Category: Chemistry of Organisms

pH in Living Systems

 

 

pH and Living Systems

 

Introduction:

Scientists use something called the pH scale to measure how acidic or basic a liquid is. The scale goes from 0 to 14. Distilled water is neutral and has a pH of 7. Acids are found between 0 and 7. Bases are from 7 to 14. Most of the liquids you find every day have a pH near 7. They are either a little below or a little above that mark. When you start looking at the pH of chemicals, the numbers go to the extremes. Substances with the highest pH (strong bases) and the lowest pH (strong acids) are very dangerous chemicals. Molecules that make up or are produced by living organisms usually only function within a narrow pH range (near neutral) and a narrow temperature range (body temperature). Many biological solutions, such as blood, have a pH near neutral.

The biological molecule used in this lab is a protein found in milk. Proteins are used to build cells and do most of the cell’s work. They also act as enzymes. For proteins to work, they must maintain their globular shape. Changing the shape of a protein denatures and the protein will no longer work.

Materials:

Small squares of wide-range pH paper, pH color chart, paper towels, 4 dropper bottles, ammonia, lemon juice, skim milk, distilled water, forceps, 50 ml beakers, small squares of narrow-range pH paper, 2 stirring rods

Procedure (part A): Testing the pH of Substances

  1. Line up 4 squares of wide-range pH paper about 1 cm apart on a paper towel.
  2. Put one drop of distilled water on the pH square.
  3. Compare the color of the pH paper to the color chart and record the pH in data table 1.
  4. Repeat this procedure for the ammonia, lemon juice, and skim milk.

Questions (Part A): Determining the pH of Solutions

  1. Which substance was the most acidic?
  2. Which substance was the most basic?
  3. Did any of the substances have a pH close to neutral? Name them.

Procedure (part B): Showing the Effect of pH on a Biological Molecule (Milk Proteins)

  1. Place 100 drops of skim milk in a 50 ml beaker.
  2. Pick up a piece of narrow-range pH paper with forceps.
  3. Touch the pH paper to the milk and remove it.
  4. Compare the color of the pH paper to the pH color chart.
  5. Record the initial pH in data table 2.
  6. Add a drop of lemon juice to the milk in the cup & stir with a stirring rod. Keep track of how many drops you add to the milk!
  7. Measure and record the pH of the solution with the narrow-range pH paper.
  8. Repeat step 7 until you notice an obvious change in the appearance of the milk. record this final pH and appearance of the milk in your data table.
  9. Repeat steps 1-8 using a clean 50 ml beaker and fresh milk, and substitute ammonia for the lemon juice.
  10. Add drops of ammonia to the milk until the change in pH of the milk is equal to the change in pH you measured in step 8. Be sure to keep track of the number of drops added. HINT: If the pH changed by 2 units with the lemon juice, then add ammonia until you also get 2 pH units of change!

Data:

Table 1

 

Substance Tested pH Acid Base Neutral

 

Table 2

Substance Tested Substance used to Produce Change Starting pH of Milk Final pH of Milk Original Appearance of Milk Final Appearance of Milk Total Number of drops added to Produce the change
100 drops Skim Milk Lemon Juice
100 drops Skim Milk Ammonia

Questions:

1. Which substance tested from table 1 was the most acidic?

2. Which substance was most basic?

3. Did any substance from table 1 have a neutral, or near neutral pH? If so, which substance was neutral?

4. Why did you use narrow-range pH paper to measure the milk’s change in pH?

 

5. Describe the change in appearance of the milk as more lemon juice was added. Explain why this change occurred.

 

 

6. How much did the pH of milk change when lemon juice was added?

7. Why do you think lemon juice “curdled”  (precipitated out the proteins) from the milk?

 

8. Did you get the same change when ammonia was used? Why or why not?

 

 

 

Effect of Detergent on Gelatin

 

“How Good Is Your Enzymatic Detergent?

 

Introduction:
In nature there are enzymes called proteases that “digest” or degrade proteins. Some of these enzymes have been genetically engineered and added to our laundry detergents in the hope that they will “digest” the protein off of our clothing. Do they work? Do they assist in cleaning? In this experiment you can compare different detergents and their ability to “digest” protein.
What is gelatin? Gelatin consists of protein chains that are easily digested into their amino acid components. Gelatin is prepared from collagen, a protein found in animal tendons and skin and taken out during the meat rendering process. Boiling collagen reduces the  weight by about one-third and separates the protein strands by breaking bonds. When the boiled collagen is cooled, it does not revert back to collagen but sets to a gel we know as gelatin.

Purpose :
To test the effectiveness  of laundry detergent brands (and their enzymes) to digest protein (in the form of gelatin)

Prelab

Hypothesis:   ____________ will decompose more gelatin in millimeters than ______________.

Materials:
Gelatin in 4 test tubes  Wax Pencil/ Permanent marker
3 detergent brands
Distilled water
Test tube rack
Parafilm®
Ruler

Procedure:
Day 1
1. Pour 5 ml of melted gelatin into 4 test tubes. Let the gelatin solidify.
2. Make 10% solutions of the five non-liquid detergents selected for testing. (Mix 10 g of detergent in 90 mL of distilled water). Label the solutions carefully and note whether enzymes are listed as a component of each.
3. Mark the top level of the gelatin with a permanent marker. Add 15 drops of each detergent solution to the top surface of the hardened gelatin in a test
tube. To one tube add 15 drops of distilled water. Label carefully.
Day 2
4. After 24 hours examine the test tubes. Notice that the gelatin has been liquefied in some tubes.  Use a ruler to measure the depth of the liquefication. Measure from the mark where the hardened gelatin started down to where it is still hard. Measure to the nearest mm. Record.
Day 3
5. Measure the depth of liquefication again after 48 hours.

