Almost are made up of one or more polypeptides,

Almostevery dynamic function of a living being depends on protein. More than 50% ofthe dry mass of most cells compose of protein.

Proteins are the moststructurally sophisticated molecules known, they are made up of one or morepolypeptides, and each folded into a specific three-dimensional structure. Themonomer of protein is amino acid, and proteins are constructed from same set of20 amino acids. Bond between amino acids is called a peptide bond.

Therefore apolymer of amino acids is called a polypeptide.            Amino acid is an organic moleculewith both an amino group and a carboxyl group. At the center of the amino acidis an asymmetric carbon atom called alpha-carbon. Surrounded by 4 differentpartners which are amino group, carboxyl group, hydrogen atom, and a variablegroup symbolized by R. R group is also known as the side chain, the physicaland chemical properties of the side chain determine the unique characteristicof a particular amino acid.

Hence affects its functional role in a polypeptide.Generally, there are two types of amino acid. Firstly, essential amino acid,which cannot be made by the body, and must be supplied by food. The second typeis non-essential amino acid which can be produced by the body, from theessential amino acid.

                        Proteinsare most abundant biomolecule with diverse function. Some of the functions arethey act as structural materials such as collagen and keratin. Besides thatproteins can act as specific carriers. Enzymatic proteins regulate metabolismby acting as catalyst, chemical agents that speed up chemical reaction.Proteins are also involved in all cell movements. For instance, actin, tubulin,and cytoskeleton protein. Other than that, proteins are also important fordefense. Thrombin and fibrinogen are blood clotting protein which prevent bloodloss when wounded.

Next, proteins are important for regulation. Insulin andglucagon are peptide hormones to regulate blood glucose level. Lastly, anotherfunction of protein is for transport. Hemoglobin is an example of protein whichacts as transport, it carries oxygen from tissues to lungs.                        Nucleicacids are macromolecules that exist as polymers called polynucleotides. Eachpolynucleotide consist of monomers called nucleotides.

In polynucleotide, eachmonomer has only one phosphate group, a five-carbon sugar, and nitrogenousbase. The main role of nucleic acid is to store information to make protein.There are two types of nucleic acid, deoxyribonucleic acid (DNA) andribonucleic acid (RNA). They enable living organisms to reproduce their complexcomponents from one generation to another. DNA directs RNA synthesis, andthrough RNA, controls protein synthesis. Gene consist of DNA, which belongs to the class ofcompounds called Nucleic Acids. The polymers of nucleic acid that made ofmonomers called Nucleotides.A nucleotide is composed of three parts :five-carbon sugar(pentose), nitrogen base, and one or more phosphate groups.

Polymers of nucleic acids are chains of nucleotides joined by condensationreactions.They are held together by covalent bonds between sugar of onenucleotide and the phosphate of another by phosphodiester bonds.Nucleic Acidact as information storage,information ransfer and energy transfer.There aretwo types of nucleic acid which are Deoxyribonucleic acid(DNA) and Ribonucleicacid(RNA) enable living oganisms to reproduce their complex components from onegeneration to the next.

DNA directs RNA synthesis and provides directons forits own replication.DNA made of two strands of nucleotides which form a doublehelix and found in cell’s nucleus.It stores hereditary information.Each nucleotide is composed of sugar-phosphatecovalently link to base which the base are Adenine (A),Thymine(T),Guanine(G)and Cytosine(C)..A polynucleotide has a sugar-phosphate backbone with variableappendages,the nitrogenous base.Moreover,DNA molecule that is composed of twostrands held together by hydrogen bonds between paired bases that is(A-T,G-C).The arrows indicate the polarity of two strands which runantiparallel to each other.

Besides,RNA is a single helix that transfersinformation from DNA to ribosomes.It also carries a protein recipe toribosome.Note that in RNA, Adenine pairs with Uracil (A-U).The type of nucleicacid are ATP called Adenine Tri-Phosphate and ADP called AdenosineDi-Phosphate. ATP is a single nucleotide that produced by cellular respirationand has high energy molecule.It act as transfers energy within cells.ADP is asingle nucleotide and has a lower energy than ATP.

