D2.3 Water potential Flashcards
define:
solute
solvent
solution
solute: the substance that is dissolved in a solvent
solvent: a substance that dissolves other substances to create a solution
solution: a liquid mixture that consists of a solute dissolved in a solvent
Define solvation
the combination of a solvent with the molecules or ions of a solute
why is water able to dissolve charged and polar molecules?
because water has polarity, which allows it to form electrostatic interactions with other polar molecules and ions
- polar solutes dissolve due to attraction btwn the partial + and - charges on water molecules and solute molecules
- positively charged ions are attracted to the partial negative oxygen pole of water
- negatively charged ions are attracted to the partial positive hydrogen pole of water
Outline the solvation of hydrophilic and hydrophobic substances.
The solvation of hydrophilic and hydrophobic substances in water is determined by whether the substance is polar or non-polar and can form hydrogen bonds with water
Hydrophilic?
These substances are “water-loving” and dissolve easily in water
They include polar molecules + can form hydrogen bonds with water, allowing them to dissolve
Hydrophobic?
These substances are “water-hating” and do not dissolve easily in water
They include non-polar molecules (ex. lipids) and CANNOT form hydrogen bonds with water, so they don’t dissolve and tend to join in groups instead
Define osmolarity
the measure of the total concentration of solute particles in a solution
the measure of solute concentration per unit volume
Define isotonic
isotonic solutions have the same concentration as the cytoplasm of the cell
look at photo
Define hypotonic
hypotonic solutions have a lower concentration than the cytoplasm of the cell
Define hypertonic
hypertonic solutions have a higher concentration than the cytoplasm of the cell
look at photo
what is unit for concentration of a solute in a volume of solution?
moles per cubic decimeter
(mol dm⁻³)
net movement of water in hypotonic solutions?
Water moves into the cell, causing it to swell or burst.
Hypotonic solutions have a lower solute concentration than the cell
net movement of water in hypertonic solutions?
Water moves out of the cell, causing it to shrivel.
Hypertonic solutions have a higher solute concentration than the cell.
net movement of water in isotonic solutions?
There is no net movement of water, so the cell’s size remains stable.
Isotonic solutions have the same solute concentration as the cell.
what does the net movement of water depend on?
it depends on the solute concentration of each solution relative to the cell
relative permeability of the plasma membrane compared to water and solutes?
The plasma membrane is more permeable to water compared to solutes
What is the relative permeability of the plasma membrane to water?
The relative permeability of the plasma membrane to water is high, allowing water molecules to pass through easily
What is the relative permeability of the plasma membrane to solute?
the relative permeability of plasma membrane to solute can vary because some solutes can pass through and some solutes need specific channels
define osmosis
the movement of water particles from a high water potential to lower water potential through a partially permeable membrane
osmosis is a form of passive transport
Explain what happens to cells when placed in:
- isotonic solutions
the cell does not change because it has reached equilibrium + water doesn’t move more in one direction than another
no net osmosis
Explain what happens to cells when placed in:
- hypotonic solutions
cytolysis happens because water moves into the cell very quickly
in plant cells, the cell bursts and in animal cells, it becomes turgid (it doesn’t burst BC animal cells have a cell wall)
net osmosis into the cell
Explain what happens to cells when placed in:
- hypertonic solutions
the cells crenate (they shrink).
both plant + animal cells undergo plasmolysis as water leaves the cell very quickly
net osmosis out of the cell
what is plasmolysis?
it is the shrinking of protoplasm away form the cell wall of a plant of bacterium
(it is often due to water loss via osmosis, causing gaps btwn the cell wall and plasma membrane)
what happens to a plant tissue’s mass/volume if put in a hypotonic solution?
water is absorbed = increase in mass/volume = swollen
what happens to a plant tissue’s mass/volume if put in a hypertonic solution?
water is lost = decrease in mass/volume = dehydrated
what is the concentration of solute if hypotonic?
lower than solution
what is the concentration of solute if hypertonic?
higher than solution
what is the concentration of solute if isotonic?
balanced with solution
Determine the concentration of solutes in a plant tissue given changes in plant tissue mass and/or length when placed in solutions of various tonicities
- If plant tissue decreases in mass and length SIGNIFICANTLY, it was in a hypertonic solution
–>
plasmolysed BC of osmosis and is pretty shriveled - If the plant cell content has shrunken a little bit, it is flaccid and was in isotonic solution
–>
Cell appears limp/flaccid - If plant cell appears slightly swollen, it was in hypotonic solution
what happens to a cell with no cell wall placed in a hypertonic solution?
cell will shrink and lead to crenation
AREA of plasma membrane DOES NOT CHANGE, so cell develops indentations (these are called crenations)
what happens to a cell with no cell wall placed in a hypotonic solution?
cell will burst and lead to cytolysis
plasma membranes are made of?
made of phospholipids
it is thin + has very low tensile strength
why must the tissue fluid in multicellular organisms be isotonic to the cells of the tissue?
it must be isotonic to maintain osmotic balance
An isotonic environment prevents water movement that could cause cells to shrink or swell, ensuring a stable cell volume
This balance facilitates:
- nutrient exchange
- waste removal
- cellular processes
*isotonic tissue fluid = essential for the proper functioning and health of cells in a multicellular organism
Outline the role of the contractile vacuole in freshwater unicellular organisms
The contractile vacuole expels excess water that continuously enters the cell due to the hypotonic environment of freshwater
The vacuole collects and pumps out water, preventing the cell from swelling and potentially bursting.
Through rhythmic contractions, it maintains the cell’s internal osmotic balance
Describe the strength and permeability of a cell wall
The cell wall is composed of cellulose
It has high tensile strength, stronger than steel
It is freely permeable unless impregnated w/ a waterproof material
Explain the effects of hypertonic and hypotonic solutions on cells with a cell wall with specific reference to turgor pressure and plasmolysis
In cells with a cell wall:
- hypertonic solutions cause water to move out of the cell, leading to plasmolysis where the cell membrane shrinks away from the cell wall, resulting in a loss of turgor pressure
Hypotonic solutions:
- cause water to enter the cell, increasing turgor pressure and inducing a firm, turgid state
Turgid is the healthy state for plants
State the effects of isotonic solutions on human cells
will help to keep the cell alive
State the effects of hypertonic solutions on human cells
cell will lose water and lead to crenation and die
State the effects of hypotonic solutions on human cells
cell will gain water and lead to cytolysis and burst
Outline the use of “normal saline” in medical procedures
Normal saline is a 0.9% solution of sodium chloride, which is isotonic with blood
during organ transplants, the organs are bathed in normal saline so that cells will not shrink
Explain the difference in function between carrier proteins and channel proteins
Carrier proteins allow both passive and active transport through them
Channel proteins allow only passive transport
Describe what happens to a protein when it enters the Golgi apparatus
It is then modified and packaged into a vesicle
Explain what facilitated diffusion is
The movement of particles down the concentration gradient through protein channels
Explain why water only diffuses slowly through plasma membranes
Water is small so can diffuse straight through the phospholipid bilayer.
However. it is polar, which means it diffuses through slowly
Explain how molecules are actively transported
Through channel proteins, against the concentration gradient, with the use ATP
from left to right
Water molecules always move from a region of high water potential to a region of low (more negative) water potential
pure water = 0 kpa
