Biochemistry Bi Worksheet

 

Biochemistry Worksheet

 

Section 3.1 – Properties of Water  

 

1. Why is water such an important molecule to living things?

 

2. Describe the chemical make up and type of bonding found in water molecules.

 

3. Explain why the hydrogen and oxygen atoms don’t share electrons equally in a water molecule.

 

4. What is the effect of this uneven sharing of electrons in water?

 

5. Sketch a molecule of water showing the charges on the molecule.

 

 

6. What is the overall charge on a water molecule? Explain why.

 

 

7. Define polar compound and give an example.

 

8. Water’s polarity makes it very effective in _____________ other substances.

9. Name 2 types of compounds that dissolve well in water.

10. What happens when an ionic compound such as sodium chloride (table salt) dissolves in water?

 

11. Water molecules are ___________ to other water molecules.

12. What type of bonding holds 2 or more water molecules together?

13. Are hydrogen bonds strong or weak bonds? Can they be easily broken?

14. Water molecules attracting other water molecules is called _________________.

15. Cohesion of water molecules produces ________________ tension making water seem like it has a “skin” on it. Surface tension enables some _____________ to walk across the surface of the water.

16. Water molecules attracting other types of molecules is called _________________.

17. Adhesion and cohesion together enable water molecules to move ____________ through narrow tubes against the force of gravity.

18. The above property of water is called _________________.

19. Give an example of an organism using capillarity.

 

20. What must be true for water to change temperature?

21. What effect does heating water have on the hydrogen bonds holding the water molecules together? What happens to the speed at which the molecules are moving?

 

22. Give an example of how this water property helps organisms in the environment.

 

Section 3.2 – Carbon Compounds

23.  What is an organic compound?

 

24. Besides carbon, name 3 other elements that make up most organic compounds.

25. Carbon dioxide, CO2, is NOT an organic compound. Explain why.

 

26. How many electrons are in the outermost energy level of carbon? How many does it need to have this energy level filled?

27. How many covalent bonds can carbon form?

28. Name 3 structural shapes that form whenever carbon atoms bond to other carbon atoms.

 

29. How many electrons are being shared in a single covalent bond? double covalent bond? triple covalent bond? quadruple covalent bond?

 

30. Draw these 3 molecules and circle a single bond, double bond, and a triple bond in your drawings — benzene, acetylene, and ethanol.

 

 

31. Explain what is meant by a functional group, & tell what effect they have on the molecules they are attached to.

 

32. Write the formula for these functional groups (use your textbook & handout) — hydroxyl, carboxyl, phosphate group, amino group, and methyl group.

 

 

33. Hydroxyl groups attached to carbon atoms forms an _____________. Name an alcohol used in humans to assemble molecules needed for life.

34. Large carbon molecules are built from smaller, simpler molecules called ____________.

35. Large carbon molecules made of monomers are called _______________.

36. What are large polymers called?

37. What type of reaction links monomers to make polymers?

38. Sketch a molecule of sucrose (table sugar) formed from condensation. Name the 2 sugars that were combined to form sucrose.

 

 

39. Condensation reactions involve the removal of a molecule of ____________.

40. What reaction is used to breakdown polymers? Is water added or removed? How does this compare to condensation?

 

41. All life processes require a constant supply of ____________. Name the molecule used by cells to get energy. Give its abbreviation.

42. ATP contains what 3 functional groups covalently bonded together? Write the formula for this functional group.

43. Which bonded phosphate group on ATP releases the MOST energy when broken?

Section 3.3 – Macromolecules

44. Name the 4 main classes of macromolecules (organic molecules) & tell what 3 elements all of these contain.

 

Carbohydrates store energy for organisms!

45. In what ratio are hydrogen & oxygen atoms in carbohydrates?

46. In what 3 forms do carbohydrates exist?

47. What are the monomers of carbohydrates called? What is their common name? Give the ratio of carbons, hydrogens, & oxygens.

48. Name the 3 MOST common monosaccharides.

49. Sketch & label a molecule of each of these monosaccharides. How do they compare? Write the chemical formula for all three.

 

 

 

50. Because all 3 simple sugars have the same chemical, but different structural formulas, they are called _______________.

51. What are double sugars called? Name & describe the process that forms them.

 

52. Name a disaccharide.

53. What forms a polysaccharide? Name a polysaccharide found in animals. Name 2 found in plants?

 

54. What chemical reaction formed these large molecule? What reaction would be needed to break these molecules?

 

Proteins are used to build cells, & they act as enzymes!

55. What are the 4 main elements making up proteins? How many covalent bonds does each of these elements form?

 

56. Sketch these two amino acids — glycine & alanine.  Circle the center carbon, place a triangle around the amino group, and put a box around the carboxyl group.

 

 

 

 

 

57. What are the monomers of proteins called? How many are there? Name the 4 things bonded to the center carbon of this monomer.