It is a rechargeable energytransfer molecule and its cellular respiration converts ADP into ATP.Carbohydrates is the main source of energy for mostof living things in this world. Plant, animal and human really needcarbohydrate in their life. Carbohydrates, also known as saccharides or carbs,are sugars or starches. They consist of carbon, hydrogen, and oxygen atoms. Itis the major source of energy for almost all living things. Plants makecarbohydrate, including structural carbohydrates such as cellulose andenergy-storage carbohydrates such as starch.

Animals use carbohydrates as foodand many including humans store energy in a carbohydrate called glycogen.Carbohydrates has various function which is astructural components in cell membranes. For cellulose in the cell walls ofplants and many protists, while for chitin it is in the exoskeleton of insectsand other arthropods. Chitin is also can used as a surgical thread as  chitin had strong and flexible but it alsodissolves over time, thus allowing patients to avoid the painful removal ofstitches.

Thepurpose of chitin is to provide support for the organisms. The material allowsthe stability rigidity and flexibility. The body will considers chitin aforeign substance so it will reacts against it to remove it. There is an enzymecalled chitanase.

The chitanase function is to produced in our body to helpbreakdown chitin. Hydrolysis separates the individual chitin molecules fromeach other. Chitin also can be used for is in treating burn patients. Chitinhas a remarkable compatibility with living tissue, and has been looked at forits ability to increase the healing of wounds. When the chitin is applied tohuman wounds and surgical cloths, it accelerates the skin healing process.

Anacidic mixture of chitin, when applied to burns, also increase the healingprocess. When it use for the longest time, it can heal a third-degree buncompletely. It also has been shown to support the immune system during certainkinds of illness-blocking procedures.There are three groups of carbohydrates which ismonosaccharides, disaccharides and polysaccharides. Monosaccharides is thesimplest sugar with multiples of OH groups, Disaccharides is two monosaccharidescovalently linked ant for polysaccharides is polymer that consisting of chainsof monosaccharides or disaccharides unit. There are two basic compounds ofcarbohydrates which is aldoses and ketoses.

An aldose is a monosaccharide (asimple sugar) with a carbon backbone chain with a carbonyl group on the endmostcarbon atom, making it an aldehyde, and hydroxyl groups connected to all theother carbon atoms. A ketose is a ketone with two or morehydroxyl groups (-OH), where at least one of the hydroxyl group at each end.Ketoses are a type of monosaccharide, which are important fuel molecules andnucleic acid building blocks. Polysaccharides is a carbohydrates molecule which composed withlarge numbers of monosaccharide units, which can be hundreds to thousands unitsof monosaccharides and being connected by a bond named glycosidic bond. Thereare two types of glycosidic bonds which are 1-4 glycosidic bonds and 1-6glycosidic bonds, it depends on the carbon atoms that are bonded to each other.Characteristic of polysaccharides are large and complex, not sweet andinsoluble in water. The main function of polysaccharides are as storage formsof energy or as structuralmaterials. There are two types of polysaccharides which arehomopolysaccharides and heteropolysaccharides.

Homopolysaccharides which onlycontain one types of monomer. It can be linear homopolysaccharides and branchedhomopolysaccharides. In linear homopolysaccharides, the bond is named 1-4 glycosidic bonds whereas the branched homopolysaccharides is 1-6glycosidic bonds. Heteropolysaccharides are made out two or more differentmonosaccharides. The structure of the heteropolysaccharide has differentrepeating units.

 Heteropolysaccharides are complex structure compared tohomopolysaccharides. The repeating unit in heteropolysaccharides determines itschemical and physical properties.There are two types of polysaccharides act as storage which arestarch for plant and glycogen for animal.

Starch is the reservoir of energy inplant cells which is made of glucose(monomer)units. Starch can be found in the chloroplast as an insoluble granule. It is ahomopolysaccharides which made up of two components; amylose and amylopectin.Amylose is a linear chain structure formed by 1-4 glycosidic bonds. Because ofthe linear structure it increase the surface area for the storage function.While, amylopectin is a glucose polymer with mainly ?-1,4 glycosidic bond, but it also has branches which is formed by ?-1,6 glycosidic bond. This gives it moreopen structure and prevent helix formation. It also can easily be broken thanamylose because of its structure.

