Biochemistry Lecture Notes PDF

BIOCHEMISTRY LECTURE GUIDE INTRODUCTION Biochemistry is a combination of two sciences, these are Biology and Chemistry. Biology is the science that deals with the study of life. Thus, living th...

BIOCHEMISTRY LECTURE GUIDE INTRODUCTION Biochemistry is a combination of two sciences, these are Biology and Chemistry. Biology is the science that deals with the study of life. Thus, living things are being studied under biology. Chemistry is the science that deals with the study of matter. In a detailed definition, it is a study of the composition, structure and properties of matter. Matter is anything that has volume and mass. The animate and inanimate objects are all considered matter since they have volume and mass. The animate object objectss pertain to living things. All living things are said to be carbon based. The chemistry that deals with study of carbon containing compound is known as Organic chemistry. Biochemistry is defined as the study of the chemical structure, composition and processes in living organism. It is defined in the “American Heritage Dictionary” as the study of the chemical substances and vital processes occurring in living organisms. Biochemistry will also deal with the different physiological processes. Scope of Biochemistry Introduction to Biochemistry primary topic will be the composition of living things. All living things are composed of organic compounds. The organic compounds can assemble to form the different macromolecules or biomolecules. There are four four biomolecules, these are the carbohydrates, lipids, proteins and nucleic acid. The combination and reaction of these biomolecules can results to different organelles and can give rise to cell. The cell can aggravate and perform a single function known as tissues and organs. The sources of these biomolecules will be also discussed such as the foods, digestion and nutrition. These biomolecules will undergo the process of metabolism. Metabolism is the sum total of all chemical reaction and catalyzed by y enzymes. Thus, metabolism and enzymes are also two of the most important topic in Biochemistry. The chemical reaction in an organism is being controlled and regulated by hormones. All end products are transported in the blood and the waste products a are re excreted in the urine. Thus, all of these are discussed in biochemistry. Organization of living things Elements Biomolecules C,H,O,N, P, S Carbohydrates, Lipids, Proteins and Nucleic Acid Organelles Nucleus, Cell Membrane, Mitochodria, ER, Golgi, etc. Tissues Organs System Organism Organic Compounds Organic compounds are carbon containing compounds except cyanides, carbonates, bicarbonates bic and oxides, such carbon dioxides. The table shows the comparison between organic and inorganic compounds. Inorganic Compounds Organic Compounds Soluble in polar solvents Soluble in non-polar solvent Non-combustible Combustible Not easy to decompose Easy to decompose Fast chemical reaction Slow chemical reaction Ionic bond Covalent bond  The main elements seen in organic compounds are the Carbon which has four bonds, the Hydrogen with one bond, Oxygen with two bonds, Nitrogen, Phosphorous and Sulfur which have variable bonds. There are more organic compounds compared with inorganic compounds because of the hybridization of bonds and formation of isomers. Hybridization of bond in carbon Sp3. It is formed when four elements rea react ct with carbon which results to four sigma bond formation. The carbon can be observed having a single bond. Sp2. It is formed when three elements react with carbon which results to three sigma bond and one pi bong. Sp. It is formed when two elements react react with carbon which results to two sigma bonds and two pi bonds. Isomers Isomers are compound with the same molecular formula but different structural formula. Examples of these compounds are the acetones and acetaldehydes. The molecular formula of both both of these compounds is C3H6O. The structural formulas are shown below. Naming of Organic Compounds Organic compounds main composition is the element carbon; because of this the naming is base on the number of carbon. There are two prefix that can be used in the naming of carbon, the IUPAC (International Union for Pure and Applied Chemistry) and the Common Name prefix. The table below shows the number of carbon with their corresponding prefix. No. of Carbon IUPAC prefix Common Name prefix 1 Meth Form 2 Eth Acet 3 Prop Propion 4 But Butyr 5 Pent Valer 6 Hex Capro 7 Hept Enanth 8 Oct Capryl 9 Non Pelargon 10 Dec Capr The ending in the naming of organic compound depends upon its classification. Organic compound are classified as Hydrocarbon and Hyrocarbon derivatives. Hydrocarbons are composed of only hydrogen and carbon and further classified into aliphatic and alicyclic alicyclic compound. Aliphatic are characterized by an open chain structures whereas alicyclic has a close chain structure. The aliphatic hydrocarbon are further classified into saturated hydrocarbon and unsaturated hydrocarbon. The saturated compounds are those th with single bond such as the alkanes whereas the unsaturated compounds are those with multiple bonds such as alkenes which are characterized by a single bond and alkynes which are characterized by a double bond. There are also aromatic hydrocarbons wh which ich can be recognized by the presence of the benzene ring with a molecular formula of C6H6. The table below shows the different organic compounds that will be encountered in the study of biochemistry.  Organic Compound Formula Alkane CnH2n+2 Alkene CnH2n Alkyne CnH2n-2 Alcohol ROH Amines RNH2 Ethers ROR Carboxylic acid RCOOH Aldehydes RCHO Ketones RCOR Amides RCONH2 Esters RCOOR The alcohol, aldehydes and ketones are commonly seen in carbohydrates. The lipids are made up of esters which is a product of a reaction of carboxylic acid and alcohol. The amines and other organic compounds are present in amino acids. Nucleic acid has also amines, aldehydes, alcohol and aromatic hydrocarbon. Chemical reaction in living organism The following are the common reaction seen in the different biomolecules. Chemical reactions occur in the functional group of the organic compound since this is their active site. Hydrolysis. It is addition of water that results to splitting of molecules or compound. The reaction is usually catalyzed by an enzyme or will take place upon application of heat. Dehydration. It is removal of water that results to joining of molecules or compounds. The reaction will take place between two hydroxyl groups. Polymerization. It is the union of similar compounds to form a polymer. Chain-growth polymerization or addition polymerization involves the linking together of molecules incorporating double or triple chemical bonds. These unsaturated monomers (the identical molecules which make up the polymers) have extra internal bonds which are able to break and link up with other monomers to form the repeating chain. Oxidation. It is the decrease in oxidation state of elements. In living organism, this is accomplished upon addition of oxygen or removal of hydrogen ion. Reduction. It is the increase in oxidation state of elements. In living organism, this is