 

 

58. The main difference among amino acids is their ___________ group. What is the R-group on glycine? on alanine?

59. Differences in R-groups give different proteins different ______________.

60. How does a dipeptide form? Sketch the dipeptide formed from glycine and alanine. What molecule had to be removed to join these 2 amino acids?

 

 

 

61. What do you call the covalent bonds that hold amino acids together? Put a box around these bond in the sketch you did on question 60.

62. Long chains of amino acids are called ___________________ and these join together to make a ________________.

63. Hydrogen bonding among individual amino acids in a chain cause what effect on the protein’s shape?

64, What is the effect of temperature on protein shape? Give an example of this.

 

65. Most proteins act as catalysts or __________________ inside of cells.

66. The substance an enzyme is acting upon is called the _____________ and it must ______ into a place called the active site on the enzyme.

67. When a substrate joins with an enzyme, what effect does this have on chemical bonding of that substrate? Is the enzyme affected temporarily or permanently? How is it affected?

 

68. When chemical bonds in a substrate are weakened, what effect does this have on activation energy needed to start the reaction?

69. After the reaction, what happens to the products? Can the enzyme be re-used & why?

 

70. Besides temperature, what else can effect how an enzyme works by changing the enzyme’s shape? Can the reaction still take place?

Lipids include fats that are used for long-term energy storage!

71. Are lipids polar or nonpolar? What happens to lipids when they are placed in water?

72. Compared to carbohydrates, what is true about the ratio of carbon & hydrogen atoms to oxygen atoms? If a compound has more bonds, what can it store more of in those bonds?

 

73. Most lipids are made of ______________ acids. Describe their shape. What functional group is found on the head end of the molecule?

 

74. Sketch these 2 fatty acids — palmitic & linoleic.  Circle the carboxyl group on the “head” of the molecule. Is this end polar or nonpolar? Will this end be attracted to  or repelled by water?

 

 

 

 

 

75. Are both ends of a fatty acid polar? Explain.

76. Hydophilic means water ___________. Which end of  a fatty acid is hydrophilic. The nonpolar end of a fatty acid is said to be _______________ or “water fearing”.

77. Which end of a fatty acid chain WOULD dissolve in water? Which WOULDN’T?

 

78. In what type of fatty acid are there only single bonds in the carbon chain? Name one such fatty acid.

79. What type of bond appears in an unsaturated fatty acid? Give an example of an unsaturated fatty acid. Go back to your fatty acid drawings in question 74 and put a box around the double bond in the unsaturated fatty acid.

 

80. Name the 3 groups of complex lipids.

81. What makes up a triglyceride? What is the difference between a saturated & unsaturated triglyceride?

 

82. What type of triglycerides tend to be solids at room temperature & why? Which are liquids & why?

 

83. What type of triglyceride would this of  substance be — vegetable oil?  butter & shortening?

84. What makes up a phospholipid? How are they different from triglycerides? What main part of a cell is made of phospholipids?

 

85. What is meant by a lipid bilayer? What makes this such an effective barrier between the inside & the outside of the cell?

 

86. Wax is another complex lipid. Describe its structure.

 

87. Waxes are highly _________________. Explain how plants make use of this property? animals?

 

88. What makes up steroids? To what group of organic compounds do steroids belong? How are they used in animals?

 

89. Name a steroid made by the body & used by nerve cells.

Nucleic acids  store genetic information for cells!

90. Give the name & abbreviation for 2 nucleic acids found in cells.

 

91. DNA and RNA are both examples of _____________ made of linked monomers called ________________.  The instructions in these molecules is used to make ____________.

92. Name the 3 parts to a nucleotide then draw and label one.

 

BACK

AP Sample Lab 2 Catalysis 3

 

 

Lab 2    Enzyme Catalysis

 

 

Introduction

The human body produces many things to keep it alive and healthy. Enzymes are proteins produced by living cells. Enzyme-catalysis binds with the active site of an enzyme, reducing the amount of energy needed to have a reaction with the substrate. Catalysis is a substance that lowers reaction energy and allows the reaction to take place in less time and at lower temperatures. Without catalysis people would die from poisons that the body produces, but would not be able to break down. Catalysis does not break down during a reaction so can be used reversibly (E is enzyme, S is substrate, and P is Product):

