PhysioEX Exercise 1: Cell Transport Mechanisms and Permeability

PhysioEX Exercise 1. Activity 4

Student instructions: Follow the step-by-step instructions for this exercise found in your lab manual and record your answers in the spaces below.

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Grading: True/False, Multiple-Choice, and Fill-in-the-blank type questions will be worth 1 point each whereas Short-answer type questions will be worth 2 points each. This lab will be worth a total of 45 points but will be converted to a percentage grade when registered in your “Gradebook”. |ACTIVITY 1: Simulating Dialysis (Simple Diffusion) |Answers | |The molecular weight of urea is approximately 60. Which of the membranes can it pass through? D | |50 MWCO membrane | | |100 MWCO membrane | | |200 MWCO membrane | | |Both the 100 and 200 MWCO membranes | | |True or False: A solution containing glucose will diffuse faster through a 200 MWCO membrane if it|True | |is heated. | | |The molecular weight of carbon C is 12; the molecular weight of hydrogen (H) is 1; the molecular |6 x 12 = 72, 6 x 16 = 96, 12 x 1 = 12 | |weight of oxygen (O) is 16. The chemical formula of glucose is: C6H12O6 .

Using some simple | | |multiplication and addition, determine the molecular weight of one molecule of glucose. |Total = 180 | |Describe two variables that affect the rate of diffusion. |MWCO of the membrane, molecular weight of the ion or molecule | |Why do you think that the urea was not able to diffuse through the 20 MWCO membrane? |Urea will not diffuse through the 20 MWCO membrane because it | | |doesn’t ionize | |Describe the results of the attempts to diffuse glucose and albumin through the 200 MWCO membrane. Glucose will diffuse through 200 MWCO membrane however albumin | | |will not | |Put the following in order from smallest to largest molecular weight: glucose, sodium chloride, |Sodium Chloride, Urea, Glucose, Albumin | |albumin, and urea. | | |ACTIVITY 2: Simulated Facilitated Diffusion |Answers | |True or False: The facilitated diffusion of glucose requires energy from ATP. false | |Which of the following might cause the facilitated diffusion of glucose from one solution to |D | |another to occur faster? | | |Add Na+Cl- to the beaker on the left. | | |Add K+Cl- to the beaker on the left. | | |Add ATP to the beaker on the left. | | |None of these would cause it to happen faster. | |True or False: If there are a sufficient large number of transport proteins present, glucose can |False | |be transported from a solution of lower concentration to a solution of higher concentration (i. e. | | |up its concentration gradient. ) | | |Explain one way in which facilitated diffusion is the same as simple diffusion; one way in which it|They are both passive processes; | |is different. Facilitated diffusion requires a protein carrier to travel, | | |simple diffusion doesn’t. | |The larger value obtained when more glucose carriers were present corresponds to an increase in the|The more glucose carriers there are, the less chance there is | |rate of glucose transport. Explain why the rate increased. |for saturation to set in to affect the transport of glucose. | |You were asked to predict what effect you thought that adding Na+ Cl- would have on the glucose |I predicted that nothing would happen given that Na+CL- crosses | |transport rate. Why did you pick the choice you did?

How well did the results compare with your |the membrane through simple diffusion and doesn’t need a carrier| |prediction? |like glucose. My predictions came out the way I believed it to | | |be. | |ACTIVITY 3: Simulating Osmotic Pressure |Answers | |True or False: Osmosis is considered a type of passive transport, i. e. it does not need energy |true | |from ATP. | | |If a cell is placed in a ________ solution of water, there will be no net movement of water in or |B | |out of the cell. | |hypotonic | | |isotonic | | |hypertonic | | |If you “cut” the concentration of a non-diffusible solute that is on one side of a membrane in |C | |half, the osmotic pressure will | | |double. | | |not change. | | |be half of what it was before. | | |Explain the effect that increasing the Na+Cl- concentration had on osmotic pressure and why it has |Na+Cl- will diffuse through the 50 MWCO membrane but won’t | |this effect. |through 20 MWCO. |Describe one way in which osmosis is similar to simple diffusion; describe one way in which it is |Both are passive processes, osmosis differs in that it diffuses | |different. |water through a selectively permeable membrane | |Solutes are sometimes measured in milliosmoles. Explain this statement: “Water chases |Water will diffuse to the side of the membrane that has the | |milliosmoles. ” |largest concentration of solutes. Thus “water chases solutes” | |The conditions were 9mM albumin in the left beaker and 10mM glucose in the right beaker ith the |There was no diffusion in Albumin, osmotic equilibrium was | |200 MWCO membrane in place. Explain the results. |reached. Osmotic pressure of 53 mmHg. | |ACTIVITY 4: Simulating Filtration |Answers | |The filtration rate of Na+Cl- in the simulation was dependent on |D | |the pore size of the membrane. | | |the hydrostatic pressure applied to the top beaker. | |the concentration of the solutes in the lower beaker. | | |both the pore size and the hydrostatic pressure applied. | | | |False | |True or False: The simulation would not function if the top beaker were open to the atmosphere | | |instead of having pressure applied to the top beaker. | |Explain in your own words why increasing the pore size increased the filtration rate. Use an |Just like a pasta strainer, the larger the pores in the metal | |analogy to support your statement. |the quicker and more effectively liquid will go through. | |Which solute did not appear in the filtrate using any of the membranes? |Activated charcoal | |Why did increasing the filtration pressure increase the filtration rate but not the concentration |The more pressure the faster the filtration rate will be | |of solutes? |working. However the concentration of solutes will not be | | |affected and will be the same. |ACTIVITY 5: Simulating Active Transport |Answers | |In this simulation, each of the following was (were) required In order for active transport to |D | |occur: | | |sodium ions (Na+) | | |potassium ions (K+) | | |energy from ATP | | |All of the above were required. | | |True or False: The amount of ATP that you dispensed did not affect the rate that the solutes |false | |passed from one beaker to the other. | | |Which of the following processes require ATP? E | |Simple diffusion | | |Facilitated diffusion | | |Filtration | | |Osmosis | | |Active transport | | |Describe the significance of using 9mM sodium chloride inside the cell and 6mM potassium chloride |3 Na+ are ejected for every 2 K+ ions entering the body. | |outside the cell. | | |Explain why there was no sodium transport even though ATP was present. |Both Na+ and k+ and ATP must be present for pump to function.

In| | |this simulation there was no K+ | |Explain why the addition of glucose carriers either had no effect or did have an effect on sodium |Glucose carriers had no effect on the sodium or potassium | |or potassium transport. |transport because glucose crosses the membrane by facilitated | | |diffusion and has no need for ATP | |Do you think glucose is being actively transported or transported by facilitated diffusion in this |Transported by facilitated diffusion because it is transporting | |experiment. Why? |down its concentration gradient. |

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