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1. Write detail about b-oxidation of FA under following headings –

I. Definition II. Site III. Steps and IV. Energetics (E-feb 08, Aug 08)

Definition:

β–oxidation is defined as sequential removal of 2 carbon acetyl CoAmolecule form beta carbon from

carboxyl end.

Site of the pathway:

It occurs in the mitochondrial matrix of all type of tissue cells.

Significance of pathway:

β – Oxidation produces reducing equivalents. These reducing equivalentsproduce ATP

through ETC.

β – Oxidation is essential energy producing pathway during starvation.

Majority of Acetyl CoA produced during starvation form β – oxidation is convertedto ketone

bodies.

In starvation brain is solely dependent on ketone bodes for energy.

Reactions:The β – oxidation is divided in to 3 phages –

1. Activation of fatty acids:

Fatty acids are converted acyl CoA molecules outside of themitochondrion.

Transport of acyl coA into mitochondria:

The acyl co Amoleules travel inside the mitochondrion with the help ofcarnitine transporter.

2. Oxidation of acyl CoA; inside the matrix the acyl CoA under goesoxidation and produce 2 carbon

acetyl CoA molecules.

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The products of β – oxidation are acetyl CoA and 2 carbons less acylcoA molecule. The oxidation

proceeds until all carbons are removed from theactivated fatty acid. The acyl coA further under goes

1 – 4 reactions. If in the case of palmitoic acid (16C) total 8 cycles are occurred.

Energetics of β – oxidation for 16 carbon palmitoic acid:

Total NADH2 produced in one cycle = 1

Total FADH2 produced in one cycle = 1

Total cyclic reactions for palmitoic acid = 8

Total NADH2 produced in palmitoic acid oxidation = 8

Total FADH2 produced in palmitoic acid oxidation = 8

Total ATP’s produced from one molecule of Palmitoic acid = 131

Total number of ATP consumed for activation of FA = 2

Net ATP from one molecule of Palmitoic acid oxidation = 129

Regulation:

Energy reserves of the body is directly regulates the b-oxidation.

Duringthe starvation glucagon is induced, which in turn induces the lipolysis, whereas insulin

decreases the lypolysis.

Glucocarticoids, catacholamines are increases the lypolysis.

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2. Discuss TCA cycle under following headings –

I. Location II. Reaction and III. Energetics (E-Aug 04, Feb 09, Aug 11, SN-

Apr 01))

It is discovered by Sir. Hans Krebs, hence called as Krebs cycle, and also called as Tricarboxylic acid

cycle/ Citric acid cycle:

Importance:

It is central and important pathway for all metabolisms.

If is most important pathway in energy metabolism.

The aerobic end product of glycolysis, namely pyruvate is precursor molecule for TCA cycle,

and it is oxidized to CO2 and H2O.

It produces reducing equivalents NADH for oxidative phosphorilyation, and intermediaties

which is converted to essential molecules, hence it is amphibolic pathway – both catabolic

and anbolic reactions are takes place.

Site of Cycle:

It is occur in mitochondrial matrix of all cell types.

Reaction proper:

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Inhibitors of TCA cycle:

Fluoro acetate – it inhibits activity of aconitase

Arsenite – inhibits the action of a-KGDH

Malonate – it inhibits the activity of SDH

Physiological inhibitors:

ADP/ATP ratio, NAD/NADH ratio,

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3. Write an essay on chemistry, functions, deficiency manifestations and hypervitaminosis

state of vitamin A (E-Aug 10)

Common names: anti xerophalmic vitamin.

Chemical name: retinol (vitamin A- alcohol), retinal (vitamin A- aldehyde), retinoic acid (vitamin A-

acid).

Chemical structure: vitamin A consists of β-ionine ring and one isoprenoid side chain.

Biochemical functions:

The major functions of vitamin A are carried by aldehyde form:

1. Vision: George wald first elucidated the visual pathway in retinal hence the name wald’s visual

cycle.

Wald’s visual cycle:

The retina contains rods and cones. Rods meant for dim light vision and cones meant for bright light

and clear vision. Rods contain visual purple called rodopsin, and cones contain 3 visual pigments

called porphyropsin for red colour, iodopsin for green, and cyanopsin for blue color. All these

pigments undergo the same pathway to generate nerveimpulse.