E+S↔ES↔E+P

Even with catalysis, enzyme reactions can be affected by many factors: salt concentration, pH, temperature, substrate concentration, enzyme concentration, activators, and inhibitors. Salt concentration affects the enzyme if it is to high or to low. Not enough salt will cause the enzyme side chains to become attracted to each other and denaturalizes it. Too much salt blocks the action site of the enzyme. The pH of a substance is determined by the amount of hydrogen (H+) in it. The scale ranges from 0-14: 0-7 is acidic, 7 is neutral, and 7-14 is basic. If the pH is too basic, the enzyme gains (H+) and eventually denaturalizes. If the pH is too acidic, then the enzyme loses (H+) and becomes denaturalized. The ideal pH is between 6 and 8. Temperature affects the kinetic energy that causes the reaction to speed up or slow down. In general, the higher the temperature the faster the molecular reaction. If the enzyme raises to a temperature above its optimum level, the tertiary structure of the protein is destroyed (denaturing it). Most enzymes denaturalize around 40-50°C. The law of mass action states the direction of enzyme-catalyzed reaction is dependent on conservation of enzyme/substrate/product. For example, when the substance has high substrate and low product, the substrate is used and more products are made. When the product is high and enzyme low, the reaction reverses and produces more substrate. If the product is immediately metabolized or removed from the cell, there will be no substrate formed. Activators increase the rate of a reaction while inhibitors slow the rate of the reaction. Inhibitors unfold an enzyme or reduce the –S-S- chains that stabilize the enzyme’s structure. Some enzyme inhibitors are poisons like potassium cyanide and curare.

Even without catalase, a reaction will still occur, but slower. The study of kinetics helps to determine the amount of product or substrate formed.

Chemical reactions occur over periods of time. The first three minutes of the reaction, the rate of change stays about the same. After a while, when there is less substrate, the reaction slows down and the rate of change becomes less. To compare the change of kinetic energy between reactions, a common point must be obtained. The first part of the reaction is called the initial rate of change. The initial rate of any enzyme-catalyzed reaction can be determined by the characteristics of the enzyme molecule. This is always the same for any enzyme and substrate at the same temperature and pH, but the substrate must have an excessive amount.

Chemical reactions can be studied by measuring the disappearance of the substrate, the rate of appearance by the product, or measuring the release or the absorbence of heat. For example, hydrogen peroxide (H2O2) is converted to water (H2O) and oxygen (O2) gas. Catalysis speeds up the reaction and sulfuric acid (H2SO4) stops the reaction by lowering the pH and denaturalizing the enzyme. Potassium permanganate (KmnO4) measure the presence of H2O2:
5 H2O2 + 2 KmnO4 +3 H2SO4 → K2SO4 + 2 MnSO4 + 8 H2O + 5 O2

After a certain amount of KmnO4 is added and the substance reaches a permanent brown or pink, no more KmnO4 should be added because it can mot be broken down.

 

Hypothesis:

 

Under perfect conditions, the rate of enzyme-catalysis should denature most of the hydrogen peroxide in a short amount of time.

 

Materials:

 

Exercise 2A

 

In Part 1, 10 mL of 1.5% of H2O2, a 50 mL beaker, and 1 mL of catalysis are needed. In Part 2, 5mL of catalysis, a water bath, and 10 mL of 1.5% H2O2 is needed. In Part 3, a 1 cm³ of liver, 50 mL beaker, and 10 mL of 1.5% H2O2. For all three parts, safety goggles, lab aprons, pencil, paper, erasers, and paper towels are needed.

 

Exercise 2B

 

To do this experiment, 10 mL of 1.5% H2O2, 1 mL of water, 10 mL of H2SO4, 50 mL beaker, 25 mL beaker, 5 mL syringe, and KmnO4 are needed. Safety goggles, lab aprons, pencil, paper, erasers, and paper towels are also needed.

 

Exercise 2C

 

To do this exercise, safety goggles, lab aprons, pencil, paper, erasers, paper towels, about 20 mL of 1.5% H2O2, 1 mL of H2O, 10 mL of H2SO4, 50 mL beaker, 25 mL beaker, 5 mL syringe, and KmnO4 are needed.

 

Exercise 2D

 

To do this experiment, about 60 mL of 1.5% H2O2, 6 mL of catalysis, 60 mL of H2SO4, 12 cups labeled 10, 30, 60, 120, 180, and 360 seconds, six cups labeled acid, a black marker, and a timer are needed. Safety goggles, lab aprons, pencil, paper, erasers, and paper towels will be needed, also.

 

Methods: * Remember to wear the goggles and apron. *

 

Exercise 2A

In Part 1, transfer 10 mL of 1.5% H2O2 a 50 mL glass beaker and add 1 mL of freshly made catalase to the solution. Remember to keep the catalase solution on ice at all times. Record the observations made. In Part 2, transfer 5 mL of the purified catalase extract to a test tube and place it in a boiling water bath for five minutes. Next, transfer 10 mL of 1.5% H2O2 into a 50 mL beaker and add 1 mL of the cooled, boiled catalase solution. Again record the results. In Part 3, cut 1 cm of liver, transfer it into a 50 mL glass beaker containing 10 mL of 1.5% H2O2, and mix it. Record the results.