accomplished upon addition of hydrogen or removal of oxygen in the system. Other common chemical reactions are decarboxylation which involves removal of the carboxyl group; transamination which involve transfer of the amine or amino group; and, phosphorylation which involves addition of phosphate group. ---------------------------------------------------------------------------------------------------------------------------------------  THE CELL AND ITS ORGANELLES All living organism are composed of the cell. The cell is the functional unit of life. Functional unit since all cell whether singular or multicellular are capable of performing the functions of life. The functions of life are growth through intussusception, tion, metabolism, reproduction, irritability and adaptation. The cell is classified into a prokaryotic and eukaryotic cell. The prokaryotic cell has no nuclear membrane and there are no organelles present, but this does not mean it has no chromosomes. The he simple chromosome of the prokaryotic cell is located near its cell membrane. It also has free ribosomes in the cytoplasm which synthesizes proteins. An example of prokaryotic cell is the bacteria. The eukaryotic cell has a nuclear membrane which protects protects a complex chromosome. The presence of the nuclear membrane give rise to the other membrane bound organelles such as the endoplasmic reticulum (ER), Golgi bodies and lysosomes. It has also two types of ribosomes unattached ribosomes which are seen floating ating in the cytoplasm and attached ribosomes which are seen in rough endoplasmic reticulum. The plant and animal cells are example of eukaryotic cell. The table below shows the main difference between a plant and animal cell. Plant Cell Animal Cell With large central vacuole With small food vacuole With plastids No plastids With cell wall No cell wall The rest of the organelles are common both in plants and animal cell and perform a specific action for its survival. THE CELL Cell Organelles Cell membrane.. The cell membrane is a delimiting membrane. It regulates the passage of substances inside the cell. It is capable of recognizing substances needed by the cell. It also protects the cell from harmful substances. The cell membrane is composeded of a phospholipid bilayer which can be represented by the fluid mosaic model shown below. The mosaic pertains to the protein part, the channel and carrier proteins. The fluid is the phospholipid layer, but it is not entirely liquid since there are embedded cholesterol in between which causes rigidity of the cell membrane. The glycogen can combine with the protein called glycoprotein and it can also combine with the lipid called glycolipids. Thus,, the biomolecules present are carbohydrates, proteins and lipids. Membrane bounded organelles Nucleus. The nucleus is known as the command center or the control center of the cell. This function is made possible by the presence of the chromosomes which contain the DNA reponsible for the synthesis of RNA which in turn responsible for the synthesis of prot proteins. eins. Most of these proteins will end up as enzymes reponsible for the chemical reaction inside and outside the cell. The nucleus also has a dark staining body called the nucleolus which is the site for the active synthesis of RNA. The chromosomes are being b protected by a nuclear membrane which has a nuclear pore that serves as passageway for messenger RNA. The nuclear membrane is composition is almost similar with the cell membrane. Thus, the biomolecules present are carbohydrates, proteins, lipids and and nucleic acid. The DNA and RNA are both present in the nucleus. Endoplasmic Reticulum (ER). ). The ER is an extension of the nuclear membrane. The endoplasmic reticulum is classified into smooth ER and rough ER. The smooth ER has no ribosomes; therefor therefore, e, it is not capable of protein synthesis. Its main function is to synthesize non-protein protein compounds such as carbohydrates and lipids. Since it is a membrane bounded organelle, the biomolecules present in the smooth ER are carbohydrates, lipids and proteins. protein The rough ER has attached ribosomes and therefore, capable of synthesizing proteins. The proteins made by rough ER are usually for extracellular use and will be transported outside the cell. The proteins being synthesized by unattached ribosomes are for for intracellular use or for cell “own” use. The biomolecules present in rough ER are also carbohydrated, lipids, proteins and it has RNA because of the ribosomes. Golgi bodies.. At the end of the ER, there will be a formation of flat vesicles known as the Golgi bodies or apparatus. These are responsible for packaging the products such as carbohydrates, lipids and proteins being made by the ER. The Golgi bodies can also combine resulting to combination and sorting of compound such as the formation of glycoprotein oprotein and lipoprotein. The package proteins or enzymes of the Golgi bodies which was produced by the rough ER can also develop into lysosomes. The biomolecules present in Golgi bodies are also carbohydrates, lipids and proteins. Lysosomes. The lysosomes mes contain hydrolytic enzymes. Thus, these enzymes are capable of splitting molecules by addition of water. This reaction is also known as digestion. The lysosomes are therefore capable of digesting substances. It is also known as scavengers of the cell cell since it will digest non-functional non organelles. The enzymes in certain conditions can also released its enzymes content into the cytoplasm causing self destruction of the cell known as autolysis. The biomolecules present in lysosomes are the carbohydrates, carbohydrates, lipids and proteins. Mitochondria. The mitochondria are an organelle with a structure similar to a prokaryotic cell. It has an inner mebrane and an outer membrane. Inside, it has a foldings known as cristae that increases surface area for exchange e of ions during the oxidative phosphorylation reaction that give rise to Adenosine Triphosphate or ATP. Thus, the mitochondria are the power house of the cell since it is capable of producing large amount of ATP through the aerobic pathway such as the Kreb’s Kr cycle. The mitochondria also have a simple chromosome which can replicate. Mitochondria are therefore capable of self-regulation and self-replication. replication. The biomolecules present in mitochondria are proteins, lipids, carbohydrates, DNA and RNA. Non-membrane bounded organelle Microfilaments. The microfilaments are composed of actin and myosin. These are proteins rensponsible for the cytoplasmic movement. It also supports the different cell organelles therefore serving as framework of the cell. Centrioles. The centrioles are made from tubulin proteins which are capable of assembly and disassembly. It is capable of forming asters and spindle fibers during cell division. The asters function is to anchor the centrioles to the cell membrane and the spindle fiber function is to move the chromosomes towards the opposite pole. Inorganic component of the cell Water. The water is known as universal solvent because it is capable of dissolving almost all substances. It is a polar solvent. Thus, it can serve as a medium of chemical