Biomolecules

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Synopsis

Living bodies are built up with biomolecules. The sequence that relates biomolecules to living organism is as follows.

Biomolecules → organelles → cells → Tissues → organs → living organism

Some important biomolecules are carbohydrates, proteins, nucleic acids, lipids, vitamins and hormones.

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Cell-energy-Photosynthesis

The basic structural and functional unit of living organism is the "cell". Molecules like those of glucose undergo oxidation by means of enzymes and liberate energy. The reaction which has Gibb's energy change (Δ G) greater than zero is

called endergonic reactions. The reaction which has Gibbs energy change $$(\Delta G) less than zero is called exergonic reactions. Ex :- Some metabolic processes (ΔG>0) in human body take place by

coupling with the exergonic reaction like the conversion of ATP to ADP. The process, in which the green parts of plants absorb sunlight to prepare

glucose and oxygen from CO2 and H2O is called photo synthesis.

6CO2+6H2O+2880KJ−→−−−−SunlightC6H12O6+6O2

Depending on the nature of plants and the reaction type, glucose is converted to disaccharides and polysaccharides like starch,cellulose (or) proteins (or) oils. Photosynthesis takes place in the presence of light followed by dark reaction which does not need light. Here, ATP undergoes hydrolysis and carries the dark reaction with the energy liberated from its hydrolysis. ATP−→−−−−−−31kJ/molADP−→−−−−−−31kJ/molAMP−→−−−−−−14kJ/molA

The following reaction takes place in the respiration process where animals and plants release energy.

C2H12O6+36ADP+36H3PO4+6O2→6CO2+36ATP+42H2O

Carbohydrates

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FORMULA

Classification

General formula Cn(H2O)m

They can be better described as optically active polyhydroxy aldehydes (or) ketones (or) the compounds which yield them on hydrolysis. Most of them are similar to sugar in taste, and hence they are also known as Saccharides.

( Latin word for sugar is saccharum)

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FORMULA

Monosaccharides

These cannot be hydrolysed to simple compounds. Depending upon the total number of carbon atoms in monosaccharides and on nature of functional groups present (aldehyde or ketone), the terms for their classification are as follows:

No. of

Term

Carbon Atoms

Aldose

General

Ketose

3 Triose Aldotriose Keto triose

4 Tetrose Aldotetrose Keto tetrose

5 Pentose Aldopentose Keto pentose

6 Hexose Aldohexose Keto hexose

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Disaccharides

Disaccharide: A disaccharide on hydrolysis gives 2 monosaccharide units

Ex:- Sucrose, Maltose and Lactose

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Oligosaccharides

These undergo hydrolysis and yield 3 to 10 monosaccharide units. Example: A disaccharide on hydrolysis gives two simple monosaccharide units.

C12H22O11+H2O−→−H+C6H12O6+C6H12O6

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Polysaccharides

These undergo hydrolysis and give more than 10 monosaccharide units. Example:Starch and cellulose-General fomula (C6H10O5)n

(C6H10O5)n+nH2O−→−−−−−303k,H+2−3atmnC6H12O6

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Preparation of glucose

Glucose is known as dextrose because it occurs in nature as the optically active dextro rotatory isomer. Glucose is prepared in the laboratory by acid hydrolysis of cane sugar in alcoholic solution.

C12H22O11+H2O−→−H+C6H12O6+C6H12O6

Sucrose Glucose Fructose

It is obtained in large scale by the hydrolysis of starch with dil. H2SO4(or) HCl

at 2-3 atm pressure & 393 K temp.

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Properties & structure elucidation of glucose

Molecular formula of glucose is experimentally found as C6H12O6

Acylation of Glucose with acetic anhydride gives glucose penta acetate. Hence, Glucose molecule contains 5 'OH' groups

Glucose reacts with NH2OH and one molecule of HCN and forms monoxime

and cyanohydrin respectively. These reactions suggest the presence of

one carbonyl group. Glucose reduces Tollen's reagent to metallic silver and also reduces Fehling's solution to reddish brown cuprous oxide and itself gets oxidised to gluconic acid. These reactions suggest that the carbonyl group is an aldehydic group. On oxidation with HNO3 both glucose and gluconic acid form saccharic acid, a

dicarboxylic acid. It suggests the presence of primary alcoholic

group (−CH2OH) Glucose on prolonged heating with HI gives n-hexane. It suggests the linear arrangement of all the 6 carbon atom in glucose. D-Glucose on reaction with excess of phenyl hydrazine ( 3 moles of phenyl

hydrazine per mole of glucose), forms a dihydrazone known as osazone.

