Intro to Diffusion Flashcards
Define diffusion
The spontaneous and random movement of solutes across the plasma membrane from areas of high concentration to areas of low concentration
How does diffusion relate to the random movement of particles
Diffusion depends on the random thermal motion of solutes
ie., an individual molecule is equally likely to move into a region of higher or lower concentration
How does diffusion relate to entropy and equilibrium
entropy is the thermodynamic law of disorder. Molecules will move in accordance with increasing entropy/disorder. there will be spontaneous net movement of molecules along a concentration gradient until their concentrations are equal
molecules will move with their concentration gradients to reach equilibrium - molecules will continue to move but influx will = efflux
How does diffusion relate to concentration gradients
if there are molecules in a given volume of a high concentration region, on average, more molecules will move from that region to a lower concentration region
what are the first and second laws of thermodynamics?
- energy cannot be created or destroyed only converted from one form to another
- everything tends towards disorder
ie. , it takes energy to maintain an ordered state = disorder is more energetically favourable
Summarize the basis of solute diffusion through membranes in terms of Gibbs free energy
Gibbs free energy (G) measures whether a reaction requires energy to proceed (endergonic) or proceeds spontaneously (exergonic)
for movement of an uncharged molecule into a cell is expressed by:
delta G = RTln([Ci]/[Co])
R = gas constant T = temp in K Ci = concentration INSIDE cell Co = concentration OUTSIDE cell
Define endergonic reactions
A reaction that requires energy to proceed
Positive delta G
energy will be in the reactants
Define exergonic reactions
A reaction that occurs spontaneously
negative delta G
energy will be in the products
Describe simple diffusion
Give examples of molecules that can do this
Spontaneous movement of particles along a concentration gradient without the help of proteins
ex. gasses and hydrophobic lipid (steroids)
Water and small polar molecules CAN but not very effective
Describe facilitated diffusion
Give examples of molecules that do this
Spontaneous movement of particles along a concentration gradient with the help of proteins
ex. water, large molecules, polar molecules
What types of membrane proteins are involved in facilitated diffusion transport?
channel proteins
ion channels
carrier proteins
Describe channel proteins and given an example
like tunnels that are always open for movement of specific molecules
ex. aquaporins for water
Describe hypotonic solutions
when the solute concentration is higher inside the cell than outside
Describe hypertonic solutions
When the solute concentration is higher OUTSIDE of the cell than inside
Describe isotonic solutions
When the solute concentration is equal inside and outside of the cell
What happens to an animal cell in hypotonic solution?
the solute concentration is higher inside the cell, so water will move into the cell and the cell will burst
How does water move across the membrane?
from areas of HIGH [WATER] to areas of LOW [WATER]
from areas of LOW [SOLUTE] to areas of HIGH [SOLUTE]
How does water move across the membrane?
from areas of HIGH [WATER] to areas of LOW [WATER]
from areas of LOW [SOLUTE] to areas of HIGH [SOLUTE]
T or F: water moves from areas of high water concentration to low water concentration?
TRUE
T or F: water moves from areas of low solute concentration to high solute concentration
TRUE
What happens to an animal cell in hypotonic solution?
the solute concentration is higher inside the cell, so water will move into the cell and the cell will burst
T or F: water moves from areas of low solute concentration to high solute concentration
TRUE
What happens to an animal cell in hypertonic solution?
There is higher concentration of solutes outside the cell, so water will move from the cell to the outside and the cell will shrink
What happens to an animal cell in isotonic solution?
this is an animal cells happy state
there is no net movement of water because the concentration of solutes is equal inside and outside the cell
What is an animal cell’s ‘happy state’
Isotonic solution
What happens to a plant cell in hypotonic solution?
a plant cell’s happy state
there is a higher concentration of solutes inside the plant cell than outside so water will move into the cell and the cell will become turgid and firm
the cell will not burst due to the cell wall
What happens to a plant cell in hypertonic solution?
the solute concentration is higher outside the cell, so water from inside the cell will leave the cell making it PLASMOLYZE - membrane will peel away from cell wall
What does it mean for a plant cell to plasmolyze?
the cell is in a hypertonic solution and water is leaving the cell, forcing the membrane to peel away from the cell wall
What is a plant cell’s ‘happy’ state?
hypotonic solution
What provides energy for spontaneous movement?
the energy that is stored in a concentration gradient
What provides energy for spontaneous movement?
the energy that is stored in a concentration gradient
What will happen in the [Ci] is less than the [Co]? in terms of Gibbs free energy and diffusion
[Ci]/[Co] will be less than 1 and ln([Ci]/[Co]) will be negative –> delta G will be negative
this means the rxn will occur spontaneously along its gradient
What 3 things happen as solute moves into cell
- concentration gradient decreases
- stored energy is dissipated
- delta G decreases until equilibrium (delta G = 0)
What does the movement of molecules across the membrane through proteins frequently involve?
conformational changes of the proteins moving the molecules
What are conformational charges?
changes in protein shape that do not break covalent bonds
How do the conformational changes in proteins occur?
changes to the protein environment that alter how the side-chains interact
including:
pH voltage temperature ion concentration ligand bonding phosphorylation