reaction for substances inside the cell. The water also maintains the osmotic pressure that gives shape to the cell and prevents the membrane from collapsing. The water also helps in the regulation of the temperature inside the cell. Ions. The ions can be positively charge known as cations or negatively charge known as anions. The ions are responsible for the conduction of nerve impulses such as in sodium potassium pump. These are therefor responsible for cell irritability. Salts. The salts serve as inorganic buffer inside and outside the cell. It maintains the pH as much as possible near neutral pH and it prevents sudden change in pH. Increased and decreased in pH causes denaturation of protein that can result to destruction of important enzymes. Gases. The gases that can be seen in the cell are the oxygen and carbon dioxide. The oxygen is used in oxidation reaction and very important in the formation of ATP (oxidative phosphorylation). The carbon dioxide is the waste product produced during the oxidative phosphorylation and will be eliminated by the cell. In plants, because of the presence of plastids, it can convert carbon dioxide in combination with water and light into carbohydrates. This reaction is known as photosynthesis.  CARBOHYDRATES An organic compound composed of carbon, hydrogen, and oxygen, with the general chemical formula of Cx (H2O)y. where x and y are whole numbers that differ depending on the specific carbohydrate. They are the most abundant of the four major classes of biomolecules, which also include proteins, proteins lipids and nucleic acids. They fill numerous roles in living things, such as the storage and transport of energy and structural components (cellulose in plants, chitin in animals). Animals (including humans) break down carbohydrates during the process of metabolism to release lease energy. C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy Animals obtain carbohydrates by eating foods. These carbohydrates are manufactured by plants during the process of photosynthesis. photosynthesis Plants harvest energy from sunlight light to run the reaction just described in reverse: 6 CO2 + 6 H2O + energy (from sunlight) C6H12O6 + 6 O2 As noted, the formulas of many carbohydrates can be written as carbon hydrates, Cn(H2O)n, hence their name. The carbohydrates are a major source of metabolic energy, both for plants and for animals that depend on plants for food. Aside from the sugars and starches that meet this vital nutritional role, carbohydrates also serve as a structural material (cellulose), a component of the energy transport compound ATP,, recognition sites on cell surfaces, and one of three essential components of DNA and RNA. RNA Additionally, carbohydrates and their derivatives play major major roles in the working process of the immune system, fertilization, pathogenesis, blood clotting, clotting and development. Carbohydrates are called saccharides or, if they are relatively small, sugars. CLASSIFICATION OF CARBOHYDRATES Monosaccharide Monosaccharides are the simplest carbohydrates in that they cannot be hydrolyzed to smaller carbohydrates. The general chemical formula of an unmodified monosaccharide is (C H2O)n, where n is any number of three or greater. Monosaccharides are classified according to three different characteris characteristics: tics: the placement of its carbonyl group, the number of carbon atoms it contains, and its chiral handedness. If the carbonyl group is an aldehyde,, the monosaccharide is an aldose; if the carbonyl group is a ketone,, the monosaccharide is a ketose. Monosaccharides (from Greek monos: monos single, sacchar:: sugar) are the most basic unit of carbohydrates. They consist of one sugar and are usually colorless, water-soluble, crystalline solids. Some monosaccharides have a sweet taste.. Examples of monosaccharides include glucose (dextrose), fructose, fructose galactose, xylose and ribose. Monosaccharides are the building blocks of disaccharides such as sucrose (common sugar) and polysaccharides (such as cellulose and starch). ). Further, each carbon atom that supports a hydroxyl group (except for the first and last) is chiral,, giving rise to a number of isomeric forms all with the same chemical formula. For instance, galactose and glucose are both aldohexoses,, but have different chemical and physical properties. List of Monosaccharide This is a list of some common monosaccharides, not all are found in nature while some have been synthesized:  Trioses: o Aldotriose: glyceraldehyde o Ketotriose: dihydroxyacetone   Tetroses: o Aldotetrose: erythrose and threose o Ketotetrose: erythrulose o  Pentoses: o Aldopentoses: arabinose,, lyxose, ribose, deoxyribose, and xylose o Ketopentoses: ribulose and xylulose  Hexoses: o Aldohexoses: allose, altrose, altrose galactose, glucose, gulose, idose, mannose and talose o Ketohexoses: fructose, psicose, psicose sorbose and tagatose  Heptoses: o Keto-heptoses: mannoheptulose, mannoheptulose sedoheptulose  Octoses: octolose, 2-keto-3-deoxy deoxy-manno-octonate  Nonoses: sialose TRIOSES A triose is a monosaccharide containing three carbon atoms.. There are only two trioses, an aldotriose (glyceraldehyde) and a ketotriose (dihydroxyacetone dihydroxyacetone). Trioses are important in respiration. respiration The D-aldotriose is D-Glyceraldehyde The ketotriose is dihydroxyacetone TETROSES A tetrose is a monosaccharide with 4 carbon atoms. They either have an aldehyde functional group in position 1 (aldotetroses) or a ketone functional group in position 2 (ketotetroses). ( ). The aldotetroses have two chiralatrial centres ("asymmetric carbon atoms") and so 4 different stereoisomers are p possible. CH=O CH=O CH2OH | | | HC-OH HO-CH C=O | | | HC-OH HC-OH HC-OH | | | CH2OH CH2OH CH2OH D-Erythrose D-Threose D-Erythrulose PENTOSES A pentose is a monosaccharide with five carbon atoms. They either have an aldehyde functional group in position 1 (aldopentoses), or a ketone functional group in position 2 (ketopentoses).). The aldopentoses have three chiral centers ("asymmetric carbon atoms") and so 8 different stereoisomers are possible. The 4 D-aldopentoses are: CH=O CH=O CH=O CH=O | | | | HC-OH HO-CH HC-OH HO-CH | | | | HC-OH HC-OH HO-CH HO-CH | | | I HC-OH HC-OH HC-OH H-C-OH | | | I CH2OH CH2OH CH2OH CH2OH D-Ribose D-Arabinose D D-Xylose D-Lyxose The ketopentoses have 2 chiral centres and therefore 4 possible stereoisomers — ribulose (L- and D-form) and xylulose (L- and D-form). The D-isomers isomers of both are known to occur naturally as is the L-isomer L of xylulose:  CH2OH CH2OH | | C=O C=O | | HC-OH HO-CH | | HC-OH HC-OH | | CH2OH CH2OH D-Ribulose D-Xylulose The aldehyde and ketone functional groups in these carbohydrates react with neighbouring hydroxyl functional groups to form intramolecular hemiacetals or hemiketals, respectively. The resulting ring structure is related to furan, and is termed a furanose. The ring spontaneously opens and closes, allowing rotation to occur about the bond between the carbonyl group and the neighbouring carbon atom. Thus, yielding two distinct configurations (α and β). This process is termed mutarotation. Ribose is a constituent of RNA, and the related deoxyribose of DNA. A polymer composed