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DIAGRAM

Properties and Structure Elucidation of glucose

With dil. NaOH solution, glucose under goes reversible isomerisation and gives a mixture of D-mannose and D-fructose. This reaction is known asLobry de Bruyn-Van

Ekenstein rearrangement.

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Cyclic Structure of glucose

The open chain structure of Glucose proposed by Baeyer explained most of its properties. But it could not explain the following. Glucose does not give schiff's test and does not react

with NaHSO3and NH3, inspite of presence of -CHO group

Pentacetate of glucose does not react with −NH2OH group indicating

absence of -CHO group

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Mutarotation of glucose

When glucose was

crystallised from a concentrated solution at 30oC, it gives α - form with melting

point 146oC and [α]D=+111o. But glucose crystallised from a hot saturated

aqueous solution at a temperature greater than 98oC, given β-form with a

melting point 150oC and [α]D=+19.2o. These two forms of glucose differ in the

stereochemistry at C-1 These two α and β forms, when separately dissolved

in water and allowed to stand, their specific rotation gradually change and

reach to a specific constant value 52.5o. This spontaneous change in

specific rotations of an optically active compound is called mutarotation.

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Alpha and Beta glucose

The one with OH group on the right side is known as α−D-Glucose and that

with -OH group on the left asβ−D −glucose. The two forms are not mirror

images of each other that are not super imposable hence are not enantiomers. The groups projected to the right in Fischer projection are written below the plane of the ring in Howarth structure and those on the left are written above the plane of the ring.

The α and β forms are confirmed by the reaction of glucose, with methanol in

the presence of dry HCl to give methyl α−D - Glucoside and methyl β-D-

Glucoside.

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Fructose

Fructose is a ketohexose. It is also called Laevalose and fruit sugar. Preparation C12H22O11+H2O→C6H12O6+C6H12O6

Sucrose Glucose Fructose

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Structure of fructose

It has the molecular formula C6H12O6.

Its chemical properties suggest that if C-2 is C=O group and all six carbons in

a straight chain similar to glucose open chain structure. It is laevorotatory compound and belongs to D-series. D-(-) fructose. Its structure is To explain all of fructose properties it is suggested with two cyclic structures

i.e. α−D−(−)−fructofuranose and β−D−(−)−fructofuranose.

The stereochemistry of all sugars is determined with respect to D-or L-

glyceraldehyde.

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Oligosaccharides

The disaccharides are composed of 2 molecules of monosaccharides. These on hydrolysis with dil acids(or) enzymes yield two molecules of either the same (or) different monosaccharides.

C12H22O11−→−−H3O+C6H12O6+C6H12O6

In disaccharides, the two mono- saccharides are joined together by glycosidic linkage(-O-) A glycoside bond is formed when hydroxy group of the hemiacetal carbon of one monosaccharide condenses with a hydroxy group of another monosachharide, to give -O-bond.

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Surcose

It is the most common disaccharide present in plants. It is non reducing. It's obtained mainly from sugarcane (or) beetroot.

It is dextro rotatory, [α]D=+66.5o.

Even though sucrose is a dextro rotatory, on hydrolysis with dil.acids(or)enzyme invertase, it gives equimolar mixture of dextro rotatory glucose and laevo rotatory fructose.

As the laevo rotation of fructose (−92.4o) is more than dextrorotation of

glucose (+52.5o), the mixture is laevorotatory.

In the hydrolysis of sucrose there is a change in the sign of rotation from 'd' to 'l'. This change is known as inversion and the mixture is called invert sugar. 1. α−D Glucose and β−D fructose units are linked through α,β-glycosidic

linkage between C-1 of α−D−Glucose and C-2 of β−D−fructose.

2. Glucose unit is in pyranose and fructose unit is in furanose form.

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Maltose

It's obtained by partial hydrolysis of starch by diastase enzyme present in Malt.

2(C6H10O5)n+nH2O−→−−−−DiastasenC12H22O11

Starch Maltose It's a reducing sugar. On hydrolysis, one mole of maltose yields 2 moles of D-Glucose.

The two α-D-glucose units in maltose are linked through a α -Glycosidic

linkage between C-1 of one unit and the C -4 of another. Both the glucose units are in pyranose form.

