Unit 5- Cell (Plasma) Membrane Flashcards
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
What is Osmolarity?
total solute concentration of the solution
What is Hypotonic?
extracellular fluid has lower solute concentration than cell; water enters cell ( expands)
What is Hypertonic?
extracellular fluid has high solute concentration than cell; water exits cell (shrinks)
What is Isotonic?
solute concentration of cell= sae as extracellular fluid
True or False: Active Transport does not require ATP
False
Define active transport
Primary active transport moves ions across a membrane and creates an electrochemical gradient ( charge +/- concentration diffusions). Change the shape and opening of the protein to allow the molecule to enter or exit requires energy
Electrochemical gradient vs. Concentration gradient:
With active transport there is usually an electrochemical gradient that exists
A charged difference because ions involved
Ions or molecules can be excluded or the cell can accumulate them
Equilibrium does not have to be accomplished
Concentration gradient is a chemical gradient
Difference of molecules on one side of the membrane compared to the other
What is the function of a Uniporter?
arries 1 molecule or ion in one direction
What is the function of symporters?
Carries 2 different molecules or ions both in the same direction
What is the function of Antiport?
Carrie 2 different molecules or ions in different directions
One moves in and one moves out
What is the function of bulk movement?
Some molecules are simply too large or exit a cell by passive or active transport
Some molecules are needed in bulk, not one at a time
Bulk movement involves_______
the formation of vesicles that either use the cell membrane or recycle the cell membrane
What is Endocytosis?
When a molecule(s) enters the cell
What is exocytosis?
When a molecule(s) exits the cell
Bulk movement always_________
Recycles the cell membrane
What is Phagocytosis?
When one cell consumes another “ cell eating”
What is pinocytosis?
A cell drinks a mass of water “ cell drinking”
What is Receptor-mediated endocytosis?
Proteins can bond to the receptors on surface of membranes and if it fits will form a vesicle around it to take it in
Viruses are able to enter the cell through___________
Receptor-mediated endocytosis
Explain the process of phagocytosis
Cells ingest large particles or even cells by enclosing them in an extension of the cell membrane and budding off a new vaculos
Cell eating
CELL MEMBRANE IS USED TO ENVELOPE
Endosymbiosis is a unique example
Explain the process of pinocystosis
Cell takes in molecules by drinking in the extracellular fluid
Cell drinking
Explain the process of receptor-mediated endocytosis
Receptor proteins in the plasma membrane ensure only targeted substances are brought into the cell
A vesicle forms around and the substance is brought in
Explain the process of exocystosis
Water material for example is enveloped in a vesicle and fuses with the plasma membrane
Waste materials is expelled into the extracellular space
Secretion of proteins and neurotransmitters
What imparts rigidity and some resistance to flow?
cholesterol
The recognition of self facilitated by the plasma membrane plays an important role in ________.
the immune response
The surface of the plasma membrane is ________ due to the ________.
hydrophilic; phospholipids
All types of endocytosis include ________.
he formation of a plasma membrane pocket around the target
________ form specialized sites on the cell surface that allow cells to recognize each other.
Carbohydrates
In ________, the energy required is provided by an electrochemical gradient.
secondary active transport