 

Exercise 2B

 

To form a baseline for this experiment, put 10 ml of 1.5% H2O2 into a clean glass beaker. Add 1 mL of H2O and then add 10 mL of H2SO4 (1.0 M). Be careful when using acid. Mix this solution well. Remove a 5 mL sample and place it into another beaker. Assay for the amount of H2O2 as follows. Place the beaker containing the sample over white paper and use a 5 mL syringe to add one drop of KMnO4 at a time to the solution until it becomes a persistent pink or brown color. Gently swirl the solution after adding each drop. Record all results.

 

Exercise 2C

 

To determine the rate of spontaneous conversion of H2O2 to H2O and O2 in an uncatalyzed reaction, put about 20 mL of 1.5% H2O2 in a beaker. Store it uncovered at room temperature for approximately 24 hours. Put 10 ml of 1.5% H2O2 into a clean glass beaker (using the uncatalyzed H2O2 that set out). Add 1 mL of H2O and then add 10 mL of H2SO4 (1.0 M). Be careful when using acid. Mix this solution well. Remove a 5 mL sample and place it into another beaker. Assay for the amount of H2O2 as follows. Place the beaker containing the sample over white paper and use a 5 mL syringe to add one drop of KMnO4 at a time to the solution until it becomes a persistent pink or brown color. Gently swirl the solution after adding each drop. Record all results.

 

Exercise 2D

If a day or more has passed since Exercise B was performed, it is necessary to reestablish the baseline. Repeat the assay from Exercise B and record the results. Compare with other groups to check that results are similar. To determine the course of an enzymatic reaction, how much substrate is disappearing over time must be measured. The first thing to be done is to set up the cups labeled with times and acid. Add 10 mL of H2SO4 to each of the cups marked acid. Then put 10 mL of 1.5% H2O2 into the cup marked 10 sec. Add 1 mL of catalase extract to this cup. Swirl gently for 10 seconds (use the timer for accuracy). At 10 seconds, add the contents of one of the acid filled cups. Remove 5 mL and place in the second cup marked 10 sec. Assay the 5 mL sample by adding one drop of KMnO4 at a time until the solution turns a pink or brown. Repeat the above steps except allow the reactions to proceed for 30, 60, 120, 180, and 360 seconds, respectively. Use the times corresponding with the marked cups. Record all results and observations.

Results:

Table 1     Catalysis Activity

 

 

 

Experiment

 

Observations

H 2O2 and Fresh CatalaseSmall amount of bubbles
H 2O2 and Boiled CatalaseLittle or no bubbling
Catalase with LiverVery bubbly or reactive

 

Table 2     Baseline Assay

 

 

 

Baseline Calculations

Final Reading of Burette1.5 mL
Initial Reading of Burette5.0 mL
Baseline (Final-Initial)3.4 mL of KmnO4

 

Table 3     The Uncatalyzed Rate of H2O2 Decomposition

 

 

 

Final Reading of Burette2.2 mL
Initial Reading of Burette7.0 mL
Amount of KMnO4 Titrant4.8 mL
H2O2 Spontaneously Decomposed1.3 mL
Percentage Spontaneously Decomposed in 24 hours62.9%

 

 

Table 4     New Baseline

 

 

 

Baseline Calculations

Final Reading of Burette1.4 mL
Initial Reading of Burette5.0 mL
Baseline (Final-Initial)3.6 mL of KmnO4

 

Table 5     Catalyzed Rate of H2O2 Decomposition

 

 

Time (seconds)

 

10

 

30

 

60

 

120

 

180

 

360

 

A. Baseline

3.6 mL3.6 mL3.6 mL3.6 mL3.6 mL3.6 mL
 

B. Final Reading

1.2 mL1.4 mL1.8 mL1.9 mL2.4 mL2.8 mL
 

C. Initial Reading

5 mL5 mL5 mL5 mL5 mL5 mL
 

D. Amount of KmnO4 Consumed (B-C)

3.8 mL3.6 mL3.2 mL3.1 mL2.6 mL2.2 mL
 

E. Amount of H2O2 Used (A-D)

.2 mL0 mL.4 mL.5 mL1.0 mL1.4 mL

 

 

Graph 1    Affect of Time on Enzyme-Catalyzed H2O2 (Remaining amount)

 

Exercise 2A

 

(a) What is the enzyme in this reaction?

The enzyme in the reaction is catalase.

(b) What is the substrate in this reaction?

The substrate in the reaction is hydrogen peroxide.

(c) What is the product in this reaction?

The products in the reaction are water and oxygen gas.

(d) How could you show that the gas evolved is O2?

The formula 2 H202 + catalase →2 H2O + O2 proves that water and oxygen gas can only be produced.

How does the reaction compare to the one using unboiled catalysis? Explain the reason for the difference.

The boiled catalysis was not as reactive as the regular catalysis, because boiling the catalysis denatures it.

What do you observe? What do you think would happen if the liver was boiled before being added to the H2O2?

