Osmosis Flashcards
What is the definition of osmosis?
Osmosis is the movement of water molecules from a region of higher water concentration to a region of lower water concentration (i.e. down a water concentration gradient), through a selectively permeable membrane.
What is osmosis an example of?
Osmosis is a passive process (i.e. this process does not require energy).
What is the cell cytoplasm made off?
The cell cytoplasm is mainly water with some substances dissolved in it.
What happens when a soluble substance dissolves in water?
Its molecules spread out into the spaces in between the water molecules.
What does the water concentration of an animal’s blood change according to?
The water concentration of an animal’s blood changes according to how much water the animal drinks, what the animal eats and how much water the animal loses in sweat.
How does the animals body maintain a constant water concentration?
The animals body has systems to maintain as constant a water concentration as possible so that cells work as efficiently as possible.
Describe what happens when a plant cell is placed in a solution of equal water concentration to the cell sap.
The cell is described as normal.
Vacuole containing same water concentration as solution. No overall/ net osmosis occurs.
Cytoplasm pushed against the cell wall.
Cell wall stretched a little.
Describe what happens when a plant cell is placed in high water/low salt concentration.
The cell is described as turgid.
Vacuole has swollen because water has moved into it by osmosis.
Cytoplasm pushed against the cell wall.
Cell wall stretches to a maximum.
Describe what happens when a plant cell is placed in low water/high salt concentration.
The cell is described as plasmolysed.
Vacuole shrinks because water has moved out by osmosis.
Cytoplasm pulled away from the cell wall.
Cell wall unstretched
The process of extreme water loss in plant cells is called plasmolysis.
Describe what happens to an animal cell when placed in a higher water concentration?
It swells then bursts. This is because water moves from a higher water concentration outside the cell to a lower water concentration inside the cell through the membrane.
Describe what happens to an animal cell placed in equal water concentration?
There is no change because the concentration of water inside and outside the cell are equal so no net osmosis occurs.
Describe what happens to an animal cell placed in low water concentration?
The cell shrinks. This is because water moves from a higher concentration inside the cell to a lower concentration outside the cell through a selectively permeable membrane.
