Unit: Digestion
HW 1
Read Concepts Pages 106 (Protozoa) - 112
Answer the following:
1. Define the terms intracellular and extracellular digestion.
Intracellular digestion occurs inside a cell while extracellular digestion occurs outside of a cell
2. How does mechanical digestion aid chemical digestion
Mechanical digestion physically breaks down food thus increasing the surface area of the food and allowing chemical
digestion performed by enzymes to occur faster
3. Why is a one-way digestive tract evolutionarily more efficient than a two way tract?
One way is more efficient for two reasons: (1) specialized structures allow for more efficient digestion of materials
and (2) Food can be stored for later use where in a two way tract food may be lost before digestion is completed
Unit: Nutrition
HW 2
Read Miller/Levine pages 978-984
Answer the following:
1. Discuss the importance of teeth in human nutrition
Teeth perform mechanical digestion thus increasing the surface area of food for salivary amylase to work and for
the enzymes of the stomach and small intestine to work more efficiently
2. Describe how food passes through the esophagus
Food is pushed down the esophagus to the stomach through the process of peristalsis. Wave-like contractions
alternate between contraction and relaxation to push the food through the entire digestive tract from the
esophagus through the stomach, small intestine and large intestine.
3. Why would the enzymes in your mouth not work in your stomach and the enzymes in your stomach not work in your
mouth?
Mouth enzymes, salivary amylase, would be denatured in the stomach due to the pH of 2 in the stomach. Pepsin,
stomach enzyme, would be denatured because its optimum pH is 2 and the mouth has a pH of 7.
Unit: Nutrition
HW 3
1. Using Concepts create a table of the Malfunctions of the Digestive System (pages 209 - 211)
Malfunction
Description
Ulcer
Erosion of the surface of a portion of the digestive
tract, normally in the stomach due to action of
irritants
Constipation
Too much water absorption in the large intestine
causing fecal matter to be too dry
Diarrhea
Not enough water reabsorption in the large
intestine causing fecal matter to be watery (loose
stool)
Gall stones
Salt crystals form in the gall bladder and clog the
tube connecting the gall baldder to the small
intestine. This reduces bile release, reduces lipase
activity, reduces fat digestion and causes pain
2. create a chart including mouth, stomach, small intestine, large intestine, pancreas, liver, and gall bladder. Identify the
secretions of enzymes (give specific enzyme names and substrates), if any, and the role of each structure listed. Site also
mechanical, chemical and extracellular digestion
Structure
Mouth
Secretion
Salivary amylase (enzyme);
substrate: starch
Stomach
Pepsin (enzyme); substrate:
polypeptides
Small intestine
Enzymes originate from the
pancreas
Large intestine
Pancreas
Liver
Proteases (trypsin and
chymotrypsin)
Lipase
Carbohydrases (maltase,
sucrase, lactase)
Nucleases (digest DNA and RNA)
Synthesizes bile (emulsifies
lipids)
Gall bladder
Function
Chemical digestion of
carbohydrates
Mechanical digestion
Both extracellular
Storage of food
Extracellular chemical digestion
of proteins
Kill pathogens
Site of chemical digestion
Site of nutrient absorption
Site of water absorption
Home of mutualistic bacteria
Synthesize and secrete enzymes
into the small intestine
Synthesizes and secretes
biocarbonate ions into the small
intestine
Store Bile
Release bile into the small
intestine when fats are present
Unit: Nutrition
HW 4
Read:


Concepts page 208-209 (Absorption in the small intestine)
Miller/Levine page 983
Answer the following:
1. State the functions of the small intestine. Describe how it is structured to carry out its functions.
Site of chemical digestion and nutrient absorption. Lined with villi (finger-like projections into the lumen) that
have microvilli on them. Villi and microvilli increase the surface area of the small intestine to increase the
ability to absorb nutrients. Villi absorb materials using active transport
How would the introduction of cyanide, a chemical that inhibits ATP (chemical energy) production affect
the functioning of the small intestine?
Cyanide would prevent mitochondria from producing ATP (energy) thus active transport in the small intestine would
stop and no nutrients would be absorbed
Graph the data on page 994 (Miller/Levine). Identify the independent and dependent variables.
9
8
Protein Digestion
7
6
5
4
3
2
1
0
0
20
40
60
80
100
120
Temperature (Celcius)
Copy and answer question 23 on page 993 (Miller/Levine)
The experiment was repeated a third time, using apple instead of gelatin. There was no evidence of any digestion after
48 hours at any temperature. Explain why no digestion occurred.
The enzyme used to digest the gelatin has a specific shaped active site for the substrate gelatin. The apple is a
carbohydrate thus does not fit into the active site of the protein (gelatin) digesting enzyme.
Copy and answer question 25 on page 994 (Miller/Levine)
Individuals who have had part, or even all, of their stomachs removed can survive if fed predigested food. Could
individuals with a stomach survive without a small intestine if they were fed predigested food? Support your answer
with an explanation.
The person will not survive because the small intestine is involved in nutrient absorption as well as digestion. No
small intestine means no nutrient absorption leading to death.