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BIO 1140 Study Guide - Thiourea, Cell Membrane, Sucrose

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peartortoise481
14 Jul 2014
School
University of Ottawa
Department
Biology
Course
BIO 1140
Professor
A L L

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Document Summary

Permeability of red blood cells hemolysis rate of sheep blood. Hemolysis time of sheep blood cells tested with five different solutions subdivided according to the hemolysis times recorded in seconds. <2a seconds is an indication that hemolysis took place immediately upon addition of blood to the solution. >1200b seconds is an indication that hemolysis was not observed under 20 minutes. Factors that affected the diffusion of the solutes with respect to the permeability of the experiment are: size, polarity, charge, lipid solubility, and chemical composition of the molecule: how do these factors affect the diffusion of solutes. The size of the molecule affects the rate of diffusion because evidently, smaller molecules are able to pass though the lipid bilayer more quickly by means of channels, carriers, porins, or simple diffusion. The larger the molecule, the longer it will take for it to diffuse across the membrane (i. e dextrose).

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Related Questions

1. In lecture, we described a simple osmotic pressure gradient when discussing osmosis. For question #1, describe the simple osmotic pressure gradient, in terms of osmotic pressure, that exists across the red blood cell plasma membrane when red blood cells are suspended in a severely hypotonic solution, such as a 0.2% NaCl solution. Use scientific terminology.

2. We mentioned in class that biological systems are always in a state of osmotic equilibrium due to a combination of solute diffusion in some cases and osmosis in others. In this experiment, when you add the red blood cells to a severely hypotonic solution, what substances are moving across the red blood cell plasma membrane to achieve osmotic equilibrium, Na+ and Cl- or water? Explain why based on your understanding of the permeability characteristics of biological membrane. Always use scientific language.

CAN QUESTIONS 1 AND 2 BE ANSWERED DIRECTLY AND ADEQUATLEY PLEASE.

HERE IS AN INTRO TO THE LAB EXPERIMENT

Intro:

We have known for a very long time that the mammalian red blood cell plasma membrane is very permeable to water. Even the introductory biology student understands that if you put mammalian red blood cells in water, they will rapidly swell and break open (hemolyze) due to the rapid osmosis of water into the cell. The experimental question we are asking in today's lab experiment is "Is the high water permability of mammalian red blood cell plasma membrane due solely to the lipid bilayer, or are there water channels present in the membrane?"

Experimental Design:

It has been shown by several investigators that water movement through water channels can be blocked by the known K+ channel blocker, tetraethylammonium chloride (TEAC). Brooks, Regan and Yool (2000) showed that TEAC reduces the water permeability of human water channels expressed in the plasma membranes of frog ocytes. After preincubation of the oocytes for 15 min with 100 microM TEAC, the water permeability of frog oocyte plasma membrane containing human water channels was reduced 20 to 40%. The investigators concluded that treatment of cells with TEAC can be useful in determining the presence of aquaporins in membranes.The specific objective of today's experiment is to uncover the presence of water channels in mammalian red blood cell plasma membrane by determining the effect of tetraethylammonium chloride on the water permeability of mammalian RBC plasma membrane.

The A antigen (the protein that makes A blood A blood) is embedded in the red blood cell (RBC) membrane. Blood group A individuals will automatically carry antibodies (proteins that are in the blood plasma-liquid part of blood) that will attack blood group B cells. Blood group B individuals will carry antibodies that will attack blood group A cells. Blood group O individuals, lacking either of the A or B antigens will carry BOTH types of antibodies and will attack either A or B cells. When there is a transfusion with incompatible blood groups, cells can clump creating blockages in arteries throughout the body. Other pathways can lead to the lysing of RBC’s which will release their contents into the bloodstream elevating these component in the blood which can have sever effects on the heart (potassium primarily-in case you are interested).

Remember, the Rh is a typical one gene, two allele scenario. Rh+ blood can accept Rh+ or Rh- blood. A person with Rh- blood can only receive Rh- blood. Unlike ABO where an individual manufactures the antibody to an antigen they lack without prior exposure, the Rh factor requires previous exposure to illicit an immune response. If a Rh- person is exposed to Rh+ blood, the individual will create the antibody against the Rh antigen. Now, if Rh+ blood is introduced into this individual again, the recipient’s blood contains anti-Rh antibodies and will attack the Rh+ cells-Bad news for the recipient. This is the same thing that happens with an Rh- mom who gets pregnant with an Rh+ baby. By the time the first Rh+ baby is born and blood mixing may have occurred during late pregnancy (small breaks in the placenta can cause some of baby’s blood to mix with that of mom), first baby escapes unharmed. Subsequent babies aren’t so lucky.

