bio homework lab

Enzymes Virtual Lab

Most biological processes in living systems involve metabolic pathways of chemical reactions, which occur under different physiological conditions. Fortunately, not all chemical reactions occur spontaneously. If they did our metabolism would be chaotic. Instead, most metabolic reactions are controlled by biological catalysts known as enzymes. Enzymes are proteins that speed up the rate of reactions that would otherwise happen more slowly. The enzymes is not altered by the reaction. You have hundreds of different enzymes in each of your cells. Each of these enzymes is responsible for one particular reaction that occurs in the cell. 

Enzymes bind to reacting molecules called the substrate(s), to form an enzyme-substrate complex. The area on the enzyme where the substrate(s) bind(s) is called the active site. Enzymes are made of long chains of amino acids that form complex shapes. All can be affected by temperature, pressure, and pH. Denaturation (unfolding) of an enzyme caused by changes in pH or temperature can affect the activity of the enzyme. Inhibitors that can competitively bind to the active site on the enzymes and black the actual substrate from binding can also affect the enzyme’s activity.  

The activity of an enzyme can be determined by measuring the reaction capacity between the enzyme and its target substrate. Such reaction may result in the appearance of a product which can be detected qualitatively using estimation of “bubbliness”.  

In this virtual lab, you will study enzymes that are found in the cells of many living tissues. The enzyme in today’s lab is catalase, found in liver cells. Catalase speeds up a reaction which breaks down hydrogen peroxide (H2O2), a toxic chemical, into two harmless substances – water and oxygen. 

The reaction is as follows: 

2 H2O2  2 H2O + O2 

This reaction is important to cells because hydrogen peroxide (H2O2) is produced as a byproduct of many normal cellular reactions. If the cells did not break down the hydrogen peroxide, they would be poisoned and die. We also will examine the effect of temperature and pH on catalase activity.

You will watch the video below and fill in the questions below. I advise to have both open and fill out the document as you watch the video. It is very similar to what we would of done in a face to face lab.

https://www.youtube.com/watch?v=WDFfEX3LV5M

 

Procedure 1: Observe the Normal Catalase Reaction  

Tube 1 was to determine a baseline for the reaction. Two ml of hydrogen peroxide was added to a test tube and then a piece of liver was added to the tube.

1. What happened?

2. What are the bubbles made of? Refer to the equation.

3. Was this reaction endothermic or exothermic?

4.  What liquid is now in the tube with the liver? (hint: refer to the overall equation)

 

 

Procedure 2: Is catalase reusable?  

Now the next two things will test this question. First off you saw him pour the liquid from tube 1 into tube 2. Think about question number 4. He then added a fresh piece of liver to tube 2.

5. Did a reaction occur?

6. Why or why not? Think about the equation and if you have all the parts.

Next, he went back to tube 1. Remember all that is left in this tube is a piece of liver used in the very first experiment. He added 2 ml of hydrogen peroxide to this tube.

7. Did a reaction occur?

8. Why or why not? Think about the equation and properties of enzymes.

 

Procedure 3: Observe the effect of temperature on catalase activity  

First he tested how heat changes enzyme activity in tube 3. A piece of liver was boiled for 5 minutes. Then cooled and the water was poured off. Two ml of fresh hydrogen peroxide was added to the boiled liver.

9. Did a reaction occur?

10. Why or why not? Think about properties of enzymes and how form equals function.

In tube 4 he tested the effect of cold temperature on enzyme activity. A piece of chilled liver was added to the tube with 2 ml of chilled hydrogen peroxide.

11. Did a reaction occur?

12. Why or why not?

 

Procedure 4 : Observe the effects of pH on catalase activity

This last experiment will test how pH alters enzyme activity. Tube 5 and 6 had 2 ml of hydrogen peroxide added to it then a piece of liver soaking in either an acidic or basic solution was added.

13. Which tubes correspond to acidic and basic soaked liver?

14. Did the pH alter the reaction rate in tube 5?

15. Did the pH alter the reaction rate in tube 6?