Download PreLab Questions Match the definitions with the proper term: a

PreLab Questions
1. Match the definitions with the proper term:
a. catalyst
b. control
c. enzyme
d. substrate
A
increases the rate of a chemical reaction without becoming
a part of the products
B
provides a standard of comparison for test results
C
biological catalyst; protein in nature
D
substance(s) on which a catalyst works
2. List three characteristics of enzymes:
1. accelerate the rate of a chemical reaction
2. are specific for a substrate or a group of related substrates
3. are not used up or changed during the course of the reaction
3. Name the end products of digestion of the following food types:
a.
proteins:
aminoacids
b.
carbohydrates
monosaccharides
c.
neutral fats:
fatty acids plus glycerol
4. Is bile an enzyme? Why or why not?
No, it is not an enzyme. It does not catalyze a reaction. It emulsifies fat
5.
Complete the following chart:
Enzyme
Organ(s)
Producing It
Site of Action
Substrate(s)
Optimal pH
Salivary
Amylase
Salivary
mouth
carbohydrates
6.75- 7
Trypsin
pancreas
Small intestine protein
7.6-7.8
Pancreatic
Lipase
pancreas
Small intestine lipids
7.6-7.8
glands
6.
You will use several indicators or tests in the laboratory to determine the presence or
absence of certain substances. Choose the correct test or indicator from the key to
correspond to the condition described below:
a.
b.
IKI (Lugol’s Iodine)
Litmus
c.
d.
Benedict’s solution
BAPNA
D Test for the protein hydrolysis; indicated by a yellow color
A Test for the presence of starch; indicated by a blue-black color
B Test for the presence of fatty acids; indicated by a change in
color from blue to pink
C Test for the presence of a reducing sugar (eg, maltose,
sucrose, glucose); indicated by a color change from blue to green
7.
Do you expect 37oC to be an optimal incubation temperature? Why or why not?
Yes, this is close to the core body temperature (when the enzymes are normally active)
8.
The three dimensional structure of a functional protein is altered by intense
heat or by nonphysiological pH even though peptide bonds might not be broken. Such
inactivation is called denaturation and denatured enzymes are nonfunctional. Explain why.
interaction of an enzyme and a substrate, and hence the formation of an enzyme
substrate complex, depends on the shape of the active site of the enzyme; when
enzymes are denatured (unfolded), the atoms that make up the active site may be
separated from each other and substrate binding may not occur
9.
Pancreatic and intestinal enzymes operate at a pH that is slightly alkaline, yet the chyme
entering the duodenum is very acidic. How is the proper pH for the function of pancreatic and
intestinal enzymes ensured?
pancreas secrete NaHCO3 (bicarbonate) into the intestinal lumen; the rate of
secretion balances precisely the rate of HCl secretion in the stomach. The duodenal
(Brunner’s) glands also secrete an alkaline mucus into the intestinal lumen
10.
People on a strict diet to lose weight begin to metabolize fat at an accelerated rate.
How does this condition affect blood pH?
the blood pH; fatty acids and ketoacids (acidic metabolic products of fatty acid
metabolism) are produced
11.
Trypsin is a protease similar to pepsin, the protein digesting enzyme of the stomach. Would
trypsin work as well in the stomach? Explain your answer.
No; the pH of the stomach is 1-2; trypsin is optimal at pH 7.6-7.8, which is the pH of its
normal site of activity (the small intestine)
12. Note the mechanism of absorption (passive or active transport) of the following food breakdown
products, and indicate by a check mark (√) whether the absorption would result in their
movement into the blood capillaries or the lymph capillaries (lacteals).
Substance
Monosaccharides
Fatty acids, glycerol
Amino acids
Water
Na+, Cl-, Ca2+
Mechanism of Absorption
Active Cotransport with Na+ or
facilitated diffusion
Diffusion into intestinal cells;
vesicular (chylomicrons)
From the intestinal cells into the IF
(Active transport)
Active transport, coupled to Na+
transport
osmosis
Active transport and diffusion
Blood
X
Lymph
Few fattyX
acids
X
X
X
13. Some of the digestive organs have groups of secretory cells that liberate hormones
(parahormones) into the blood. These exert an effect on digestive processes by acting on
other cells or structures, causing them to release digestive enzymes, expel bile, or
increase the motility of the GI tract. For each hormone below, note the organ that
produces the hormone and indicate its effects on the digestive process.
Hormone
Secretin
Produced By
duodenum
Target Organ(s) and Effects
Stomach: inhibits secretion and motility
Pancreas: stimulates secretion esp
bicarbonate
Gastrin
stomach
Liver: stimulates bile production
Stomach: increases secretion (esp HCl)
And increases motility
Small intestine: stimulates motility
Ileocecal valve: relaxes it
Cholecystokinin
duodenum
Large intestine: stimulates mass
movements
Liver/pancreas: potentiates secretin’s
effects
Pancreas: stimulates secretion of
enzyme rich pancreatic juice
Gall bladder: stimulates contraction
Hepatopancreatic sphincter: relaxes it