The liver has a high amount of catalase in it causing it to be very reactive when put with hydrogen peroxide. If the liver was boiled first, the catalysis would have been denatured and would not have reacted as much as previously.

 

Exercise 2D

 

1) From the formula described earlier recall that rate = G y/G x. Determine the initial rate of the reaction and the rates between each of the time points. Record the rates in the table below.

Time Intervals (seconds)
Initial 0-1010-3030-6060-120120-180180-360
Rates.38-.01-1/75-1/1600-1/120-1/450

 

2) When is the rate the highest? Explain why.

The rate is the highest at initial to 10, because of the high concentration of catalysis.

When is the rate the lowest? For what reason is the rate low?

The rate is the lowest at 30 to 60 seconds, because the concentration of calase and the concentration of the product are beginning to balance each other out.

Explain the inhibiting effect of sulfuric acid on the function of the catalysis. Relate this to enzyme structure and chemistry.

The sulfuric acid changes the pH of the catalase function and causes it to denature. Most enzymes work in a range of 6 to 8 and by adding the acid, the pH drops too low.

Predict the effect of lowering the temperature would have on the rate of the enzyme activity. Explain your prediction.

Lowering the temperature would slow the reaction. If the temperature is lowered a great deal (below 40ºC) it will be denatured.

Design a controlled experiment to test the effect of varying pH, temperature, or enzyme concentration.

To test the effect of temperature on enzymes: put 5 mL of catalase in the freezer until it is completely frozen, add 1 mL of catalase to 10 mL of 1.5% H2O2 (which is in a 50 mL beaker). Watch and record results.

 

Error of Analysis:

 

Errors in this experiment could have come from inaccurate measurements and timing. Also the catalase not being frozen when received most likely affected the data.

 

Discussion and Conclusion:

 

The purpose of this lab was to show the decomposition of hydrogen peroxide under different circumstances. Exercise 2A showed the affects of catalysis (added to and from living cells) in hydrogen peroxide. In Exercise 2B, the baseline was determined for the experiment (3.5). In Exercise 2C, the natural decomposition of hydrogen peroxide was viewed and found to be slower that when catalyzed. In Exercise 2D, a new baseline was made (3.6) and the decomposition of hydrogen peroxide with a catalase, over six minutes, was discovered to decompose more rapidly than an uncatalyzed reaction over 24 hours.

AP Sample Lab 2 Catalysis 2

 

 

Lab 2    Enzyme Catalysis

 

 

Introduction:

 

Enzymes are proteins produced by living cells. They are biochemical catalysts meaning they lower the activation energy needed for a biochemical reaction to occur. Because of enzyme activity, cells can carry out complex chemical activities at relatively low temperatures. The substrate is the substance acted upon in an enzyme-catalyzed reaction, and it can bind reversibly to the active site of the enzyme. The active site is the portion of the enzyme that interacts with the substrate so that any substrate that blocks or changes the shape of the active sit effects the activity of the enzyme. The result of this temporary union is a reduction in the amount of energy required to activate the reaction of the substrate molecule so that products are formed. The following equation demonstrates this process: E + S ↔ ES ↔ E + P Enzymes follow the law of mass reaction. Therefore, the enzyme is not changed in the reaction and can be recycled to break down additional substrate molecules.

Several factors can affect the action of an enzyme: salt concentration, pH of the environment, temperature, activations and inhibitors. If salt concentration is close to zero, the changed amino acid side chains of the enzyme molecules will attract one another. The enzyme will then denature and form an inactive precipitate. Denaturation occurs when excess heat destroys the tertiary structure of proteins. This usually occurs at 40 to 50º Celsius. If salt concentration is high, the normal interaction of charged groups will be blocked. An intermediate salt concentration is normally the optimum for enzyme activity. The salt concentration of blood and cytoplasm are good examples of intermediate concentrations. The pH scale is a logarithmic scale that measures the acidity or H+ concentration in a solution and runs from 0 to 14, with 0 being highest in acidity and 14 lowest. Amino acid side chains contain groups such as –COOH that readily gain or lose H+ ions. As the pH is lowered an enzyme will tend to gain H+ ions, disrupting the enzyme’s shape. If the pH is raised, the enzyme will lose H+ ions and eventually lose its active shape. Reactions usually perform optimally in neutral environments. Chemical reactions generally speed up as the temperature is raised. More of the reacting molecules have enough kinetic energy to undergo the reaction as the temperature increases. However, if the temperature goes above the temperature optimum, the conformation of the enzyme molecules is disrupted. An activator is a coenzyme that increases the rate of the reaction and can regulate how fast the enzyme acts. It also makes the active site a better fit for the substrate. An inhibitor has the same power of activator regulation but decrease the reaction rate. An inhibitor also reduces the number of S-S bridges and reacts with the side chains near activation sites, blocking them.