of pentose sugars is called a pentosan. HEXOSES In organic chemistry, a hexose is a monosaccharide with six carbon atoms having the chemical formula C6H12O6. Hexoses are classified by functional group, with aldohexoses having an aldehyde at position 1, and ketohexoses having a ketone at position 2. Aldohexoses he aldohexoses have four chiral centres for a total of 16 possible aldohexose stereoisomers (24). The D/L configuration is based on the orientation of the hydroxyl at position 5, and does not refer to the direction of optical activity. The eight D-aldohexoses are: CH=O CH=O CH=O CH=O | | | | HC-OH HO-CH HC-OH HO-CH | | | | HC-OH HC-OH HO-CH HO-CH | | | | HC-OH HC-OH HC-OH HC-OH | | | | HC-OH HC-OH HC-OH HC-OH | | | | CH2OH CH2OH CH2OH CH2OH D-Allose D-Altrose D-Glucose D-Mannose CH=O CH=O CH=O CH=O | | | | HC-OH HO-CH HC-OH HO-CH | | | | HC-OH HC-OH HO-CH HO-CH | | | | HO-CH HO-CH HO-CH HO-CH | | | | HC-OH HC-OH HC-OH HC-OH | | | | CH2OH CH2OH CH2OH CH2OH D-Gulose D-Idose D-Galactose D-Talose Cyclic Structure Most monosaccharides form cyclic structures, which predominate in aqueous solution, by forming formin hemiacetals or hemiketals (depending on whether they are aldoses or ketoses) between an alcohol and the carbonyl group of the same sugar. Glucose, Glucose, for example, readily forms a hemiacetal linkage between its carbon-11 and the hydroxyl group of its carbon carbon-5. 5. Since such a reaction introduces an additional stereogenic center, two anomers are formed (α-isomer isomer and β-isomer) β from each distinct straight--chain monosaccharide. The interconversion onversion between these two forms is called mutarotation. A common way of representing the cyclic structure of monosaccharides is the Haworth projection projection. In Haworth projection, the α-isomer has the OH- of the anomeric carbon under the ring structure, and the β-isomer, β has the OH- of the anomeric carbon on top of the ring structure. In chair conformation, the α-isomer α has the OH- of the anomeric carbon in an axial position, whereas the β-isomer β has the OH- of the anomeric carbon in equatorial position. α-D-Glucopyranose β-D-Glucopyranose Glucopyranose Ketohexoses The ketohexoses have 3 chiral centers and therefore eight possible stereoisomers (23). Of these, only the four D-isomers isomers are known to occur naturally: Only the naturally occurring hexoses are capable of being fermented by yeasts. CH2OH CH2OH CH2OH CH2OH | | | | C=O C=O C=O C=O | | | | HC-OH HO-CH HC-OH OH HO HO-CH | | | | HC-OH HC-OH HO-CH CH HO HO-CH | | | | HC-OH HC-OH HC-OH OH HC HC-OH | | | | CH2OH CH2OH CH2OH CH2OH D-psicose D-fructose D-sorbose sorbose D-tagatose Mutarotation The aldehyde and ketone functional groups in these carbohydrates react with neighbouring hydroxyl functional groups to form intermolecular hemiacetals or hemiketals,, respectively. The resulting ring structure is related to pyran, and is termed a pyranose. pyranose. The ring spontaneously opens and closes, allowing rotation to occur about the bond between the carbonyl group and the neighboring carbon atom, om, yielding two distinct configurations (α and β). This process is termed mutarotation.. Hexose sugars can form dihexose sugars with a condensation reaction to form a 1,6-glycosidic glycosidic bond. bond ISOMERISM Stereoisomers are isomeric molecules that possess identical constitution, but which differ in the arrangement of their atoms in space. Enantiomers are two stereoisomers that are related to each other by a reflection: they are mirror images of each other, which are non-superimposable. Human hands are a macroscopic example of stereoisomerism. Every stereogenic center in one has the opposite configuration in the other. Two compounds that are enantiomers of each other have the same physical properties, except for the direction in which they rotate polarized light and how they interact with different optical isomers of other compounds. For this reason, pure enantiomers exhibit the phenomenon of optical activity and can be separated only with the use of a chiral agent. Diastereomers are stereoisomers not related through a reflection operation. They are not mirror images of each other. These include meso compounds, cis-trans (E-Z) isomers, and non-enantiomeric optical isomers. Diastereomers seldom have the same physical properties. Cis-trans and E-Z isomerism Stereoisomerism about double bonds arises because rotation about the double bond is restricted, keeping the substituents fixed relative to each other. If the substituents on either end of a double bond are the same, it is not considered a stereo bond. Traditionally, double bond stereochemistry was described as either cis (Latin, on this side) or trans (Latin, across). (The terms cis and trans are also used to describe the relative position of two substituents on a ring; cis if on the same side, otherwise trans.) Due to occasional ambiguity, IUPAC adopted a more rigorous system wherein the substituents at each end of the double bond are assigned priority numbers. If the high priority substituents are on the same side of the bond it is assigned Z (Ger. zusammen, together). If they are on opposite sides it is E (Ger. entgegen, opposite). An example of double bond stereoisomerism is 1,2-dichloroethene, C2H2Cl2. Molecule I is Z-1,2-dichloroethene (chlorines on same side - the top) and molecule II (chlorines on opposite sides) is E-1,2-dichloroethene. There is no way of "superimposing" the structures on each other through bond rotation, because of the central double bond of C=C (composed of a sigma bond and a pi bond), through which rotation is not allowed. If rotation were allowed, such as a single bond would allow, these two molecules would be the same. In contrast, for 1,2-dichloroethane, C2H4Cl2, which is similar except that it has an extra H attached to each C and a single bond, the E- and Z- forms do not exist. Since the carbon atoms can rotate around the single bond, in a flat projection of the molecule, all three atoms attached to one carbon could swap places and still represent the same structure. Configurational isomers are diastereomers and can possess different physical, biological and chemical properties. Conformers Conformational isomerism is a form of isomerism that describes the phenomenon of molecules with the same structural formula having different shapes due to rotations about one or more bonds. Different conformations can have different energies, can usually interconvert, and are very rarely isolatable. Uses Monosaccharides are the major source of fuel for metabolism, being used both as an energy source and in biosynthesis. When monosaccharides are not immediately needed by many cells they are often converted to more space efficient forms, often polysaccharides. In many animals, including humans, this form is glycerol, expecially in liver and muscle cells. Disaccharides Two joined monosaccharides are called a disaccharides and these are the simplest polysaccharides. po They are composed of two monosaccharide units bound together by a covalent bond known as a glycosidic linkage formed via a dehydration reaction,, resulting in the loss of a hydrogen atom from one monosaccharide and a hydroxyl group from the other. The formula of unmodified disaccharides is C12H22O11. Although there are numerous kinds of disaccharides, a handful of disaccharides are particularly notable. Sucrose Sucrose,, pictured to the right, is the most abundant disaccharide, and the main form in which carbohydrates are transported in plants.. It is composed of one D-glucose molecule and one D--fructose molecule. The systematic name for sucrose, O-α-D-glucopyranosyl glucopyranosyl-(1→2)-D-fructofuranoside, fructofuranoside, indicates four things:  Its monosaccharides: glucose and fructose  Their ring types: glucose is a pyranose, pyranose and fructose is a furanose  How they are linked together: the oxygen on carbon number 1 (C1) of α-D-glucose α glucose is linked to the C2 of D-fructose.  