Cell Transport and Osmosis

what is the plasma membrane

the boundary that separates the living cell from its surroundings

what is selective permeability

allowing some substances to cross more easily than others

what are phospholipids

the most abundant lipid in the plasma membrane

what are amphipathic molecules

contains hydrophobic and hydrophilic religions

what do amphipathic molecules exist as

stable boundaries between two aqueous compartments

what does the fluid mosaic model state

a membrane is a fluid structure with a “mosaic” of various proteins embedded in it

proteins are not

randomly distributed in the membrane

what are hydrophobic molecules

can dissolve in the lipid bilayer and pass through the membrane rapidly

what are hydrophobic molecules

nonpolar

what is an example of a hydrophobic molecule

hydrocarbons

what are hydrophilic molecules

includes ions and polar molecules that do no cross the membrane easily

what are transport proteins

allows the passage of hydrophilic substances across the membrane

what are some transport proteins called

channel proteins

what do some transport proteins have

a hydrophilic channel

what is the purpose of a hydrophilic channel

that certain molecules or ions can use as a tunnel

what are channel proteins called

aquaporins

what do aquaporins do

facilitate the passage of water

what is osmosis

the diffusion of water across a selectively permeable membrane

water diffuses across a membrane from the

region of lower solute concentration to the region of higher solute concentration until solute concentration is equal on both sides

what is tonicity

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

what is an isotonic solution

solute concentration is the same as that inside the cell; no net water movement across the plasma membrane

what is a hypertonic solution

solute concentration is greater than that inside cell; cell loses water

what is a hypotonic solution

solute concentration is less than that inside the cell; cell gains water

what don’t exist in isolation

cells

what is one important aspect of a cell’s environment

how much solute is dissolved in the surrounding solution compared to the interior of the cell

what does tonicity also refer to

concentration of dissolved solute in the environment relative to the interior of the cell you are interested in

what is diffusion

the movement of substance from high concentration to low concentration or down the concentration gradient

what is diffusion typically powered by

internal vibration of atoms and molecule and no additional energy input is required

what is a function of the second law of thermodynamics

diffusion

what is the second function of thermodynamics

all systems naturally move toward entropy, or disorder

what does high concentration represent

order

if atoms and molecules bump into each other during diffusion what might the force of the collision also influence

the rate of diffusion

what do cells rely on

diffusion to bring nutrients into the cell and remove wastes from the cell

if a molecule is small, non-polar, and uncharged it can diffuse directly through the

phospholipid bilayer

molecules like co2 can diffuse into the cell directly because

they build up in your system as waste product causing it to naturally diffuse into your bloodstream and out your lungs

atoms and molecules that are large, polar, or charged need

help getting through the phospholipid bilayer

why can’t a large atom/molecule get through the phospholipid bilayer

because of the tightly packed fatty acid tails of the phospholipid

what do polar or charged atoms/molecules have difficulty with

navigating the hydrophobic region associated with the fatty acid tails

what do molecules and atoms rely on

facilitated diffusion

what is facilitated diffusion

transport proteins move the atoms or molecules across the membrane

what do the transport proteins that are present determine

what can or cannot move across the membrane

biological membranes are defined as

selectively permeable

different membranes have different types of transport proteins and therefore

move different solutes

individual water molecules can slip through the phospholipid bilayer but

not enough to support life

all of biology is

dissolved in water; there is water in the cytoplasm of the cell and in the environment

water can travel in

both directions; into or out of the cell

what determines whether water enters or leaves the cell

tonicity

what is osmolarity

the amount of solute dissolved in something

what is avagadros number

6.022 × 10 23

what is avagadros number

the number of atoms in one mole of a substance

one mole of a substance is the

atomic mass expressed in grams

when do we mostly use molar mass

aqueous solutions

what do we use when referring to dry mass

mole (mol)

when we dissolve dry mass in water what do we refer to it as

molar solution or molarity (M)

what are molar solutions based on

1 L total volume

what does dry mass do

displace water so you won’t actually use 1 L of water instead you have to adjust the waters volume

what is the most appropriate procedure to dissolve the dry mass of your substance

dissolve it in a smaller amount of water and add water until you have exactly 1 L total volume

if we don’t need that many molecules how can we adjust the formula

multiply by 0.2 M

if you don’t need a full 1L how can we adjust the formula

multiply by 0.5 L

what is the mathematical formula for preparing a solution from a stock solution

C1V1=C2V2

what does C1 represent

starting concentration

what does V1 represent

starting volume

what is C2

desired concentration