Diffusion, Osmosis & Active Transport Flashcards
Diffusion
Diffusion is the net movement of particles from an area of high concentration to an area of lower concentration down a concentration gradient
It is a passive process which means that no energy is needed.
It occurs until an equilibrium is reached (balanced concentration)
What factors can increase the rate of diffusion (applies to osmosis as well)
A greater difference in concentration (concentration gradient)
A higher temperature as the particles have more kinetic energy and move faster
A larger surface area of membrane for particles to diffuse across
A shorter diffusion distance
Dilute
high water (solvent) concentration
Concentrated
low water (solvent) concentration
Osmosis
Osmosis is the net movement of water molecules from a region of high water concentration to a region of low water concentration (down a concentration gradient) across a partially permeable membrane (a material that only only certain substances through it in this case water molecules).
It is a passive movement (no energy needed)
Hypotonic Solution
Outside the cell is less concentrated than inside the cell (more water outside)
Will draw water into a cell as there is a greater concentration of water molecules surrounding the cell than inside. Water enters a cell by osmosis.
Isotonic Solution
Concentration is equal inside and outside the cell
Concentrations are equal inside and outside the cell, so there will be no net water movement.
Hypertonic Solution
Outside the cell is more concentrated than inside the cell (less water outside)
Draw water from a cell as there is less water in the surrounding solution than inside. Water leaves a cell by osmosis
Lysis
When the outside of the ANIMAL cell is more dilute (more water) than the inside (hypotonic), too much water may enter and the cell will swell until it bursts.
Crenation
When the outside of the ANIMAL cell is more concentrated (less water) than the inside (hypertonic), too much water may leave and the cell will shrink and shrivel
Turgid
Plants cells have an inelastic cell wall, so won’t shrivel or burst.
When water enters the PLANT cell by osmosis it fills the vacuole. This pushes against the cell wall and causes it to swell.
Flaccid
Plants cells have an inelastic cell wall, so won’t shrivel or burst.
When water leaves a PLANT cell by osmosis, the vacuole shrinks.
Plasmolysed
If too much water leaves the PLANT cell, the cytoplasm moves away from the cell wall.
What is Active Transport
Active transport occurs across a partially permeable membrane and moves particles from an area of low concentration to an area of higher concentration. This is against (up) the concentration gradient.
Transport or carrier proteins are needed to get these molecules into the cells and these use energy.
Cells that do active transport contain large numbers of mitochondria. This means they carry out lots of aerobic respiration to release energy (in form of ATP - Adenosine Triphosphate) to carry out active transport
How do Marine Fish use active transport
Gill cells filter & pump salt back into salty seawater
