Bio Lab conclusion

The purpose of this lab is

To see if the enzymes in the liver can successfully break down hydrogen peroxide into water and oxygen.

The name of the enzyme and substrate

The enzyme used in this lab was catalase, a protein found in liver cells that speeds up chemical reactions without being used up itself. The substrate (the substance the enzyme acts upon) was hydrogen peroxide, a compound that is toxic to cells if allowed to build up. Catalase job is to break the hydrogen peroxide down into safer substances before it can damage the cell.

The equation

2 H₂O₂ → 2 H₂O + O₂

Part 1 of the reaction: explain the steps and what occurred. Include changes you didn't see and why 

In steps 1-4 water was added to test tub #1, and a nickel-sized piece of liver was placed inside. Nothing happened-no bubbling, no temperature change, and no visible reaction. This is expected because water is not a substrate for catalase. Catalase is specific to hydrogen peroxide, so without that substrate present there was nothing for the enzyme to react to. This tube acted as our control, showing us that the liver itself doesn't cause bubbling–only the reaction with hydrogen peroxide does. 

In steps 5-8, hydrogen peroxide was added to the test tube #2 along with a piece of liver. This time, bubbling occurred immediately, and the mixture separated, showing that a reaction was taking place

Part 2 of the reaction: explain the steps and what occurred. Include changes you saw and why they happened

In test tube #3 1-4, hydrogen peroxide was added and a glowing splint was inserted about a third of the way into the tube. This test for oxygen gas, since a glowing splint reignites in an oxygen rich environment. Without the liver present, there was no catalase to break down the hydrogen peroxide, so no oxygen was being produced and the splint did not relight. 

In steps 5-10, hydrogen peroxide and liver were combined in test tube 4. Bubbling occurred, showing that oxygen gas was being released as catalase broke down the hydrogen peroxide. A glowing splint touched these bubbles relit, confirming that oxygen was present.

State why we boiled and/or made the liver cold in relation to optimal heat

Enzymes work best within a specific optimal temperature range. We boiled one piece of liver and kept another cold to see how temperature outside optimal heat affects the enzymes. Boiling was expected to denature the catalase–the heat breaks apart the enzyme shape (its active site), so it can no longer bind to the hydrogen peroxide, and the reaction should mostly stop. 

Cooling, on the other hand, doesn't destroy the enzyme's shape; it just slows down molecular movement, so the reaction should still occur, just more slowly than at normal/optimal temp.

State what should have happened to the boiled and cold liver in comparison to what happened in yours.  If you did NOT get the expected result, give a reason as to why your result may have been different.

We expected the cold liver to bubble slowly, since the enzymes were intact, just moving at a slower rate. We expected the boiled liver to show little to no bubbling, since its catalase should have been denatured and unable to function.

Why did bubbles form

Bubbles formed because catalase was breaking hydrogen peroxide down into water and oxygen gas. As oxygen gas was released, it collected and escaped as visible bubbles in the liquid.

The water in the test tube should have risen.  **You may not have noticed it.  Why did it rise?

The water should have risen because oxygen gas was building up inside the tube as the reaction occurred.

Why did we use a popsicle stick?

Was used to create a glowing ember, which allowed us to test for the presence of oxygen gas without needing lab equipment

Why did the stick re-light when placed into the bubbles

The stick relit because the bubbles contained a high concentration of oxygen gas released by the reaction. Oxygen supports combustion, so when the glowing ember was exposed to that oxygen-rich environment.