BMB 1203 Final Exam Notes on Medical Biochemistry II for Nursing

Week 5 Metabolism of Gylcogen
 Gluconeogenesis
 Glycogenolysis
 Hormonal regulation of glycogen metabolism

Week 6 Disorders/ diseases of carbohydrate metabolism
Week 7 Lipid metabolism
 Lipid digestion and absorption
 Fatty acid oxidation
 Ketone bodies: formation and clinical significance

Week 8 CAT 1

Week 9 Protein metabolism
Week 10  Protein digestion and absorption




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 Amino acid degradation
 Nitrogen excretion, Urea cycle

Week 11 Nucleotide metabolism

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 Purine biosynthesis e.
 Pyrimidine biosynthesis
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 Disorders of nucleotide metabolism
Week 12 CAT 2
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Integration and hormonal regulation of metabolism
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Week 13 Biochemistry of starvation
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Week 14 REVISION
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WEEK 15 EXAMS
WEEK 16
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Assessment
Two continuous assessment tests will be given. Both will contribute 15% of the total marks. Two
assignments will be given and will contribute 5% of the total marks. At least four Practicals will
be given and will contribute 10% of the total marks.


Distribution of marks:
Continuous Assessment Tests 30 Marks
End of Semester Examination 70 Marks




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,Required learning materials:
1. David L. N. & Michael M. C. (2008). Lehninger. Principles of Biochemistry, New York.
2. Stryer L. (1995). Biochemistry, 4th ed. WH Freeman, 0-7167-2009-4
3. Donald V. (2004). Biochemistry, 3rd ed. John Wiley & Sons, New York. U.S.A.
4. Garret R. H. & Grisham C. M. (1999). Biochemistry 2 nd ed. Saunders College Publishing,
Orlando. U.S.A.
5. Any general biochemistry textbook will be helpful too.


Overview of Metabolism

Thousands of chemical reactions are taking place inside a cell in an organized, well co-ordinated,
and purposeful manner; all these reactions are collectively called as Metabolism. The




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metabolism serves the following purposes:
1. Chemical energy is obtained from the degradation of energy rich nutrients.


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2. Food materials are converted into the building block precursors of cellular macromolecules.
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These building blocks are later made into macromolecules, such as proteins, nucleic acids,
polysaccharides, etc. Biomolecules required for specialized functions of the cell are synthesized.
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3. Metabolic pathways are taking place with the help of sequential enzyme systems. These
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pathways are regulated at three levels:
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a. Regulation through the action of allosteric enzymes, which increase or decrease the activity
under the influence of effector molecules.
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b. Hormonal regulation. Hormones are chemical messengers secreted by different endocrine
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glands.
c. Regulation at the DNA level; the concentration of the enzyme is changed by regulation
at the level of synthesis of the enzyme.
Types of Metabolic Pathways
A. Catabolic (degradation) pathways, where energy rich complex macromolecules are
degraded into smaller molecules. Energy released during this process is trapped as
chemical energy, usually as ATP.
B. Anabolic (biosynthesis) pathways. The cells synthesize complex molecules from simple
precursors. This needs energy.

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,C. Amphibolic pathways are seen at cross-roads of metabolism, where both anabolic and
catabolic pathways are linked.
Stages or Phases of Metabolism
The degradation of foodstuffs occurs in three stages.
i. In the first stage, digestion in the gastrointestinal tract converts the macromolecules into small
units. For example, proteins are digested to amino acids. This is called primary metabolism.
ii. Then these products are absorbed, catabolized to smaller components, and ultimately oxidized
to CO2. The reducing equivalents are mainly generated in the mitochondria by the final common
oxidative pathway, citric acid cycle. In this process, NADH or FADH 2 are generated. This is
called secondary or intermediary metabolism.
iii. Then these reduced equivalents enter into the electron transport chain (ETC, or Respiratory




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chain), where energy is released. This is the tertiary metabolism or Internal respiration or
cellular respiration.



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METABOLIC PROFILE OF ORGANS
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The metabolic pattern or metabolic profile of different organs is different depending on its
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function. Moreover, the organs are able to adapt to metabolic alterations in fed state and
starvation. The storage forms of fuels are shown in Table 8.1.
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Calories are stored in the body as fat and glycogen. The approximate percentage of storage form
of energy (total fuel reserve) present in a normal human body is, fat 85%, glycogen 1%, and
proteins 14%. Fat stores are mobilized actively only on prolonged fasting, even though adipose
tissue fat is undergoing turnover on a daily basis. Caloric homeostasis is maintained regardless of
whether a person is well fed, fasting, or in a state of starvation. Similarly metabolic profile of
various organs and tissues change to adapt to physiological and pathological states, so that
caloric homeostasis is maintained unless extreme conditions set in. The reciprocal regulation of
glycolysis and gluconeogenesis is the major deciding factor in the flux of metabolic
intermediates through these pathways.
1. Brain
i. Although brain represents only 2% of adult body weight, it needs 10–20% cardiac output.

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, About 750 ml of blood circulates through the brain per minute. Neurons can survive only a
few minutes without blood supply. Occlusion of blood supply to brain causes unconsciousness
within 10 seconds.
ii. There is no stored fuel in the brain. Glucose, the preferred fuel for the brain, should be in
continuous supply. Glucose can freely enter the brain cells.
ii. The total consumption of glucose by brain is about 120 g/day (480 kcal). Thus, about 60%
of the total carbohydrate intake by the body is metabolized by the brain. Moreover, about
25% of the oxygen consumed by the adult body is due to glucose oxidation in brain. In
children, this may be as high as 50%.
iii. Brain under conditions of anoxia: In anoxia, the rate of lactate production by glycolysis




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rises to 5 or 8 times within one minute. The Pasteur effect is the brain's protection against
conditions of anoxia. Blood glucose level below 30 mg/dl is fatal.
v. Brain and acetoacetate: The brain is unable to utilize fatty acids as a source of fuel since the

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fatty acids complexed to albumin are unable to traverse the blood brain barrier. But, brain can
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effectively utilize acetoacetate. This is again a survival technique in diabetic and starvation
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ketosis.
vi. Brain and starvation: During starvation, a significant part (60-70%) of the energy
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requirement of the brain is then met by ketone bodies.
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vii. Under conditions of partial anoxia, the production of ammonia is increased. This is
immediately trapped as glutamine. The NH group of glutamine and glutamate can be used
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for synthesis of other amino acids.
2. Skeletal Muscle
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i. The skeletal muscle forms about 45% of the total weight of the body. About 0.5% muscle
weight is due to glycogen content. Following a meal, the muscle glycogen content increases
by about 1% of the total weight.
ii. Muscle metabolism after a meal: The uptake and storage of glucose by the skeletal muscle is
under the influence of insulin. Following a meal, the level of the glucose and insulin are high. So
glycogen synthesis is enhanced (Fig. 8.2). The resting muscle uses fatty acids as a major fuel
(85%).
Muscle metabolism during exercise: Muscle uses glycogen for short active spurts of activity.




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