The -oside suffix indicates that the anomeric carbon of both monosaccharides participates in the glycosidic bond. Lactose (also referred to as milk sugar) sugar is a sugar which is found most notably in milk. milk Lactose makes up around 2–8% 8% of milk (by weight). The name comes from the Latin word for milk, plus the -ose ending used to name sugars. Its systematic name is β-DD-galactopyranosyl-(1↔4)β-D-glucopyranose. Lactose is a disaccharide that consists of β β-D-galactose and β-D-glucose fragments bonded through a β1-4 β1 glycosidic linkage. Infant mammals are fed on milk by their mothers. To digest it an enzyme called lactase (β-D-galactosidase) is secreted by the intestinal villi,, and this enzyme cleaves the molecule into its two subunits glucose and galactose for absorption. Since lactose occurs mostly in milk, in most mammals the production of lactase gradually decreases with maturity. Many people with ancestry in Europe,, the Middle East, India, or parts of East Africa,, maintain normal lactase production into adulthood. In many of these cultures, mammals such as cattle, goats, goats and sheep are milked for food. Hence, it was in these regions that genes for lifelong lactase production first evolved. The genes of lactose tolerance have evolved independently in various ethnic groups. The glycosidic bond can be formed between any hydroxyl group on the component monosaccharide. So, even if both component sugars are the same (e.g., glucose), ), different bond combinations (regiochemistry) and stereochemistry (alpha- or beta-)) result in disaccharides that are diastereoisomers with different chemical and physical properties. Depending on the monosaccharide constituents, disaccharides are sometimes crystalline, sometimes water- soluble, and sometimes sweet-tasting and sticky-feeling. Lactose Intolerance Lactose intolerance is the inability to metabolize lactose, a sugar found in milk and other dairy products, because the required enzyme lactase is absent in the intestinal system or its availability is lowered. Some people also mention pasteurized dairy products as a cause such as raw milk contains small amounts of lactase. It is estimated that 75% of adults show some decrease in lactase activity during adulthood worldwide. The frequency of decreased lactase activity ranges from nearly 5% in northern Europe to more than 90% in some Asian and African countries. Disaccharides cannot be absorbed through the wall of the small intestine into the bloodstream, so in the absence of lactase, lactose present in ingested dairy products remains uncleaved and passes intact into the colon. The operons of enteric bacteria quickly switch over to lactose metabolism, and the resultant in vivo fermentation produces copious amounts of gas that is a mixture of hydrogen, carbon dioxide, and methane. This, in turn, may cause a range of abdominal symptoms, including stomach cramps, bloating, and flatulence. In addition, as with other unabsorbed sugars such as sorbitol, mannitol, and xylitol, the presence of lactose and its fermentation products raises the osmotic pressure of the colon contents, thereby preventing the colon from reabsorbing water, and causing osmotic diarrhea. There are three major types of lactose intolerance: 1. Primary lactose intolerance. Environmentally induced when weaning a child in non-dairy consuming societies. This is found in many Asian and African cultures, where industrialized and commercial dairy products are uncommon. 2. Secondary lactose intolerance. Environmentally induced, resulting from certain gastrointestinal diseases, including exposure to intestinal parasites such as giardia. In such cases the production of lactase may be permanently disrupted. A very common cause of temporary lactose intolerance is gastroenteritis, particularly when the gastroenteritis is caused by rotavirus. Another form of temporary lactose intolerance is lactose overload in infants. 3. Congenital lactase deficiency. A genetic disorder which prevents enzymatic production of lactase. Present at birth, and diagnosed in early infancy. Maltose, or malt sugar, is a disaccharide formed from two units of glucose joined with an α(1→4) linkage. It is the second member of an important biochemical series of glucose chains. The addition of another glucose unit yields maltotriose; further additions will produce dextrins (also called maltodextrins) and eventually starch. Maltose can be broken down into two glucose molecules by hydrolysis. In living organisms, the enzyme maltase can achieve this very rapidly. The production of maltose from germinating cereals, such as barley, is an important part of the brewing process. When barley is malted, it is brought into a condition in which the concentration of maltose-producing amylases has been maximized. Mashing is the process by which these amylases convert the cereal's starches into maltose. Metabolism of maltose by yeast during fermentation then leads to the production of ethanol and carbon dioxide. List of Common disaccharides Disaccharide Unit 1 Unit 2 Bond Sucrose (table sugar, cane sugar, saccharose, or beet sugar) glucose fructose α(1→2) Lactose (milk sugar) galactose glucose β(1→4) Maltose glucose glucose α(1→4) Trehalose glucose glucose α(1→1)α Cellobiose glucose glucose β(1→4) Maltose and cellobiose are hydrolysis products of the polysaccharides, starch and cellulose, cellulose respectively. Less common disaccharides include: Disaccharide Units Bond Gentiobiose two glucose monomers β(1→6) Isomaltose two glucose monomers α(1→6) Kojibiose two glucose monomers α(1→2) Laminaribiose two glucose monomers β(1→3) Mannobiose two mannose monomers →3), α(1→4), or α(1→6) either α(1→2), α(1→3), a glucose monomer and a galactose Melibiose α(1→6) monomer Nigerose two glucose monomers α(1→3) a rhamnose monomer and a glucose Rutinose α(1→6) monomer Xylobiose two xylopyranose monomers β(1→4) OLIGOSACCHARIDES An oligosaccharide is a saccharide polymer containing a small number (typically three to ten) of component sugars, also known as simple sugars.. The name derived from the Greek oligos,, meaning "a few". They are generally found either O- or N-linked linked to compatible amino acid side chains in proteins or to lipid moieties. Fructo-oligosaccharides (FOS), which are found in many vegetables, consist consist of short chains of fructose molecules. Inulin has a much higher degree of polymerization than FOS and is a polysaccharide. Galactooligosaccharides (GOS), which