Rodopsin is made up of protein part opsin and nonprotein part 11-cis-retinal. When light strikes the

pigment divided into two parts opsin andall-trans-retinal. In the conversion of 11-cis-retanl to all-

trans-retinal thereis generation so many intermediates namely prelumirodopsin,lumirhodopsin,

metarhodopsini, 2, 3, and finally to all-trans retinal andopsin. Among which metarodopsin 2 is

important because it activates theinactive transdusin. The activated transdusin activates the

inactivephosphodiesterase. The activated phosphodiesterase degrades the cyclicGMP to linear form,

which is important for opening of sodium channel. So,a dieresis in cGMP leads to closing of channel

and finally generation ofAP.

The all-trans-retinal is generated in the retina is partially converted to11-cis-retinol by retinal

isomerase. The most of all-trans-retinal transportedto liver and converted to 11-cis-retinal by two

liver enzymes, namelyalcohol dehydrogenase, and isomerase.

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Other functions:

1. Alcohol and acid forms of vitamin A acts as steroid hormone andcontrols the cell growth and

differentiation.

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2. retinyl esters are necessary for synthesis of glycoproteins,mucopolysaccharde and hence it

necessary to maintain properhealthy epithelium.

3. Retinol and retinoic acid are involved in synthesis of transferritin.

4. It is involved in immunity.

5. Involved in cholesterol synthesis.

6. β-Carotene is acts as antioxidant at stops the oxidative reactions.

Sources:

1. Animal sources: organ meats (liver, kidney), egg yolk, milk, cheese,butter. Fish liver oils contain

more amount of vitamin-A.

2. Plant sources: green leafy vegetables, carrots, spinach,amaranthus, pumpkins, mango, and

papaya.

RDA: RDA represented as IU, RE etc,

1 RE (retinol equivalent) = 1 microgram of retinol

= 6 micrograms of β-carotene

= 3.33 of retinol

= 10 IU of β-carotene.

Deficiency of vitamin-A:

The deficiency of vitamin –A is unusual, and is related to vision, growth.

The primary affected organ is eye; the features are as follows –1. The first symptom of deficiency is

nictolopia (night blinded ness).

2. In severe deficiency leads to epithelial degeneration and conditioncalled xerophalmia (dryness of

conjunctiva and corneas), and finallyleads to keratization of epithelial tissues of lacrimal glands.

3. If xerophthalmia persists long time it leads to keratomalacia(ulceration and degeneration of

cornea).

4. Other manifestations of vitamin are retardation of growth,degeneration of germinal epithelium of

gonads, keratization ofepithelial tissues, and formation of urinary stones.

Hypervitaminosis

Excessive intakes lead to accumulation beyondthe capacity of binding proteins, so that unbound

vitaminA causes tissue damage. Symptoms of toxicity affectthe central nervous system (headache,

nausea,ataxia, and anorexia, all associated with increased cerebrospinalfluid pressure), the liver

(hepatomegaly withhistologic changes and hyperlipidemia), calcium homeostasis(thickening of the

long bones, hypercalcemiaand calcification of soft tissues), and the skin (excessivedryness,

desquamation, and alopecia).

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4. Write short notes on:

a. Define and classify polysaccharides with examples

Polysacchardies are the polymers of sugar units. Based upon the subunits involved they can divided

into homopolysacchardes and heteropolysacchardides

Homopolysaccharides: they are polymers single type of sugar molecules.

E.g. Starch – it is a homopolymer of glucose and abundantly found in plants such as cereals,

potaotes, legumes etc. called a glucosanor glucan. it has two main constituents, they are amylose

(15–20%), which has a nonbranchinghelical structure; and amylopectin(80–85%), which consists of

branched chainscomposed of 24–30 glucose residues united by 1 → 4linkages in the chains and by 1

→ 6 linkages at thebranch points.

Glycogen – it is quite same as starch, but it possess more complex branching than starch

Cellulose – it is a polymer of glucose and the glucose molecules are held by beta glycosidic bonds

Inulin – it is polymer of fructose, it is used in measuring GFR

Heteropolysaccharides: these are made up one 2 or more different type of sugar molecules. E.g.

Hyaluronic acid - , chondroitin sulphate, heparin, dermatan sulphate etc.

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b. Define and classify enzymes with examples (SN-Apr 2001)

In early days dnzymes are classified and named according to their type of reaction catalyzed,

followed by the suffix -ase. For example, dehydrogenases remove hydrogen atoms,

proteaseshydrolyze proteins, and isomerasescatalyze rearrangements in configuration. International

union of biochemistry and molecular bilogy suggested the system of nomenclature of enymes. It is

complex but unamibuous and internationally accepted.

