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Exercise 6
ENZYMES
Results and Discussion
Name: Ivy Ann C. Carba
Section: HJK
Group name: Hale’s Prodigal Daughters
Date Performed: Dec. 4-5, 2009
Date Submitted: Dec. 22, 2009
A. Hydrolyses
a.
Amylase
Iodine test of 0.1% starch solution with corn seedling root after incubation
→ Emergence of a dark purple color.
Iodine test of 0.1% starch solution after incubation period (control)
→ Emergence of a dark purple color.
b. Sucrase
Benedict’s test of 2% sucrose solution with fresh corn seedling root
→ A red-yellowish color was perceived that indicates the the presence of
reducing sugar.
Benedict’s test of 2% sucrose solution without corn seedling root (control)
→ A blue color was perceived that indicates the absence of reducing sugar.
B. Oxireductases
a.
Dehydrogenase
Color intensity of methylene blue
After incubation
Blue
After Aeration
With fresh mungbean seedlings
initially, the solution appeared
to be white and then
became blue again yet seemed
to be lighter after the
performed incubation
Without mungbean seedlings (control)
Blue
Blue
b. Catalase
Potato tuber strips in 3% H2O2
Appearance of large bubbles in large amounts.
Boiled potato tuber strips in 3% H2O2
→ Appearance of gas bubbles in small amounts.
C. Factors affecting enzyme activity
a.
Enzyme concentration
Color Intensity of Starch –Iodine Solutions
With undiluted amylase
With half diluted amylase
With ¼ diluted amylase
After 45 minutes of incubation
dark color with light yellowish tinge
darker color with yellowish tinge
darkest color with brownish tinge
b. Hydrogen-ion concentration (pH)
Color Intensity of Starch-Iodine Solutions + Amylase
(scale of 1 to 7, dark to light)
pH 4 buffer
2
(purplish black)
pH 5 buffer
−
pH 6 buffer
−
pH 7 buffer
4
(bluish green)
pH 8 buffer
−
pH 9 buffer
−
pH 10 buffer
6
(light blue)
c. Temperature
Color intensity of Starch –iodine solutions
After 45 minutes of incubation
At 5-10 ̊C
darkest lavender coloration
At 28-30˚ C
lavender coloration
At 98-10 ˚ C
lightest lavender coloration
Study Questions
1.
Give (i) the name of the enzymes catalyzing the following chemical reactions, (ii)
their cellular localization, and (iii) the plant physiological process they are involved
a) Pyruvate + NAD+ + CoA ----------- acetyl- CoA + NADH + H+ + CO₂
(i)
Pyruvate dehydrogenase
(ii)
Mitochondrion
(iii)
Citric acid cycle
b) Ribulose- 1,5- bisphosphate + CO2 -------------- 2 (3-phosphoglyceric acid)
c)
2.
(i)
Ribulose-1,5- bisphosphate carboxylase
(ii)
Chloroplast
(ii)
Carbon fixation
Fructose-6-phosphate + ATP ---------------- Fructose-1,6-biphosphate
(i)
Phosphofructokinase
(ii)
Chloroplast
(iii)
Glycolysis
Describe the rate of enzyme-catalyzed reaction with increasing substrate
concentration.
→ The rate of reaction catalyzed by an enzyme increases linearly with the
substrate concentration up to a point, but it soon reaches the maximum value called
Vmax beyond which there is no further increase in reaction rate; this is called
substrate saturation. This is so because all of the active sites would be occupied by
each substrate.
3. In what ways does hydrogen concentration affect enzyme activity?
→In this case, at pH 7, the enzyme activity would be at its optimum
level which at this point, the reaction would be at its best activeness. But then,
when a pH is reached at this case 10 the, this would cause the denaturation of the
proteins yielding a light coloration. And this would mean that the stach-iodine
solution changed its structural configuration due to the extreme pH.