also occur naturally, consist of short chains of galactose molecules. These compounds can be only partially digested by humans. Oligosaccharides are often found as a component of glycoproteins or glycolipids and as such are often used as chemical markers, often for cell recognition. An example is ABO blood type specificity. A and B blood types have two different oligosaccharide glycolipids embedded in the cell membranes of the red blood cells, AB-type AB blood has both, while O blood type has neither. Mannan-oligosaccharides (MOS) are widely used in animal feed to encourage gastrointestinal health and performance. rformance. They are normally obtained from the yeast cell walls of Saccharomyces cerevisiae. cerevisiae Some brand names are: Bio-Mos, SAF-Mannan, Y-MOS MOS and Celmanax. Nott all natural oligosaccharides occur as components of glycoproteins or glycolipids. Some, such as the raffinose series, occur as storage or transport carbohydrates in plants. Others, such as maltodextrins or cellodextrins,, result from the microbial breakdown of larger polysaccharides such as starch or cellulose. POLYSACCHARIDES As the name implies, polysaccharides are large high-molecular high molecular weight molecules constructed by joining monosaccharide units together by glycosidic bonds. They are sometimes called glycans. glycans The most important compounds in this class, cellulose, starch and glycogen are all polymers of glucose. This is easily demonstrated by acid-catalyzed catalyzed hydrolysis to the monosaccharide. Since partial hydrolysis of cellulose gives varying amounts of cellobi cellobiose, ose, we conclude the glucose units in this macromolecule are joined by beta-glycoside bonds between C-1 1 and C-4C 4 sites of adjacent sugars. Partial hydrolysis of starch and glycogen produces the disaccharide maltose together with low molecular weight dextrans, dextran polysaccharides in which glucose molecules are joined by alpha alpha-glycoside links between C-1 and C-6, 6, as well as the alpha C C-1 to C-4 links found in maltose.  Over half of the total organic carbon in the earth's biosphere is in cellulose. Cotton fibres are essentially pure cellulose, and the wood of bushes and trees is about 50% cellulose. As a polymer of glucose, cellulose has the formula (C6H10O5)n where n ranges from 500 to 5,000, depending on the source of the polymer. The glucose units in cellulose are linked in a linear fashion. The beta-glycoside bonds permit these chains to stretch out, and this conformation is stabilized by intramolecular hydrogen bonds. A parallel orientation of adjacent chains is also favored by intermolecular hydrogen bonds. Although an individual hydrogen bond is relatively weak, many such bonds acting together can impart great stability to certain conformations of large molecules. Most animals cannot digest cellulose as a food, and in the diets of humans this part of our vegetable intake functions as roughage and is eliminated largely unchanged. Some animals (the cow and termites, for example) harbour intestinal microorganisms that breakdown cellulose into monosaccharide nutrients by the use of beta-glycosidase enzymes. Cellulose is commonly accompanied by a lower molecular weight, branched, amorphous polymer called hemicellulose. In contrast to cellulose, hemicellulose is structurally weak and is easily hydrolyzed by dilute acid or base. Also, many enzymes catalyze its hydrolysis. Hemicelluloses are composed of many D-pentose sugars, with xylose being the major component. Mannose and mannuronic acid are often present, as well as galactose and galacturonic acid. Starch is a polymer of glucose, found in roots, rhizomes, seeds, stems, tubers and corms of plants, as microscopic granules having characteristic shapes and sizes. Most animals, including humans, depend on these plant starches for nourishment. The structure of starch is more complex than that of cellulose. The intact granules are insoluble in cold water, but grinding or swelling them in warm water causes them to burst. The released starch consists of two fractions. About 20% is a water soluble material called amylose. Molecules of amylose are linear chains of several thousand glucose units joined by alpha C-1 to C-4 glycoside bonds. Amylose solutions are actually dispersions of hydrated helical micelles. The majority of the starch is a much higher molecular weight substance, consisting of nearly a million glucose units, and called amylopectin. Molecules of amylopectin are branched networks built from C-1 to C-4 and C-1 to C-6 glycoside links, and are essentially water insoluble. Hydrolysis of starch, usually by enzymatic reactions, produces a syrupy liquid consisting largely of glucose. When cornstarch is the feedstock, this product is known as corn syrup. It is widely used to soften texture, add volume, prohibit crystallization and enhance the flavor of foods. Glycogen is the glucose storage polymer used by animals. It has a structure similar to amylopectin, but is even more highly branched about every tenth glucose unit. The degree of branching in these polysaccharides may be measured by enzymatic or chemical analysis._______________________________________________  LIPIDS AND RELATED COMPOUNDS Lipids are a heterogenous group of compounds related, either actually or potentially, to the fatty acids. They are water insoluble organic molecules that can be extracted from cells and tissues by non- polar solvents. Lipids are derivatives of fatty acids, and their naturally existing compounds. Biologically, lipids have a wide range of uses such as source of fuel, protective coat and component of membranes of every living cell. Lipids are classified as; Simple lipids which are esters of fatty acids with various alcohols and include: 1. Neutral Fats - esters of fatty acids with glycerol - liquid fats are known as oils 2. Waxes - esters of fatty acids with higher molecular weight nonhydric alcohols Complex lipids are esters of fatty acids containing other groups in addition to an alcohol and a fatty acid such as: 1. Phospholipids - contain a phosphoric acid residue and frequently have nitrogen-containing bases and other compounds like: a. glycerophospholipid (alcohol is glycerol) b. sphingophospholipid (alcohol is sphingosine) 2. Glycolipids (Glycosphingolipids) - contains fatty acid, sphingosine, and carbohydrates 3. Other complex lipids - includes sulfolipids and aminolipids Precursor and Derived lipids - products of hydrolysis of simple and complex lipids but still exhibiting the general physical characteristics of lipids - these include fatty acids, glycerol, steroids, alcohols (in addition to glycerol and sterols), fatty aldehydes and ketone bodies, hydrocarbons, lipid-soluble vitamins, and hormones - glycerides, cholesterol, and cholesterol esters are called neutral fats because they are without charge. - Lipids can be found from the following sources: - true fats generally constitute the storage material for energy in both plants and animals. - fat depot of animal body which is made up of excess fats derived from ingested food. - found in the subcutaneous and intra molecular connective tissues (omentum) which serves as heat insulator and reserves supply for energy. - compound