Transport across membranes Flashcards
What is diffusion?
Movement of molecules or ions from a region of high concentration to one of low concentration.
How does concentration gradient effect the rate of diffusion?
The greater the difference in concentration gradient of molecules in the areas, the more molecules diffuse in a given time
How does the size of the diffusing molecules effect the rate of diffusion?
Smaller molecules diffuse faster than larger molecules. This is because larger molecules cannot readily diffuse through the membrane as it is selectively permeable and therefore they have to travel through intrinsic proteins.
How does the temperature effect the rate of diffusion?
Increased temperature increases the rate, as the molecules or ions have more kinetic energy
How does lipid solubility felt the rate of diffusion?
Fat-soluble molecules diffuse faster than water-soluble molecules, and polar molecules diffuse slower than non-polar ones.
How does the thickness of the membrane effect the rate of diffusion ?
The thinner the me,brand the faster the rate of diffusion because it means there is a shorter distance that diffusion needs to take place over and therefore the more molecules diffuse in a given time.
How does the surface area effect the rate of diffusion?
The larger the area the more molecules have room to diffuse in a given time.
What is the formula linked to surface area that expresses the rate of diffusion?
Surface area x difference in concentration / length of the diffusion path
What is facilitated diffusion?
The passive transfer of molecules or ions down a concentration gradient, across a membrane, by protein carrier molecules in the membrane. (No ATP)
Where and why does facilitated diffusion need to occur?
It occurs down a concentration gradient at specific sites on the plasma membrane where there are protein molecules. It needs to happen because ions and molecules such as glucose cannot directly diffuse through the plasma membrane because they are insoluble in it.
What are the two types of proteins involved in facilitated diffusion?
Channel and carrier proteins
How do the channel and carrier proteins effect the rate of diffusion?
They increase the rate of diffusion down a concentration gradient without energy in the form of ATP from respiration
Increase the rate of transport across the membrane for polar molecules
What is active transport?
The movement of molecules or ions across a membrane against a concentration gradient, using energy from the hydrolysis of ATP made by the cell in respiration
Describe the diffusion graph with oxygen concentration against rate of uptake
The rate of uptake is directly proportional to the oxygen concentration, as the concentration gradient increases between the inside and outside of cell the oxygen diffuses faster
Describe the graph of facilitated diffusion with amino acid concentration against rate of uptake
The rate of uptake is directly proportional to the amino acid concentration at first however the line starts to plateau and this is because all of the carrier proteins become saturated and therefore the number of proteins becomes the limiting factor .
