Cell Transport Chapter 7.3

Importance of regulating transport in and out

Cell Membrane ______________________of molecules in and out to keep the inside of the cell relatively constant (What’s that called?)

Cell Membrane Regulates movement of molecules in and out to keep the inside of the cell relatively constant (What’s that called?)

Passive Transport Diffusion – particles moving from an area of high concentration to low concentration Takes place by __________ _______and spreading out of molecules in gas or liquid Eg dye diffusing through a bowl of water (without being stirred)

Passive Transport Diffusion – particles moving from an area of high concentration to low concentration Takes place by random collisions and spreading out of molecules in gas or liquid Eg dye diffusing through a bowl of water (without being stirred)

Down the concentration gradient

Diffusion across a permeable membrane Permeable to a substance = _____________ _____________________________________ Eg – moving through a bowl of water with a sieve in it – the dye moves in and out of the sieve freely

Diffusion across a permeable membrane Permeable to a substance = that substance can move across it freely Eg – moving through a bowl of water with a sieve in it – the dye moves in and out of the sieve freely

Equilibrium Equilibrium = __________________________ _____________________________________ There is still movement of the molecules in both directions across the membrane, but in equal numbers

Equilibrium Equilibrium = when there is an equal concentration on both sides of the membrane There is still movement of the molecules in both directions across the membrane, but in equal numbers

True or false: When equilibrium is reached, the molecules stop moving across the membrane

Facilitated Diffusion Movement of molecules across the membrane ______________than would have been expected Molecules that are large or have a + or – charge or are polar – should not pass through the lipid easily Happens because proteins imbedded in the membrane act as channels or carriers Each protein is specific for one kind of molecule to pass through The movement is still down the concentration gradient, and still does not require energy, so is still a form of passive transport

Facilitated Diffusion Movement of molecules across the membrane much faster than would have been expected Molecules that are large or have a + or – charge or are polar – should not pass through the lipid easily Happens because proteins imbedded in the membrane act as channels or carriers Each protein is specific for one kind of molecule to pass through The movement is still down the concentration gradient, and still does not require energy, so is still a form of passive transport

Semi-permeable membrane Selectively permeable membrane Lets through some things but not other things Due to Size Charge

Osmosis Facilitated Diffusion of Water Osmosis is diffusion of water through a selectively permeable membrane Still moving from an area of higher to lower concentration, but looking at concentration of water rather than the solute

What is osmosis?

Osmosis moves water to where there is more solute Equilibrium will be reached when there is an equal concentration of solute on both sides of the membrane (even if the water has to push against the pressure of gravity)

Concentrations Isotonic – _________ strength (on both sides) Hypertonic – ________ strength Hypotonic – __________ strength Tonicity always refers to __________________

Concentrations Isotonic – same strength (on both sides) Hypertonic – higher strength Hypotonic – lower strength Tonicity always refers to the solution rather than the cell

Hypertonic Hypotonic Isotonic

Effect of Osmosis on Cells

Osmotic Pressure Movement of water into or out of cells produces osmotic pressure A cell in hypertonic fluid will _______ from water being forced out A cell in hypotonic fluid will ________ from water being forced in Plant cells have rigid walls that do not let them shrink or swell

Osmotic Pressure Movement of water into or out of cells produces osmotic pressure A cell in hypertonic fluid will shrink from water being forced out A cell in hypotonic fluid will swell from water being forced in Plant cells have rigid walls that do not let them shrink or swell

Active Transport Movement of molecules up (against) the concentration gradient From ____________________concentrated area Requires ________________ from the cell

Active Transport Movement of molecules up (against) the concentration gradient From less to more concentrated area Requires energy from the cell

Molecular Transport Accomplished by protein pumps – proteins _____ __________that change shape to carry the molecule across

Active Transport Accomplished by protein pumps – proteins in the membrane that change shape to carry the molecule across

Which is passive and which is active transport? What are the two differences? Left passive, right active With or against concentration gradient; use of ATP (cellular energy)

Is diffusion active or passive transport?

If a cell is in an isotonic solution, what happens to it? Draw a diagram

If a cell is in an hypertonic solution, what happens to it? Draw a diagram

If a cell is in an hypotonic solution, what happens to it? Draw a diagram