Ch13: Diffusion and Osmosis Flashcards
Definition of selectively permeable membrane?
Allows some but not all molecules to pass through
Name a thing* that is permeable in biological membranes and a thing* that is impermeable
Permeable: oxygen, carbon dioxide, water
Impermeable: Keratin
Name 2 ways substances move in and out of cells
-Diffusion
-Active transport
Definition of diffusion?
The spreading out of molecules from a region of high concentration to a region of low concentration
Definition of active transport?
The movement of molecules from a less concentrated area to a more concentrated area, with the use of energy
Name an example of diffusion:
1. in everyday life
2. in biology
- Smell of perfume
- CO2 and 02 diffusing in and out of body cells/leaves
Definition of osmosis?
The movement of water molecules, across a semi-permeable membrane, from a region of high water concentration to a region of low water concentration
Definition of solvent?
Liquid that dissolves other substances
Definition of solute?
Substance that has been dissolved
Definition of solution?
Mixture of a solute and a solvent
Is osmosis a form of active transport or passive transport? What does this mean?
Passive transport
-means it does not require energy
What happens when an animal cell is in a solution with the same concentration of solute as its cytoplasm?
What is this solution called?
Give examples of this
-Water will move in and out at the same rate, and the cell remains intact
-Isotonic medium
-Animals that live in the sea must have the same concentration
-In land animals, the kidneys ensure that the blood concentration is the same as the cell’s cytoplasm
What happens when an animal cell is in a less concentrated (less solute) solution as its cytoplasm?
What is this solution called?
Give examples of this
-Water will move into the cell and may cause the cell to burst and die
-Hypotonic medium
-Amoeba
What happens when an animal cell is in a more concentrated (more solute) solution as its cytoplasm?
What is this solution called?
-Water will move out of the cell causing it to shrivel and possibly die
-Hypertonic medium
What is the optimum concentrated solution that an animal cell would like to be in?
Isotonic (equal concentration)
Are cell walls permeable, impermeable or selectively permeable?
Fully permeable to water, gases and many solutes
Definition of turgor pressure?
The outward pressure of the cytoplasm and vacuole against the cell wall of a plant
Explain the cell wall in turgor pressure and its use
-The cell wall is rigid and prevents the cell from swelling
-Turgor pressure gives plant cells strength
What happens when a plant cell is surrounded by a less concentrated (less solute) solution than its cytoplasm?
What is this solution called?
Give examples of this
Water moves into the cytoplasm and vacuole and gives the cell turgidity and strength
Hypotonic solution
This is how roots absorb water from soil
What happens when a plant cell is surrounded by a more concentrated (more solute) solution?
What is this solution called?
Give examples of this
Water moves out of the cell and causes plasmolysis
Hypertonic solution
Lettuce leaves in salty dressing
What is plasmolysis?
When the vacuole and cytoplasm shrivel due to the loss of water in a cell.
Causes the cell membrane to move away from the cell wall and the surrounding solution to fill the gap.
Causes the cell to lose turgor
How are plant cells described in a:
1. Hypotonic solution
2. Isotonic solution
3. Hypertonic solution
Which is the optimum solution for a plant cell?
- Turgid
- Flaccid
- Plasmolysed
Hypotonic solution is optimum
What are the most common cause of food spoilage?
Bacteria and fungi
How can osmosis be used during food preservation?
If food is placed in a salty or sugary solution, any bacteria or fungi present will lose water from their cells, shrivel and die
Examples of osmosis in food preservation?
-Fish and meat soaked in a brine (salty solution) e.g. canned tuna
-Fruit is preserved in jams by using a high sugar concentration
Describe an experiment used to test for osmosis
-2 visking tubing (1 with sucrose solution, one distilled water)
-Weigh both
-Let sit in beaker of distilled water for 15 mins
-Dry both tubes and weigh again
-Note change in weight and appearance
