Biochemical Reactions: What Impacts Enzyme Activity?

Grade Level: 6th-8th

Duration: 45-60 minutes

Objective

Students will understand the basic concept of enzymes and how factors like temperature, pH, and substrate can impact enzyme activity. They will perform a simple experiment to observe these effects firsthand.

Materials Needed

• Plastic cups (9 cups per group)

• Hydrogen peroxide (H2O2)

• Fresh potato slices (9 slices per group)

• Warm water bath

• Ice bath

• Vinegar (to adjust pH)

• Baking soda (to adjust pH)

• Measuring spoons

• Stopwatch or timer

• Experiment instructions and a blank data table

• Science journals

Introduction (10 minutes)

Ask your students: "Have you ever wondered how your body digests food or how wounds heal?" (Give them a moment to think about it and respond.) Explain that our bodies rely on tiny proteins called enzymes to speed up these processes.

Enzymes are the body's own little workers. Like a mechanic using tools to fix a car, enzymes help chemical reactions happen faster in our bodies. They're involved in everything from breaking down the food we eat to helping our cells grow and divide.

But what if the tools aren't quite right? What if the mechanic uses a wrench that's too small or too big? It would take longer to fix the car. Enzymes are similar—they work best under certain conditions, and their activity slows down or stops altogether when those conditions aren't right.

Let's break down what these "conditions" are. Three main factors can affect how well an enzyme works:

1. Temperature

2. pH

3. The amount of substrate (the substance on which an enzyme acts).

Activity: Investigating Enzyme Activity (30 minutes)

Let's experiment with how temperature, pH, and substrate affect enzyme activity. The enzyme we'll examine is catalase, found in many living things, including potatoes.

Step-by-Step Instructions

Setting Up the Experiment

1. Split your students into small groups (3-4 students per group).

2. Give each group three plastic cups to begin.

3. Add an equal amount of hydrogen peroxide to each cup.

Testing Temperature

1. Take a slice of potato and cut it into three equal pieces.

2. Place one slice in a warm water bath (around 104°F/40°C), one in an ice bath, and leave the third at room temperature.

3. After a few minutes, drop each potato slice into a separate cup of hydrogen peroxide.

4. Observe the bubbles and note which cup has the most activity (most bubbles). This reaction shows how temperature affects enzyme activity.

Testing pH

1. Add an equal amount of hydrogen peroxide in another set of three cups.

2. Adjust the pH in each cup: one stays neutral (as is), one gets a splash of vinegar (acidic), and one gets a pinch of baking soda (basic).

3. Drop a (new) potato slice into each cup and observe the bubbles. Record which pH level shows the most enzyme activity.

Testing Substrate

1. Set up three new cups with different amounts of hydrogen peroxide—one small, one medium, and one nearly full.

2. Drop a (new) potato slice into each cup and compare the amount of bubbling. This helps show the effect of substrate on enzyme activity.

Discussion (10 minutes)

After the experiment, gather your students and discuss the results. Ask questions like: "Which temperature made the most bubbles?" and "How did pH levels affect the activity?"

Encourage your students to think about why enzymes behave the way they do. For example, you can ask, "Why do you think enzymes in our bodies work best at body temperature?"

Conclusion (5 minutes)

Summarize the lesson's key points. Emphasize that enzymes are crucial for many processes in our bodies and that their activity can be influenced by temperature, pH, and substrate concentration.

Ask your students to think about how this knowledge might be useful. For instance, what happens if someone has a fever? How might that affect enzyme activity? Or why do pickled foods (which are acidic) stay preserved longer?

Finally, have them write down what they've learned in their science journals, including a summary of the experiment and their observations. This will help reinforce the day's lesson and allow them to review it later.

Extension Activity or Homework

Have your students research how enzymes are used in everyday products, such as laundry detergents or meat tenderizers. Then, have them present their findings during the next class.

Assessment

• Review the students' observations and conclusions from the experiment in their science journals.

• Optional: Have your students complete a short quiz or worksheet based on the lesson's content.

Written by Brooke Lektorich
Education World Contributor
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