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Lactose

Lactose occurs in milk and also called as milk sugar. Hydrolysis of Lactose with dil acid yields equimolar mixture of D-Glucose and D-Galactose. It's a reducing sugar

The hydrolysis occurs in presence of enzyme emulsin.

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Polysaccharides

Carbohydrates containing large number of monosaccharide units joined through glycosidic linkages are called polysaccharides.

They have general formula (C6H10O5)n

Ex : Starch, cellulose, dextrin, glycogen etc.

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Starch

Starch is a white amorphous powder with no taste or smell. It is almost insoluble in cold water,but relatively more soluble in boiling water. Starch is easily hydrolysed in saliva by an enzyme amylase. Its solution gives blue colour with iodine solution in cold but the colour disappears on heating On hydrolysis it forms D-glucose. When treated with enzyme, diastase, it yields maltose.

2(C6H10O5)+nH2O→nC12H22O11

Starch Maltose Starch is not oxidised by Tollen's reagent or Fehling's solution and it does not form osazone. These facts indicate that hemiacetal hydroxy groups of glucose units at c-1 are in glycosidicform. Glycosides are acetals in which the anomeric hydroxy group has been replaced by an alkoxy group. Glycosides are carbohydrate derivatives obtained by the replacement of anomeric -OH by some of the substituent and are termed -O, N-, S-, glycosides etc, depending on the atom attached to the anomeric carbon. Starch is a mixture of two polysaccharides. (i)Amylose (ii)Amylopectin. Natural

starch contains 10-20% of amylose and 90-80% of amylopectin.

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Cellulose

Cellulose is formed in the photo synthesis process.

It is a polysaccharide composed of large number β- D-glucose,units joined

by β(1,4) glycosidic linkages.

In the hydrolysis of cellulose finally, D-glucose is formed. Cellulose is a colourless amorphous solid. It is mainly linear and its individual strands align with each other through H-bonds,because of which it becomes rigid and cell wall material. It does not reduce Tollen's reagent (or) Fehling's solution and does not form

osazone.

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Glycogen

The carbohydrates are stored in animal bodies as glycogen. It is also called animal starch because its structure is similar to amylopectin. It is present in liver, muscles, and brain.

It is also present in yeast and fungi.

Amino acids

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Synopsis

1. Amino acids are organic compounds

containing both amino group (−NH2) and carboxylic acid (-COOH) i.e. they

are di-functional. 2. The bond between two amino acid molecules is peptide bond or amide bond, and the resultant is known as di-peptide. 3. The peptide chain extended to three amino acid molecules is tri-peptide and extended to four amino acid molecules in tetra-peptide, and soon. 4. The peptide chains with less than 50 amino acids are usually called Poly peptides and the polypeptides that contain more than 50 amino acid units are proteins. 5. Depending on the location of the amino group on carbon chain, that contains the carboxylic acid functional group, amino acids are classified as ,b,g and d etc. 6. The amino acids, which can not be synthesized,in the body but can only be

supplied to the body through diet, are called essential amino acids.They are valine, Leucine, Isoleucine, Arginine, Lysine, Threonine, Methionine, Phenylalanine,Tyrptophan and Histidine. 7. The amino acids, which are synthesized in the body, are known as non essential aminoacids. 8. The general formula of α -amino acids is

9. Though there are more than 700 different amino acids that occur naturally, only 20 of them are important in the formation of proteins. 10. All these 20 amino acids are amino acids. And all of them except proline contain primary amino group. 11. Proline is a secondary amine

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Side chains

Amino acids exist as zwitter ion, showing acidic

character due to group N+H3 and basic character due to COO− group.

Amino acids with non polar side chain are :

1. Glycine H Gly G

2. Analine - CH3 Ala A

3. Valine −CH(CH3)2 Val V

4. Leucine −CH2−CH(CH3)2 len L

5. Iso Leucine -CH−CH2−CH3 Ile I

6. Phenylalanine -CH2−C6H5 Phe F

7. Proline

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Side Chains

Amino acids with acidic side chain are : If -COOH groups are more it is acidic. 1. Glutamic acid -CH2−CH2−COOH Glu E

2. Aspartic acid -CH2−COOH Asp D

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Physical properties of amino acids

