Download SMU-DDE-Assignments-Scheme of Evaluation PROGRAM Bachelor

SMU-DDE-Assignments-Scheme of Evaluation
PROGRAM
SEMESTER
SUBJECT CODE &
NAME
BK ID
SESSION
MARKS
Q.
No
1.
A
Bachelor/Diploma in Medical Imaging Technology
II
BMI 201 – Basics of Biochemistry
B1947
WINTER 2015
60
Criteria
(Unit 2, Page No. 29 - 32 )
1
10
Define Amino acids.
 Amino acids are a group of organic compounds containing two
functional groups namely amino and carboxyl. Amino group is
basic while carboxyl group is acidic in nature.
9
Discuss the classification of amino acids:
 Classification based on structure: amino acids with aliphatic side (3+2+2+2)
chains, amino acids containing hydroxyl group, sulphur
containing amino acids, acidic amino acids, basic amino acids,
aromatic amino acids and imino acids.
 Classification based on polarity: non polar amino acids, polar
amino acids with no charge on R group, polar amino acids with
positive R group, polar amino acids with negative R group.
 Nutritional classification: Essential or indispensable amino
acids, Nonessential or dispensable amino acids.
 Classification based on their metabolic fate: glucogenic and
ketogenic amino acids.
List and explain the colour reaction of carbohydrates.
A
List the color reactions of carbohydrates :
 Molisch test
 Benedict’s test
 Benedict’s test after hydrolysis
 Barfoed’s test
 Selwinoff’s test
 Osazone formation
 Iodine formation
Explain the color reactions of carbohydrates:
 Any four reactions
A
Total
Marks
Define Amino acids. Discuss the classification of amino acids.
2.
3.
Marks
(Unit 3, Page No. 65-70)
2
10
8
Discuss the classification of enzymes. Add a note on enzyme specificity.
(Unit 5, Page No. 98-100)
6
10
Classification enzymes:
 Based on the chemical reaction catalyzed, enzymes are
classified into six classes:
SMU-DDE-Assignments-Scheme of Evaluation

4.
A
Oxidoreductases: catalyze the oxidation reduction reaction. Eg:
LDH
 Trnasferases: catalyze the transfer of groups from one substrate
into another. Eg: AST
 Hydrolases: catalyzes the breakdown of compounds by utilizing
a molecule of water. Eg: Trypsin
 Lyases: catalyze the removal of a group from a substrate
without using a molecule of water or combine two molecules to
form a new molecule without using energy. Eg: Fumarase
 Isomerases: catalyze the isomerization of substrate. Eg:
phosphohexose isomerase.
 Ligases: catalyse the reactions involving the joining together of
two substrate using ATP as the energy source. Eg: DNA ligases
4
Specificity of enzymes:
 Stereospecificity: in this, enzyme exhibit steros specificity i.e., act
only one isomer.
 Reaction specificity: same substance can undergo different types
of reactions and each reaction is catalyzed by different enzymes.
 Substrate specificity: absolute substrate specificity: certain
enzyme act only on one type of substrate. Relative substrate
specificity: some enzyme act on structurally related substances.
Broad specificity: certain enzyme act on closely related
compounds.
Explain the different glycogen storage disorders. Add a note on significance of glycogen
metabolism.
(Unit 8, Page No. 157 )
7
10
Glycogen storage disorders:
 Type I: Von Gierke’s disease: The defective enzyme is glucose 6
phosphatase. The primary organ involved is liver. Features of
this disease are hypoglycemia, lactic acidosis, hyperlipidemia,
hyperuricemia and ketosis.
 Type II: Pompe’s disease: The defective enzyme is lysosomal
acid maltase. All organs with lysosomes are affected. The main
features are accumulation of glycogen in the lysosomes, cardiac
failure and death in early life.
 Type III: Cori’s/ Forbes disease/ limit dextrinosis: The defective
enzyme is debranching enzyme and the affected organs are
mainly liver, skeletal and heart muscle. The features are
hypoglycemia, accumulation of abnormal glycogen having short
outer chains.
