membrane Flashcards
solute
the particles which are being dissolves e.g. sugar, salt
solvent
the substance that does the dissolving. water is the universal solvent
solution
the solute dissolved int eh solvent (mixture of the two)
components of the phospholipid
has a phosphate head (hydrophilic, lipophobic)
and a fatty acid tail (hydrophobic, lipophilic)
how does the bilayer form
the phospholipids in the bilayer have phosphate heads which are attracted to water and hydrophobic fatty acid tails which repel water. this attraction between the heads and tails and water causes the phospholipid bilayer to spontaneously fall into place due to the way the molecules naturally arrange themselves
transmembrane
refers to proteins which are embedded within and span the plasma membrane but have parts exposed to the exterior and interior of the cells
integral proteins
fundamental components of the plasma membrane which are embedded into the phospholipid bilayer
peripheral proteins
are either anchored into the exterior of the plasma membrane through bonding of lipids or are indirectly associated with the plasma membrane through interactions with integral proteins in the membrane
carrier proteins
carrier proteins allow ions to move across the membrane
they have a conformational change (they change shape)
specific in enabling one type of molecule to move across. after binding to it specific cargo molecule, the carrier protein undergoes a change in shape as it delivers it’s cargo to the other side of the plasma membrane
hydrophobic
if a compound repels water it is said to be hydrophobic, non polar
hydrophilic
If a compound is attracted to water it is said to be hydrophilic, polar
the fluid mosaic model
the plasma membrane contains many molecules (mosaic). the plasma membrane is fluid and flexible meaning molecules are not fixed in place. they can move through the membrane
diffusion
the passive net movement of a substance from a region of high concentration to a region of low concentration
what can cross the membrane
non polar, small lipophilic molecules can pass through the membrane. e.g. oxygen, CO2, alcohol
facilitated diffusion
diffusion with help!
the passive net movement of a substance from a region of a high concentration to a region of low concentration, through a membrane via a specific channel or carrier protein.
what characteristic require facilitated diffusion
Polar
large
lipophobic molecules
e.g. sodium, chloride, potassium, glucose
osmosis
the net movement of water from an area of low solute concentration to an area of high solute concentration across a semipermeable membrane
hypertonic
a solution that has a higher solute concentration than another
hypotonic solution
a solution that has a lower solute concentration than another
isotonic solution
two solutions containing the same concentrations of solutes
active transport
the movement of molecules against the concentration gradient using the energy required by ATP
from an area of low concentration to an area of Hugh concentration
endocytosis
the bulk movement of solids or liquids into the cell by englufment
phagocytosis is solids
pinocytosis is bulk movement of liquids
exocytosis
movement of materials out of the cell via vesicles in the cytoplasm
four factors which affect which substances can pass through the membrane
- molecular size: small molecules can pass, macro molecules (nucleic acids) can’t
- presence of a net charge: uncharged molecules can pass, charged cannot
- solubility in lipid solvents: lipophobic (hydrophilic) can’t cross easily, lipophilic (hydrophobic) can
- direction of concentration gradient. down the gradient does not require energy, movement against cannot occur by diffusion
