis = fluid diffusion Water’s net mov is from the side of ____ solute concentration to side of ____ solute concentration.
Water’s net mov is from the side of low solute concentration to side of high solute concentration.
Osmosis = fluid diffusion Water’s net mov is from the side of ____ solvent concentration to side of ____ solvent concentration.
Water’s net mov is from the side of high solvent concentration to side of low solvent concentration.
An animal cell in a hypotonic solution will be: While a plant cell is:
• lysed (pop) • turgid (normal)
When an animal cell is normal in an isotonic solution, a plant cell is:
flacid.
In a hypertonic solution, an animal cell is: and a plant cell is:
• shriveled/crenated • plasmolyzed
tonicity in plant cells ex: When water seeks to exit cell, solution surrounding cells is: plant looks sad
hypertonic no turgor pressure on cell wall
osmoregulation: control water balance Paramecium is ____ to the pond in which it lives. To solve this problem, paramecium cells have a specialized organelle, the contractile vacuole, which functions as a pump to force water ____ the cell.
hypertonic, out of
Definition of “tonicity”
Tonicity is a measure of osmotic pressure related to the concentration of impermeable solutes in a particular solution. hypotonic / hypertonic / isotonic
Definition of “osmolarity”
Osmolarity is a measure of molarity of all solutes (permeable + impermeable) dissolved in a particular solution. hyperosmotic / hypo-osmotic / isosmotic