5E Lesson: Role of Enzymes

DAY 1 ENGAGE: Cracker Spit! (6 min) - Demo Materials: Cheez-It™ crackers, test tubes or disposable cups,

saliva, stirring rod, Lugol’s iodine, disposable pipette

**Pre-Lab set up**

Hand a cracker to a student and ask him/her to place the cracker in mouth.

Have another student spit into a test tube to collect about 5ml of saliva.

Have another student crush up a saltine cracker until well grounded.

1. Have students draw the following data table in their journals.

Observations for Cracker Spit Investigation Cracker + water Cracker + spit

Prediction

Initial Color

Final Color

Result of starch test

2. Place a small piece of the crushed cracker in a test tube. Add 5 ml distilled

water.

3. In another test tube ask the student to spit out his cracker mixture into the tube. Add the 5 ml of saliva.

4. Stir both tubes.

5. Let the tubes sit while you review that the food you eat contains different macromolecule. Ask students

what macromolecules are in a cracker. What test can you use to test the presence of starch?

6. Have the students make a prediction in their journal of the results of the two test tubes when you add

one of drop of iodine to each.

7. Add one drop of iodine to both tubes.

8. The tube with the saltine and water should turn black, but the one with the saltine and saliva should turn

yellow.

9. Ask the student to explain what they think caused the saliva and cracker mixture did not turn positive.

10. The teacher further tells the students that the saliva contains an enzyme called amylase. See if the

student can come up with a definition of an enzyme.

11. Teacher note -- Amylase, an enzyme found in saliva, breaks down amylose into, ultimately, it's individual

glucose subunits. As amylose is broken apart and the remaining sections grow shorter, at some point

they can no longer accommodate the iodine molecules. The color reaction does not occur and iodine

remains its normal brownish color (or the color reverses, if the reaction has already occurred).

Scaffolded Questions: 1. What do you think happened to the starch present in the cracker? The starch was broken down by the

enzyme into simple sugars.

2. What further indicator tests should you perform? Benedict’s for simple sugars (glucose) and Biuret’s for proteins (amylase)

3. Describe how this demonstration showed both a physical change as well as a chemical change? Physical change when chewing and chemical change when amylase helped break down starch.

4. Which of the human body’s systems uses enzymes to break down food? Digestive 5. What would happen if a person’s cells did make the enzyme to break down a

specific food compound? The food would not get broken down chemically. 6. Give an example of a condition a person may have that makes that person unable

to break down a molecule from food. Answers may vary but could include lactose intolerance, in which the enzyme lactase is not produced and lactose cannot be broken down.

EXPLORE: Enzyme Catalase Pre-lab (Observational and Comparative Investigation) Time: 25 min Advanced Prep: Make enough copies of Enzyme Catalase Pre-lab Instructions for each group. Materials: Enzyme Catalase Pre-lab (laminated), potato pieces, Petri dish, catalase solution, hydrogen peroxide, stopwatches, two test tubes, medicine cups, stopwatch, ruler Teacher’s Note:

1. In this activity, each student is responsible for a different job, but all students are responsible for their own lab write up in their journals.

2. Materials and procedure can be used for individuals or pairs of students. 3. Put scaffolding questions on a PowerPoint to help with the whole group discussion that follows. 4. Instruct students to follow the procedures in the enzyme pre-lab. 5. Explain that students will document qualitative and quantitative data as well as questions that arise

from their observations. 6. Inform students that their questions will provide the basis for designing the next investigation.

Student 1 Material Specialist Gathers all the materials for the experiment, properly disposes of used materials, replaces used materials for the next group to use, and makes sure that the lab station is clean and dry.

Student 2 Data Specialist keeps time for the length of the experiment and counts aloud and records data accurately during the experiment, helps to clean up the lab station

Student 3 Experimenter Performs the experimental procedure safely and accurately and helps to clean up the lab station.

Procedure:

1. Place students into cooperative groups of four. 2. Inform students of the time frame for completing the activity. 3. Explain to students that they will observe the change in the rate of an

enzymatic reaction.

4. Obtain a piece of potato on a Petri dish, 10 mL of potato catalase solution, and 15 ml of hydrogen peroxide (H2O2) in medicine cups. Drop a few drops of H2O2 onto a piece of potato. Record your observations and write down questions that come to mind.

