Class Photos (2000)

• Careful work and cooperation during lab pays off! 
• It really helps to read and study Marieb and the Supplement before you come to lab. 
• Keys to success in this A&P lab:

Being ready to begin work immediately after the quiz.
Being familiar with the procedures and the terminology because you READ the Supplement and Marieb exercises before lab. 
Read and follow the instructions carefully.
LISTEN and take notes as Dr. Ross reviews the Supplement and Marieb procedures at the start of lab.  Annotate Marieb to include the revisions and additions listed in the Supplement.
Cooperate with your classmates and do your fair share.
Ask questions when you need clarification or confirmation of your observations. Figure out (&/or ask questions) about WHY a particular result was expected.
• Complete the Marieb Review Sheet and Fill-in the data forms in the Supplement be ready to discuss your results, the calculations, and the questions posed here during lab and when you come to class on Friday.

This is included in the PhysioEx CD you received with you Marieb lab manual.  Ex. 5B has several "virtual" lab activities on the topic. 

The guide to Ex5A and a Review Sheet is near the end of the Marieb lab manual (following the cat dissection exercises).  See pages PEx-5 through pEx-19.  The answer key to the Ex 5B review sheet is available on the shared directory  \\facstaff\biology (along with the answer key for Ex5A and the part of 37A for this week's lab).

Exercise 5: Diffusion: 

• Record your data on a chart first (Elapsed Time and Distance for each substance) then graph your data (plot TWO lines, one for each chemical). Compare the slopes of the 2 lines.  How does the rate of diifusion relate to the molecular weight of the substance?  The molecular weight of Methylene Blue is 320. the molecular weight of KMnO₄ is 158.  (You do not have to memorize the numbers!)
• KNOW for the Quiz:

Which chemical do you EXPECT to diffuse at a faster rate? Why? (What's the mathematical relationship between MW and diffusion rate?)
Did your team's results agree with your prediction?

• Note the distinction between observations and conclusions. (Observations are your data. What did you see macroscopically and microscopically?) Thus, "crenated" or "cloudy" are NOT conclusions.
• Macroscopic observations: What was the appearance of each test tube (blood in solution)? [I.e., cloudy vs. clear.]

Did this appearance change upon later observation?
• REMEMBER: If the solution was clear you did NOT need to make a slide! WHY? 
• Refer to the Lecture slides for Hole Ch. 3 material and read the sections in Hole on Osmosis (including the examples using RBC's). 
• REVIEW THE TEXT AND SUPPLEMENT (Hole Ch. 3) and REMEMBER THESE POINTS: 
• 1.0 M NaCl = (molecular wt. of NaCl in grams) + H₂O to Total volume of 1 liter. [1 liter = 1,000 mL]. (Given:  MW of NaCl is 58.45) 
• Percent means parts per 100. Therefore, 1.0% NaCl = 1.0g NaCl to Total volume of 100 mL. 
• A solution of NaCl is ISOTONIC to human cells if it is a 0.15M NaCl solution. This is the SAME as a 0.877% NaCl solution (rounded to 0.9% NaCl). 
• EXPECTED RESULTS: 
• Do your team's results agree with what was expected?

Did your team record enough data to be sure of your results? 
Can you now recognize crenated RBC's and normal-shaped RBC's? 
Did you get to see any cells in the process of lysis and crenation? 
Remember how water moves to produce lysis & crenation. 
• KNOW for the Quiz: 
• Which concentration of NaCl is ISOTONIC to RBC's?

Which concentrations of NaCl used in lab were expected to make the RBC's lyse? Why?
Which concentrations of NaCl used in lab were expected to make the RBC's crenate? Why?
• REMIND yourself about the ionization of NaCl in H₂O (to form Na⁺ and Cl^-). 

Why does it require about TWICE as much glucose as NaCl to make a solution isotonic the RBC's (0.15M NaCl and 0.28 M glucose are both isotonic to RBC's)? 
• Given the following molecular weights:

NaCl 58.45
glucose 180.09
Express each of the following Molar solutions as percent solutions:
0.15M NaCl = _____% NaCl
0.30M NaCl = _____% NaCl
0.28M glucose = _____% glucose
 
• If RBC's are placed in a solution which contains a greater concentration of solute molecules than the cell, which way will water move (into or out of the cells)? 

What will be the appearance of such cells (will they lyse or crenate)? 
What term is used to describe the concentration of the solution compared to the cells? 
Give examples of solutions used in lab that are expected to produce this effect. 
Answer the same questions for a solution that contains a lesser concentration of solute molecules than the cell.

• This includes how to use the pH meter. 
• EXPECTED RESULTS: 
• Best buffer: Diluted sheep blood 

(Remember if this was used in lab it was probably a 1:10 dilution!) 
• 2^nd best buffer: Albumin suspension. 

(Egg white albumin is used in lab, but a similar albumin is one of the proteins in your blood serum.) 
• 3^rd best buffer: Bicarbonate buffer 

KNOW the Bicarbonate system example.
Be able to write the formulas and name the components. 
(Not just because it will be on the Quiz.) 
This buffering system operates in your blood stream! 
• No buffering capacity: Water 

You should see a decrease in pH when even a small amount of 0.01M HCl is added.  And an increase in pH when 0.05M NaOH is added.
• KNOW FOR THE QUIZ: 
• Was there a difference inhow weel the buffer handled added HCL vs. added NaOH?
• How do you judge the relative buffering capacity of the solutions with the data you collected? 

For example, which is the better buffer? 
• Buffer A. Starting pH = 7.3 After adding 3 mL of 0.01 M HCl, pH was lowered to 7.1
• Buffer B. Starting pH = 7.3 After adding 4 mL of 0.01 M HCl, pH was lowered to 7.2
• Do your team's results agree with what was expected? 

Did your team record enough data to be sure of your results? (If a team didn't follow the instructions, their data cannot be easily be compared to the results from other teams.) 
 
• Can you now explain why you had to add so much HCl to get any change in the pH of the buffers? 
• Chemically, what happened to the H⁺ added to a buffer if the pH did not go down?  (For the bicarbonate buffering system, be able to show this in molecular formulas.)

• Tutorials on fundamental chemistry topics.
• Molarity and solutions
• The Bicarbonate Buffering System (Arizona)
• Osmosis  (Colorado State)     Osmosis Examples
• Acid, Base and pH Tutorial  (Univ. British Columbia)
• Acid Base Tutorial  A clinical perspective (Tulane University School of Medicine)

• A&P lab #4 will deal with tissues and skin. (Lecture Unit 2 material)
• There are lots of Microscope slides plus digital images and images on the PhysioEX CD! Following lab, and before the Quiz, you will want to take advantage of Study Lab times in AH 107 to review this material.
• You should look through Marieb and the textbook BEFORE the tissues & skin lab. 
• It will also help if you take a look at Hole Chs. 5 & 6, the Ch. 5 & 6 "slides" in the Supplement, the Ch. 5 & 6 worksheets, and the lab #4 guide in the Supplement BEFORE the tissues & skin lab! Of course, you'll need to study portions of this material more thoroughly for the lab Quiz on the lab #4 material.