The simplest amino acid is glycine NH2CH2COOH

Its IUPAC name is 2 amino ethanoic acid

The physical properties of α amino acids are, a) They are generally

colourless crystalline solids. b) They are highly polar and in aqueous solution they form zwitter ions. c) In acidic solution, they form +ve ion and in basic solution they form ve ion. d) At a particular PH, the dipolar ion acts as neutral ion (iso electronic point)

e) Except glycine, all other naturally occurring α amino acids are optically

active due to asymmetry at α Carbon.

f) Most of the naturally occurring amino acids are with L-Configuration

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Physical Properties

At a particular pH, the dipolar ion of amino acid (zwitterion) acts as neutral ion and does not migrate to cathode or anode in electric field. This pH is known

as iso electric point of the amino acid The iso electric point depends on different groups present in the molecule of the amino acid. In neutral amino acids the pH range is 5.5 to 6.3 At iso-electric point, amino acids have least solubility. So, it is used in the separation of different amino acids obtained from the hydrolysis of proteins. Except, glycine all other naturally occurring -amino acids are optically active

due to a symmetry at α carbon. So, α -amino acids exist in D and L forms.

In Fischer projection, formulae carboxyl group is at the top and in the D-form

amino (−NH2) group is written on the right and in L form on the left side.

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FORMULA

Polypeptides

A dipeptide called aspartame being 160 times sweeter to srcrose is used as substitute for sugar.

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Proteins

Their structures are studied at four different levels as, 1. Primary 2. Secondary 3. Tertiary and 4. Quarternary structures PRIMARY STRUCTURES: For a given polypeptide, amino acids are linked with each other in a specific sequence. This is considered as primary structure of that polypeptide. Any change in this sequence produces a different protein. Primary structure indicates the location of disulphide bridges if present. SECONDARY STRUCTURE: It explains the shape of poly peptide chain and describes the conformation of segments of the back bone chain of a protein.To minimise the energy, a protein chain tends to fold in a repeating geometric structure. This is based on (i) the regional planarity about each peptide bond (ii) maximising the number of peptide groups that engage in hydrogen

bonding. (iii) sufficient separation between nearby R groups to avoid steric hindrance and repulsion of like charges. TERTIARY STRUCTURE: It indicates the three dimensional arrangement of all the atoms in the protein.The tertiary structure is understood from its primary structure and further folding of secondary structure in fibrous and globular shapes. The forces that stabilise secondary and tertiary structures are H-bonds, disulphide linkages,vander Waals forces and electrostatic forces of attraction. QUARTERNARY STRUCTURE: Proteins that have more than one peptide chain are known as oligomers. The individual chains are called subunits. The subunits are held together by hydrogen bonding, electrostatic attractions, hydrophobic interactions etc. Quarter- nary structure explains the way the sub units are arranged inspace. i.e. Proteins have four levels of structure: i. Primary: Amino acid sequence.

ii. Secondary: Shape of back bone.Examples: α - helix, β - pleated sheet.

iii. Tertiary: Folding of helix. Examples:Folded helix in a globular protein. iv. Quaternary: Interactions between two or more protein molecules. EXAMPLES:The association of four globins inhemoglobin. Peptides are formed by the condensation of two or more same or different amino acids. They contain peptide linkage CO NH-. Proteins are complex long polymers of amino acids linked by CO NH- bonds.

The most energetically stable state of a protein is called its native state.

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Denaturation of proteins

The process which changes the physical and biological properties of a protein is called denaturation. The denaturation is caused by changes in pH, temperature, presence of some salts or certain chemical agents. Denaturation is carried out by a) Changing the pH b) Adding reagents c) Adding detergents d) Heating Denaturation can be carried out with out effecting the primary structure of protein

Denaturation may be reversible or irreversible. The coagulation of egg white on boiling is an irreversible denaturation. Renaturation is the reverse of denaturation.

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Enzymes

Enzymes are biological catalyst produced by living cells which catalyze the biochemical reactions. These are simple or conjugated proteins. These are highly specific. The non protein component of enzyme molecule is called a prosthetic group. The prosthetic group that is covalently bonded with the enzyme component is called cofactor. The prosthetic groups attached to the enzyme at the time of reaction are

called coenzymes.

Vitamins

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Synopsis

Vitamins are naturally occurring low molecular weight carbon compounds, which are essential dietary factors. Their absence in the human body causes deficiency diseases or disorders. They participate in the production of co-enzymes and also in the regulation

of biochemical processes.

