Chapter 7: Cell Membrane Flashcards
How thick is the cell membrane?
8 nm
What does the plasma membrane do?
It’s the boundary that separates the living cell from its surroundings.
What does the plasma membrane exhibit?
Selective permeability
What is selective permeability designed to do?
Keep damaging materials out of the cell
Allow needed material into the cell.
Help control chemical reactions in the cell
What is the plasma membrane made of?
Phospholipids
Proteins
Cholesterol
Carbohydrates
What did scientists find out about the membrane in 1915
It was made out of proteins & lipids
What did scientists in 1935 Hugh Davison & James Danielli thought the cell membrane was like?
They thought the cell membrane was like a sandwich w/ the protein in the middle.
In 1972, J. Singer & G. Nicolson thought the cell membrane was like?
They thought the proteins were within the bilayer
What can phospholipids in the plasma membrane can do?
They can move within the bilayers
How do most lipids move through move through bilayer?
They move sideways
How do molecules rarely move in the bilayers?
Flip-Flop cross across the membrane
What do the proteins in the membrane do?
The proteins determine the membrane’s specific functions
What are peripheral proteins?
Bound to the surface of the membrane
What are integral proteins?
They penetrate through the hydrophobic core
What are the six major functions of membrane proteins?
Transport
Enzymatic Activity
Signal Transduction
Cell-Cell Recognition
Intercellular Joining
Attachment to the cytoskeleton and extra cellular matrix
Diffusion
The movement of anything from a region of higher concentration to a region of lower concentration.
The membrane structure is a result of what?
Selective Permeability
What type of movement is diffusion for?
Small to no energy along the membrane
How do hydrophilic molecules interact with the membrane?
They don’t cross the membrane easily & require a protein
How do hydrophobic molecules interact with the membrane?
They can dissolve in the lipid bilayer, and pass through the layer rapidly
What factors influences the behavior of the membrane?
of double bonds b/tw the carbons in the phospholipid’s hydrophobic tail
length of the tail
of cholesterol molecules in the membrane
Temperature
What is the permeability of lipid bilayer w/ short & unsaturated hydrocarbon tail?
Higher permeability & fluidity
What is the permeability of lipid bilayer w/ long & saturated hydrocarbon tail?
Lower permeability & fluidity
What does cholesterol do to the membrane?
Adding cholesterol decreases membrane permeability.
What does temperature do to the membrane?
Membrane fluidity decreases as temperature drops
What are the three types of passive transport?
Diffusion
Facilitated Diffusion
Osmosis
Diffusion
Cross membrane through phospholipid spaces
Facilitated Diffusion
molecules cross using proteins within the membrane
Osmosis
a specific type of facilitated diffusion/ allows for the diffusion of water across the selectively permeable membrane
What is created by the difference in solute concentration?
Concentration Gradient
What is diffusion along a concentration gradient?
Its spontaneous & goes from higher concentration to a lower concentration
3 things to remember about diffusion
Substances diffuse down their concentration gradient
No energy needed
Passive transport
Concentration Gradient
the unequal distribution of ions b/tw intercellular and extracellular fluids
What do transport proteins allow the cell to do?
allows the passage of hydrophilic substances across the membrane
What are channel proteins?
Proteins that have a channel that allows certain molecules & ions can use as a tunnel
What do aquaporins facilitate?
the passage of water
Cystinuria
no transport protein available to transport the amino acid cysteine from kidney back to blood, this creates kidney stones.
How many water molecules do the channel protein aquaporin allow to pass through?
3 billion water molecules per second
Tonicity
the way cell will lose or gain water depending on the solution it is in.
Isotonic Solution
solute concentration is the same as that inside the cell; no net movement across the plasma membrane
Hypertonic Solution
Solute concentration is greater than that inside the cell; cell loses water
Hypotonic Solution
solute concentration is less than the inside of the cell, cell gain water
Active Transport
Requires energy
Used for moving up a concentration gradient
Used for charged ions (like the nervous system)
Used when a shape change occurs
