Movement of substances in and out of cells Flashcards
State the definition of diffusion
Diffusion is the net movement of particles from a region of high concentration to a region of low concentration
State the definition of osmosis
Osmosis is the net movement of water from a region of high water concentration to a region of low water concentration through a partially permeable membrane
State the definition of active transport
Active transport is the net movement of molecules and substances from a region of low concentration to a region of high concentration using energy
What are carrier proteins?
Active transport works with the use of carrier proteins. They are in the cell membrane and pick up specific molecules to take through the membrane
How does the surface area to volume ratio affect the rate of movement of molecules?
The larger the cell, the smaller the surface area to volume ratio
How does temperature affect the movement of molecules?
The higher the temperature the faster the molecules will move. This is because they have more kinetic energy leading to more successful collisions against the cell membrane
How does concentration gradient affect the movement of molecules?
The greater the concentration gradient, the faster the molecules will move. This is because on the side of the cell membrane with the higher concentration, there will be more successful collisions due to the kinetic energy
How does the distance the molecules have to travel affect the movement of molecules?
The shorter the distance the molecules need to travel, the faster the molecules will move. This is because the cell walls are only one cell thick creating a shorter diffusion pathway
Describe the experiment for diffusion in a non-living system
Add a crystal (potassium permanganate) to water (solvent.
The potassium permanganate would diffuse through the water
At the end of the experiment, the crystal would be less concentrated in one place.
The higher the concentration, the darker the purple colour would be
Describe the experiment for diffusion in a living system
Air rich in oxygen would enter the alveoli.
There is a higher concentration of oxygen inside the alveoli than in the bloodstream outside the alveoli.
Therefore, oxygen would diffuse out of the alveoli into the blood.
There is a higher concentration of carbon dioxide in the bloodstream.
Therefore, carbon dioxide would diffuse into the alveoli
This is how gas exchange takes place in living systems
Describe the experiment for osmosis in a non-living system
A visking tubing bag is filled with sucrose solution, and placed into a beaker of water
A capillary tube is placed in the bag.
The concentration of water particles is higher in the beaker of water.
The water molecules would move into the visking tube by osmosis through the partially permeable membrane of the visking tube.
Describe the experiment for osmosis in a living system
Cut cylinders of potato and placing them into distilled water and sucrose solutions of increasing concentration
The potato cylinders are weighed before placing into the solutions
They are left in the solutions for 20 – 30 minutes and then removed, dried to remove excess liquid and reweighed
The potato cylinder in the distilled water will have increased its mass the most as there is a greater concentration gradient in this tube between the distilled water (high water concentration) and the potato cells (lower water concentration)
This means more water molecules will move into the potato cells by osmosis, making them turgid and increasing the mass of the cylinder
The potato cylinder in the strongest sucrose concentration will have decreased its mass the most as there is a greater concentration gradient in this tube between the potato cells (higher water concentration) and the sucrose solution (lower water concentration)
This means more water molecules will move out of the potato cells by osmosis, making them flaccid and decreasing the mass of the cylinder
If there is a potato cylinder that has not increased or decreased in mass, it means there was no overall movement of water into or out of the potato cells
This is because the solution that cylinder was in was the same concentration as the solution found in the cytoplasm of the potato cells, so there was no concentration gradient
