Dear Students,
As you can see, I am out today. Please follow the instructions on this page. It is very important that you complete today's assignment so you can perform a lab, which you will design, on Wednesday of next week. Start by reading the description of enzymes below. You will have about 10 minutes to read over this description before the substitute will play the video about enzymes for the class. If you finish early please click through the reading on this website for more information: https://www.bbc.co.uk/education/guides/zdt4jxs/revision
As you can see, I am out today. Please follow the instructions on this page. It is very important that you complete today's assignment so you can perform a lab, which you will design, on Wednesday of next week. Start by reading the description of enzymes below. You will have about 10 minutes to read over this description before the substitute will play the video about enzymes for the class. If you finish early please click through the reading on this website for more information: https://www.bbc.co.uk/education/guides/zdt4jxs/revision
Enzymes ReadingA substance that helps a chemical reaction to occur is a catalyst, and the special molecules that catalyze biochemical reactions are called enzymes. Almost all enzymes are proteins, made up of chains of amino acids, and they perform the critical task of lowering the amount of energy needed for the chemical reaction to take place inside the cell. Enzymes do this by binding to the reactant molecules, and holding them in such a way as to make the chemical bond-breaking and bond-forming processes take place more readily.
The chemical reactants to which an enzyme binds are the enzyme’s substrates. There may be one or more substrates, depending on the particular chemical reaction. In some reactions, a single-reactant substrate is broken down into multiple products. In others, two substrates may come together to create one larger molecule. Two reactants might also enter a reaction, both become modified, and leave the reaction as two products. The location within the enzyme where the substrate binds is called the enzyme’s active site. The active site is where the “action” happens, so to speak. Since enzymes are proteins, there is a unique combination of amino acids in the enzyme's active site. The unique combination of amino acid, their positions, sequences, structures, and properties, creates a very specific chemical environment within the active site. This specific environment is suited to bind to a specific chemical substrate (or substrates). Due to this jigsaw puzzle-like match between an enzyme and its substrates, enzymes are known for their specificity. The “best fit” results from the shape and the attraction to the substrate of the amino acids in the active site . There is a specifically matched enzyme for each substrate and, thus, for each chemical reaction. Each enzyme will work with only one type of substrate. This is called the "lock and key" hypothesis. |
Watch this video as a whole class.
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The fact that active sites are so perfectly suited to provide specific environmental conditions also means that they are subject to influences by the local environment. This means that changing the local pH or temperature can change the nature of the active site, changing how it is attracted to the substrate. Increasing or decreasing the temperature outside of an optimal range can affect chemical bonds within the active site in such a way that they are less well suited to bind substrates. High temperatures will eventually cause enzymes, like other biological molecules, to denature, a process that changes the natural properties of a substance. Likewise, the pH of the local environment can also affect enzyme function. Active site amino acid residues have their own acidic or basic properties that are optimal for catalysis. These residues are sensitive to changes in pH that can impair the way substrate molecules bind. Enzymes are suited to function best within a certain pH range, and, as with temperature, extreme pH values (acidic or basic) of the environment can cause enzymes to denature.
This text is adapted under a Creative Commons 4.0 license. You can find the original source here.
This text is adapted under a Creative Commons 4.0 license. You can find the original source here.
Hi Students,
Now that you know a little about enzymes it is time to put this information into practice. As you know, enzymes are biological molecules (typically proteins) that significantly speed up the rate of virtually all of the chemical reactions that take place within cells.
Some enzymes help break large molecules into smaller pieces that are more easily absorbed by the body. Other enzymes help bind two molecules together to produce a new molecule. Enzymes are highly selective catalysts, meaning that each enzyme only speeds up a specific reaction. The molecules that an enzyme works with are called substrates. The substrates bind to a region on the enzyme called the active site.
Next week you are going to perform a lab to test the effect of temperature, concentration, or surface area to volume ratio of the substrate on the function of an enzyme. The enzyme you will be working with is bromelain. Bromelain is a protein digesting enzyme that is found in pineapples. Bromelain is also used as a meat tenderizer. In fact, some people are very sensitive to the enzyme and find that it makes their lips and tongue sore. This is because the bromelain is working to tenderize your tongue! Don’t worry—once it gets to your stomach, there shouldn’t be much of a problem.
You will be testing the effect of bromelain on the protein found in gelatin. Gelatin is made out of animal proteins, particularly collagen. When you add water to the gelatin, long chains of protein form, making an invisible protein “spaghetti”. Water gets trapped in the middle of these long chains, turning what should be a liquid into a semi-solid. Since pineapple bromelain digests proteins, when the pineapple meets the gelatin, it begins to eat away at it. The long protein chains collapse, making everything watery again.
Watch the video below. It shows the basic setup and theory behind the lab you will be running next week.
Now that you know a little about enzymes it is time to put this information into practice. As you know, enzymes are biological molecules (typically proteins) that significantly speed up the rate of virtually all of the chemical reactions that take place within cells.
Some enzymes help break large molecules into smaller pieces that are more easily absorbed by the body. Other enzymes help bind two molecules together to produce a new molecule. Enzymes are highly selective catalysts, meaning that each enzyme only speeds up a specific reaction. The molecules that an enzyme works with are called substrates. The substrates bind to a region on the enzyme called the active site.
Next week you are going to perform a lab to test the effect of temperature, concentration, or surface area to volume ratio of the substrate on the function of an enzyme. The enzyme you will be working with is bromelain. Bromelain is a protein digesting enzyme that is found in pineapples. Bromelain is also used as a meat tenderizer. In fact, some people are very sensitive to the enzyme and find that it makes their lips and tongue sore. This is because the bromelain is working to tenderize your tongue! Don’t worry—once it gets to your stomach, there shouldn’t be much of a problem.