Data   1 data table, 1 graph (time vs. mm. liquefied)

Enzymes listed? Liquefied After 24 hours (mm.) Liquefied After 48 hours (mm.)
Distilled Water
Detergent 1 ?
Detergent 2 ?
Detergent 3 ?

 

Conclusion:

1. What is the job of enzymes?

 

2. Why do laundry detergents often contain enzymes?

 

3. Why was gelatin used in this lab?

 

4. How is gelatin made?

 

5.  Name each of the laundry detergents you used and describe the effect each one had on the gelatin.

 

 

 

6.  Did any of the laundry detergents contain enzymes? If so, which one(s)?

 

7. Was your original hypothesis correct? Explain.

 

 

Elements in Living Things

 

Elements in Living Things

 

 

Use the following Interactive Periodic Table to determine the physical and chemical properties of the most common elements found in organisms.

http://www.webelements.com/

 

Carbohydrates – C H O          Lipids – C H O

Proteins – CHON S     Nucleic Acids – CHON P

Common Minerals – Fe, I, Zn, Na, K, Ca

 

 
CARBON

Family ______________   Period ___________________

Atomic # ___________    Atomic Mass ____________

Biological Role:

 

 

 

Amount of C in your body ___________________

Hazards & Risks:

 

 

 

 

 HYDROGEN

Family ______________   Period ___________________

Atomic # ___________    Atomic Mass ____________

Biological Role:

 

 

 

Amount of C in your body ___________________

Hazards & Risks:

 
OXYGEN

Family ______________   Period ___________________

Atomic # ___________    Atomic Mass ____________

Biological Role:

 

 

 

Amount of C in your body ___________________

Hazards & Risks:

 

 

 

 NITROGEN

Family ______________   Period ___________________

Atomic # ___________    Atomic Mass ____________

Biological Role:

 

 

 

Amount of C in your body ___________________

Hazards & Risks:

 

 

 

 
SULFUR

Family ______________   Period ___________________

Atomic # ___________    Atomic Mass ____________

Biological Role:

 

 

 

Amount of C in your body ___________________

Hazards & Risks:

 

 

 

 

 POTASSIUM

Family ______________   Period ___________________

Atomic # ___________    Atomic Mass ____________

Biological Role:

 

 

 

Amount of C in your body ___________________

Hazards & Risks:

 

 

 

 
IRON

Family ______________   Period ___________________

Atomic # ___________    Atomic Mass ____________

Biological Role:

 

 

 

Amount of C in your body ___________________

Hazards & Risks:

 

 

 

 

 ZINC

Family ______________   Period ___________________

Atomic # ___________    Atomic Mass ____________

Biological Role:

 

 

 

Amount of C in your body ___________________

Hazards & Risks:

 

 

 

 
IODINE

Family ______________   Period ___________________

Atomic # ___________    Atomic Mass ____________

Biological Role:

 

 

 

Amount of C in your body ___________________

Hazards & Risks:

 

 

 

 

 CALCIUM

Family ______________   Period ___________________

Atomic # ___________    Atomic Mass ____________

Biological Role:

 

 

 

Amount of C in your body ___________________

Hazards & Risks:

 

 

 

 
SODIUM

Family ______________   Period ___________________

Atomic # ___________    Atomic Mass ____________

Biological Role:

 

 

 

Amount of C in your body ___________________

Hazards & Risks:

 

 

 

 

 POTASSIUM

Family ______________   Period ___________________

Atomic # ___________    Atomic Mass ____________

Biological Role:

 

 

 

Amount of C in your body ___________________

Hazards & Risks:

 

 

 

 

Now write the symbol for each element in the proper place on the periodic table.

 

 

 

 

 

 

Energy in Food Writeup

Energy in Food Write Up

Introduction:

Use your lab and your textbook to locate and include the following information in your introduction.

  • What organisms are capable of making their own food?
  • What process do they use to do this?
  • Where do these organisms get their energy for food-making?
  • This energy is captured with the help of what pigment?
  • This energy is stored in what organic molecules?
  • Where exactly in the organic molecules is the energy stored and so it can be used again later? (Hint: Energized electrons form these and then energy is released again when they are broken.)
  • What process takes place in plants & animals to release energy?
  • What gas is required for the process to occur?
  • When foods are “burned” in our bodies, where is the energy being released from? Where did this energy originally come from?
  • What is the usable form of energy for our cells?
  • Define calorimetry and explain how it can be used to measure energy stored in chemical bonds of food.

Hypothesis:

  • Write a statement explaining that calorimetry can be used to detect the amount of energy stored in the chemical bonds of foods.

Materials:

In sentence form, write a statement listing the materials required for this lab.

Procedure:

  • In paragraph form, write the procedures for completing this lab.

Results:

  • Draw and fill in table 1 showing the results of burning
  • Draw and fill in table 2 showing your data analysis for nut calorimetry
  • Write out and answer the questions on the lab. Remember to write and underline the question, but do NOT underline the answer.

Conclusion: (Write in paragraph form.)

  • Restate your hypothesis.
  • Tell how were you able to measure the amount of energy in each nut
  • Did all three nuts contain the same amount of food energy? Explain by giving data from your experiment..
  • Explain why some foods contained more energy than others
  • Tell where this energy originally come from and how it got into the nuts
  • Explain any errors you might have made in lab that could have affected your results