5. Obtain 1 mL of potato catalase solution in a test tube. 6. Using a dropper pipette add 1 mL of H2O2 to the test tube. Record your observations and write down

questions that come to mind. 7. Use the stopwatch and ruler to gather data about the rate of the chemical reaction. Start the

stopwatch when the hydrogen peroxide is dropped in, and stop it when the bubbles stop being produced. Record your observations and write down questions that come to mind.

8. Repeat Steps 3-4 except using 2 mL of H2O2. Record your observations and write down questions that come to mind. What did you notice about the rate of reaction?

9. What two questions would you investigate regarding enzyme action?

10. Clean your area when the experiments are completed. 11. Read about enzymes and be ready to discuss in class. 12. Allow time for each group to present their results and conclusions. 13. Allow time for dialogue between the presenters and the whole class.

EXPLAIN Discussion Questions

1. What happened when you put the hydrogen peroxide on the potato? 2. How did you measure how fast the enzyme worked? 3. What difference did you observe in reaction rate when you increased the amount of hydrogen

peroxide? 4. What questions do you have about enzymes?

DAY 2 ENGAGE (5-10 min) – Teacher Selected EXPLAIN: (15 min to read/15 min to explain) Reading to Learn - Role of Enzymes Materials: Reading to Learn: Role of Enzymes print out for each student or student pairs.

1. Pair students as reading partners. 2. Ask students to read Reading to Learn: The Role of Enzymes and take notes in their journals. After

completing each short section, partners share what they understand and what they learned and note questions that require clarification.

Scaffolded Questions 1. What are enzymes? Enzymes are proteins that help cells manage chemical reactions more efficiently. 2. Why are enzymes important? They help chemical reactions run more efficiently by lowering the amount of energy that is required thereby making it possible for metabolism to take place fast enough to sustain life. 3. How do enzymes work? Enzymes bind substrates to their binding sites and either break apart larger molecules or put together smaller molecules. 4. Looking at the diagram, what do you notice are the biggest differences between an anabolic reaction and

a catabolic reaction?

Anabolic build larger molecules and requires and input of water, while catabolic reactions break down molecules and release water. 5. What types of things affect how an enzyme works? Temperature, pH, substrate concentration, cofactors, coenzymes, competitive inhibitors, non-competitive inhibitors. 6. How is efficiency in a process beneficial? It saves time and energy. 7. What are other examples of processes or products that have increased efficiency in the real world? Answers will vary. 8. Have you heard of products like cleaners with enzymes in them? Yes 9. What is the purpose of having enzymes in cleaners? It makes the cleaner work better or more efficiently.

EVALUATE (5 min): Teacher Selected DAY 3 & 4 ENGAGE: Investigable vs. Noninvestigable Questions Procedure:

1. After students have completed the pre-lab, as for volunteers to share their observations. 2. Draw a T-chart on the board and write the word Investigable on the left of the dividing line and

Noninvestigable on the right of the dividing line. 3. Explain to your students that investigable questions can be answered through experimentation, and

noninvestigable questions are answered with additional research. 4. Ask for volunteers to read their questions. 5. Ask the whole group if the question is investigable or noninvestigable. 6. Write the main idea of the question on the appropriate side of the T-chart. 7. Continue until several of the questions have been categorized.

ELABORATE: Catalase Enzyme Experimental Design (Experimental Investigation) Advanced Prep:

1. Make enough copies of Experimental Design Templates and the Design Your Own Experiment Cards for each group.

2. Prepare the catalase ahead of time and place it on ice. It degrades within 2-3 hours. Make fresh solution for afternoon classes. To prepare the catalase solution, blend a raw potato in distilled water in a blender or chop a raw potato with a chopper, place the pieces in a cup, and pour distilled water over the pieces. Place a basket-type coffee filter in a cup or beaker and pour the potato solution through the filter. Remove the filter and set it aside. Cover the cup or beaker with plastic wrap and set it in ice.

3. Inform students that they are to designing an experiment about enzymes using an investigable question.

4. Use the questions listed under the Investigable heading to create lab groups according to student interest.

5. Distribute a copy of the Experimental Design Template to every group. 6. Allow class time for students to design the experiment and another class period to perform the

investigation. 7. Explain that each lab group is responsible for reporting the data, data analysis, and conclusion.

