cell membrane and transport Flashcards
what’s another term for cell membrane
plasma membrane
what molecules make up the bilayer
phospholipids, proteins, cholesterol
which parts of the bilayer are polar?
heads of the phospholipids
which parts of the bilayer are hydrophobic
tails
which parts of the bilayer are nonpolar
tails
which parts of the bilayer are hydrophilic
heads
how do the phospholipids aid in structure
the hydrophilic heads face towards the water while the hydrophobic tails cluster inward, creating a stable barrier
cholesterol job in the bilayer
influence membrane fluidity
membrane proteins job in bilayer
embedded in the structure- enabling various cellular processes
types of membrane proteins
integral (transmembrane), peripheral (surface)
peripheral protein function
signal transduction, cell recognition,attachment to cytoskeleton
integral protein function
some are receptors for cell communication, some receptors have have carbohydrates attached, some are transport proteins that move material in/out of the cell
cholesterol location in cell membrane
interior of the bilayer
cholesterol function in cell membrane
Strengthen and Support: reduces membrane fluidity by reducing phospholipid movement, hinders solidification at low temperatures, interferes with saturated hydrocarbons, restrains movement at high temps
How does this cholesterol chemical properties allow for its function
Cholesterol is hydrophobic, which allows it to interact with the hydrophobic tails of phospholipids, helping stabilize the membrane fluidity
carbohydrates location in cell membrane
outer surface of cell membrane
carbohydrates function in cell membrane
help cells distinguish one cell from another
main functions of cell membrane
Forms a boundary between inside and outside of cell, controls transport of materials going in and out of cell, involved in communication/recognition and binding between cells, involved in cell signaling and sending messages
How does the phospholipid bilayer help achieve the function of selective permeability?
The hydrophobic tails prevent most molecules from simply diffusing across, only allowing non-polar molecules to easily pass through. Larger molecules only pass through with the assistance of membrane proteins (channels, carriers, pumps)
definition of selective permeability
Enables a cell to maintain homeostasis(maintaining inside conditions despite the outside environment), allows molecules to cross several ways
What is the criteria for substances to be able to diffuse across membrane?
Size, solubility, charge
Which types of molecules can pass with ease?
Small, hydrophobic(nonpolar), neutral molecules
What part (and its properties) of the membrane makes it selectively permeable?
Two phospholipid layers, heads on the outside (philic,polar), tails on inside (phobic, nonpolar)
what is simple diffusion
passage of material through the membrane with concentration gradient, without the help of a transport protein or energy
what drives simple diffusion
concentration gradient
identify substances that can diffuse freely compared to substances that use a protein
gases, small uncharged molecules, nonpolar, small lipids, oxygen, carbon dioxide
describe facilitated diffusion
diffusion across membrane through transport proteins
what drives/is responsible for facilitated diffusion
concentration gradient
how faciliated is this different than simple diffusion
molecules transport through the transport proteins
Give an example of substances that would need facilitated diffusion to move across the membrane.
Charged/polar/large molecules, glucose, chloride ions
describe osmosis
facilitated diffusion of water molecules across a semi permeable membrane
what drives osmosis
Concentration gradient (high to low) with aquaporin
describe isotonic
same concentration of solutes and solvents in/outside of cell, = amount of water exiting/entering cell, no net movement , cell remains same size
describe hypertonic
solution it is sitting in has more solutes, net movement of water will move out of cell, cell will decrease in size and mass
describe hypotonic
if a cell is sitting in a hypotonic solution it is sitting in a solution w/ less solutes (more water), than inside cell, hypo=more water
how is active transport different from passive transport
Requires energy input from the cell, passive does not
Which way are molecules/substances moving in terms of concentration for active transport
Low to high concentration
What powers active transport
energy (ATP)
what is endocytosis
cell membrane takes in macromolecules by folding in on itself and forming new vesicles derived from cell membrane
what is exocytosis
internal vesicles containing macromolecules move to the cell surface and fuse with the cell membrane. The macromolecules are released into the extracellular space.
what powers Endo and exocytosis
energy (ATP)
