Lab 8 - Chemical and Physical Processes of Digestion

Topics: Enzyme, Digestion, Starch Pages: 12 (2093 words) Published: February 22, 2011
Lab 8 - Chemical and Physical Processes of Digestion (p.105)


In this lab, I will study how digestion of carbohydrates, proteins, and fats occurs. I will define Key Terms that describe what will occur in the experiments; I will conduct an experiment for each Activity and provide all resulting Data as well as answer Questions from each Activity. I will then provide a short Summary for what I learned in each Activity.

Key Terms:

Enzymes (p. 105) – Speed up chemical reactions in living things. Biological catalysts.

Catalysts (p. 105) - is any substance which makes a chemical reaction go faster, without itself being changed.

Hydrolases (p. 105) – Reaction with water. A chemical process in which a molecule is cleaved into two parts by the addition of a molecule of water. Substrates (p. 105) - the substance upon which an enzyme acts

Enzyme Assay (p. 106) - laboratory methods for measuring enzymatic activity. They are vital for the study of enzyme kinetics and enzyme inhibition.

Deglutition (p. 115) – The act or process of swallowing.

Activity 1: Assessing Starch Digestion by Salivary Amylase


Chart 1 – Salivary Amylase Digestion of Starch

Tube #1234

AdditivesAmylase, StarchAmylase, Starch Amylase, DI Water DI Water, Starch

pH 7.0 bufferpH 7.0 bufferpH 7.0 buffer pH 7.0 buffer

Incubation Cond. Boil, Inc. 37 deg.C37 degrees C37 degrees C 37 degrees C

for 60 minutes

IKI Test+--+

Benedict's Test-++--

Chart 1 – Salivary Amylase Digestion of Starch (continued)

Tube #567

AdditivesDI Water, Maltose Amylase, Starch Amylase, Starch

pH 7.0 buffer pH 2.0 buffer pH 9.0 buffer

Incubation Cond. 37 degrees C 37 degrees C 37 degrees C

IKI Test-++

Benedict's Test++++


1-1: What do tubes 2, 6, and 7 reveal about pH and amylase activity? Hint: What variable was changed in the procedure?

The pH level was changed. Tube 2 had a pH of 7, tube 6 had a pH of 2 and tube 7 had a pH of 9. They all show how pH effects amylase activity.Tests 6 & 7 shows that the amylase was not being broke down because of the pH level differences. Test 2 shows that with a low pH there was a lot of activity.

1-2: Which pH buffer allowed the highest amylase activity? pH = ___7.0____

1-3: Which tube indicates that the amylase was not contaminated with maltose? Tube #___3____

1-4: Which tubes indicate that the deionized water did not contain contaminating starch or maltose? Tubes ___3___, __4____, __5____

1-5: If we left out control tubes 3,4, or 5, what objections could be raised to the statement: "Amylase digests starch to maltose"? (Hint: Think about the purity of the chemical solutions). In other words, what else might have happened other than digestion?)

If tubes 3, 4, or 5 were left out, an objection to the statement, “Amylase digests starch to maltose,” can be made that the enzyme maltose and starch would be polluted.

1-6: Would the amylase present in saliva be active in the stomach? Explain your answer (why or why not)? (Hint: think about pH.)

No. Amylase would not be active in the stomach because the pH level found in gastric acids is low, which will cause amylase to be defective.

1-7: What effect does boiling have on enzyme activity?

The activity rises until the temperature gets to high, then the enzyme will be inactivated.


In this Activity, I learned/observed that:

I learned the lower the PH level is then the more responsive the enzyme will react, and the higher the pH is the less active the enzyme will...
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