Effect of Temperature and pH

Enzymes Home Lab

 

Objectives:

  • Observe enzymes in action
  • Determine factors that denature enzymes
  • Describe enzyme specificity

 

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Terms:

  • Denature
  • Enzyme

 

Materials Needed:

 

  • Potato
  • Hydrogen Peroxide
  • Vinegar

 

  • Hot water
  • Tap water
  • 5 beakers (or clear containers such as cup)

 

Introduction

 

Enzymes are proteins that act as catalysts in reactions. A catalyst is something that increases the rate of a reaction by lowering the activation energy needed to start the reaction. Most chemical reactions have a certain amount of energy that is required before they can occur. Often this energy need is met by adding heat to a reaction. Your body however needs to be able to perform reactions without adding high amounts of heat as that same heat would harm or breakdown the other molecules in your body. So organisms use enzymes to make their reactions occur without adding heat. Each enzyme is substrate specific meaning it only binds to a specific molecule or molecules. For instance lactase is an enzyme in your digestive system that breaks down the lactose in milk. Lactase will only react with lactose it will not break down other molecules. Individuals who are lactose intolerant either do not make enough lactase or their lactase enzymes do not form correctly. This makes its so they can’t break down lactose and aren’t able to drink milk based products. Figures 1 & 2 shows how an enzyme is substrate specific.

Figure 1: The enzyme catalase binds to two hydrogen peroxide (H2O2) molecules. This forms an enzyme-substrate complex. The enzyme causes the reaction to occur and releases three products; two water molecules (H2O) and one oxygen (O2) molecule. The enzyme remains unchanged by the reaction and is ready to be used again.

(Image source: Professor Mello)

Figure 2: The enzyme catalase attempts to bind to two water (H2O) molecules. Water is the wrong shape though and the enzyme-substrate complex is unable to form. No reaction occurs and no products are formed. This is because catalase is substrate specific and can only bind with hydrogen peroxide as seen in figure 1.

(Image source: Professor Mello)

 

 

Some enzymes will take smaller substrates and bind them together to form a new larger molecule. This is known as anabolism. Other enzymes make take a large substrate and break it down into smaller products. This is known as catabolism. Metabolism in organisms is built on enzyme reactions that breakdown or buildup molecules as needed.

Exercise 1: Enzyme specificity

 

First we will look at enzyme specificity with the enzyme catalase which can be found in potatoes. Catalase reacts with hydrogen peroxide to form water and oxygen. The oxygen can be seen as bubbles forming in the solution.

 

Procedure:

 

  1. Obtain a potato

 

  1. Cut two slices approximately the same size

 

  1. Place one potato in a beaker labeled water

 

  1. Cover the potato with enough water so that it is completely submerges with at least 2-3 cm of liquid above it.
  2. Place the second potato in a beaker labeled Hydrogen

 

  1. Cover the potato with enough hydrogen peroxide so that it is completely submerges with at least 2-3 cm of liquid above it (approximately the same amount of water you placed in the other beaker).
  2. Observe both beakers for oxygen

 

  1. Record the results in the student

Exercise 2: Factors that affect enzymes

 

Enzymes are proteins. Proteins can be denatured by different environmental factors. To be denatured means the protein is unfolded and no longer able to function. This experiment will analyze whether temperature and pH can affect a proteins function.

 

Procedure:

 

  1. Obtain a potato

 

  1. Cut three slices approximately the same size

 

  1. Place one potato in a beaker labeled vinegar and pour in enough vinegar to submerge the

 

  1. Place the second potato in a beaker labeled hot water and cover the potato with boiling

 

  1. Place the third potato in a beaker labeled water and cover the potatoe with room temperature

 

  1. Allow all three beakers to sit for 15

 

  1. At the end of 15 minutes drain all beakers but leave the potato

 

  1. Cover the potato in each beaker with enough hydrogen peroxide so that it is completely submerged with at least 2-3 cm of liquid above
  2. Observe all 3 beakers for oxygen

 

  1. Record the results in the student

 

Name:                                               

 

Biology 1406

Lab 1: Student Handout

 

Exercise 1 Enzyme specificity

Record your observations in the table below. Rank the amount of bubbles produced on a scale of 0-5. With 0 being no bubbles formed and 5 being lots and lots of bubbles formed.

 

Substrate Bubbles Produced (Scale of 1-5) Any observations
 

Water

   
 

Hydrogen Peroxide

   

 

 

  1. Which substrate produced the most bubbles?

 

 

 

 

 

  1. Why did the other substrate produce little to no bubbles?

 

 

 

 

 

  1. Do you think bubbles would be produced if you put the potato in something else like apple juice? Why or why not?

 

Exercise 2 Factors that affect enzymes

Record your observations in the table below. Rank the amount of bubbles produced on a scale of 0-5. With 0 being no bubbles formed and 5 being lots and lots of bubbles formed.

 

Treatment Bubbles Produced (Scale of 1-5) Any observations
Water (Control)    
Vinegar

(Acid treatment)

   
 

Boiling water (Temperature treatment)

   

 

  1. Which treatment produced the most bubbles?

 

 

 

 

 

  1. Did the vinegar treatment produce the same amount of bubbles as the regular water treatment? If not why did it fail to produce bubbles? What happened to the enzyme?

 

 

 

 

 

  1. Did the hot water treatment produce the same amount of bubbles as the regular water treatment? If not

why did it fail to produce bubbles? What happened to the enzyme?

 

 

 

 

 

  1. List some factors that can affect enzyme You may use your results here along with your textbook and lecture material to answer this question.

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