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Exercise 8, Activity 4: Assessing Fat Digestion by pancreatic lipase and the action of bile. **Really need help on this activity****
1.) Explain the difference in activity between tubes 1 & 2?
2.) Can we determine if fat hydrolysis has occurred in tube 6?____
b) explain your answer._____________
3.) Which ph resulted in maximum lipase activity?___
4.) Can we determine if fat hydrolysis has occurred in tube 5?
5.) In theory, would lipase be active in the mouth?____
6.) Would it be active in the stomach?___
b) Explain your answers? ______
7.) What is the substrate, and what subunit is formed in this experiment??


Exercise 8, Activity 1: Assessing Starch Digestion by Salivary Amylase
1,) What do tubes 2, 6, and 7 reveal about PH and amylase activity?_____
2.) Which ph buffer allowed the highest amylase activity?___
3.) Which tube indicates that the amylase was not contaminated with maltose? ___
4.) Which tubes indicate that the deionized water did not contain contaminating starch or maltose?___
5.) If we left out tubes 3, 4 or 5 what objects could be raised to the statement "amylase digests starch to maltose.?"___
6.) Would amylase present in saliva be active in the stomach? Explain answer ____
7.) What effect does boiling have on enzyme activity? ____

Thanks Caitlyn

Tube 1 investigated the action of bile on enzyme activity, and tube 2 examined lipase activity without bile. Bile enhances fat digestion by lipase. Yes, you can determine if activity occurred in tube 6 because the pH would drop below pH 9.0. A small amount of fat digestion occurred because pH decreased from 9.0 to 8.97. The optimim pH for lipase activity was pH 7.0. Using a pH method to assay for activity at pH 2.0 does not work because the buffer is already quite acidic. There could have been activity at pH 2.0 that was not detectable by this method. In theory, lipase would be active in the mouth because its pH optimum is relatively neutral. However, it would not be active in the stomach because of the acidic pH condition. The substrate is vegetable oil (fat). The subunit formed is fatty acid (and monoglycerides).

Here are the answers to Activity 1, Exercise 8!!

The first two tubes acted as control tubes. The first tube displayed the presence of starch
with no enzyme; the second tube displayed the presence of enzyme but no starch.
You can conclude from tubes 3 and 4 that boiling disrupted the action of amylase. Tubes 3
and 4 contained the exact same additives; the only difference was that tube 3 was boiled,
and tube 4 was not. Digestion took place in tube 4 but did not take place in tube 3.
Tubes 4, 6, and 7 demonstrate that amylase has an optimal pH at which it works. Maximal
digestion of starch takes place at the optimal pH of 7.0. Some digestion still takes place at
nonoptimal pH levels, but very little occurs compared to digestion at pH 7.0.
The optimal pH for amylase is 7.0.
Yes.
Maltose.
Tubes 4, 5, 6, and 7.
Tube 1 had no enzyme; tube 2 had no starch; and tube 3 was boiled, inactivating the enzyme.
The pH of the stomach approaches 1.0, and this would greatly inactivate the enzyme.

review sheet answers physioEX 39B

1-20 please help physioEx Review sheet exercise 39B

Activity 1: Assessing Starch Digestion by Salivary Amylase (pp. 104–105)
10. Tubes 2, 6, and 7 showed the effect of pH on amylase activity. The results of this experiment
indicate that the activity maximum of amylase is at pH 7.0, whereas pH 2.0 and
pH 9.0 demonstrated very little activity.
In this experiment, pH 7.0 showed the highest level of amylase activity.
Tube 3 showed that amylase did not contain maltose contamination.
Tubes 3, 4, and 5 showed that water had no starch or maltose contamination. Tube 3
directly showed that water did not have maltose or starch contamination. Tube 4 was a
starch control (with the same water) that showed no maltose, and tube 5 was a maltose
control (also with water) that showed no starch.
If control tubes 3, 4, or 5 were not done, then what is perceived as digestion might really
be starch or maltose contamination.
Saliva would not be active in the stomach because the stomach pH is too low.
Boiling inactivates, or denatures, enzymes.

Activity 4: Assessing Fat Digestion by Pancreatic Lipase and the Action of Bile
(pp. 109–111)
7. Tube 1 investigated the action of bile on enzyme activity, and tube 2 examined lipase
activity without bile. Bile enhances fat digestion by lipase.
Yes, you can determine if activity occurred in tube 6 because the pH would drop below
pH 9.0. A small amount of fat digestion occurred because pH decreased from 9.0 to 8.97.
The optimim pH for lipase activity was pH 7.0.
Using a pH method to assay for activity at pH 2.0 does not work because the buffer is
already quite acidic. There could have been activity at pH 2.0 that was not detectable by
this method.
In theory, lipase would be active in the mouth because its pH optimum is relatively neutral.
However, it would not be active in the stomach because of the acidic pH condition.
The substrate is vegetable oil (fat). The subunit formed is fatty acid (and monoglycerides).

 hope this helps, if so mark as solved. ;)

I'm not sure what you mean, that you need help with 39B, on the review sheet...  Explain and maybe I can help.  In the meantime, here are a few reviews sheet answers.  Let me know if you need more. 

2. List two factors that play key roles in the efficacy of digestive enzymes, and explain their effects.
     1) temperature—boiling an enzyme will denature it; however,        freezing has no effect after incubation
     2) pH level—too high or too low a pH level will disrupt enzyme efficacy to ingest food, break down food to its simplest components, extract nutrients from these components for absorption into the body, and expel wastes It means that enzymes work on some substances but not others.

5. What are the three primary categories into which food molecules fall?
     1) carbohydrates, 2) proteins, 3) lipids

8. What is meant by hydrolysis?
     Hydrolysis is the process of adding water to a molecule in order to break it down into subunits.

15. Where is pepsin secreted?  from stomach glands

16. What was the optimal pH for pepsin?  any pH less than 3.0; in these experiments, pH 2.0

17. Where is lipase secreted?  from pancreatic juice

The pH optimum of pepsin is pH 2.0 and the pH in the mouth is relatively neutral.