How cells move things in and out CELL TRANSPORT How cells move things in and out We are going to learn how substances move into and out of cells We will talk about two different ways: passive transport (a way that does not use energy) and active transport (a way that does use energy) Why do things move in and out of cells: to maintain constant conditions within the cell

Solutions Solution: combination of solute and solvent (Solution= solute + solvent) Solute: substance being dissolved (ex. Salt) Solvent: substance doing the dissolving (ex. Water) Concentration: amount of solute in a solvent (difference in concentrations = “concentration gradient”) Before we talk about movement of substances across the membrane, we need to understand some vocabulary: What is a solution (a salt solution, for example)? it is composed of a substance that is being dissolve (salt) and the substance that is doing the dissolving (solvent) solute is solid (t) while solvent is flowing (v) Solutions have “concentrations” that are dependent on the amount of solute that is dissolved in the solvent more solute = higher concentration eg., lot of salt = high salt concentration while little salt in same amount of water = low salt concentration If X = solute and * = solvent, then concentration = X/* Demonstrate several examples on board (students compute concentration): 1. 3 X and 2 * 2. 2 X and 4 * 3. 4 X and 8 * 4. 1 X and 4 * Which has highest concentration? #1 Lowest concentration? #4 Equal concentrations? #2 and #3 If we have a difference in concentrations, then we have a concentration gradient demo with #1 and #4 above (one inside cell and one outside cell) high to low / low to high depending on what we are looking at (solute or solvent)

How substances move PASSIVE TRANSPORT- movement across a cell membrane that does NOT require energy Now that we have learned some basic vocabulary, let’s talk about how substances move across the membranes of cells Passive transport – cell does not have to use any energy for this type of transport to occur; it occurs naturally (on its own) ENERGY

Types of Passive Transport Diffusion: Molecules move from areas of HIGH concentration to LOW concentration to create an equilibrium Osmosis: Diffusion of water in and out of the cell to create an equilibrium Facilitated Diffusion: Uses carrier proteins to transport substances to create an equilibrium (Fig. 4- pg. 80) Diffusion = molecules moving from HIGH to LOW concentration until reach an equilibrium (condition in which conc. are same) Demonstrate diffusion with drop of food color in beaker of water molecules are in constant motion (even though we can’t see it) color molecules will slowly move from where they are most concentrated, to the area where they are not, eventually coloring the entire beaker of water The difference in concentration of molecules is called the concentration gradient Many substances dissolved in the cytoplasm or the fluid outside cells center or leave cells by diffusing across the cell membrane conc. of substances are often different inside than outside the cell (conc. gradient exists) to diffuse across the membrane, the substance must be able to pass through the cell membrane cell membrane is selectively permeable (only lets some things pass through) very small molecules or nonpolar molecules (nonpolar interior of cell membrane repels ions and most polar molecules) can diffuse across the cell membrane Osmosis = diffusion of water through cell membrane (moves from higher to lower conc. of water) Facilitated Diffusion = no energy required, but uses carrier proteins that are embeded in the cell membrane to transport substances still move from high to low conc. molecules that are too large to diffuse across the cell membrane can enter the cell this way have students look at page 80 (Figure 4)

Types of Solutions Isotonic: “iso”- same Concentration is the same inside and outside of the cell (Water moves in/out at SAME rate) Take notes on next three slides and then have students work out some problems with conc. and water movement Cytoplasm and fluid outside cell have same concentration of water molecules water moves in and out at same rate, so no net movement cell stays same size (state of equilibrium)

Type of Solutions Hypotonic: “hypo”- lower/below Concentration is LOWER outside the cell than inside (Water goes INTO the cell faster than out) Hypotonic solution conc. of solute is lower outside cell than inside this means that there is more water outside than inside, so water goes into the cell cell swells Hypo  o is big and is what happens to the cell when in hypotonic solution

Type of Solutions Hypertonic: “hyper”- higher/above Concentration is HIGHER outside the cell than inside (Water moves OUT of the cell faster than in) Hypertonic solution conc. of solute is higher outside than inside cell this means that water is lower outside than inside the cell, so water moves out of cell this causes cell to shrink Example: water a plant with salt water, it will wilt because water will leave the cells to make up for extra salt it takes in Hyper  e is like a shriveled o and is what happens to the cell when in hypertonic solution

Type of Solutions- Video Watch video and then have students work some problems In cell = 3X/2* out cell = 2X/4* hypotonic (water in) In cell = 2X/4* out cell = 4X/8* isotonic (water in/out at same rate) In cell = 1X/4* hypertonic (water out) After work problems, move on to egg demo

How substances move ACTIVE TRANSPORT: requires energy to move substances in/out of the cells WHY? Against concentration gradient Too large Used to transport substances: Carrier proteins Vesicles Endocytosis: carry into a cell Exocytosis: carry out of a cell Now we will talk about how substances get into cell when conc. is higher outside than inside or when substance is too big to diffuse or be transported with carrier proteins Sometimes cells need to bring in substances (amino acids, sugars, etc) that have higher conc. inside than outside cell diffusion or faciliated diffusion would cause these molecules to move out of cells rather than in To move molecules against (or across) the conc. gradient (meaning low to high), cell must use energy (active transport) How cell do this 1. use carrier proteins (similar to faciliatated diffusion) 2. some substances too large (eg. Proteins, polysaccharides) to be transported with carrier proteins – use vesicles endocytosis – use vesicle to carry something into a cell (endo  into) exocytosis – use vesicle to carry something out of cell (exo  out of) see page 83 (Figure 6)