Exam 2 CH5 Info Flashcards
What factors affect the ability of solutes to pass through a phospholipid bilayer?
Polarity
Charge (like an ion)
Concentration (of inside to outside of the molecule we want to move across)
Size of the molecule
Selectively Permeable
A selection to what is allowed across the plasma membrane
What can pass through the membrane easy? (highly permeable)
Gasses (very small, uncharged molecules)
What molecules are moderately permeable?
Water and Urea
What has low permeability?
Polar, organic molecules (too charged to pass through the bilayer) [sugars]
What are the two types of passive transport?
Simple and facilitated diffusion
Simple diffusion vs Facilitated diffusion
Simple: Substance moves across a membrane by passing directly through the phospholipid bilayer
Facilitated: diffusion of a solute through a membrane with the aid of a transport protein [less permeability molecules]
What is Passive transport?
Requires no input of energy
Movement of solutes from high to low concentration (down the concentration gradient) until reaches equilibrium
Osmosis
The movement of water across membrane via diffusion
Balance solute concentration with impermeable solutes
Outside isotonic
The solute concentration outside the cell is isotonic (or equal) to the inside of the cell
Outside hypertonic
The solute concentration outside the cell is hypertonic to the inside of the cell
More solute [sugar concentration] outside than inside
less water outside of the cell than inside the cell (higher concentration of water inside the cell than the concentration of water outside the cell)
Outside hypotonic
The solute concentration outside the cell is hypotonic to the inside of the cell
more solute inside than outside
more water outside of the cell than inside (higher concentration of water outside the cell than the concentration inside the cell)
Diffusion vs. Osmosis
Diffusion: solUTE molecules move from high to low concentration
Osmosis: solVENT molecules move from low to high concentration
Can a solute pass the membrane?
NO
H2O can
Why is osmosis important?
it helps maintain the cell shape and integrity of the cell when the environment of the cell changes
Describe cell’s shape in an isotonic solution
Cells maintain normal shape
Describe cell’s shape in a hypertonic solution
The cells undergo shrinkage (crenation) because water exits the cell
Describe the cell’s shape in a hypotonic solution
Cell’s swell up and may undergo osmotic lysis because water is taken into the cell
7% red blood cell placed in 100% pure water. What happens?
well there’s 93% water in the cell, and 100% water outside of the cell
Diffusion of water into the cell, causing it to swell
7% red blood cell placed in 20% salt solution. What happens?
80% water in the salt solution and 93% inside the cell. The water will leave the cell to create equilibrium, which causes the cell to shrink
You drop a raisin into a glass of water. How would you describe the solute concentrations of the raisin compared to the water? What would the raisin look like after 24 hours in the water glass?
Raisin is low water and high solute. Inside of raisin is hypertonic compared to the water in the glass.
The raisin would swell
Facilitated diffusion: Transport proteins
Transmembrane proteins [embedded in the membrane]
Provide a passageway for movement of ions and hydrophilic molecules across membranes
two classes based on type of movement (channels and transporters)
Channels vs Transporters
Channels: gated
Transporters: conformational change [more specific]
Transporter proteins:
change their conformational shape based on the solute binding them
also known as carriers