The enzyme used in this lab is catalase. It has four polypeptide chains that are each composed of more than 500 amino acids. One catalase function is to prevent the accumulation of toxic levels of hydrogen peroxide formed as a by-product of metabolic processes. Many oxidation reactions that occur in cells involve catalase. The following is the primary reaction catalyzed by catalase, the decomposition of hydrogen peroxide to form water and oxygen:

2 H2O2 → 2 H2O + O2 (gas) Without catalase this reaction occurs spontaneously but very slowly. Catalase speeds up the reaction notably.

The direction of an enzyme-catalyzed reaction is directly dependent on the concentration of enzyme, substrate, and product. For example, lots of substrate with a little product makes more product. Another example is lots of product with a little enzyme forms more substrate. Much can be learned about enzymes by studying the kinetics of enzyme-catalyzed reaction. It is possible to measure the amount of product formed, or the amount of substrate used, from the moment the reactants are brought together until the reaction has stopped.

 

Hypothesis:

Enzyme catalase, when working under optimum conditions, noticeably increases the rate of hydrogen peroxide decomposition.

 

Materials:

 

Exercise 2A

The materials needed for exercise 2A of the lab are: 30 mL of 1.5% (0.44 M) H2O2, a 50- mL glass beaker, 6 mL of freshly made catalase solution, a test tube, boiling water bath, 1 cm³ of liver, a knife for maceration, paper towels, safety goggles, lab apron, pencil, eraser, and paper to record results.

Exercise 2B

The materials needed for exercise 2B are: 10 mL of 1.5% H2O2, two clean glass beakers, 1 mL of H2O, 10 mL of H2SO4, a white sheet of paper, a 5 mL syringe, approximately 5 mL of KMnO4, paper, pencil, eraser, safety goggles, and lab aprons.

Exercise 2C

The materials needed for exercise 2C of the lab are: 20 mL of 1.5% H2O2, two glass beakers, 1 mL of H2O, 10 mL of H2SO4, a white sheet of paper, a 5 mL syringe, approximately 5 mL of KMnO4, paper, pencil, eraser, safety goggles, and lab aprons.

Exercise 2D

For this part of the experiment, the materials needed are 12 cups labeled 10, 30, 60, 120, 180, and 360 on two each, six cups labeled acid, 60 mL of 1.5% H2O2, a clean 50-mL beaker, 6 mL of catalase extract, two 5-mL syringes, KMnO4, a timer, paper, pencil, black marker, eraser, safety goggles, and lab aprons.

 

Methods:

 

Exercise 2A

Transfer 10 mL of 1.5% H2O2 into a 50-mL glass beaker and add 1 mL of freshly made catalase solution. Remember to keep the catalase solution on ice at all times. Record the results. Then transfer 5 mL of purified catalase extract to a test tube and place it in a boiling water bath for five minutes. Transfer 10 mL of 1.5% H2O2 into a 50-mL beaker and add 1 mL of the cooled, boiled catalase solution. Again record the results. To demonstrate the presence of catalase in living tissue, cut 1 cm of liver, macerate it, and transfer it into a 50-mL glass beaker containing 10 mL of 1.5% H2O2. Record these results.

Exercise 2B

Put 10 ml of 1.5% H2O2 into a clean glass beaker. Add 1 mL of H2O. Add 10 mL of H2SO4 (1.0 M) using extreme caution. Mix this solution well. Remove a 5 mL sample and place it into another beaker. Assay for the amount of H2O2 as follows. Place the beaker containing the sample over white paper. Use a 5-mL syringe to add KMnO4 a drop at a time to the solution until a persistent pink or brown color is obtained. Remember to gently swirl the solution after adding each drop. Record all results. Check with another group before proceeding to see that results are similar.

Exercise 2C

To determine the rate of spontaneous conversion of H2O2 to H2O and O2 in an uncatalyzed reaction, put about 20 mL of 1.5% H2O2 in a beaker. Store it uncovered at room temperature for approximately 24 hours. Repeat the steps from Exercise 2B, using the uncatalyzed H2O2, to determine the proportional amount H2O2 of remaining after 24 hours. Record the results.

Exercise 2D

If a day or more has passed since Exercise B was performed, it is necessary to reestablish the baseline. Repeat the assay and record the results. Compare with other groups to check that results are similar. To determine the course of an enzymatic reaction, how much substrate is disappearing over time must be measured. First, set up the cups with the times and the word acid up. Add 10 mL of H2SO4 to each of the cups marked acid. Then put 10 mL of 1.5% H2O2 into the cup marked 10 sec. Add 1 mL of catalase extract to this cup. Swirl gently for 10 seconds. (Calculate time using the timer for accuracy.) At 10 seconds, add the contents of one of the acid filled cups. Remove 5 mL and place in the second cup marked 10 sec. Assay the 5-mL sample by adding KMnO4 a drop at a time until the solution obtains a pink or brown color. Repeat the above steps except allow the reactions to proceed for 30, 60, 120, 180, and 360 seconds, respectively. Use the times’ corresponding, marked cups. Record all results and observations.

