PhysioEx 8

At which pH do you think pepsin will have the highest activity?

pH 2.0

At what pH was the amylase activity the most active? Describe the significance of this result.

pH 7.0 was when amylase activity was the most active. When pH is 7.0, salivary amylase is the most active in the mouth.

In this activity the substrate you will be using to detect protein digestions is

BAPNA

Describe the process of bile emulsification of lipids and how it improves lipase activity.

Bile works by a physical process to increase the surface area accessible to lipase enzymes. Bile salts act as a detergent, separating the lipid clumps. This allows more lipase activity.

Do you think test tube 3 (amylase, cellulose, pH 7.0 buffer) will show a positive Benedict's test?

yes

Explain how bacteria can aid in digestion.

Cellulose is found in plants and provides rigidity to their cell walls. Bacteria can break down cellulose because we don't make it nor can we digest it.

with more enzyme activity the optical density a. increased b. decreased c. stayed the same

a. increased

Negative results with the negative controls

are expected and validate the experiment

When fatty acids are liberated by lipase, the pH a. increases b. decreases c. stays the same

b. decreases

pepsin would be most active a. in the mouth b. in the stomach c. in the small intestine d. in the mouth and in the stomach

b. in the stomach

Which tube is included to detect contaminating amylase in the buffer or in cellulose?

none of them

a spectrophometer measures

optical density

the substrate for pepsin is

protein and peptides

which tube do you think will have the highest lipase activity?

tube 3 (lipase, deionized water, bile salts, pH 9.0 buffer)

This activity includes a number of negative controls. Which tube indicates that the amylase solution was not contaminated with maltose?

tube 4 (amylase, deionized water, pH 7.0 buffer)

which tube confirms that there is no lipase in bile salts or vegetable oil?

tube 4 (deionized water, vegetable oil, bile salts, pH 7.0 buffer)

which tube allows you to conclude that the buffer was not contaminated with amylase?

tube 5 (peptidase, starch, pH 7.0 buffer)

which of the following tubes are negative control tubes?

tubes 3 (pepsin, deionized water, pH 2.0 buffer) and 4 (deionized water, BAPNA, pH 2.0 buffer)

cellulose and starch are both a. found in the cell walls of plants b. polymers of glucose c. polysaccharides d. polymers of glucose and found in the cell walls of plants e. polymers of glucose and polysaccharides

e. polymers of glucose and polysaccharides

Tube 2 appears to have the same amount of starch digested as tube 3 because

freezing had no effect on the enzyme

The results of tube 5 (peptidase, starch, pH 7.0 buffer) demonstrated that

peptidase does not digest starch

You included tube 2 (amylase, glucose, pH 7.0 buffer) to

see what a positive Benedict's test should look like

the reagent IKI tests for the presence of

starch

The substrate for amylase is

starch and carbohydrate

why was the cellulose in tube 6 (bacteria, cellulose, pH 7.0 buffer) hydrolyzed to glucose?

the bacterial suspension contained the enzyme cellulase, which digested the cellulose

Where in the body does protein digestion begin?

the stomach

which two tubes validated the results of the experiment?

tubes 3 (pepsin, deionized water, pH 2.0 buffer) and 4 (deionized water, BAPNA, pH 2.0 buffer)

Which tubes indicate that the deionized water did not contain contaminating starch or maltose?

tubes 4 (amylase, deionized water, pH 7.0 buffer), 5 (deionized water, starch, pH 7.0 buffer), and 6 (deionized water, maltose, pH 7.0 buffer)

Explain where and why salivary amylase would be most active.

Salivary amylase would be most active in the mouth because pH 7 is where its peak activity is.

Which of the following is true of enzymes and substrates? a. the substrate forms a covalent bond at the active site of the enzyme b. the enzyme is acted upon by the substrate c. enzymes are specific about the substrates they can act upon d. if the product of catalysis is present, the enzyme is not acting on the substrate

c. enzymes are specific about the substrates they can act upon

proteins and peptides are formed by joining amino acids with a special type of covalent bond called a peptide bond. which of the following enzymes do you thing would be specific for a peptide bond? a. amylase b. cellulase c. peptidase d. lipase

c. peptidase

if pepsin were digesting an actual protein substrate, the product would be a. peptides b. amino acids c. peptides and amino acids d. BAPNA

c. peptides and amino acids

the Benedict's assay tests for the presence of a. starch b. cellulose c. reducing sugar d. peptides

c. reducing sugar

which of the following is true of enzymes? a. they become part of the product b. they are sued up in the reaction c. their activity can be affected by temperature and pH d. they slow down the rate of the reaction

c. their activity can be affected by temperature and pH

which of the following is not true of controls? a. with a negative control, a negative result is expected b. with a positive control, a positive result is expected c. a positive result with a negative control could mean that a contamination substance is present d. a negative result with a positive control is required to validate the test

d. a negative result with a positive control is required to validate the test

What does the pH measure? a. lipase activity b. fatty acid release c. bile salt hydrolysis d. both lipase activity and fatty acid release e. both lipase activity and bile salt hydrolysis

d. both lipase activity and fatty acid release

One of the products of the chemical digestion of lipids is a. bile salts b. lipase c. monosaccharides d. fatty acids

d. fatty acids

what is the product of lipase hydrolysis? a. bile salts b. triglycerides c. phospholipids d. fatty acids

d. fatty acids

What is the usual substrate for the pancreatic enzyme peptidase? a. starch b. cellulose c. glucose d. peptides

d. peptides

Where in the body does pancreatic lipase hydrolyze triglycerides? a. mouth b. stomach c. large intestine d. small intestine

