General Cell Membrane Questions Flashcards
Why is the cell surface membrane a fluid mosaic model?
Fluid- the phospholipid molecules can move freely within the membrane which is why it’s fluid
Mosaic- proteins are distributed in a mosaic pattern
Model- it has been proven chemically and experimentally
Why do phospholipids form a bilayer in the plasma membrane?
— Phospholipids have a polar phosphate group which are hydrophilic and will face the aqueous solutions
— The fatty acid tails are non-polar and hydrophobic and will move away from an aqueous environment
— As both tissue fluid and cytoplasm is aqueous phospholipids form two layers with the hydrophobic tails facing inwards and phosphate groups outwards interacting with the aqueous environment
How can polar and non-polar molecules pass through the membrane
— Polar molecules require proteins to enable them to pass through the membrane
— Non-polar molecules can diffuse directly through the phospholipid bilayer
What is the definition of simple diffusion?
Diffusion is the net movement of molecules (or ions) from a region of high concentration to a region of lower concentration, down a concentration gradient.
What type of process is diffusion?
It’s a passive process which means no energy is used to make the molecules move, they have a natural kinetic energy
How do the molecules move in diffusion because of the kinetic energy?
They move randomly
What is a result of diffusion?
Molecules reach an equilibrium where they are evenly spread out. This is when there is no net movement of molecules from one place to another.
What are the factors affecting the rate of diffusion?
— The steepness of the concentration gradient
— Distance
— Surface area
How does the steepness of the concentration gradient affect the rate of diffusion?
The bigger the difference between the two sides the membrane the quicker the rate of diffusion.
How does distance affect the rate of diffusion?
The shorter the route the faster the rate of diffusion
How does the surface area affect the rate of diffusion?
The greater the surface area the faster diffusion can take place. This is because the more molecules or ions can cross the membrane at any one moment.
What is the formula for ficks law?
Rate of diffusion is proportional to = Surface area x difference in concentration / length of diffusion path
Under what conditions would particles diffuse at the highest rate?
— The higher the concentration of particles, the higher the rate of diffusion
— The higher the mass of particles , the lower the rate of diffusion
— The higher the radius of particles, the lower the rate of diffusion
— The higher the temperature, the higher the rate lf diffusion
What is facilitated diffusion?
— Polar molecules cannot diffuse directly across the phospholipid bilayer
— These molecules pass through protein channels instead. Diffusion through these channels is called facilitated diffusion
