Diffusion Flashcards
What type of molecules can diffuse through cell membranes?
Small, non-polar molecules like oxygen and carbon dioxide.
Also water as it is small enough, even though it is polar.
How does the concentration gradient affect the rate of diffusion?
The higher it is, the faster the rate of diffusion.
How does the thickness of the exchange surface affect the rate of diffusion?
The thinner the exchange surface (shorter the distance), the faster the rate of diffusion as particles have less distance to travel.
How does the surface area affect the rate of diffusion?
The larger the surface area, the faster the rate of diffusion.
How does the temperature affect the rate of diffusion?
Higher the temperature, faster the rate of diffusion as the particles have more kinetic energy so move faster.
What is facilitated diffusion?
The movement of larger molecules and ions from a high to low concentration with the use of carrier or channel proteins.
A passive process.
What do carrier proteins do?
They move large molecules into or out of the cell, down the concentration gradient.
What do channel proteins do?
They form pores in the membrane for charged particles to diffuse through.
What is active transport?
The movement of molecules or ions into or out of a cell from a region of low to high concentration, against the concentration gradient.
It requires energy and carrier proteins.
Describe how active transport works.
1) A molecule binds to the receptors on the carrier protein.
2) Inside the cell ATP binds to the carrier protein and a Phosphate ion becomes attached.
3) The carrier protein changes shape and the molecule transports inside the cell.
4) The Phosphate rejoins to make ATP.
5) The carrier protein goes back to its original shape.
Diffusion is passive. What does this mean?
No energy is needed for it to happen.
What is bulk transport?
The movement of large molecules, hormones and bacteria into and out of the cell by endocytosis or exocytosis.
What is endocytosis?
When a cells surrounds the substance and engulfs it by forming a vesicle around it.
When a cell takes in a substance.
What kind of molecule is taken into a cell by endocytosis?
Large molecules like proteins, lipids and some carbohydrates.
Does endocytosis use ATP for energy?
Yes
