Week 1 Lecture 1 Flashcards
What is the cell membrane composed of?
A phospholipid bilayer
What substances can diffuse through the cell membrane?
Lipid-soluble molecules and gases
What substances cannot cross the cell membrane?
Water-soluble molecules and organic anions (proteins)
What does permeability depend on?
Molecular size, lipid solubility, and charge
What is membrane permeability?
If a substance can cross a membrane, the membrane is permeable to that substance
Can gases diffuse across the membrane?
Yes, they can
Can polar molecules and ion diffuse across the membrane?
No, they need the help of proteins e.g. channels or transporters to cross
What is simple diffusion
small, lipid-soluble molecules and gases pass either directly through the phospholipid bilayer or through pores
Is simple diffusion passive or active transport?
Passive, no energy is required, movement is down [] gradient
What is the relative rate of simple diffusion proportional to?
The gradient across the membrane, the greater the concentration gradient, the greater the rate of diffusion
What does simple diffusion require?
brownian motion
How is facilitated diffusion similar to simple diffusion?
Both are passive, involve substance moving down it’s [] gradient
How is facilitated and simple diffusion different?
Facilitated diffusion requires carrier proteins while simple diffusion does not (substance passes directly through phospholipid bilayer or pores)
What is facilitated diffusion?
process of diffusion in which molecules diffuse across the membrane with the assistance of carrier proteins
What are carrier proteins?
aid the movement of polar molecules across the cell membrane
