Cell Transport PDF

 Cell Membrane Structure Phospholipid-bilayer Proteins embedded as channels for transfers  Plasma Membrane Hydrophilic heads oriented TOWARD aqueous environments Hydrophobic tails are facing inwards AWAY from aqueous environments Cholesterol helps maintain fluidity at high...

 Cell Membrane Structure Phospholipid-bilayer Proteins embedded as channels for transfers  Plasma Membrane Hydrophilic heads oriented TOWARD aqueous environments Hydrophobic tails are facing inwards AWAY from aqueous environments Cholesterol helps maintain fluidity at high and low temps High temp: reduces movement Low temp: reduces tight packing of phospholipids  Selective Permeability Some substances can cross the membrane more easily than others Easy passage across the membrane: Small nonpolar, hydrophobic molecules ○ Examples: Hydrocarbons CO2, O2, N2 Difficult passage or protein assisted passage: Hydrophilic, polar molecules, large molecules, ions ○ Examples: Sugars, water As a cell increases in size what do you think are the positive and negative impacts on a cell?  Cell Size Cellular metabolism depends on cell size Cellular waste must leave Dissipate thermal energy Nutrients and other resources/chemical materials must enter At a certain size, it begins to be too difficult for a cell to regulate what comes in and what goes out of the plasma membrane  Surface Area and Volume The size of a cell will dictate the function Cells need a high surface area-to-volume ratio to optimize the exchange of material through the plasma membrane  Formulas Formulas for cuboidal cells ○ Total SA= height x width x number of sides x number of boxes (or SA = 6S2 if only 1 box) ○ Total V= height x width x length x number of boxes ( or V = S3 if only one box) ○ SA to V ratio = SA/V Formulas for spherical cells ○ SA = 4πr2 All formulas are ○ V = 4/3πr3 given to you on ○ SA:V ratio = SA/V tests  Practice Example: cuboidal cell #1 #2 SA = 3 x 3 x 6 x 1 = 54 units 2 SA = 1 x 1 x 6 x 27 = 162 units2 V= 3 x 3 x 3 x 1 = 27 units3 V= 1 x 1 x 1 x 27 = 27 units3 SA:V = 54/27 = 2 SA:V = 162/27 = 6 Which would have the best exchange of material through the plasma membrane? Option 2: SA:V ratio is higher  Practice How does the radius affect the SA:V ratio in spherical cells? SA = 4πr2 V =4/3πr3 SA:V ratio = SA/V r SA 1 4πr 2 3 As r 1 4 r increases, V πr3 3 3 the ratio of SA:V decreases  Try it Example: spherical cell #1 #2 r=5 r=8 SA = 4 x π x 52 = 314 units2 SA = 4 x π x 82 = 803.8 units2 V= 4/3 x π x 53 = 523.3 units3 V= 4/3 x π x 83 = 2143.6 units3 SA:V = 314/523.3 = 0.6 SA:V = 803.8/ 2143.6 = 0.37 Which would have the best exchange of material through the plasma membrane? Option 1: SA:V ratio is higher What Does This Mean for a Cell? Cells tend to be small Small cells have a high SA:V ratio ○ Optimizes exchange of materials at the plasma membrane Larger cells have a lower SA:V ratio ○ Lose efficiency exchanging materials The cellular demand for resources increases Rate of heat exchange decreases  Checkpoint Two cube cells have the lengths of 2 cm and 4 cm respectively. Determine their SA:V. Show your work. Which cell would be more efficient at transferring materials across the membrane? Which cell would be better for storage of materials? Circle the molecules will diffuse easily across the membrane? 02 H20 nonpolar polar glucose hydrophobic hydrophilic gases  Background Information ▪ Particles of matter in constant motion. ▪ Solid particles move less than liquids & gases. ▪ Particles move randomly until evenly dispersed -from crowded area to less crowded area Dynamic Equilibrium: molecules evenly distributed (spread out) Molecules continue to move once reached  Concentration gradient -The difference in the amount of substance in two places. Ex: water with food coloring - concentration of food coloring greatest where added - least everywhere else - difference in concentration of food coloring: concentration gradient Concentration & Diffusion Worksheet Concentration Gradient  Two categories of Transport Passive Transport: Requires no energy Down concentration gradient Active Transport: Requires energy in the form of ATP Against/up concentration gradient Put it in your own terms: compare passive and active transport to sitting on a boat it a river.  Passive Transport movement down concentration gradient cells do not use additional energy ; (ATP) - particles move by kinetic energy includes: Diffusion Osmosis facilitated diffusion  Diffusion Definition - movement of molecules from areas of HIGH concentration to LOW concentration - molecules move DOWN the concentration gradient ⇓ - diffusion stops when dynamic equilibrium has been reached (constant concentration)  Facilitated Diffusion ❖ Carrier protein; molecules in cell membrane “help” substances move in/out of cell ❖ Specific protein for each molecule ❖ Type of Passive Transport ❖ Used for; Molecules too large for fluid membrane Molecules not soluble in lipid bilayer Ex: glucose  Diffusion Through Ion Channels o Membrane proteins transport ions Na+, K+, Ca+2, Cl-1 o Ion Channels specific for each ion Ion Channels controlled by: Concentration Gradient Other signals  Osmosis Osmosis: movement of water across cell membrane from high concentration to area of lower concentration -Water moves DOWN Concentration Gradient. -Also referred to as the diffusion of water.  