Bio 111 Structure & Function of Plasma Membranes

cell/plasma membrane

encloses cell to separate it from the outside environment, has a fluid (mobility within membrane) and mosaic (mix of different components) structure

components of plasma membrane

phospholipids (mainly), cholesterol, and proteins

integral proteins

transmembrane segments that span membrane and are integral to its structure

peripheral proteins

associate with the surface

glycoproteins

sugars attached to proteins on outer surface of the cell

glycolipids

sugars attached to lipids on outer surface of the cell

extracellular

outside of cell

cytosolic

inside of cell

phospholipids and cell membrane

main component of membrane; amphipathic; when tossed into water they automatically form a structure to protect the philic tails from water and create a fatty core

lateral movement

individual phospholipids move laterally within the same layer of the membrane because the membrane is fluid and the philic tails are not exposed to water when moving laterally

unsaturated lipid

fluid membrane, double bonds and kinks, shorter fatty acid tails

saturated lipid

solid membrane, single bonds, longer fatty acid tails because more availability for Van der Waal reactions which increase electron interactions with hydrogen to be hydrogen packed

cholesterol and membrane fluidity

mostly phobic due to carbon-carbon and carbon-hydrogen bonds; rigid molecule

if an organism lives in a cold environment what is their membrane like

they will have a more fluid membrane so they don’t completely freeze; that means it will be unsaturated with shorter and fluid (kinked) tails

if an organism lives in a warm environment what is their membrane like

they will have a more solid membrane to prevent them from melting; that means it will be saturated with longer and solid tails

selectively permeable

what the membrane is, meaning molecules can pass across the membrane sometimes, always, or never depending on the needs of the cell at that time

two types of transport through the membrane

passive and active

passive transport

move from high to low concentration “downhill,” includes osmosis, facilitated diffusion, and simple diffusion; does not require energy input

osmosis

movement of water through the membrane from its high concentration to low concentration

simple diffusion

movement of molecules directly through the membrane from high to low concentration all by itself; only small, uncharged, and/or non-polar molecules that can easily get through hydrophobic core of membrane

facilitated diffusion

movement of molecules from high to low concentration through the membrane with assistance from proteins that create channels for them to pass through; larger, charged, and polar molecules

diffusion

molecular movement (molecules are ALWAYS moving in cells), leads to molecules spreading out

solute

stuff that is dissolved in the solvent

describe the water to solute relationship

high solute means low water, low solute means high water

in osmosis if there is high water concentration inside the cell what does this mean will happen

there is low solute in the cell and high solute out of the cell; water will flow out of the cell (high to low)

aquaporin

tunnel for water to travel through in transport since they are polar molecules, it lets them get through the hydrophobic core

active transport

molecules move against their concentration gradient (from low to high concentration, “uphill’), so they need help from energy (ATP) to move

primary active transport

ATP is directly used to make a molecule move from low to high concentration (against the gradient)

secondary active transport

two steps to move a molecule from low to high concentration, ATP is used indirectly; a molecule creates an electrochemical membrane using ATP that stores energy, then molecule 1 moves down its concentration gradient, and that stored energy is released to move the other molecule against its gradient

ATP

composed of phosphate, sugar, and a base, → nucleic acid → protein

transport pump

protein that uses ATP to move ions against their concentration gradients

antiporter

pump that moves molecules in opposite directions

symporter

pump that moves molecules in same direction

sodium potassium pump (Na^+/K^+)

pumps 3 Na ions out of the cell for every 2 K ions it brings in, against their concentration gradients, directly using ATP (so primary); every time something new detaches or sticks to it, it changes its conformation which changes its function

electrochemical gradient

stores energy to move something against its concentration gradient; created by a different molecule going from high to low concentration

what does it mean to concentrate something in a cell

go from high to low concentration, against the concentration gradient