 

Results:

Table 1: Test of Catalysis Activity

 

 

 

Experiment

 

Observations

Hydrogen Peroxide + Fresh CatalaseBubbling in solution with the release of oxygen.
Hydrogen Peroxide + Boiled CatalaseNo reaction occurred.
Hydrogen Peroxide + LiverMuch bubbling in solution with the release of O2.

 

Table 2: Establishing a Baseline #1

 

 

Baseline Calculations (syringe contains KMnO4)

 

Readings

Final Reading of Syringe1.2 mL
Initial Reading of Syringe5.0 mL
Baseline3.8

 

Table 3: Uncatalyzed H2O2 Decomposition

 

 

(Syringes Contain KMnO4)

 

Results

Final Reading of Syringe1.3 mL
Initial Reading of Syringe5.0 mL
Amount of H2O2 Spontaneously Decomposed3.7 mL
Percent of H2O2 Spontaneously Decomposed in 24 Hours94.3%

 

Table 4: Establishing a Baseline #2

 

 

Baseline Calculations (syringe contains KMnO4)

 

Readings

Final Reading of Syringe1.5 mL
Initial Reading of Syringe5.0 mL
Baseline3.5

 

Table 5: Time-Course Determination

 

 

 

Potassium Permanganate (mL)

Time in Seconds

103060120180360
Baseline3.53.53.53.53.53.5
Final Reading1.31.61.82.02,42.7
Initial Reading5.05.05.05.05.05.0
Amount of KMnO4 Consumed3.73.43.23.02.62.3
Amount of H2O2 Used0.20.10.30.50.91.2

 

 

Effect of Time on the Amount of H2O2 Remaining after an Enzyme Catalyzed Reaction

Exercise 2A:

1.a. What is the enzyme in this reaction? The enzyme in this reaction is the catalase solution.

1.b. What is the substrate in this reaction? The substrate is hydrogen peroxide.

1.c. What are the products in this reaction? The products are water and oxygen gas.

1.d. How could you show that the gas evolved is oxygen? Referring to the equation 2H2O2 + Catalase solution→H2O + O2, the only gas released is oxygen.

2. How does the reaction compare to the one using the unboiled catalase? Explain the reason for this difference. With the boiled catalase, there was no sign of bubbling because the catalase was denatured by the heat and caused no reaction.

3.a. What do you observe? I observe quite a bit of gas being released from the solution.

3.b. What do you think would happen if the liver were boiled before being added to the hydrogen peroxide? I think that no signs of a reaction occurring would be shown. The catalase that occurs naturally within the liver would have been denatured.

4. From the formula described earlier recall that rate = G y/G x . Determine the initial rate of the reaction and the rates between each of the time points. Record the rates in the table below.

 

Time Intervals (seconds)
Initial 0-1010-3030-6060-120120-180180-360
Rates37/100-3/200-1/150-1/300-1/150-1/600

 

 

5. When is the rate the highest? Explain why. The rate is the highest in the first ten seconds because the rate decreases as the concentration of the catalase decreases over time.

6. When is the rate the lowest? For what reason is the rate low? The rate is lowest during the last time period of 360 seconds because the most time has passed. The catalase concentration has been reduced and the product amount has increased, blocking the enzymes from reacting with the hydrogen peroxide.

7. Explain the inhibiting effect of sulfuric acid on the function of the catalysis. Relate this to enzyme structure and chemistry. The sulfuric acid’s high concentration of H+ ions gives the acid a low pH. Because enzymes can only function in the pH range of six to eight, the addition of an acidic solution denatures the enzyme, stopping the reaction.

8. Predict the effect of lowering the temperature would have on the rate of the enzyme activity. Explain your prediction. Enzymes generally only work at the between the temperatures of forty and fifty degrees Celsius. Lowering the temperature would slow the reaction until the enzyme is denatured and no longer able to react.

9. Design a controlled experiment to test the effect of varying pH, temperature, or enzyme concentration.

 

Part One (the effects of a strong acid on enzyme activity): Add 10 mL of 1.5-% hydrogen peroxide to a 50-mL beaker, and add 1 mL of catalase solution. Mix well and then add 1 mL of (0.5 M) HCl to the beaker. Observe the reaction and record the results.

Part Two (the effects of a neutral solution on enzyme activity): Add 10 mL of 1.5-% hydrogen peroxide to a 50-mL beaker, and add 1 mL of catalase solution. Mix well and then add 1 mL of pure water with a pH of 7.0. Observe the reaction and record the results.