d. small intestine

why is it difficult to detect whether lipase is active in tube 5 (lipase, vegetable oil, bile salts, pH 2.0 buffer)? a. the substrate is missing b. the enzyme is missing c. the bile salts are missing d. the pH is already very low, so a decrease in pH might be difficult to detect

d. the pH is already very low, so a decrease in pH might be difficult to detect

an optical density greater than zero indicates that a. BAPNA digestion has occurred b. BAPNA digestion has not occured c. pepsin is not active d. pepsin is active e. BAPNA digestion has occurred and pepsin is active

e. BAPNA digestion has occurred and pepsin is active

which of the following is/are reducing sugars? a. starch b. cellulose c. maltose d. glucose e. both glucose and maltose

e. both glucose and maltose

which of the following is an end product of starch digestion? a. amylase b. maltose c. glucose d. amylase and maltose e. maltose and glucose

e. maltose and glucose

The substrate used in this simulation is a. fatty acids b. bile c. vegetable oil d. glycerol

c. vegetable oil

hydrolases are enzymes that break down large molecules into smaller subunits through the addition of ____________.

water

Describe the effect that boiling had on pepsin and how you could tell that it had that effect

Boiling inactivates pepsin. Test tube 1 was boiled and pepsin showed no activity. Test tube 2 wasn't boiled and pepsin was very active.

What effect do you think boiling and freezing will have on the activity of the amylase enzyme?

Boiling will decrease amylase activity and freezing will have no effect.

Describe why the results in tube 1 (amylase, starch, pH 7.0 buffer) and tube 2 (amylase, glucose, pH 7.0 buffer) are the same.

In test tube 1, starch was hydrolyzed into maltose and in test tube 2, glucose had already been hydrolyzed.

Was your prediction correct about the optimal pH for pepsin activity? Discuss the physiological correlation behind your results.

My prediction was correct. At pH 2.0 pepsin showed the highest activity which was 0.40. At pH 7.0 the activity was 0.03 and for pH 9.0 the activity was 0.00. Activity was the highest at pH 2.0 because it is the most similar to the pH in the stomach. The stomach is very acidic which is why pepsin works the best in it.

What effect did boiling have on enzyme activity? Why? How well did the results this compare with your prediction?

My prediction was correct. Boiling test tube 1 decreased the activity of amylase. And freezing test tube 2, had no effect on the activity of amylase.

Which tube had the highest lipase activity? How well did the results compare with your prediction? Discuss possible reasons why it may or may not have matched.

My prediction was incorrect. Test tube 1 showed the highest lipase activity. The pH buffer was 7.0 and the final pH was 6.21. It was the only tube to show a decrease in pH. Test tube 3, (the one I predicted would have the highest lipase activity) had no lipase activity and showed no decrease in pH.

Describe the result in tube 3 (amylase, cellulose, pH 7.0 buffer). How well did the results compare with your prediction?

My prediction was incorrect. Test tube 3 did not show a positive Benedict's test, because amylase doesn't digest cellulose.

Explain why pancreatic lipase would be active in both the mouth and the pancreas.

Pancreatic lipase is the most active at a pH of 7.0. The mouth and pancreas have a pH of around 7.0 which is why the enzyme should be active in these two places.

Describe the significance of using a 37°C incubation temperature to test salivary amylase activity.

The incubation temperature used was 37 degrees C which converts to 98.6 degrees F. This temperature is similar to the heat in our mouths (our body temperature) if we test salivary amylase activity.

List the substrate and the subunit product of amylase.

The substrate of amylase is starch and carbohydrate. The subunit product of amylase is maltose and glucose.

Describe the usual substrate for peptidase.

The usual substrate for peptidase is peptides. I think an example of this in the experiment would be test tube 5. Peptidase + starch + pH 7.0 buffer resulted in a breakdown of starch. That's what peptidase does - it digests peptides and can break down starch.

Briefly describe the need for controls and give an example used in this activity.

We need controls in an experiment because they provide a standard against which comparisons can be made. An example of a control in this experiment is test tube 3. Test tubes 1, 2, and 3 contained the same 3 reagents; the only difference was what treatment was done on each. Test tube 1 boiled, test tube 2 froze, and test tube 3 was left alone. There wasn't any treatment done on test tube 3 so that we could compare it to test tubes 1 and 2.

Explain why you can't fully test the lipase activity in tube 5 (lipase, vegetable oil, bile salts, pH 2.0 buffer).

When fatty acids are liberated by lipase, the pH decreases. Since the pH buffer in test tube 5 was 2.0, we didn't see a decrease in pH because it remained at 2.0. Therefore when can't really test the activity of lipase.

What do you think would happen if you reduce the incubation time to 30 minutes for tube 5 (pepsin, BAPNA, pH 7.0 buffer)?

With more enzyme activity the optical density increases. If I reduced the incubation time to 30 minutes for tube 5, optical density would likely decrease or be 0.00. Time allows for more enzyme activity.

The substrate(s) for amylase is/are a. starch b. cellulose c. peptides d. starch and cellulose e. starch and peptides

a. starch

Tubes 3 (amylase, starch, pH 7.0 buffer), 7 (amylase, starch, pH 2.0 buffer), and 8 (amylase, starch, pH 9.0 buffer) reveal that

amylase activity was highest at pH 7

Which of the following is/are true of bile? a. it works by a chemical process b. it works by a physical process c. it is an enzyme d. it works by a chemical and physical process

b. it works by a physical process

From your results, which pH is ideal for pancreatic lipase digestion? a. pH 2.0 b. pH 7.0 c. pH 9.0

b. pH 7.0