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Classification of vitamins

Vitamins are classified into two broad groups.These are (a) Fat soluble vitamins (b). Water soluble vitamins FAT SOLUBLE VITAMINS: Vitamins A,D,E and K are fat soluble. Liver cells are rich in fat soluble evitamins (Vitamins A& D) WATER SOLUBLE VITAMINS: Vitamins C and B-complex are water soluble. These are present in much

smaller amounts in cells.

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EXAMPLE

Important vitamins

Vitamin D2 is also called sunshine vitamin. Since it is obtained by sunlight

irradiation of ergosterol present in oils and fats Vitamin B1 is a derivitive of pyrimidine as well as such it conforms both N and

S

Vitamin B12 contains both N and P

Pro vitamins are the biologically inactive compounds which can be easily converted into biologically active vitamins B-carotene is provitamin A

Nucleic acids

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Synopsis

1. Nucleic acids are biologically significant polymers of nucleotides with poly phosphate Ester chain. 2. These are present in all living cells. 3. They direct the synthesis of proteins and are responsible for the transfer of genetic information i.e hereditary. 4. Nucleo-proteins are formed by combining proteins with nucleic acids

.Nucleo-proteins = protein + Nucleic acid

5. Proteins have polyamide chains. 6. The repeating units of nucleic acids are called nucleotides. 7. Types of Nucleotides ( Nucleic acid ) are a) Ribonucleic acid ( RNA)

b) Deoxyribonucleic acid ( DNA )

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Chemical composition

1. DNA+Hydrolysis→Deoxyribose+phosphoricacid+purine/pyrimidine base

2. RNA+Hydrolysis→ribose+ phosphoric acid + purine / pyrimidine base

3. Ribose (or) de-oxyribose is a pentose sugar a) α−D− ribose present in RNA

b) α−D− deoxyribose present in DNa

4. Pyrimidines and purines are nitrogen containing hetrocyclic bases 5. Pyrimidinen bases are

a) Thymine (T) C5N2H6O2

b) Cytosine (C) C4N3H5O

c) Uracil (U) C4N2H4O2

6. Purine bases are

a) Adenine (A)C5N5H5

b) Guanine (G) C5N5H5O

7. a) Thymine contains two oxo and one methyl groups b) cytosine contains one amino and one oxogroups c) Uracil contains two oxogroups d) Adinine contains one amino group e) Guanine contains one amino and oneoxogroups.

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Chemical composition

DNA contains A, G,T and C RNA contains A , G, U and C

Thymine is not present in RNA.

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Nucleoside

1. N- Glycosides are called Nucleosides.

2. Nucleoside = Nucleic acid bases + pentose sugars

3. The bond present between sugar and base is called N-Glycoside bond. 4. This bond is formed between first numbered nitrogen of pyrimidine and first carbon of sugar. 5. This bond is formed between ninth numbered nitrogen of purine and first carbon of sugar. 6. These are called as adenosine . guanosine ,cytidine , thymidine and uridine, when they contain adenine, guanine, cystosine, thymine and uracil

respectively.

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Nucleottide

Nucleotide = Base + Sugar + phosphate

1. Base is nothing but purine ( or ) pyrimidine 2. Base bonded with sugar at 1I carbon.

3. Phosphate group bonded with sugar at 3I or 5I carbons.

4. 1 to 3 phosphate groups may attach with sugar.

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Nucleic acids

1. Nucleic acids = Nucleotide sub-units linked by phosphate diester bonds.

2. AMP , ADP , ATP , d AMP , d ADP etc are called Nucleotide sub-units. 3. These nucleotides connected by mono , di (or) tri phosphate groups at 5I

OH of one nucleotide.

4. A Nucleic acid contains one nucleotide and 3I OH of another nucleotide.

a) Phosphate diester bonds which links two sugar rings.

b) α - Glycoside bond which links Sugar and base.

5. a) A nucleotide contains two nucleotide sub-units called dinucleotide. b) A nucleotide contains 3 10 subunits is called Oligonucleotide c) A nucleotide containing many subunits is called Polynucleotide 6. DNA and RNA are Polynucleotides. 7. A nucleic acid chain is abbreviated by one letter code with 5 end of the chain.