Glycogen is the polysaccharides storage for animals. It is mostlyfound in muscle and liver cells. In the liver cell, glycogen maintain theblood-glucose level in the human body. The structure of glycogen is alwaysbranched-chain of ?-D glucose. It has a-1,4 glycosidic bond and  a-1,6glycosidic bond. Glycogen is similar to starch exceptit is highly branched. As glycogen is so highly branched, it can bemobilised (broken down to glucose for energy) very quickly. It is broken downto glucose by the enzyme glycogenphosphorylase.

Starch and glycogen can be digested. To produce glucose,starch and glycogen must be hydrolyzed. These enzymesare known as ?-amylase and ?-amylase which attack glycosidicbonds.

?-amylase is an endoglycosidasewhich can hydrolyzed glycosidic bond anywhere along the chain to produceglucose and maltose. While ?-amylase is an exoglycosidasethat cleaves from non reducing end ofpolymer to produce maltose.The three types of structural polysaccharidesarecellulose (?-D-glucose)for plant, chitin (N-acetyl-?-D-glucosamine) for animal and peptidoglycan for bacteria cell walls.Cellulose is an organic compound which make plants have rigid cell wall, thusit withstand osmotic pressure.

It gives(mechanical/structural) support and strength to plant. The monomer of cellulose is ?-D-glucose. There bond in cellulose which is ?(1,4)glucose polymer form cellulose microfibrils.Microfibrils are very strong and rigid which give strength to plant cells. The ?-glycosidic bond cannot be easily broken down byamylase, but it needs a specific cellulase enzyme.Chitin is the component of theexoskeleton of invertebrates. The strength is similar to cellulose. Chitin is alinear homopolysaccharides of ?(1,4)-linked N-acetyl-D-glycosamine (NAG).

One of the function of chitinis; it can extends the shelf life of fruits and meats. Lastly, peptidoglycan isa major structural of cell wall for bacteria. It is also heteropolysaccharideswhich contain two alternating amino sugar; N-acetylglucosamine (NAG) andN-acetylmuramic acid (NAM). Gram staining is a method of staining bacteria.There are two types of gram staining; gram-positive bacteria has thickpeptidoglycan (cell wall) while gram-negative bacteria has thin peptidoglycan(cell wall). Lipid arebiological compound that consist of nonpolar group and have limited solubilityin water. But dissolve freely in organic solvents (chloroform or acetone).  Fats and oil are lipids and lipids exhibitgreater structural variety than other classes if biological molecule.

Some ofthe function of lipids are it act as structural components of biologicalmembranes such as Phosphoglycerol and sphingolipids. Lipid containinghydrocarbon chain serve as energy store, triacylglycerols is one of theexample. there is also many intra and intercellular signaling events involvelipid molecules such as steroids and phospholipids. There is classification oflipids based on chemical structure. It is saperated into two groups, openchained compound with polar head group and nonpolar tail, the other class isthe one that consist of fused ring compound.

Fatty acid hascarboxyl group at polar end and hydrocarbod chain at the non polar tail. It isan amphiphatic molecule because the head is hydrophilic and the tail ishydrophobic. Saturated hydrocarbon only consist of single bond bun unsaturatedhydrocarbon consist of double bond(monosaturated or polysaturated). Meltingpoint of fatty acid is the temperature at which the fatty acid undergoes  transition from solid to liquid state. Themelting point is affected by the length of the acylchainand the number ofdouble bonds.

The longer the chain, the higher the melting point because itconsist more van der waals forces. More double bond will lowering the meltingpoint because the double bond inhibit packing into solid solid state and thevan der waals forces interaction is reduced.Tryglycerols which also known as triglycerides is the compound thatconsist of three fatty acid and one one glycerol(alcohol that contain hydroxidegroup).

The OH group can form ester linkages with fatty acids. The fatty acidis differ in chain and number of double bonds. It can be hydrolyzed bysaponification, a treatment with base to yield glycerol and fatty acid salts.

