Passive transport: Diffusion & osmosis Flashcards
What is diffusion?
The random movement of molecules that cause a net movement from a region of high concentration to a region of low concentration.
Is diffusion a passive or active process?
Diffusion is a passive process requiring no energy input from cells.
Can diffusion occur without a membrane?
This can occur with or without a membrane. This process will appear to stop when the particles are evenly distributed (reaching an equilibrium/dynamic equilibrium).
What is the relationship between concentration gradients and diffusion? What is an example of how our body uses this relationship?
When two substances undergo diffusion, their concentration gradient is brought down. Our bodies use diffusion in the lungs/blood, where diffusion is used to move oxygen and carbon dioxide in and out of blood cells.
What factors influence diffusion?
If the temperature of the particles is increased, the rate of diffusion increases. (increased movement of the particles when at a higher temperature)
Increasing the concentration gradient will increase the rate of diffusion. (can be done by making the diffusing substance more concentrated) This also works inversely, by making the substance that is being diffused into less concentrated.
Additionally, reducing the distance through which diffusion has to happen increases the rate of diffusion. (less resistance for particle movement)
Lastly, increasing the surface area for diffusion increases the rate of diffusion.
What does a concentration gradient mean?
Concentration Gradient: The difference between an area of high concentration and an area of lower concentration.
What does equilibrium mean in diffusion/osmosis?
Equilibrium: An equal concentration on both sides of the membrane, when the net movement of water molecules between both solutions is net zero.
Can a diffused set of solutions that have reached equilibrium have different liquid levels?
A diffused set of solutions that have reached an equilibrium can have a different liquid level from the solution on the other side of the membrane.
What is osmosis?
The diffusion of water across a selectively permeable membrane, from a less concentrated solution to a more concentrated solution
What qualifications are required for osmosis to occur?
Two solutions with different concentrations and a selectively permeable membrane to separate the two solutions.
In the case of a plasma membrane being the selectively permeable membrane, small nonpolar molecules are usually the only ones able to pass through the membrane. However, exceptions like water molecules exist.
How do plants use osmosis? What exact does the water do to enter the plant?
This process is often used by the body to allow water to cross the membranes of cells and in the roots of plants to absorb underground water.
Water also uses osmosis to enter guard cells, opening the stomata.
What are plant cells that are filled with water called? How about ones lacking water?
Cells that are filled with water are called turgid, and ones that lack it are called flaccid.
If u had two solutions of water separated by a semi-permeable membrane in a beaker, how would the water react if u added urea to one side of the beaker?
It would react with the water molecules on its side (because it is too large to pass through the membrane) and reduce the amount of free water molecules.
This would cause water molecules from the other side of the membrane to diffuse into the less concentrated side of the membrane, creating an equilibrium and increasing the water level of the side that urea was added to.
What are the two possible results of osmosis?
1) If the osmotic concentrations of the two solutions are equal, the solutions are isotonic
2) When the solutions have unequal osmotic concentrations, the solution with the higher concentration of solutes is hypertonic, and the solution with the lower concentration is hypotonic.
What is a Solute?
Solute: The substance that is being dissolved in a solution (ex. sugar).
What is a solvent?
Solvent: The substance that is the dissolving medium in a solution (ex. water).
What does concentration mean in osmosis/diffusion?
Concentration: The amount of substance in a defined space (ex. mg/L or ppm).
Is osmosis a passive or active process?
Osmosis is a passive transport process, meaning it doesn’t require energy expenditure by the cell to move water across a semipermeable membrane from an area of high water concentration to an area of low water concentration.
What is an example of molecules that can/can’t go through the selectively permeable membrane in osmosis?
Some molecules can go through the membrane (ex., Water and glucose), and others cannot (ex., Starch).
What are the main differences between passive and active transport for cells?
Active transport requires energy for the movement of molecules, whereas passive transport does not require energy for the movement of molecules.
In active transport, the molecules move against the concentration gradient.
In passive transport, the molecules move along the concentration gradient.
You walk by a student spraying Axe at their locker. You move 20 metres away, but after 10 minutes, you start to smell it again. What happened? Why?
Diffusion. The AXE molecules moved from an area of high concentration (at their locker) to an area of low concentration (20m away).
An egg was placed in a syrup solution. What will happen? Why?
Since the syrup is very concentrated, water will move out of the egg (osmosis: water moves from dilute to very concentrated solution), and the egg will shrink.
What is the difference between passive transport and osmosis?
Osmosis is a more specific term than passive transport. Passive transport is any process where a substance moves without the use of energy. Osmosis specifically refers to the movement of water without the use of energy.
