Osmosis Flashcards
Pure water is what type of solution?
Hypotonic
What are cells like in pure water?
Turgid
Cell membrane swells- cell membrane is pressed against the cell wall
What solution is the cell in when it is plasmolysed?
Concentrated sugar solution
What is the cell like when it is plasmolylsed?
Cell membrane has been pulled in away from the cell wall
Smaller volume of cytoplasm
What is osmosis?
The diffusion of water from a region of higher water potential to a region of lower water potential across a partially permeable membrane
What does a partially permeable membrane mean?
Water moves but solute cannot cross
What is water potential?
The ability for water molecules to move freely
How does water potential decrease?
Adding solutes decreases the number of water molecules moving freely due to the ionic dipole interaction (the force of attraction)
What are water molecules like in a glucose solution?
Water molecules form hydrogen bonds with glucose
Decreased water potential
What water potential does pure water have?
0
What is water potential measured in?
KPa
What type of value does water potential have?
A negative value
The more solute you add…
The lower the water potential
Bigger negative value
Hypertonic solution?
More concentrated than the cell
Lower water potential
What is the cell like in a hypertonic solution?
Crenated (shrivelled)
Less cytoplasm- less chemical reactions occurring
Smaller SA
Affects cells function
Water will move out of the cell
Isotonic solution?
Same water potential as cell
No net movement
Hypnotic solution?
Less concentrated than the cell Lower water
Higher water potential
What is the cell like in a hypotonic solution?
Water will move into the cell
Cell swells-lysis
Loses biconcave shape- becomes more circular
Cell membrane bursts
What is the osmotic potential the same as?
The solute potential
What is turgor pressure the same as?
Hydrostatic pressure
Formula for water potential?
Osmotic potential + turgor pressure
What happens when water potential is zero?
There is no net movement
What is osmotic potential?
Water potential of the cytoplasm
Always a negative value
What is turgor pressure?
Pressure exerted by the cell wall against the cell’s contents
Always a positive value
Why do plants have to be turgid?
In order to keep the plant upright
