LEC 13-14 Flashcards
Osmosis
The diffusion of water molecules across a selective (semipermeable) barrier from high concentration to low concentration
Selective (semi permeable) barrier
Allows water molecules to pass through, but not most of the molecules dissolved in water
What is an example of a selective barrier?
Plasma membrane
Solutes
Molecules dissolved in water
How is the concentration of water determined?
By the concentration of solutes (dissolved) in water
Solute Potential
A measure of the concentration of solutes dissolved in water
What is the solute potential of pure water?
0 (pure water has no solutes)
What is the highest value of solute potential?
0
When is the water concentration the highest?
When solute potential is equal to zero
How does adding solutes affect solute potential and water concentration?
Lowers solute potential and water concentration
What does the water follow?
Water follows the solute
What is relationship between solute potential and water concentration?
Directly related; As solute potential increases so does water concentration
What is the relationship between solute potential and solute concentration?
Indirectly related; As solute potential increases, solute concentration decreases
What is the relationship between solute concentration and water concentration?
Indirectly related; As solute concentration increases, water concentration decreases
How does water move?
Water moves from areas of higher solute potential to areas of lower solute potential
Why is it important that plasma membranes are semi permeable membranes?
Cells depend on the regulated diffusion of water molecules across the plasma membrane to stay alive
Isotonic
If solute potential is equal inside and outside the cell (water is entering and leaving the cell in equal amounts)
Hypotonic
If solute potential is higher outside the cell than inside
What are the consequences of a hypotonic solution?
Water will diffuse into the cell causing it to swell and possible burst
Hypertonic
If solute potential is higher inside the cell than outside
What are the consequences of a hypertonic solution?
Water diffuses outside out of cell causing it to shrink and cell could dehydrate and die
Brain Capillaries
Fine blood vessels that feed brain tissues
Capillary Wall Cells (CWCs)
Form walls of tube
Intercellular Junctions
Physical connections between capillary wall cells
Can the molecules pass between the CWCs through the intercellular junctions?
No, molecules must pass through the plasma membrane of CWCs
Blood Brain Barrier
The strict control of what molecules can enter the brain and what cannot
Why does the blood brain barrier cause trouble for doctors?
For certain diseases, doctors need to introduce medicines into the brain but the blood brain barrier keeps most medicine from entering the brain
How do you breach the blood brain barrier?
Inject a solute into the blood, causing water concentration to be higher inside CWCs than blood –> water diffuses out of CWCs into blood –> CWCs shrink slightly and create wide openings between cells
Energy
The capacity to do work
What are the two forms of energy?
Kinetic and potential energy
Kinetic Energy
Energy of motion
Potential Energy
Stored energy
What are some forms of kinetic energy?
Heat, light, mechanical (wind, water)
What are some forms of potential energy?
Concentration gradients and chemical bonds
Thermodynamics
Branch of chemistry that deals with energy transformation (changes)
What are the two laws of thermodyanmics?
First Law of thermodynamics and Second Law of thermodynamics
First Law of Thermodynamics
Conservation law: energy cannot be destroyed or created, they only changed from one form to another
What is true about the total amount of energy in the universe?
It remains constant because the universe is a closed system: nothing can get out of the universe and nothing can get in
Second Law of Thermodynamics
No energy transfer is 100% efficient – some energy is always lost (usually to heat) and becomes unusable energy
Entrophy
Unusable energy
Free Energy
Usable energy
What is true about entrophy in the universe?
Continuously increasing
What is true about free energy in the universe?
Continuously decreasing
What is free energy known by?
The letter “G” for “Gibbs Free Energy”
What does G stand for?
The energy availabe to do work
Free Energy Equation
G = H - TS
What does H stand for in Gibbs Free Energy equation?
Enthalpy, the total amount of energy contained in a molecule
What does TS stand for in Gibbs Free Energy equation?
Amount of disorder in a molecule
What does T stand for in Gibbs Free Energy equation?
Absolute temperature (K)
What does S stand for in Gibbs Free Energy equation?
Entrophy, unusable energy
What is true about the amount of free energy in products compared to reactants?
The products will either have more or less free energy than the reactants
What is the reaction called when G < 0?
Exergonic reaction (products has less free energy than reactants)
What happens in an exergonic reaction?
Free energy is released to do work and it “can be spontaneous”; reaction has the potential to occur on its own without extra energy input
What is the reaction called when G > 0?
Endergonic reaction (products have more free energy than reactants)
What happens in an endergonic reaction?
Energy is absorbed and it is “never spontaneous”; reaction will not occur without an input of energy
Reaction Coupling
The free energy released by exergonic reactions can be used to drive endergonic reactions forward
Adenosine Triphosphate (ATP)
“Energy currency” of the cell
ATP Hydrolysis
Exergonic reaction; reactants (high free energy) include ATP and H20 and products (low free energy) include ADP and other products