EVALUATE: Journal Check to see that Experimental Design is complete. DAY 4 EXPLAIN: Class Discussion

1. Groups share their results with the class. 2. Students will complete the following data table in their journal.

Variable How does it affect enzyme rate of reaction?

Temperature

pH

Substrate Concentration

Enzyme Concentration

EVALUATE: Teacher Selected DAY 5 ENGAGE: Pineapple Jell-O Demo Conduct a demo of the pineapple/Jell-O "experiment" as a hook to get the students interested in the topic of enzymes.

1. Prepare Jell-O with fresh pineapple, Jell-O with canned pineapple and plain Jell-O. Prepare a plastic tub to conduct the demonstration over to collect any Jell-O from the demo.

2. Ask students if they like Jell-O, if they like fruit in their Jell-O. Play up the cooking and time spent on preparing the Jell-O.

3. Hold up the plain Jell-O and turn the cup upside down and we agree that you did a good job.

4. Do the same with the canned pineapple.

5. Lastly turn the Jell-O with fresh pineapple cup upside down. Of course the fresh pineapple/Jell-O does not set. Act puzzled by what happened.

6. Then, re-read the directions aloud and exclaim that you indeed made a mistake.

7. Continue the lesson about enzymes and at the end come back to the discussion about the pineapple. Prior to the canning process, the pineapple is cooked and the enzyme that digests the proteins in Jell-O are denatured.

EXPLORE: Enzyme-Substrate Manipulative Activity EXPLAIN: Class Discussion Bring back the engage and have students explain why they think the canned pineapple addition prevented the Jello-O from setting.

EVALUATE: Role of Enzymes Quiz References: Texas Education Agency, Biology EOC Success Participant’s Guide. 2010.

ENGAGE

Observations for Cracker Spit Investigation

Cracker + water Cracker + spit

Prediction

Initial Color

Final Color

Result of starch test

Questions: 1. What do you think happened to the starch present in

the cracker? 2. What further indicator tests should you perform? 3. Describe how this demonstration showed both a

physical change as well as a chemical change?

Metabolic processes in cells often result in a buildup of toxins such as

hydrogen peroxide (H2O2). Cells also produce an enzyme known as

catalase (cat-uh-layss) to break down hydrogen peroxide before cell

function is affected. The enzyme reaction is observable.

What is YOUR ROLE? Investigation Responsibilities

Materials Specialist

Gathers all the materials for the experiment, properly disposes of used materials, replaces used materials for the next group to use, and makes sure that the lab station is clean and dry.

Data Specialist

Uses the stopwatch to control time intervals of reactions, keeps time for the length of the experiment, counts aloud and records data accurately during the experiment, and helps to clean up the lab station.

Experimenter

Performs the experimental procedure safely and accurately and helps to clean up the lab station.

Procedure 1. Obtain a piece of potato on a Petri dish, 10 mL of potato catalase

solution, and 15 ml of hydrogen peroxide (H2O2) in medicine cups.

Drop a few drops of H2O2 onto a piece of potato. Record your

observations and write down questions that come to mind in your

journal.

2. Obtain 1 mL of potato catalase solution in a test tube.

3. Using a dropper pipette add 1 mL of H2O2 to the test tube. Record

your observations and write down questions that come to mind.

4. Use the stopwatch and ruler to gather data about the rate of the

chemical reaction. Start the stopwatch when the hydrogen peroxide

is dropped in, and stop it when the bubbles stop being produced.

Record your observations and write down questions that come to

mind.

5. Repeat Steps 3-4 except using 2 mL of H2O2. Record your

observations and write down questions that come to mind. What did

you notice about the rate of reaction?

6. What two questions would you investigate regarding enzyme action?

7. Clean your area when the experiments are completed.

Catalase Enzyme Pre-Lab

MATERIALS

Potato catalase solution

Clear plastic cups

Disposable pipette

Forceps

Ruler

Hydrogen peroxide

Paper towels

Petri dish

Potato pieces

Stopwatch

2 test tubes

SAFETY

Safety Goggles Wear safety goggles to protect your eyes in any activity involving chemicals, flames or heating, or glassware.

Lab Apron Wear a laboratory apron to protect your skin and clothing from damage.