If there are small tears in the placenta (which are normal), mom’s anti Rh antibodies can go in and attack the Rh+ baby’s blood. This can kill the baby. Now, Rh- moms are given a substance that will coat the baby’s RBC’; kind of like putting them into stealth mode so they can’t be seen by mom’s immune system. Later-poof, out pops unaffected baby.

1. What blood type(s) can be given to an A positive individual?

2. If you have B negative blood, what blood types can you receive?

3. What blood types can an O negative receive? O positive?

4. If a man is blood group B and his wife is blood group A what blood type(s) are you 100% sure they could produce in their children?

5. If you have a blood group O father and a blood group B mother, can they produce an O child? Explain your answer.

6. You have a male friend who is blood group AB. He is successful in business but knows very little about biology. His wife just had an O child. Knowing that you have been studying the genetics of blood groups, he asks you for an education on blood groups. What do you think about this situation?

7. A woman is AB and her husband is A. They have a B child. What are all the blood groups possible in their children if he is heterozygous?

8. A woman is Rh- and her husband is Rh+. Their first baby is Rh-. What is the genotype, with respect to Rh, of the parents? What is the probability their next child will be Rh+? Does the woman have to worry about any issues with future children? Explain!

Cell Membranes Lab Report

  1. Diffusion

  1. Compare the following terms: solvent, solute, andsolution.

  1. Go to Lab, Section I, Exercise 1 to explore the factorsinfluencing the rate of diffusion and complete the following:

  1. Predict how molecular mass and temperature may affect theoutcome of this experiment.

  1. Record the data from information in the Lab in the tablebelow.

Time

(min)

Diameter (mm)

5°C MB

5°C PP

23°CMB

23°C PP

0

15

30

45
  1. Construct a line graph of the data from the table above. Yourgraph should include labeled axes, units, and a legend indicatingwhich treatment is presented. Sign, date and prepare an image ofyour graph and include it with this lab report.
  1. Osmosis

  1. Go to Lab, Section II, Exercise 2 to view a demonstration ofosmosis and answer the following questions:

  1. Describe the net movement of water in osmometer 1.
  1. How is the movement of water molecules related to theconcentration gradient of the solution?

  1. Go to Lab, Section II, Exercise 3 to observe the effect ofsolute concentration on the rate of osmosis. Answer the followingquestions:

  1. Was the net movement of water in bags 1 to 4 into or out of thebags?
  1. Explain the results from bags 4 and 5.
  1. Selective Permeability of Membranes

  1. Go to Lab, Section III, Exercise 4 to learn about theimportance of selectively permeable membranes, then complete thetable and answer the following questions:

Contents of Beaker

0 Min

30 Min

Starch

Chloride ion
  1. Which substances diffused through the dialysis membrane?

  1. How does dialysis tubing model the selective permeability of aplasma membrane?
  1. Tonicity

  1. Go to Lab, Section IV, Exercise 5 and 6 to observe plasmolysisin Elodea cells and tonicity in red blood cells. Summarizethe concept of tonicity using blood and Elodea cells asexamples. Your description should incorporate these terms: turgid,plasmolysis, hemolysis, and crenation.

Cells

Isotonic Solution

Hypertonic Solution

Hypotonic Solution

Elodea

RBC

  1. Based on your previous work, reproduce the table below and drawan illustration of a single cell in each box. Include arrows toshow the direction of water flow relative to each cell and dots tosymbolize solutes. Sign, date and prepare an image of your drawingand include it with this lab report.

Cells

Isotonic Solution

Hypertonic Solution

Hypotonic Solution

Elodea

RBC

Summary Questions

  1. Compare diffusion and osmosis. Give an example of each.

2. In which direction will osmosisoccur if a 15% sugar solution is separated from a 25% sugarsolution by a selectively permeable membrane?

3. Why did osmosis, but not diffusionof sucrose molecules, occur across the dialysis membrane containing20% sucrose solution?

4. You are having a party and thecelery is limp. What might you do to make the celery crisp (turgid)again? What will occur in the cells?

5. A small amount of fertilizer(mineral salts) will stimulate plant growth, but over fertilizationcan kill plants? Why?

6. Michael adds sugar to his coffee.Explain what in this drink is the solvent, solute, and solution.

7. You add a cube of sugar to yourdrink. How could you speed up the diffusion of sugar moleculeswithout stirring?

8. How is dynamic equilibriumestablished within a solution?