lipids such as cerebrosides are constituents of highly specialized brain and nervous tissues. - phospholipids and sterols are intimately related with bile acids, vit. D and sex hormones. The following are some common lipids: Fatty acids - most abundant naturally occuring lipids. - building blocks of several classes of lipids like the neutral fats, phospoglycerides, glycolipids, cholesterol esters, and waxes - possesed long hydrocarbon chain and a terminal carboxyl group - chain may be saturated (without double bonds) or unsaturated (with 1 or more double bonds) - with few exceptions, they have an even number of carbon atoms. There are two types of fatty acids: 1. Saturated Fatty Acids: - belong to the acetic acid series and have the general formula CnH2nO2. - IUPAC name ends in IC + acid. - Have single bond only in their structure. - With low molecular weight. - Liquid at ordinary temperature. - With low melting point and are volatile. Their melting point increases with increasing molecular weights. - Characteristic of animal fats. The following are examples of saturated fatty acids: Butyric Acid CH3(CH2)2 COOH Caproic Acid CH3(CH2)4 COOH Caprylic acid CH3(CH2)6 COOH Capric Acid CH3(CH2)8 COOH Lauric acid CH3 (CH2)10 COOH Myriatic acid CH3 (CH2)12 COOH Palmitic acid CH3 (CH2)14 COOH Stearic acid CH3 (CH2)16 COOH Arachidic acid CH3 (CH2)18 COOH Lignoceric acid CH3 (CH2)20 COOH 2. Unsaturated Fatty Acids: - unstable and reactive due to the presence of double bonds. - IUPAC name ends in EIC + acid. - reactivity increases with increasing double bonds. - liquid at ordinary temperature and are non-volatile. - the greater the degree of unsaturation, the lower are their meting point and congealing points. - characteristic of vegetable fats. The following are examples of unsaturated fatty acids: Myristoleic acid CH3 (CH2) 3CH=CH(CH2) 7COOH Palmitoleic acid CH3 (CH2) 5CH=CH(CH2) 7COOH Oleic acid CH3 (CH2) 7CH=CH(CH2) 7COOH Linoleic acid CH3(CH2) CH=CH2CH=CH(CH2)7COOH Linolenic acid CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH - Palmitic acid makes up about 50% of total fatty acids in fats. - Oleic acid is the most abundant fatty acid in nature forming about 50% of the total fatty acids in many fats and is found in all naturally existing fats. Neutral fats 1. Triglycerides - esters of glycerol and fatty acid - When R, R1, and R2 are the same, the compound is a simple triglyceride. - Natural fats possess mixed glycerides; thus if R is oleic acid, R1 is stearic acid, and R2 is palmitic acid, the glyceride is called alphaoleyl, beta-stearyl, alpha'-palmitin - Glycerides of saturated fatty acids have higher melting points than glycerides of unsaturated fatty acids, thus vegetable fats, olive oil, castor seed oil contain more unsaturated fatty acids than animal fats such as lard and tallow - Ester groups are readily broken down by alkali through a process called saponification, a commercial method for the production of glycerol and soap. 2. Waxes - neutral fats that are esters of fatty acids and high molecular weight of alcohols, the most important of which is cholesterol. - alcohols range in length from 14-34 carbon atoms Examples: sperm oil, beeswax, lanolin Complex lipids 1. Phosphoglycerides - sometimes called phospholipids - esters formed by the union of different alcohols with phosphatidic acid in which the alpha' and beta positions are esterified with fatty acids and the alpha position with phosphoric acid - fatty acid in alpha' position is usually a long chain saturated fatty acid, such as palmitic or stearic; fatty acid in beta position usually unsaturated such as oleic , linoleic, or arachidonic acid. - Phospholipids of physiologicalimportance are:  a. phosphatidyl cholines (lecithins) - present in eggyolk, liver and nervous tissue. - soluble in all fat solvents except acetone - white, waxy substances that form emulsions - soybean lecithin used as emulsifying agent in food industry. - Enzyme lecithinase found in cobra venom and poisonous spiders hydrolysis lecithin producing lysolecithin which has hemolyzing effect upon RBC thus poisonous effects of the venom of cobra and some insects. b. phosphatidyl ethanolamines and phosphatidyl serines (collectively referred to as cephalins) - found in all tissues and cells but particularly abundant in brain and other nerve tissues - property very much similar to the lecithins. - A thromboplastic substance which initiates blood clotting. c. phosphatidyl inositols (lipositol) - occur in all cells and tissues 2. Sphingolipids (glycolipids) - formed by some fatty acids called ceramides nd sphingosine - general structure of sphingolipids indicated below where ceramides are in ether linkage to different compounds a. sphingomyelins - found in all tissues but very abundant in brain and nervous tissue b. cerebrosides - found in the membranes of brain tissue, particularly in the white matter c. gangliosides - usually found on the surface of cell membranes, especially of nerve cells 3. Prostaglandins - family of compounds comprising 14 fatty acids each containing 20 carbon atoms and having the same basic skeleton of prostanoic acid - involved in a number of biochemical interactions like regulation of blood supply, development of inflammatory response, regulation of ion influx across epithelial membrane, etc. 4. Steroids - found in association with fats and seperated from the fats after saponification in the "unsaponifable residue" - all possess similar cyclic nucleus resembling phenanthrene (rings A, B, and C), to which a cyclopentane ring is attached a. cholesterol - widely distributed in all cells particularly in the nervous tissue - major component of the plasma membrane - parent compound of all steroids synthesized in the body - occurs in animal fats, but not in plant fats b. ergosterol - occurs in plants and isolated from yeasts and certain mushrooms. - also found underneath the skin and serves as the precursor of vitamin D synthesis. c. coprosterol - occurs in feces as a result of the reduction of the double bond of cholesterol by bacteria in the intestine d. bile salts - constituent of bile - strongemulsifying agent that help disperse fatty materials - stimulate intestinal motility e. steroidal hormones - sex hormones; testosterone, estrogen, progesterone - ACTH  GENERAL PROPERTIES OF FATS B. Physical Properties: 1. Greasy. 2. Penetrate some materials like paper producing a translucent effect. 3. Neutral fats when pure are odorless, tasteless, and colorless. 4. Insoluble in ordinary solvents but soluble in organic solvents. 5. Non-volatile. 6. Produce characteristic crystals with definite melting point. 7. Maybe solid or liquid (oil) at ordinary temperature. 8. Floats on water because of its low specific gravity. When shaken with water, fats break into fine particles forming a temporary emulsion. C. Chemical Properties: 1. Hydrolysis – readily broken down by acids, enzymes or superheated stream liberating fatty acids and alcohol. 2. Saponification – formation of a metallic salt of fatty acid (soap) when heated with alkali. 3. Rancidity – becomes rancid or acidic when exposed to air. This is due to hydrolysis resulting in the liberation of volatile fatty acids, which are then oxidized forming odoriferous volatile aldehydes and ketones. 