Corrosive Chemical Avoid getting acid or other corrosive chemicals on your skin or clothing or in your eyes. Do not inhale the vapors. Wash your hands after the activity.

Disposal Dispose of chemicals and other laboratory materials safely. Follow the instructions from your teacher.

Cells are possibly the smallest chemical factories in the world and yet they are exquisitely efficient and productive. They build chemical compounds (anabolism) from imported raw materials and break down larger molecules (catabolism) to access the necessary elements and energy to help maintain proper function. Cellular chemical processes are referred to as metabolism. Metabolic reactions require a great amount of energy to take place (activation energy or EA). One way cells manage metabolic reactions is through the presence of enzymes. Enzymes are a type of protein that helps control and manage cell metabolism by making chemical reactions happen more efficiently than if the cell functioned without them. Enzymes lower the activation energy normally required for chemical reactions to take place. Enzyme compounds are three-dimensional molecules that have special bonding areas called active sites. At the active site of some enzymes, large molecules are broken into smaller molecules (catabolism). Other enzymes bond small molecules together to make larger compounds (anabolism). The molecules an enzyme metabolizes are known as substrates. The shape of an enzyme’s active site is matched to the shape of the molecule it metabolizes. The substrate bonds to the active site and the enzyme molecule firms up the attachment. The substrate joined with the enzyme is called the enzyme-substrate complex. If possible, take a moment to shake hands with someone. The way hands fit together and firm up in a handshake is similar to how an enzyme-substrate complex bonds. This is called an “induced fit.” Enzymes function best in specific conditions; environmental factors within the cell can affect how well an enzyme functions. High temperatures can denature (break down) an enzyme, changing its shape. Most enzymes work best in environments where pH range is 6-8. Higher or lower values in cells negatively affect enzyme function and thus cell function. An exception is digestive enzymes in the human stomach, which work best in pH 2. Some enzymes work only in the presence of two other types of compounds, cofactors (such as zinc or iron) and coenzymes (such as vitamins). Other compounds inhibit enzyme function by either blocking the active site (competitive inhibitor) or bonding to the enzyme and changing its shape (noncompetitive inhibitor). Enzymes are often referred to as catalysts because they increase efficiency in chemical reactions without being affected. Because of enzymes, cells manage millions of chemical reactions per second without breaking a sweat. Because of enzymes, cells can harvest energy and raw materials from the food you eat to build a better you.

Reading to Learn: The Role of Enzymes

You will now investigate how temperature and pH affect

enzyme activity.

Procedure Temperature 1. Clean your area when the experiments are completed.

pH 2. Obtain 1 mL of potato catalase solution in a test tube.

Catalase Enzyme Lab

MATERIALS

Potato solution

Clear plastic cups

Disposable pipette

Forceps

Ruler

Hydrogen peroxide

Paper towels

Petri dish

Potato pieces

Stopwatch

3 test tubes

SAFETY

Safety Goggles Wear safety goggles to protect your eyes in any activity involving chemicals, flames or heating, or glassware.

Lab Apron Wear a laboratory apron to protect your skin and clothing from damage.

Corrosive Chemical Avoid getting acid or other corrosive chemicals on your skin or clothing or in your eyes. Do not inhale the vapors. Wash your hands after the activity.

Disposal Dispose of chemicals and other laboratory materials safely. Follow the instructions from your teacher.

Design Your Own Experiment Card

How does changing the temperature affect the rate of the chemical reaction?

Choose from the following materials to investigate how changing the temperature would affect the rate of the chemical reaction:

Beaker Forceps

Clear plastic cups Hotplate

Disposable pipette Single-hole puncher

Graduated cylinder Stopwatch

Petri dish Thermometer

Catalase solution Paper towels

Copper sulfate solution (non-competitive inhibitor)

Cone-shaped coffee filter

Hydrogen peroxide Ice

Potato pieces

Vinegar (acid)

Design Your Own Experiment Card

How does changing the enzyme concentration affect the rate of the chemical reaction?

