The Cell Membrane and Tonicity Flashcards
What is diffusion?
The movement of particles from an area of higher concentration to an area of lower concentration.
What is concentration?
The amount of substance in a given space
What does selective permeability in a cell membrane mean?
Only some things can get through the membrane
Think of a tea bag - only water can get through, but the tea leaves cannot
What makes up a cell membrane?
a double layer of phospholipids (phospholipid bilayer)
What is a phospholipid?
a molecule with a charged phosphate head, a glycerol (an alcohol) backbone, and two fatty acid chains.
What does hydrophilic mean?
they love water
polar molecules are hydrophilic
What does hydrophobic mean?
they hate water
non-polar molecules are hydrophobic
When does a solution reach equilibrium?
When there is an equal number of particles on each side of a membrane
What types of molecules can easily move across a cell membrane?
molecules that are small and non polar
examples - ethanol & water (polar, but small)
Oxygen (non-polar)
What is osmosis?
refers to the movement of water across a semi-permeable membrane
a type of diffusion - water moves from high to low concentration
What factors speed up diffusion?
Increased temperature
Smaller molecules
Increasing the concentration gradient
Explain the application of osmosis in relationship to penicillin
penicillin weakens the cell wall of bacteria
your body has a higher concentration of water than the bacteria does
water from your body rushes in and bursts the cell
What are integral membrane proteins in a cell wall?
Special protein channels in a cell wall that allow large or polar molecules to cross into the cell
They regulate the flow of molecules into and out of the cell.
What are some examples of large or polar molecules that require special protein channels to cross into the cell
Glucose (sugar)
Charged ions (Na+ and K+)
What is tonicity?
It refers to the concentration of solutes in solution.
What happens when you place a cell in a hypertonic solution?
water moves out of the cell via osmosis
(water moves from higher concentration to lower concentration)
also called CRENATION
example: eating salty food can make your lips feel wrinkled
What happens when you place a cell in a hypotonic solution?
water moves into the cell via osmosis
(water moves from higher concentration to a lower concentration)
A cell can eventually burst in a hypotonic solution - called LYSIS
example: water diffusing into plant cells.
