UNIVERSITI TUNKU ABDUL RAHMAN
CENTRE FOR FOUNDATION STUDIES
FOUNDATION IN SCIENCE
MAY 2015

FHSB1214
BIOLOGY I

TUTORIAL 4
ENZYMOLGY ESSENTIAL

Student’s Guide:
At university level, the tutor facilitates student learning without spoon-feeding. Therefore, you are expected to: • Read your textbook, attempt the questions before the tutorial • You may enter the class and sign your attendance after showing your tutor that all tutorial questions have been completed; even if you don’t know how to do, write something - you’re not advised to leave answers blank in the finals. • Write answers on board if you wish to receive tutor feedback (no answer, no feedback) • Be independent: consult textbooks or dictionaries on your own first before asking the tutor • All questions are compulsory. 1 mark may reflect 1 answer point. (No half mark is awarded in the finals marks)

(Source : Final Examination, Apr 2015)

Q1. (a) Pyruvate kinase is an enzyme that catalyse the transfer of a phosphate group from phosphoenolpyruvate to adenosine diphosphate during glycolysis. i) Define the term “enzyme” and state its function. (2 marks)

ii) Explain why pyruvate kinase can only catalyse this reaction but not other reactions. (3 marks)

(b) Figure 1.1 shows the result of an investigation using enzyme sucrose to break down sucrose into its monomer. In this investigation, 1g of sucrose was dissolved in 100 cm3 of water and 2 cm3 of 1% sucrose solution was added.

[pic]

Based on Figure 1.3, answer the following questions.

i) State the products of this enzymatic reaction. (2 marks)

ii) Briefly explain what happens at 0 – 60 minutes interval. (2 marks)

iii) Describe the reaction at point X. (1 mark)

[1]

iv) Briefly describe ONE(1) chemical test that could be used to differentiate sucrose from its substrate, sucrose. (3 marks)

(Source: Final examination, Dec 2014)
Q2. (a) Figure 2.1 shows the dehydration synthesis of maltose.
[pic]
Figure 2.1

With reference to Figure 2.1, answer the following questions.

(i) Identify components labelled as X and Y. (2 marks)

(ii) Suggest whether the reaction progress shown in Figure 1.1 is exergonic or endergonic. Provide an explanation to your answer. (2 marks)

(b) Figure 2.2 shows the activity of three different enzymes (salilvary amylase, pepsin and trypsin) in human digestive system.

[pic]
Figure 2.2

Chewing breaks food into smaller pieces so that chemical digestion can occur faster. Bicarbonate ions in saliva act as buffers, maintaining a pH between 6.5 and 7.5. in the stomach, HCl maintains a pH in the stomach of approximately 2.0. Pancreatic trypsin has an optimal operating pH of about 7.5-8.5.

(i) Match the curves (A, B, and C) to amylase, pepsin and trypsin. (3 marks)

(ii) Explain what will happen to enzyme A if the surrounding pH increases to 7.0. Include a reference to enzyme structure in terms of level of protein organization, active site, bonds and hydrogen ion. (4 marks)

(Source: Final examination Apr, 2013)
Q3. Lipase is an enzyme that can digest lipids. An experiment was set up to study the effect of temperature on the action of lipase enzyme. Nine test tubes were prepared separately and the experimental set up was designed in a way as shown in Figure 3.1. The nine test tubes which contain 10cm3 of corn oil and 1cm3 of lipase were kept at a range of temperatures between 20°C and 100°C. At the start of the experiment, the pH of the contents in each test tube was constant, which was 6.5.

[pic] Figure 3.1

Each test-tube was left for 30 minutes and the reading on the digital pH meter was then recorded. The pH readings against different temperatures are plotted in a graph, shown in Figure 3.2.

[pic] Figure 3.2

(a) State the products of hydrolyzed corn oil. (2 marks)

(b) With reference to Figure 3.2, state the optimum temperature for lipase to perform its catalytic activity. (1 mark)

(c) Briefly explain how lipase activity at this optimum temperature leads to the respective pH in Figure 3.2. (2 marks)

(d) Explain why the pH did not change between 80°C and 100°C at the end of the experiment. (4 marks)