Choose from the following materials to investigate how changing the enzyme concentration would affect the rate of the chemical reaction:

Beaker Forceps

Clear plastic cups Hotplate

Disposable pipette Single-hole puncher

Graduated cylinder Stopwatch

Petri dish Thermometer

Catalase solution Paper towels

Copper sulfate solution (non-competitive inhibitor)

Cone-shaped coffee filter

Hydrogen peroxide Ice

Potato pieces

Vinegar (acid)

Design Your Own Experiment Card

How does changing the substrate concentration affect the rate of the chemical reaction?

Choose from the following materials to investigate how changing the substrate concentration would affect the rate of the chemical reaction.

Beaker Forceps

Clear plastic cups Hotplate

Disposable pipette Single-hole puncher

Graduated cylinder Stopwatch

Petri dish Thermometer

Catalase solution Paper towels

Copper sulfate solution (non-competitive inhibitor)

Cone-shaped coffee filter

Hydrogen peroxide Ice

Potato pieces

Vinegar (acid)

Design Your Own Experiment Card

How does adding a non-competitive inhibitor to the enzyme affect the rate of the chemical reaction?

Choose from the following materials to investigate how adding an enzyme inhibitor would affect the rate of the chemical reaction:

Beaker Forceps

Clear plastic cups Hotplate

Disposable pipette Single-hole puncher

Graduated cylinder Stopwatch

Petri dish Thermometer

Catalase solution Paper towels

Copper sulfate solution (non-competitive inhibitor)

Cone-shaped coffee filter

Hydrogen peroxide Ice

Potato pieces

Vinegar (acid)

Design Your Own Experiment Card

How does changing the pH affect the rate of the chemical reaction? Choose from the following materials to investigate how changing the temperature would affect the rate of the chemical reaction:

Beaker Forceps

Clear plastic cups Hotplate

Disposable pipette Single-hole puncher

Graduated cylinder Stopwatch

Petri dish Thermometer

Catalase solution Paper towels

Copper sulfate solution (non-competitive inhibitor)

Cone-shaped coffee filter

Hydrogen peroxide Ice

Potato pieces

Vinegar (acid)

Student Handout: Experimental Design Practice Lab Partners: _______________________

Question/Problem

_____________________________________________________________________________________________________________

____________________________________________________________________________________________________________

Tentative Hypothesis

_____________________________________________________________________________________________________________

_____________________________________________________________________________________________________________

Materials List (What materials will you need?)

Safety (What safety precautions should you consider?)

Groups (fill in the table with the appropriate information from your experiment)

Control Group (Which set of the experiment is left unchanged and will be used

as a standard for comparison?

Experimental Group(s) (Which set(s) of the experiment will have one variable

manipulated in order to test your hypothesis?)

Variables (fill in the table with the appropriate information from your experiment)

Independent Variable (What single variable will you change in order to test it in this

experiment?) Note: There should only be one item listed in this area.

Dependent Variable (What will you be measuring or observing?)

Variables kept constant (What will you keep the same in ALL of the groups during your experiment?)

Experimental Plan (Write a brief description of your experimental plan)

Sketch of Experimental Setup (Draw a labeled sketch of your experimental plan)

QUIZ: The Role of Enzymes 1. List and describe three conditions that affect the rate of enzyme reactions.

A .

B .

C .

2. Which statement best describes the role of enzyme?

A Enzymes synthesize molecules.

B Enzyems are specific to the molecules in a reaction.

C Enzymes reactions are maximized within a specific range of conditions.

D Enzymes decrease the activation energy necessary for cell metabolism.

Use the graphic above to answer questions 3-4.

3. Which structure is indicated by the letter X?

A Active site

B Substrate

C Enzyme-Substrate Complex

D Competitive Inhibitor

4. Which statement best describes the specificity of enzymes for the substrate in a chemical reaction?

A The suffix –ase is used to identify the specific enzyme-substrate pairing.

B The bonding sites of enzymes to substrate fit like pieces in a jigsaw puzzle.

C Cells use enzymes to manage cell metabolism.

D Enzymes are created during protein synthesis.

5. A group of students is interested in learning how enzymes work in conditions of varying pH, and they

discuss several questions to use as a focus for an investigation. Which is the most appropriate investigable

question for an experiment about enzyme reaction rates and pH?

A Which enzyme work in solutions with a pH of 8?

B How does the pH of citric acid compare to the pH of hydrochloric acid?

C What is the optimal pH for catalase?

D What type of solutions have a pH of 6?