Bio 120 LAB #9- ENZYME ACTIVITY AND
CELLULAR METABOLISM
Lab Objectives
After completing this lab topic, you should be able to:
1. describe how enzymes influence metabolic pathways.
2. explain enzyme activity can be measured.
3. describe how factors such as salt or alcohol concentrations influence
enzyme activity.
Enzymes are biological catalysts – often proteins – that are critical to all life.
Enzymes are molecules whose tertiary structures allow them to interact with their target
molecules, called substrates, in myriad ways: enzymes can cleave substrates into smaller
parts, add molecules together, add functional groups to them, remove functional groups
from them, fold them, etc. In short, enzymes do the work of the cell, and what kind of
work they do depends on their three-dimensional shape. Recall that enzymes lower the
activation energy required for the reaction to occur.
In this laboratory session we will be using an enzyme that “cuts” other proteins--a
protease called bromelain found in pineapple and kiwi. If you have ever prepared gelatin
with fruit in it, you have probably seen the warning label which states "do not add fresh
or frozen pineapple/kiwifruit." Many fruits, including pineapple and kiwi, contain
proteases. The addition of fresh pineapple with its protease will cleave the gelatin peptide
bonds, thus preventing setting or solidifying.
We will use a simple assay – or experimental read-out – to determine the activity
of bromelain. Crushing pineapple allows us to collect pineapple juice, which will contain
the enzyme bromelain. We will then experiment with active and inactivated enzyme.
Before performing lab,
Think about how and why salt levels or high temperature levels will influence
enzyme activity. Your goal is to attempt inactivate the bromelain enzyme using salt or
temperature. You should develop a specific question and hypothesis, and you should
design an experiment design to test your hypothesis. As you design your experiment
using multiple levels of treatment of the chosen independent variable, also think about
our discussions of replicates and sample size, and standardizing your procedure. This
experiment demands the use of positive and negative “controls”.
To help you plan your experiment, you will have the following supplies available
for your use:
Test tubes and rack
Pineapple with Mortar /pestle
0%, 1%, and 9% salt solutions
Hot plates, ice buckets
pipets
Gelatin
glassware
1
Name__________________________________
Bio 120 Pre-lab
Due BEFORE STARTING lab.
1. Write your specific research question. (2 pts)
2. Write out your specific hypothesis. (2 pts)
3. If your hypothesis is correct, what should happen in your experiment? Why? (3 pts)
4. What were the components of your negative control? What is the point of a negative
control? What is the point of a positive control? (3 pts)
2
Name__________________________________
Bio 120 Lab Homework #10
Due Friday, Nov 20 at 9:00.
Identify the following parts of your experiment:
Independent variable (1 pt)-
Dependent variable (1 pt)-
Controlled/Standardized variables (2 pts)-
Levels of treatment (1 pt)-
# replicates (1 pt)-
Turn in a figure of your results. (4 pts)
3