Osmosis: Diffusion of Water Osmosis: net diffusion of water across a semi-permeable membrane Figure 3.6 Slide 3.6  “Solution” for your Transport Solution is: A solute dissolved in a solvent Solvent is: Generally is water in living systems Solute is: Glucose, oxygen, salt etc; that which is dissolved in the solvent WHAT is THE SOLVENT in soda??? What is the SOLUTE in soda???  Direction of Osmosis Isotonic: Cell and environment have equal concentration of solute Hypotonic: Environment has a lower concentration of solute than the cell Hypertonic: Environment has greater concentration of solute than the cell  Isotonic Environment Cell and environment have equal H20 & solute conc.  Hypotonic Environment Environment has lower solute conc. than the cell  Hypertonic Environment Environment has greater solute conc. than the cell For each slide, examine the cell as shown in a solution. A solute is any dissolved substance in the water, like salt. Solution is… Water will Cell will … move… 50 % H2O 1 1 1 Hypertonic Both Shrink 50 % directions solute 2 2 2 Isotonic Into the Swell 80 % cell H2O 20 % 3 3 3 solute Out of the Stay the Hypotonic cell same Solution is… Water will Cell will … move… 50 % H2O 1 1 1 Hypertonic Both Shrink 50 % directions solute 2 2 2 Isotonic Into the Swell 50 % cell H2O 50 % 3 3 3 solute Out of the Stay the Hypotonic cell same Solution is… Water will Cell will … move… 10% H2O 1 1 1 Hypertonic Both Shrink 90 % directions solute 2 2 2 Into the 20 % Isotonic Swell H2O cell 80 % solute 3 3 3 Out of the Stay the Hypotonic cell same Solution is… Water will Cell will … move… 90 % 1 1 1 H2O Hypertonic Both Shrink 10 % directions solute 2 2 2 Into the 10 % Isotonic Swell H2O cell 90 % solute 3 3 3 Out of the Stay the Hypotonic cell same Solution is… Water will Cell will … move… 60 % 1 1 1 H2O Hypertonic Both Shrink 40 % directions solute 2 2 2 Into the 70 % Isotonic Swell H2O cell 30 % solute 3 3 3 Out of the Stay the Hypotonic cell same Solution is… Water will Cell will … move… 30 % 1 1 1 H2O Hypertonic Both Shrink 70 % directions solute 2 2 2 Into the 50 % Isotonic Swell H2O cell 50 % solute 3 3 3 Out of the Stay the Hypotonic cell same Solution is… Water will Cell will … move… 70 % 1 1 1 H2O Hypertonic Both Shrink 30 % directions solute 2 2 2 Isotonic Into the Swell 75 % cell H2O 25 % 3 3 3 solute Out of the Stay the Hypotonic cell same Solution is… Water will Cell will … move… 65 % 1 1 1 H2O Hypertonic Both Shrink 35 % directions solute 2 2 2 Into the 65 % Isotonic Swell H2O cell 35 % solute 3 3 3 Out of the Stay the Hypotonic cell same  Dealing With Osmosis Contractile Vacuoles (protozoa) Pumps excess water out Plasmolysis (plant cells) Water loss; turgor pressure drops, plant wilts Cytolysis (animal cells) High turgor pressure; cell explodes “All Together Now”  Active Transport - Movement from LOW concentration to HIGH concentration (UP concentration gradient!) - Cells use energy (ATP) Example: plant roots pull in minerals from soil Active v.s. Passive Transport Endocytosis -Includes; o Phagocytosis (solids) o Pinocytosis (liquids) - Cell membrane; o surrounds a substance o pinches off o forms a vesicle o brings substance IN Phagocytosis 1 2 3  Exocytosis -Vescicle contents are released at the cell membrane  Active Transport Examples of pumps: Electrogenic pumps: proteins that generate voltage across membranes, which can be used later as an energy source for cellular processes Sodium potassium pump ○ Animal cells will regulate their relative concentrations of Na+ and K+ 3 Na+ get pumped out of the cell 2 K+ get pumped into the cell Results in a +1 net charge to the extracellular fluid Active Transport Sodium potassium pump All Together Now Ion channel Facilitated Application of Diffusion / Osmosis Dialysis o Kidney job: filter wastes from your blood o Damaged kidney → hook patient up to dialysis - Blood is run from body to dialysis machine - Machine filters out wastes by diffusion. - Cleansed blood is returned to the body Kidneys  Fish Gill Function This is a close-up of a thin channel in the fish's gills. Water flows through it and is surrounded by blood vessels, that flow in opposite direction. The oxygen leaves the water, and goes into the blood. From there, it is carried all around the body of the fish!