Question

You are working in a lab and inadvertently place your test tube with enzyme in a 70 °C water bath. Your enzyme is no longer functional and you boss says the excess heat denatured the enzyme. Which of the following types of intermolecular interactions that stabilize the enzyme structure were likely disrupted?

Question 7 options:

	hydrogen bonds
	salt bridges
	hydrophobic interactions
	all of the above

Acids disrupt salt bridges that stabilize protein structure, contributing to denaturation. Why was it possible to add HCl, a strong acid, to your pepsin reaction and still have enzyme activity?

Question 8 options:

	Pepsin is not active when HCl is present
	Any salt bridges in pepsin are stable at low pH
	Pepsin is not a protein
	Pepsin requires HCl

Why did the quick test for fats activity use a brown paper bag instead of a solution in a test tube?

Question 9 options:

	Because it would be difficult to clean up the test tubes after a fat test
	Because fats react with glass in the test tube
	Because there are no enzymes that break down fats
	Because fats are not soluble in water so experiments in the test tube would require an emulsifying agent

In the experiment "modeling the intestinal digestion of starch" you know that digestion occurred if

Question 10 options:

	the sample shows the presence of starch using the Biuret test
	the sample shows the absence of starch using the Biuret test
	the sample shows the presence of starch using the iodine-potassium iodine test
	the sample shows the absence of starch using the iodine-potassium iodine test

Answer 1

7. The protein has hydrogen bonds, hydrophobic bonds and the salt bridges which are the intermolecular interaction that stabilise the protein structure and if the protein is denatured then all of these bonds are broken. Hence the correct answer is: all of the above.

8. Pepsin is an enzyme that is active in the acidic environment of the stomach. Hence the salt bridges of the pepsin enzyme don't denature due to low pH. Hence the correct answer is: Any salt bridges in pepsin are stable at low pH.

9. The paper bag acts as a hydrophobic surface for the hydrophobic fats. Hence the correct answer is: Because fats are not soluble in water so experiments in the test tube would require an emulsifying agent.

10. In intestine the starch should be broken down to say that digestion has occurred. Starch is detected by the iodine test and if the iodine test is negative then digestion of starch was complete. Hence the correct answer is: the sample shows the absence of starch using the iodine-potassium iodine test

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