As per thissystem enzyme are represented as EC (enzyme class) number with 4 digigts

Firt digit represent the class, second for the subclass, third for sub-sub class, and fourth represents

specific enzyme in list

The enzymes are classified major classes

1. Oxidoreductases – these class of enzymes catalyze oxidations and reductions

AH2 + B A + BH2

Eg: alcohol dehydrogenase, oxidases, reductases

2. Transferases– these class of enzymes catalyze transfer of moieties between substrate such

as glycosyl, methyl, or phosphoryl groups

A-R + B A + B-R

Eg: hexokinase, transaminase

3. Hydrolases– these class of enzymes catalyzehydrolytic cleavage of C—C, C—O, C—N, and

other bonds by adding of water

Eg: Acetyl choline + H2O Choline + Acetate catalysed by Acethyl choline esterase

4. Lyases – These class of enzymes catalyze cleavage of C—C, C—O, C—N, and other bonds by

atom elimination, leaving double bonds.

Eg: Frucsotse-1,6bisphosphate Glyceraldehyde -3-phosphate + DHAP by aldolase

5. Isomerases – these class of enzymes catalyze geometric or structural changes within a

molecule

Eg:Recemases, epimerase, cis-trans isomerases

6. Ligases -these class of enzymes catalyze the joining together of two molecules coupled to

the hydrolysis of ATP)

Eg: Acetyl CoA carboxylase

Acetyl CoA + CO2 + ATP Malonyl CoA + ADP +Pi

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c. Protein Energy Malnutrition(SN-Apr 01, Feb 08,11)

Disorders of malnutrition commonly manifested as Protein energy malnutrition (PEM). PEM is wide

spread nutritional problem in developing world and is mainly affecting school going children. There

are two major types of malnutritional diseases,

Marasmus: This is due to malnutrition of carbohydrates primary to proteins. Marasmus means to

waste

Kwashiorkor:This is due to the malnutrition of proteins. Kwashiorkor means sickness the older child

gets, when the next child is born

The differences between these two malnutrition conditions as tabulated

Marasmus kwashiorkor

Age of onset Below one year 1-5y

Growth retardation of child Marked Severe

Attitude Irritable and fretful Lethargic and apathetic

Appearance Shrunken skin and bones, dehydrated

Edema on face & limbs

Appetite Normal anorexia

Skin Dry & atrophic Crazy pavement dermatitis

Hair No change Sparse, soft & thin

Other Watery diarrhoea, weakness

Angular stomatitis, cheilosis, watery diarrhea, muscle wasting

Serum albumin 2-3g < 2g

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d. Acute Intermittent Porphyria (SN-apr01, SN-feb06)

It is one of the major disorders in heme synthesis. It is an inherited autosomal dominant trait

The enzyme PBG-deaminase involved in the conversion of porphobiliogen to uroporphyrinogen.

The levels of ALA and PBG are elevated in blood and urine. Fresh urine is colorless, but on standing it

become colour due to photooxidation of PBG to porphobilin. Because this reason urine sample

should collected freshly and transported in dark colour bottle

Patients have acute abdominal pain. In some cases neurological symptoms like sensory and motor

disturbances, agitation ad confusion.

Female have less severe manifestations than male, since female sex hormones have a stimulatory

effect on ALA synthase

Treatment: starvation, carbohydrate rich diet, drugs like barbiturates

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e. Role of cytochromes in ETC

All cytochromes present in ETC components are hemoproteins and all except Cytochrome oxidase

are anaerobic dehydrogenases.Eg: Cytochrome b, cytochrome C1 and Cytochrome

Complex III/Cytochrome reductase: it is a cluster of iron sulphur proteins and contains cytochrome b

and cytochrome c1 and these both contain heme as prosthetic group. During the electron transfer

the iron in heme group shuttles between Fe3+ and Fe2+. The free energy change is -10 kcal/mol and

4 protons are pumped out

Cytochrome C: it contains one heme as prosthetic group. It collects electrons from complex II and

transfers them to complex IV

Complex IV/Cytochrome oxidase: it is a cluster of protein and contain cytochrome a and cytochrome

a3.and both these proteins contain two heme and two copper ions. It is tightly bound to

mitochondrial inner membrane. Four electrons are accepted from cytochrome cyt c and passed on

to molecular oxygen. And 2 protons are pumped out to the inter membrane space

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f. Comparison between prokaryotic and eukaryotic cells

The anatomical and physiological differences between prokaryotic and eukaryotic cells are tabulated

as follows –