bio unit 2 chap 7

lipids, proteins

what are the staple ingredients of a membrane

amphipathic

a molecule that has both hydrophilic and hydrophobic regions

fluid mosaic model

the membrane is a mosaic of protein molecules drifting laterally in a fluid bilayer of phospholipids

no (groups of proteins are associated in long lasting, specialized patches, where they carry out common functions)

are proteins randomly distributed in the membrane?

hydrophobic interactions

a weak chemical interaction caused when molecules that do not mix with water come together to exclude water

hydrophobic interactions

what are membranes mainly held together by?

yes

can some of the phospholipids and proteins shift around and change places within the membrane?

yes

can a membrane solidify?

type of lipids it’s made of

what does the temperature the membrane solidifies at depend on?

unsaturated (the kinks in their tails caused by double bonds makes it harder for them to pack close together to make solids, therefore enhancing membrane fluidity)

what kind of tails do phospholipids that stay liquid at lower temperatures have?

saturated (tails have no double bonds and are straighter, allowing them to pack closer together and solidify easier)

what kind of tails do phospholipids that solidify at higher temperatures have?

yes

do unsaturated lipids have double bonds?

no

do saturated lipids have double bonds?

between phospholipids in membranes

where is cholesterol located?

cholesterol (at high temperatures, it restrains the movement of phospholipids, making them less fluid, however it also hinders the close packing of phospholipids, making them less prone to solidify)

this steroid helps the membrane resist changes in fluidity with changes in temperature

fluidity

this affects the permeability of the membrane and the ability for membrane proteins to move where they are needed to function

proteins (different kinds of cells contain different kinds of membrane proteins)

what determines the membrane’s function?

integral proteins

transmembrane proteins that penetrate and often span the hydrophobic portion of a membrane. They have both hydrophobic and hydrophilic regions

transmembrane proteins

a protein that spans the entire membrane

hydrophilic channels

channels in some proteins that allow hydrophilic substances to pass through hydrophobic areas (cell membrane)

peripheral proteins

proteins loosely bound to the surface of a membrane or to an integral protein. NOT embedded in the lipid bilayer

transport, enzymatic activity, transferring signals, cell recognition, intercellular joining, attachment to cytoskeleton or ECM

what are the six functions of membrane proteins

glycolipid

carb attached to a lipid

selective permeability

allowing some substances to cross the plasma membrane easier than others

nonpolar

which molecules have a easier time passing through the cell membrane? non polar or polar/ions?

transport proteins

proteins that span the membrane that help polar/ionic/hydrophilic substances pass through the cell membrane

aquaporins

a type of transport/channel protein that facilitates osmosis- or the diffusion of free water across the membrane

channel proteins

proteins that have hydrophilic channels that functions as tunnels so hydrophilic molecules can pass thru the hydrophobic interior of the cell membrane

carrier proteins

transport proteins that change shape around the hydrophilic molecules to bring them inside/outside the cell

diffusion

the movement of particles so they spread out into a space- in this case the movement of a substance from a region where it is more concentrated to a region where it is less concentrated

passive transport

the diffusion of a substance across a membrane that uses NO ENERGY- it moves WITH the concentration gradient (high conc to low conc)

osmosis

the diffusion of free water across a selectively permeable membrane- high to low

hypotonic

more solvent, less solute

lysed

the cell bursts in bio terms, when animal cells are in a hypotonic environment

hypertonic

more solute, less solvent

tonicity

the ability for a surrounding solution to cause a cell to gain or lose water

isotonic

equal concentrations of solute and solvent

turgid

optimum state for plant cells, plant cells are in a hypotonic environment, meaning water will flow into the cell and create pressure

hypertonic

in what environment do both plant and animal cells shrivel up/plasmolyze?

hypotonic

what environment should plant cells be in?

isotonic

what environment should animal cells be in?

facilitated diffusion

a type of passive diffusion with the assist of transport proteins (to move ions and etc.)

gated channels

channels that open/close in response to a stimulus

active transport

the movement of a substance across the cell membrane AGAINST its concentration gradient, expends energy (ATP) and is mediated by specific transport proteins

sodium potassium pump

a transport protein that actively transports sodium out of the cell and potassium in, also the main pump for animals

membrane potential (also usually the inside of the cell is negative to the outside of the cell, so cations (positive ions) are attracted in and anions (negative ions) are pushed out)

the difference in electrical charge across a cell’s plasma membrane due to the differential distribution of ions. It affects the activity of all excitable cells and the transmembrane movement of all charged substances

electrochemical gradient

the combination of chemical (concentration diff) and electrical forces (membrane potential/charge diff) acting on an ion

electrogenic pump

a transport protein that generates voltage across a membrane

proton pump (H+ ions)

what is the main electrogenic pump for bacteria/plants/fungi?

cotransport

the coupling of the downhill diffusion of one substance to the uphill transport of another against its own concentration gradient

FOR EXAMPLE… sucrose can enter the cell but ONLY ON H+ ions, so, sucrose and H+ diffuse TOGETHER INTO THE CELL WITH THEIR CONCENTRATION GRADIENTS, then after H+ has performed its duty, it gets pumped back out

vesicles

what do large molecules enter and leave the cell on??

exocytosis

the secretion of molecules by the cell by the fusion of vesicles containing them with the plasma membrane

endocytosis

the cell takes in molecules via formation of vesicles form the plasma membrane

pinocytosis, phagocytosis, receptor mediated

what are the three types of endocytosis

phagocytosis

LARGE particles are taken up by endocytosis (cellular eating)

pinocytosis

cell ingests extracellular fluid and its dissolved solutes (cellular drinking)

receptor mediated endocytosis

a type of endocytosis/pinocytosis that takes in specific substances in the extracellular fluid, even if those substances aren’t particularly abundant. Works by having receptors in the vesicle that is forming that attracts specific substances.