 

Part Three (the effects of a strong base on enzyme activity): Add 10 mL of 1.5-% hydrogen peroxide to a 50-mL beaker, and add 1 mL of catalase solution. Mix well and then add 1 mL of (0.5 M) NaOH to the beaker. Observe the reaction and record the results.

 

Error Analysis:

Several errors could have occurred throughout the experiment. Miscalculations involving numbers and amounts of solutions would have a severe effect upon the results. Mathematical errors may also have of occurred. When the catalase arrived, it had melted. Because it is to remain on ice at all times, this may have caused errors. The age of the hydrogen peroxide effected results. For example, when calculating the percent of hydrogen peroxide spontaneously decomposed after 24 hours, new hydrogen peroxide yielded a much higher percentage than the aged hydrogen peroxide. Errors occur in every experiment and that is why is it is necessary to repeat an experiment several times for the most accurate results.

Discussion and Conclusion:

Catalase, or enzymes, drastically increases the rate of hydrogen peroxide decomposition. This lab shows how catalase added to hydrogen peroxide leads to the release of oxygen, boiled catalase is denatured, and the presence of catalase in living things can lead to the breaking down of hydrogen peroxide in the body. In the lab it was shown that the natural decomposition hydrogen peroxide is slower than decomposition taking place with the addition of enzymes. If hydrogen peroxide was required to decompose naturally, life could not survive. The addition of catalase increases this decomposition rate allowing life to continue.

 

AP Lecture Guide 05A – Macromolecules

 

AP Biology: CHAPTER 5A

MACROMOLECULES

 

1. Define the following:

a. monomer _______________________________________________________________

___________________________________________________________________________

b. polymer _________________________________________________________________

___________________________________________________________________________

c. condensation reaction _____________________________________________________

___________________________________________________________________________

d. hydrolysis _______________________________________________________________

___________________________________________________________________________

2. Which foods do you think will enter the blood the quickest? Why?

___________________________________________________________________________

___________________________________________________________________________

3. What are the general roles of carbohydrates? ______________________________________

___________________________________________________________________________

___________________________________________________________________________

4. List some monosaccharides with their molecular formulas.

___________________________________________________________________________

___________________________________________________________________________

5. Double sugars are called ______________________________________________________

6. List the monosaccharides that form each:

a. maltose _________________________________________________________________

b. sucrose _________________________________________________________________

c. lactose __________________________________________________________________

6. Polymers of sugars form _______________________________________________________

7. Which forms of polysaccharide is best for each function:

a. Strength of structure _______________________________________________________

b. Storage and sugar release __________________________________________________

c. What theme is this addressing? ______________________________________________

8. How does the alpha differ from the beta form of glucose and why is it significant to animals?

___________________________________________________________________________

___________________________________________________________________________

9. How do the role and structure of the following polysaccharides compare?

a. starch___________________________________________________________________

b. glycogen ________________________________________________________________

c. cellulose_________________________________________________________________

10. Ninety percent of Asians, 75% of African-Americans, and a much smaller percent of

northern Europeans are lactose intolerant. Why do you suppose we see this pattern?

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

 

 

AP Lecture Guide 05B – Macromolecules

 

AP Biology: CHAPTER 5B

MACROMOLECULES

 

1. What is the characteristic common to lipids? _______________________________________

___________________________________________________________________________

2. Lipids are synthesized by the chemical reaction ____________________________________

and broken down by the reaction ________________________________________________

3. What makes fats hydrophobic? _________________________________________________

___________________________________________________________________________

___________________________________________________________________________

4. State at least two differences between saturated and unsaturated fats.

a. _________________________________________________________________________

___________________________________________________________________________

b. _________________________________________________________________________

___________________________________________________________________________

5. How do phospholipids interact in an aqueous solution?

___________________________________________________________________________

___________________________________________________________________________

6. Make a diagram of phospholipid interactions that form membranes.

 

 

7. Sketch the common building block of steroids.

 

8. List several functions of proteins.

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

9. What are the three properties used to classify amino acids?

___________________________________________________________________________

___________________________________________________________________________

___________________________________________________________________________

10. Sketch two amino acids side-by-side, on one of them label the functional groups, then show how the two can be joined together.

 

 

11. What determines the primary structure of a protein? _________________________________

___________________________________________________________________________

12. Describe the four levels of protein structure:

a. Primary _________________________________________________________________

___________________________________________________________________________

b. Secondary ______________________________________________________________

___________________________________________________________________________

c. Tertiary _________________________________________________________________

___________________________________________________________________________

d. Quaternary ______________________________________________________________

___________________________________________________________________________

13. What happens to a protein during denaturation? ____________________________________

___________________________________________________________________________

14. What are the building blocks of nucleic acids? ______________________________________

15. Briefly describe two functions of DNA in the cell.

a. ________________________________________________________________________

___________________________________________________________________________

b. ________________________________________________________________________

___________________________________________________________________________