Unit 5- Cell (Plasma) Membrane Flashcards
(53 cards)
What is The Fluid Mosaic Model?
Plasma membranes are dynamic and constantly in flux.
The fluid nature: due to fatty acids tails and cholesterol embedded in the membrane (in animal cells)
The mosaic nature: proteins and protein- carbohydrate complexes found throughout the membrane
Diversity of different macromolecules
Bilayers- two layers of phospholipids and proteins embedded in those layers
Sugars were attached to the exterior surface of the membrane
Cholesterol imparts rigidity and some resistance to flow- Important in the viscus nature of membrane
Who came up with the fluid mosaic model?
Nickelson and Singer-1972
What is the structure of Phospholipids in the plasma membrane/
Phospholipids form a 2-layer cells membrane that separates fluid within the cell from the fluid outside the cell
the plasma membrane has phospholipids structure that is Amphipathic- _________ heads and ________ tails
hydrophilic/hydrophobic
The plasma membrane is________
Selective permeability- they allow some substances to pass through, but not others
The selective permeability process is called
Diffusion
Which substances can pass through the membrane?
lipid-soluble substances (fat soluble vitamins or hormones)- Nonpolar molecules
O2, H2O, CO2- small molecules essential to life.
They have to diffuse through quickly
Which substances cannot pass through the membrane?
Substances that cannot pass through the membrane and must pass through transport proteins channels
Ions- Na+, K+
Simple sugar and amino acids- any molecule that has polarity
What is Passive transport?
No energy ( ATP) required
Substance move from an area of _______ concentration to an area of ______concentration
higher/lower
What are Factors affecting the rate of diffusion:
Diffusion gradient- The steeper, the higher the rate
Size of molecules or ions- The smaller the size the higher the rate
Temperature- the higher the temp, the higher the rate
Diffusion medium- rate in gas> rate in liquid> rate in solide
Surface area- the larger the surface area, the higher the rate
Why cells are microscopic- allows diffusion to be faster
What is facilitated transport
A type of passive transport that does not require energy to move molecules down their concentration gradient. Uses membrane proteins to move molecules across the membrane that are large or charged (ions)
Examples of facilitated transport?
Glucose and amino acid transport- Since glucose is a large polar molecule, it cannot pass through the lipid bilayer of the membrane. Thus, it needs carriers called glucose transporters to pass through.
______ molecules need a channel or carrier
Polar- because they cannot pass through the plasma membrane
Name three forms of passive transport
1) DIffusion
2) Osmosis
3) Transport protein
Channels are_______
always open
Explain channel proteins
Molecules can easily flow
Like water and oxygen- easier for them to diffuse
Carrier proteins_______
change shape
True or false: Carrier proteins are always open?
False
Explain the process of carrier proteins
bind to substance -> protein shape changes-> bound molecule moves into/put of cell
What is osmosis?
molecules move from high->low concentration across semi-permeable membrane (often water)
What is a solute?
something that is dissolved in a solvent (e.g sugar)
What is a Solvent
It does the dissolving (e.g. water)
What is Tonicity?
water potential of 2 solutions separated by semipermeable membrane
Solute concentration outside the cell and water respond the that