Tryglycerols can be synthesized by dehydration and one water molecule is lostper ester bond formed. The functions are it act as energy storage, waterrepellent, insulator and soap making.Glycerolphospholipid which also known as phosphoacylglycerol orphosphoglycerides. It is major component of biological membrane. Biologicalmembrane or also known as plasma membrane composed mainly lipid and protein.Plasma membrane plays an important role in our life as it saperate beteween theinter and outer space of the cells. Its consist of phosphoglycerides.

Cholesterol, plycolipiods and phytosterol.            Sphingolipidsis constitute a class of lipids defined by their 18 carbon amino-alcoholbackbones which are synthesized in the ER from non-sphingolipid precursors. Modification of thisbasic structure will gives rise to the vast family of sphingolipids that playsignificant roles in membrane biology and produce many bioactive metabolitesthat will regulate cell function. Another function of sphingolipids is their creation anddestruction are governed by common synthetic and catabolic pathways. In thisregard, sphingolipid metabolism can be imagined as an array of interconnectednetworks that diverge from a single common entry point and converge into asingle common breakdown pathway. It is important in both plants and animal.

Only one major phospholipid that contains ceramide (N-acyl-sphingosinephosphocoline), an important structural lipid of nerve cell membranes.Most sphingolipids are sphingolycolipids, that is,their polar head groups consist of carbohydrate units. The lipids providing thecarbohydrates that covers the external surfaces of eukaryotic cells aresphingoglycolipids. The principal classes of sphingoglycolipids arecerebrosides (ceramide monosaccharides), sulfatides (ceramide monosaccharidesulfates), globosides (neural ceramide oligosaccharides), and gangliosides(acidic, sialic acid-containing ceramide oligosaccharides). The carbohydrateunit is glycosidically attached to the N-acylsphingosine at its C1 OH group. Insphingomyelin, primary alcohol group of sphingosine is esterified to phosphoricacid, which in turn, is esterified to amino alcohol, choline. Galactocerebroside(1-?-galactosylceramide) and glucocerebroside (1-?- glucosylceramide) are thetwo most common cerebrosides. Both are synthesized from ceramide by addition ofa glycosyl unit from the corresponding UDP-hexose.

Glucocerebroside, although relatively uncommon, isthe precursor of globosides and gangliosides and it is the common component ofbrain lipids. Biosynthesis of both globosides and gangliosides is catalyzed bya series of glycosyltransferases. The pathway begin with transfer of agalactosyl unit from UDP-Gal to glucocerebroside to form a ?(1-4) linkage. Thebond is referred to as lactosyl ceramide. Lactosyl ceramide is the precursor ofboth globosides and gangliosides. Gangliosides are the most complexglycosphingolipids. They are ceramide with attached oligosaccharides that includeat least one sialic acid residue.The steroid core structure is composed of seventeencarbon atoms, bonded in four rings: three six-member cyclohexane rings and onefive-member cyclopentane ring.

Steroids vary by the functional groups attachedto this four-ring core and by the oxidation state of the rings. Fused ringsgive sterols a rigid hydrophobic structure. Examples of some steroids such astestosterone, cortisone, Vitamin D, cholesterol and etc. Sterols, the majorclass of steroids, have a hydroxylgroupat C-3. The major sterol in animal cell is cholesterol.

Cholesterol is referredas an amphipathic molecule, that it contains its hydrophilic and hydrophobicparts. The hydroxyl group (-OH) in cholesterol is aligned with the phosphatehead of the phospholipid on cell membrane, which the rest of the cholesterolgoes with the fatty acid of the membrane. It is very important that cholesterolis present on all the cell membrane due to its properties keep the cell firmand avoid being overly fluid. The steroid core structure is composed of seventeencarbon atoms, bonded in four fused rings: three six-member cyclohexane ringsand one five-member cyclopentane ring. Steroids vary by the functional groupsattached to this four-ring core and by the oxidation state of the rings.Cholesterol is usually synthesized in animals and smaller cholesterol can begenerated in plants. They are important in the composition of cell membranesand also steroid hormones. Cholesterol has played an important role on everycell in our body, especially abundant on the cell membrane, which function as acommunicator with other cells in our body.

Small amount of cholesterol can alsobe found on the membrane of some organelles inside the cells, such as themitochondrion and the endoplasmic reticulum.