8. The abbreviated ACG trinucleotide shown as A C G.

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DIAGRAM

DNA-Double helix

1. It explains base equivalence and duplication of DNA. 2. All species contains

a) A = T b) C=G

c) no. of purines = no. of pyrimidines (A+G)=(C+T) 3. The AT / GC ratio varies from species to species Ex . a) In human

being AT/GC=1.52/1

b) In E. coli AT/GC=0.93/1

4.It is composed of two right handed helical polynucleotide strands. 5. The two strands are anti parallel with each other. 6. 5 3 phospho diester linkages run in opposite direction. 7. The base groups are present inside and perpendicular with the axis.

8. The two stands are held together by hydrogen bonds due to A=Tand G=C

9. Always A pairs with T and G pairs with C only. 10. A forms two hydrogen bonds with T. G forms three hydrogen bonds with C A does not form Hydrogen bonds with C G forms only one hydrogen bond with T. 11. The length of all hydrogen bonds are similar 12. DNA strands are twisted but base pairs are planar and parallel with each other. 13. Primary structure of nucleic acids explains order of bases. 14. Secondary structure gives double helix. 15. The stability of helix is due to 16. Hydrogen bond between A=T and G=C

17. Hydrophobic interactions between bases. 18. The diameter of double helix is 2 nm.

19. The length of one complete turn (3600) is 3.4nm.

20. The DNA rotates at both sides i.e right hand side or left hand side.

21. The right hand helices is more stable and is called α conformation.

22. At melting temperature, DNA separates into two strands, called as melting. 23. When the melted DNA is cooled, the strands hybridise. This is called Annealing. 24. In the secondary structure of RNA , helices are present but only single

stranded.

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Protein synthesis Translation

1. The process by which the genetic message in DNA that has been passed to mRNA is decoded and used to build proteins is called translation. 2. During the transcription, the DNA language changes to language of Amino acids. 3. The sequence of three bases is called codon. 4. The amino acid, specified by each three bases sequence, is called the

genetic code. 5. Total of 64 codons and 20 amino acids are present. 6. One amino acid may have more than one codon. Ex : CUU and CUC both code for leucine. 7. A difference of simple base in the DNA molecule causes a change in the amino acid sequence which leads to mutation. 8. Every t RNA molecule has an amino acid attachment site. 9. The genetic code has four important features. a. it is universal b. it is commaless c.it is degenerate

d.The third base in the codon is not always specific.

Lipids

1

Synopsis

Lipids are naturally occurring carbon compounds related to fatty acids and include esters of fatty acids or substances capable of forming such esters. Lipids are insoluble in water but soluble in organic solvents like chloroform, ether, benzene etc. The common lipids are oils, fats, waxes, steroids, terpenes, phospolipids & glycolipids. These are all stored in adipose tissues and are present in all organisms including viruses.

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Classification of lipids

Lipids are classified into three types: i. Simple lipids (homolipids) ii. Compound lipids (hetero lipids) iii. Derived lipids (compounds obtained from simple and compound lipids) Simple lipids are alcohol esters of fatty acids and include neutral fats and waxes. These are long chain, fatty acid esters of trihydric alcohol glycerol. These fatty acids contain even number of carbon atoms and are both saturated and unsaturated carboxylic acids Simple lipids are known as triglycerids (or) triacyl glycerols. Some of these are

solids while other are liquids at room temperature. Solids are known as fats

and liquids are known as oils.

Hormones

1

Synopsis

Hormones are molecules of carbon compounds, that transfer biological information from one group of cells to distant tissues or organs. Hormones are of animal (Human) origin and plant origin. Animal (or human) hormones are produced by specialized tissues in the body in small amounts. These tissues are called the endocrine or ductless glands. Hormones are liberated directly into the blood stream and are carried from there to the remote tissues or vicera, called target organs. The hormones exert characteristic physiological effects on the target organs and also control metabolic activities. Plant hormones are called growth hormones. Hormones name indicates the stimulating action (in greek hormosin means to excite). Hormones are all generally proteins but not all of them are proteins.

In many cases, hormones act by influencing the enzymes.

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Classification of hormones

Hormones are classified into three groups on bases of their chemical structures. 1. Steroid hormones : These are produced by the adrenal cortex, testis and ovary. 2. Protein hormones : These are produced by pancreas, parathyroid, pituitary and the gastro internal mucosa. 3. Amino acid derivatives : These are produced by thyroid and adrenal

medulla.

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DIAGRAM

Structure

Steroid hormones are

compounds, whose structure is based on four ring network.

Three of these rings are 6-carbon rings and one is 5-carbon ring.

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