E9: Digestive System Processes: Chemical and Physical

Assume you have been chewing a piece of bread for 5-6 minutes. How would you expect its taste to change during this interval? Why?

It would start to taste sweet. The amylase would convert the starch to maltose. Starch decreases + sugar increases = digestion occurs.

S + E = P + E

S = substance E = enzyme P = product

Assume you have made the statement to a group of your peers that amylase is capable of starch hydrolysis to maltose. if you had not done control tube 1A, what objection to your statement could be raised?

The control is needed to validate the results of the experiment. It is used to compare experimental results within.

How id the tubes containing bile compare with those not containing bile?

The ones containing bile had more hydrolysis.

Pancreatic and intestinal enzymes operate optimally at a pH that is slightly alkaline, yet the chyme entering the duodenum from the stomach is very acidic. How is the proper pH for the functioning of the pancreatic-intestinal enzymes ensured?

The pancreas also secretes an alkaline fluid into the duodenum which ensures proper pH for the pancreatic-intestinal enzymes.

When starch was incubated with amylase at 0 degrees C , did you see any starch digestion? Why or Why not?

Yes. The freezing temp did not affect starch digestion.

The two major types of propulsive movements that occur in the small intestine are ______ and ______. One of these movements, ______, acts to continually mix the foods and to increase the absorption rate by moving different parts of the chyme mass over the intestinal mucosa, but it has less of a role in moving foods along the digestive tract.

peristalsis and segmentation segmentation

End product of digestion for: proteins fats carbs

amino acids monoglycerides and fatty acids monosaccharides

Control

provides a standard of comparison for test results

Salivary amylase Organ producing it: Site of action: Substrate: Optimal pH:

salivary gland mouth starch 6.7 - 7.0

IKI iodine

starch

Substrate

substance on which a catalyst works

What conclusions can you draw when an experimental sample gives both a positive starch test and a positive maltose test after incubation?

the starch was brown down to the maltose and maltose is a disaccharide

Litmus

used to test for the presence of FATTY ACIDS which was evidenced by a color change from BLUE to PINK

Lugol's iodine (IKI)

used to test for the presence of STARCH which was indicated by a BLUE BLACK color

Benedict's solution

used to test for the presence of reducing SUGARS ( glucose, maltose, sucrose) as indicated by a BLUE to GREEN or ORANGE color change

During swallowing, the ______ rises to ensure that its passageway is covered by the epiglottis so that the ingested substances don't enter the respiratory passageways. It is possible to swallow water by standing on your head because the water is carried along the esophagus involuntarily by the process of ______.

uvuid and larynx peristalsis

Enzyme

biologic catalyst, protein in nature

One of of these phases, the ______ is voluntary. During the voluntary phase, the ______ is used to push the food into the back of the throat.

buccal tongue

Swallowing or ______ occurs in two phases - the ______ and ______.

deglutition buccal and pharyngeal-esophageal

Why did the limits indicator change from blue to pink during fat hydrolysis?

fat digestion has occured

Pancreatin 1% (litmus crem)

fats color changes from BLUE to PINK enzyme is lipase

The pressure exerted by the foodstuffs on the ______ sphincter causes it to open, allowing the foodstuffs to enter the stomach.

gastroesophageal

What specific experimental conditions resulted in denatured enzymes?

high temp and low pH

Why was 37 degrees C optimal incubation temperature?

human body temp

Catalyst

increases the rate of a chemical reaction without becoming part of the product

Why is bile not considered an enzyme?

it is a PHYSICAL reaction, not a chemical one.

Benedict's solution

maltose

Lipase (pancreatic) Organ producing it: Site of action: Substrate: Optimal pH:

pancreas small intestine fat 7.5 - 8.0

Trypsin Organ producing it: Site of action: Substrate: Optimal pH:

pancreas small intestine protein 1.5 - 2 (but less than 2)

What role does bile play in fat digestion?

It breaks down large particles into smaller ones and increases surface area allowing the enzyme to work better.

Three Characteristics of enzymes

1. Enzymes are substrate specific. 2. Enzymes are affected by both pH and temp. 3. Enzymes speed up chemical reactions but remain after a product is formed.

In the procedure concerning pancreatic lipase digestion of fats and the action of bile salts, how did the appearance of tubes 1E and 2E differ? Explain.

1E - oil floating on top 2E - fat droplets throughout the water Bile breaks down the larger fat particles into smaller one. So it provides better surface area for enzymatic activity.

Why did very little, if any, starch digestion occur in the test tube 4A?

Amylase was boiled and denatured so it could not break down the starch.

The 3D structure of a functional protein is altered by intense heat or non physiological pH even though peptide bonds may not break. Such inactivation is called denaturation, and denatured enzymes are nonfunctional. Why?

Denaturation disrupts the secondary and tertiary structures of proteins and thus their ability to function.

People on a strict diet to lose weight begin to metabolize stored fats at an accelerated rate. How does this condition affect blood pH?

Fatty acids acidify solutions by decreasing the pH.

The enzymes of the digestive system are classified by hydrolyses. What does this mean?

They break down substances by adding water to the molecular bond. It means the bonds are between the chemical building blocks.