Download SULIT UNIVERSITI MALAYSIA PERLIS Peperiksaan Pertengahan

UNIVERSITI MALAYSIA PERLIS
Peperiksaan Pertengahan Semester 1
Sidang Akademik 2010/2011
Ogos 2010
ERT 106-Biochemistry
[Biokimia]
Masa : 1 jam
Please make sure that this question paper has FIVE (5) printed pages including this
front page before you start the examination.
[Sila pastikan kertas soalan ini mengandungi LIMA (5) muka surat yang bercetak termasuk muka
hadapan sebelum anda memulakan peperiksaan ini.]
This question paper has FOUR (4) questions. Answer ALL questions in the provided
space. Each question contributes 25 marks.
[Kertas soalan ini mengandungi EMPAT (4) soalan. Jawab SEMUA soalan dalam ruang yang
disediakan. Setiap soalan memberikan 25 markah.]
Name
:.......................................................................................
Matrix No. : .....................................................................................
SULIT
Question 1
a. “Life is a complex phenomenon”. Explain this statement.
[10 marks]
ANSWER

All organisms are mainly composed of organic [carbon-based] molecules that
have complex, 3-dimensional shapes

Growth and development in living processes involve thousand of chemical
reactions that interact, collide, and rearrange to form new biomolecules
b. Describe 3 major differences between prokaryotic and eukaryotic cells.
[15 marks]
ANSWER
Differences
Structure
PROKARYOTES Cell wall
semi rigid
composed of
peptidoglycan
Respiration
Anaerobicfermentation
[lacking
mitochondrion]
Movement
Tumbling
rotation of
flagellum
EUKARYOTES
Aerobic
respiration
[Kreb’s cycle]has
mitochondrion
Cilia,
flagella and
pseudopod
movement.
These
microtubules
have the
classic 9+2
pattern
Cell wall has
plasma
membrane
that is
composed of
lipid bilayer
and
glycocalyx on
the external
surface –
lacks
peptidoglycan
2
Reproduction[DNA]
DNA in single strand
and floating freely
without a nucleus;
asexual binarry
fission
DNA in
chromosomes inside
nucleus; sexual
zygote udergoes
meiosis and mitosis
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SULIT
Question 2
a)
Substances such as salts are easily dissolved in water. With the aid of diagram or
structure, explain the solvent properties of water that enable such situation.
[15 Marks]
- The polar nature of water makes it an excellent solvent for polar and ionic
materials that are water loving (hydophillic)
- An ion immersed in a polar solvent such as water attracts the the oppositely
charged ends of the solvent dipoles and becomes surrounded by one or more
concentric shells of orientated solvent molecules.
- The ion becoming solvated or hydrated when water is the solvent
- The capacity of solvent to reduce the attractive forces between ions is
indicated by its dielectric constant.
- Water has a very large dielectric constant.
(5 points x 2 marks = 10 marks)
(5 marks for diagram)
b) Calculate the ratio of lactic acid and lactate required in a buffer system of
pH 5.5. The pKa of lactic acid is 3.86.
[10 Marks]
Answer
The equation
pH = pKa + log
[lactate]
………… 2
[lactic acid]
Can be rearranged to
Log [lactate]
= pH – pKa ……………2
[lactic acid]
= 5.5 – 3.86 = 1.64 …….2
Therefore the required ratio is
[lactate]
= antilog 1.64 …………….2
[lactic acid]
= 43.6
…………… 2
3
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SULIT
Question 3
a. Differentiate between the cis-isomers and trans-isomers of unsaturated lipids.
[10 marks]
ANSWER
Unsaturated: contain one or more double bonds
cis: identical groups are on the same side of a double bond
Trans: identical groups are on opposite sides of a double bond
Cis
Trans
b. i. Name two fatty acids found in abundance in living organisms.
[5 marks]
ANSWER
Refer p.333 of Mckee textbook: oleic acid and linoleic acid
ii. Write and explain the abbreviation symbols used for these two fatty acids.
[10 marks]
ANSWER
Abbre. Symbol for oleic acid – 18:1Δ9
The number to the left of the colon is the total number of carbon atoms and the
number to the right is the number of double bonds.
This symbol indicates that this acid contains 18 carbon atoms; 1 indicates that it
is a single-bonded monounsatutated acid; Δ9 signifies that there are 8 carbons
between the carboxyl [-COOH] group and the double bond, i.e. the double bond
occurs between carbons 9 and 10.
Abbre. Symbol for linoleic acid – 18:2 Δ9,12
This is a double-bond poyunsaturated fatty acid having 18 carbon atoms and
double bonds between carbons 9 and 10; and carbons 12 and 13. The double
bonds are separated by the methylene groups [-CH2-].
4
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SULIT
Question 4
a.
Proteins are composed of 20 standard amino acids. Briefly describe with
simple diagram the general structure of amino acid.
[5 Markah]
b.
Amino acids are classified according to their capacity to interact with water.
Based on this criterion, explain briefly the classes of amino acids.
[20 Marks]
4 classes of amino acids :
a) neutral nonpolar
- amino acid contain hydrocarbon R groups
b) neutral polar
- amino acids have functional group capable of forming hydrogen bonding, so
easily interact with water (hydrophilic)
c) acidic
- amino acids contain carboxylate R group. So negatively charge at
physiological pH
d) basic
- amino acids contain amine R group. So positively charge at physiological pH
5
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