 Type IV: Andersen’s disease/ amylopectinosis: The defective
enzyme is branching enzyme. The primary organ involved are
liver, kidney and heart muscle. The features are accumulation of
abnormal glycogen having a few branches, death due to cardiac
and liver failure within 1 year of life.
 Type V: McArdle’s disease: the defective enzyme is muscle
glycogen phosphorylase. The primary organ involved is skeletal
muscle. The feature are exercise induced muscular pain, cramps,
and decreased serum lactate after exercise.
SMU-DDE-Assignments-Scheme of Evaluation


5.
A
Type VI: Her’s disease: The defective enzyme is liver glycogen
phosphorylase. The primary organ involved is liver. The features
are high content of liver glycogen, mild hypoglycemia and
ketosis.
Type VII: Tarui’s disease: The defective enzyme is
phosphofructokinase in muscle and erythrocytes. The organs
involved are muscle and RBCs. The features are exercise
induced muscular pain, cramps, decreased serum lactate after
exercise, hemolytic anemia.
3
Significance of glycogen metabolism:
 Liver glycogen functions to store and export glucose to maintain
blood glucose level between meals. After 12-18 hours of fasting,
liver glycogen is almost totally depleted.
 Muscle glycogen serves as a fuel reserve for the supply of ATP
during muscle contraction.
 Although muscle glycogen doesn’t yield free glucose, pyruvate
formed by glycolysis in muscle can undergo transamination to
alanine, which is exported from muscle and used for
gluconeogenesis in liver.
Discuss the ketone body metabolism.
(Unit 9, Page No. 222-225)
10
10
Ketone body metabolism:
 Ketone bodies are the water soluble compounds, which are
produced as the by-products when fatty acids are broken down
for energy. When the carbohydrate levels are too low, such as
in the periods of prolonged fasting, the fat cells are utilized for
the generation of energy. During this process, ketone bodies
are produced as the byproducts. The compounds categorized as
ketone bodies are acetone, acetoacetate and beta hydroxy
butyrate. Ketone bodies are important sources of energy for the
peripheral tissues because they are soluble in aqueous solution,
and therefore, do not need to be incorporated into lipoproteins
or carried by albumin as do the other lipids; they are produced
in the liver during periods when the amount of acetyl CoA
present exceeds the oxidative capacity of the live and they are
used in proportion to their concentration in the blood by extra
hepatic tissues, such as the skeletal and cardiac muscle and
renal cortex.
 Formation of ketone bodies: The synthesis of ketone bodies
occurs in the liver. The enzymes required for their synthesis
are located in the liver mitochondria. During a fast, the liver is
flooded with fatty acids mobilized from adipose tissue. The
resulting elevated hepatic acetyl CoA produced primarily by
fatty acid degradation inhibits pyruvate dehydrogenase, and
activates pyruvate carboxylase. The OAA thus produced is
used by the liver for gluconeogenesis rather than for the TCA
cycle. Therefore, acetyl CoA is channeled into ketone body
synthesis.

Synthesis of 3-hydroxy-3-methylglutaryl (HMG) CoA: the
SMU-DDE-Assignments-Scheme of Evaluation
6.
A
first synthetic step, formation of acetyl CoA, occurs by
reversal of the thiolase reaction of fatty acid oxidation.
Mitochondrial HMG CoA synthase combines a third molecule
of acetyl CoA with acetoacetyl CoA to produce HMG CoA.
HMG CoA synthase is the rate limiting step in the synthesis of
ketone bodies, and is present in significant quantities only in
the liver.
 Synthesis of the ketone bodies: HMG CoA is cleaved to
produce acetoacetate and acetyl CoA. Acetoacetate can be
reduced to form 3-hydroxybutyrate with NADH as the
hydrogen donor. Acetoacetate can also spontaneously decarboxylate in the blood to form acetone- a volatile,
biologically non-metabolized compound that can be released in
the breath. The equilibrium between acetoacetate and 3hydroxybutyrate is determined by the NAD+/NADH ratio.