You will be testing the effect of bromelain on the protein found in gelatin. Gelatin is made out of animal proteins, particularly collagen. When you add water to the gelatin, long chains of protein form, making an invisible protein “spaghetti”. Water gets trapped in the middle of these long chains, turning what should be a liquid into a semi-solid. Since pineapple bromelain digests proteins, when the pineapple meets the gelatin, it begins to eat away at it. The long protein chains collapse, making everything watery again.
Watch the video below. It shows the basic setup and theory behind the lab you will be running next week.
Ok, so as you can see in the video, boiling a pineapple will denature the enzyme making it non-functional. One option for the experiment you will design is to see if cold temperature also denatures bromelain and to see if temperatures close to boiling, but not boiling, also have the same effect on the enzyme. If you choose this option you will be testing the effect of temperature on the enzyme bromelain. You will make different temperature of pineapple juice, mix them with cubes of gelatin, and see how much gelatin is dissolved in a set amount of time.
Another option you have is to test the effect of bromelain concentration on the rate of the reaction. For this experiment you will make different concentrations of pineapple juice and you will soak cubes of gelatin in the different concentrations, for a set amount of time, and then you will measure how much of the cubes dissolved.
The final option is to test the effect of surface area to volume ratio of the substrate on the rate of the reaction. Basically, will the reaction occur faster with a larger cube (smaller surface area to volume ratio) or will a smaller cube dissolve faster. For this experiment you will need cubes of different sizes and you will soak them in the same pineapple juice solution, for a set amount of time, and then measure how much the cube dissolved.
In all three experiments you will know how much the cube dissolved by finding the starting mass of the cube and the ending mass of the cube. The change in mass tells you how much gelatin was dissolved by the enzyme.
Grading:
You will turn in your hypothesis, variables, equipment, procedure, data, and data analysis as a group. The conclusion you will write on your own and you will turn it in separately from your group. All work will be submitted on canvas. All written work must be typed. All tables and graphs will need to be made digitally.
What you will turn in:
You will turn in your hypothesis, variables, equipment, procedure, data, and data analysis as a group. The conclusion you will write on your own and you will turn it in separately from your group. All work will be submitted on canvas. All written work must be typed. All tables and graphs will need to be made digitally.
What you will turn in:
- A procedure and materials list – due by midnight (Feb 2nd)
- A lab report – due on canvas on Feb 9th.
- A revised procedure and materials list – based on what you actually did
- Data tables – made digitally.
- Graphs - made digitally
- Conclusion
Steps for TODAY:
1. Find your group (4 students per group, no more than 8 groups per class)
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Sign up for groups on canvas. See this link for how to join a group.
Also sign up on this google doc. Please note that there are different sheet for each class. |
2. Design your experiment
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See below "Designing your experiment: - things to consider. Make sure you answer these questions to yourself before class ends.
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3. Write your procedure and list of materials
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See below "Sample procedure for the control experiment." Use this as a guide for what your procedure should look like. Then use the handout provided in order to write the answers for questions 1, 3, and 4. Answers to those questions are due at midnight tonight (Fri-2nd).
There is also a section below called "After writing your procedure make sure..." Read this over and make sure you have met the standard for this assignment. |
4. Turn in your procedure and materials list through canvas (assignment is called "Enzyme Lab Procedure")
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If it is easier for you to type into a goole doc that is already formatted for you then please make a copy of this one. Once you have your copy, you can share it with the other members of your group. You should complete questions 1, 3, and 4. I have put comments to the right on the google doc with the specific questions to answer and things you should make sure you have explained. At the end of the class, one person should submit your copy of this document to canvas. Technically you have until midnight so if you want to do some edits thats fine but make sure you know who is responsible for turning in the assignment and when they will have it turned in by so you can check and make sure the work it turned in on time.
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Designing your experiment: Things to consider -
- What is the manipulated variable (what are you changing)?
- What is the responding variable (what are you measuring?
- What are the controlled variables (what conditions are you keeping the same with each trial)?
- How many different conditions will you be testing? (minimum 3)
- How many trials will you perform? (minimum 3)
- How will you present your data?
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Sample procedure for the control experiment:
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Preparing the gelatin:
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Things to consider:
- You might need to use more or less pineapple juice. Adjust your procedure once you have determined the right amount of liquid so the cube is completely covered.
- If you are changing the temperature you will need to heat the pineapple puree to specific temperatures then allow it to cool to room temp. Otherwise you will melt the gelatin. One of the temperatures should be boiling and one should be freezing. You should also decide how long you will keep the puree at these temperatures before allowing to cool.
- If you are changing the size of the gelatin cubes you will need cut them into different sizes and you might need to pour them into taller trays so you can get some bigger cubes as well as smaller cubes.
- If you are changing the concentration of pineapple juice you will not want to dilute it at the start as you will need a minimum of three different concentrations.
- You might want to calculate the rate of the reaction rather than just the change in the mass.
- You might want to draw a diagram showing what you plan to do for your experiment.
- You will need to find the averages of your data, it is the averages that you will graph.
After writing your procedure make sure you answer the following questions:
- Does my experiment test what I want it to test?
- Have I made sure there are no other factors that might cause variations in my results?
- Am I testing a range of variables (3+ temperatures, concentrations, etc.)? Could I test more easily?
- Have I listed all of the materials that I will need along with the quantities and sizes of each thing I need?
- Will I be able to complete my data collection during a 90 minute class?
- Are there things I can prepare in advance so that my experiment day goes smoother?
