AP BIO Unit 4:Cell membrane

Surface area

total amount of area of the outer surface

volume

total amount of space a object occupies

Surface area: Volume

determines surface area relativeness to volume ( less surface area relative to volume= decrease rate of diffusion)

Diffusion

net movement of molecules moving from high to low concentration, stops when both regions have equal concentration (random motion still continues), as distance increases rate of diffusion decreases.

solutes

dissolved substances

solvents

water

molarity

concentration of a solute in a solution (mol/L)

permeable

membrane allows water or solutes to diffuse freely

impermeable

membrane blocks diffusion entirely

Relationship between water and solute concentration

solute concentration increases the water concentration decreases.

osmosis

movement of water across a selectively permeable membrane in response to a difference in solute concentration

osmotic pressure

tendency of water to move from one solution to another through osmosis ( higher the solution concentration, higher osmotic pressure)

hydrostatic pressure

pressure that gravity exerts on the solution (=osmotic pressure)

toncity

strength of water pulled from one solution to another

hypertonic

higher solute concentration

hypotonic

lower solute concentration

isotonic

equal solute concentration

Contracticle vacuoles

organelles that take up excess water from inside the cell then expel it outside

water potential

measure of all factors that influence the movement of water

water potential formula

pressure potential

effect pressure on movement of water

solute potential

effect solutes of a solution on movement of water

formula of solute potential

Which molecules CANNOT cross the membrane on their own?

polar, charged, and large molecules

Which molecules CAN cross the membrane on their own?

nonpolar, uncharged, and small molecules

Contentration gradient

the way molecules are distributed (high/low concentration)

Passive transport

molecules move across the membrane through diffusion

Simple diffusion

molecules directly diffuse through the cell membrane

Facilitated diffusion

diffusion across a membrane through a transport protein

channel protein

provides an opening between the inside and outside of the cell, gated ( open by signal), allows molecules in based on shape and charge

Carrier protein

binds and transports specific molecules in the membrane, on both sides, changes shape based on molecule for transport

aquaporin

channels that allow water to enter/exit the cell through facilitated diffusion

phospholipids

found in cell membrane, most are made up of glycerical backbone attached to a phosphate group and two fatty acids, amiphatic

micelle

sphereical structure packed with bulky head and a single fatty acid tail

lipid bilayer

structure formed of two layers of lipids, hydrophillic heads outside to interact with water while hydrophobic tails are sandwiched in between, isolated from contact with water.

Liposomes

formed when phospholipids are at a neutral ph , cell like (inner and outer space) , outer = polar (interacts with water) protects inner, self-healing

Cell membranes are

dynamic (allows them to perform functions) and fluid ( longer fatty acid tail = less fluid)

Relationship between carbon bonds and cell membrane stability

More carbon bonds = more stability

Cholesterol

major component of animal cell membrane (30%), amiphatic , can insert into lipid bilayer, maintains homeostasis

Relationship between temperature and membrane fluidity

higher temperature=higher fluidity (fluid is not always uniform)

Lipid rafts

specific types of lipids assembled into defined patches

Lipid flip-flop

spontaneous transfer of a lipid between layers of a bilayer, requires hydrophilic groups to pass hydrophobic interior, causes exchange of layer components (differences in layer composition)

proteins

are embedded into the cell membrane, used for many different functions (speed up chemical reactions , anchors, and maintains shape)

transport protein

moving ions or other molecules across the membrane

receptor protein

allows cell to receive signals from the environment

Integral membrane protein

permanently with the cell membrane, cannot be separated

peripheral membrane protein

temporarily binds with lipid bilayer or with integral membrane proteins through weak noncovalent reactions

transmembrane protein

integral, span entire lipid bilayer, composed of 3 regions (2 hydrophilic[outer one is a receptor while the inner one posses the message inside] , 1 hydrophobic [holds protein to membrane]),