Because this ratio is low during fatty acid oxidation, 3hydroxybutyrate synthesis is favored.
 Utilization of ketone bodies: 3-hydroxybutyrate is oxidized to
acetoacetate by 3-hydroxybutyrate dehydrogenase, producing
NADH. Acetoacetate is then provided with a CoA molecule
taken from succinyl CoA by succinyl CoA: acetoacetate CoA
transferase. This reaction is reversible, but the product
acetoacetyl CoA, is actively removed by its conversion to two
acetyl CoAs. Extra hepatic tissues, including the brain but
excluding cells lacking mitochondria, efficiently oxidize
acetoacetate and 3-hydroxybutyrate in this manner. In contrast,
although the liver actively produces ketone bodies, it lacks
thiophorase and, therefore, is unable to use ketone bodies as
fuel.
 Excessive production of ketone bodies in diabetes mellitus:
when the rate of formation of ketone bodies is greater than the
rate of their use, their levels begin to rise in the bloodketonemia and eventually in the urine- ketonuria. These two
conditions are seen most often in cases of uncontrolled, type I
diabetes mellitus. In such individuals, high fatty acid
degradation produces excessive amounts of acetyl CoA. It also
depletes the NAD+ pool and increases the NADH pool, which
slows the TCA cycle. This forces the excess acetyl CoA into
the ketone body pathway. In diabetic individuals with severe
ketosis, urinary excretion of the ketone bodies may be as high
as 5000 mg/24 hr, and the blood concentration may reach 90
mg/dl. A frequent symptom of diabetic ketoacidosis is a fruity
odour on the breath, which results from increased production
of acetone. An elevation of the ketone body concentration in
the blood results in academia.
Explain the metabolic fate of ammonia. List the various genetic disorders associated with the
urea cycle.
(Unit 10,Page No. 241-244)
6
10
Metabolic fate of ammonia:
 Being highly toxic, ammonia should be eliminated or
SMU-DDE-Assignments-Scheme of Evaluation
detoxified from the body. Even a slight increase in the blood
ammonia concentration is harmful to the brain. In human and
primates, ammonia is transferred to liver, and converted to
urea through urea cycle.
 Urea cycle: urea cycle is the process by which ammonia, a
highly toxic substance is converted to a less toxic excretory
waste product urea in liver. In the first step, ammonia is
activated by ATP and it combines with CO2 to form
carbamoyl phosphate. This reaction is catalyzed by carbamoyl
phosphate synthetase-I enzyme, which requires N-acetyl
glutamate
as
an
allosteric
activator.
Ornithine
transcarbamoylase transfers the carbamoyl group from
carbamoyl phosphate to ornithine and produces citrulline.
These first two reactions occur in the mitochondria. Rest of
the reactions proceed in the cytosol. In the presence of
argininosuccinate synthetase enzyme and ATP, citrulline
combines with L-aspartate to form argininosuccinic acid.
Subsequently,
argininosuccinate
lyase
hydrolyses
argininosuccinic acid to liberate arginine and fumaric acid. In
the last step, arginine is hydrolyzed by arginase to form
ornithine and urea. Ornithine again enters the urea cycle.
 The overall reaction of Urea cycle can be summarized as :
NH3 + CO2 + Aspartate  Urea + Fumarate
Genetic disorders associated with urea cycle:
 Hyper ammonemia type I due to carbamoyl phosphate
synthetase deficiency.
 Hyperammonemia type II due to ornithine transcarbamoylase
 Citrullinemia due to argininosuccinic acid synthetase
 Argininosuccinic aciduria due to argininosuccinase
 Hyperarginemia due to arginase.
4
*A-Answer
Note –Please provide keywords, short answer, specific terms, specific examples (wherever necessary)
***********