4. Identification- by the use of certain chemical constants such as: a. Iodine number – number of grams of iodine taken up by 100 g. of fat. It is the measure of the degree of unsaturation of a given fat/mole. b. Saponification number – number of milligram of an alkali required to neutralize the fatty acids contained in 1 g. of fats. It is a measure of the fatty acids in a given fat/mole. c. Acetyl number – number of milligram of KOH necessary to neutralize the acetic acid liberated from the hydrolysis of 1 g. of acetylated fat. Measures the number of hydroxyl group present in a given fat/mole. d. Reichert-Meissl Number- amount of 0.1 N of an alkali required to neutralize the volatile fatty acids distilled from 5 g. of fat. Use in the detection of butter substitutes. FUNCTIONS Lipids functions as: 1. membrane structural components 2. intracellular storage depots of metabolic fuel 3. transport form of metabolic fuel 4. protective form of cell walls of many bacteria, of leaves of higher plants, of the exoskeleton of insects, and the skin of vertebrates 5. regulatory substances 6. transport forms of some neurotransmitters 7. receptors in nerve ending membranes 8. determinants of immunological specificity 9. enzyme cofactors --------------------------------------------------------------------------------------------------------------------------------------------------  PROTEINS Proteins are the most abundant of all organic substances in the cell. They are generally large, complex molecules that are required in different aspects of cell structure and function. Composition Proteins are made up of amino acids. Each amino acid has an asymmetrical alpha carbon to which are attached 1) a hydrogen, H; 2) an amino group NH2; 3) a carboxyl group, COOH; and 4) a radical, R which vary in different amino acids. Amino acids may be classified into different types based on the R group present. The structural formulas of some amino acids together with their three-letter three and single-letter letter abbreviations are shown below. 1. Acidic Amino Acids Aspartic Acid Glutamic Acid Hydroxyglutamic Acid 2. Basic Amino Acids Arginine Histidine Lysine 3. Branched-Chain Amino Acids Leucine Isoleucine Valine 4. Aromatic Aminod Acids Phenylalanine  Histidine Tryptophan 5. Sulfur Containing Amino Acids Cystine Cystein Methionine 6. Hydroxy Amino Acids Serine Threonine 7. Neutral Amino Acids Glycine Alanine 8. Acid Amide Amino Acids Asparagines Glutamine  9. Imino Acid Proline Hydroxyproline These amino acids are further classified into: 1) non-essential non essential or dispensable amino acids and 2) essential or indispensable amino acids. Non Non-essential essential amino acids are those amino acids which the body can synthesize. Essential amino acids are those which tthe he body cannot synthesize and thus must be supplied to the body from the diet. Of the 20 amino acids nneded in the synthesis of body proteins, the following are classified as essential: histidine, leucine, isoleucine, lysine, methionine, arginine, threonine, threonin phenylalanine, valine, and tryptophan. Under appropriate isoelectric pH for a given amino acid, the molecule may appear as a dipolar ion or Zwitterion. The COOH group may release its H becoming COO’ while the NH2 group can accept the H and is converted to NH3+. The molecule, therefore, is also amphoteric since it can behave both as an acid or proton donor and a base or proton acceptor. Peptide Bond Formation Polypeptides or proteins are formed by the chemical reaction between the amino group of one a amino acid and the carboxyl group of another amino acid forming amide linkages called peptide bonds. These bonds arise from the elimination of water from the carboxyl group of one amino acid and the amino group of the next amino acid. Structural Levels of Proteins Proteins exhibit four structural levels: primary, secondary, tertiary, and quaternary structures. These levels are manifested in the shape of the molecule which is the result of the type of bonding that the R group can form. 1) The primary structure refers to the sequence of amino acids in the polypeptide chain. These amino acids are covalently linked by peptide bonds resulting in a long unbranched molecule. 2) The secondary structure refers to the regular recurring arrangement of the polypeptide chain along one dimension. It is the result of H bonds formed between oxygen of C=O and the hydrogen of –N-H. the molecule may be helical like in myosin or in the form of a pleated sheet as in stretched chain keratin.  3) The protein’s tertiary structure is formed by folding, refolding, and supercoiling of the polypeptide chain. The type of bonds present are hydrophobic, ionic, covalent, disulfide, and H bonds. It results in either a compact pact globular structure as in ovalbumin or a fibrous or rod-like rod like structure as in fibrinogen and collagen. 4) The quaternary structure of proteins refers to how individual polypeptide chains of protein having 2 or more chains are arranged in relation to each other. Each component chain is called a protomer. The chains may be held by –S-S- bonds or by covalent bonds bonds of the R groups. This type is exemplified by insulin with 2, thrombin with 3 and hemoglobin with 4 protomers respectively. Characteristics Proteins are easily denatured or destroyed upon exposure to high temperature or extremes of pH. Due to o their large size, all are undialyzable or they cannot pass through plant or animal membranes. They give specific color reactions to certain reagents that can be used to detect their specific chemical composition. They can behave both as an acid and as a base and above all have the property of specificity. Chemical Properties Proteins are hydrolyzed by dilute acids, alkalis and enzymes and are precipitated by acids, salts of heavy metals and alcohol. They may form complexes with nucleic acids, carbohydrates, lipids, enzymes, and pigments. Regardless of its amount, it has a constant solubility Classification Proteins may be classified on the basis of the following: A. Composition 1. Simple protein – contain only amino acids 2. Complex or Conjugated proteins prote – contain additional non-amino amino acid materials a. chromoproteins – wit ha pigment like hemoglobin, cytochromes, flavoproteins b. nucleoproteins – with nucleic acids like histones nad protamines c. glycoproteins – with carbohydrates like mucin in saliva d. Phosphoproteins – with phosphoric acid like the enzyme phosphodiesterase e. Lipoprotein – with fatty substances found in brain tissue B. conformation of three-dimensional dimensional shape of molecule 1. Fibrous protein where the polypeptide chains are arranged in parallel cha chains ins along a single axis to form long sheets or fibers. Elastin, collagen, and keratin are examples of this type. 2. Globular protein where the polypeptide chains are tightly folded into spherical or globular shapes as exemplified by enzymes, serum albumin, antibodies, an and hormones. C. Solubility 1. Albumins – soluble in water and salt solution; with no distinctive amino acid 2. Globulins – sparingly soluble in water but insoluble in salt solution; with no distinctive amino acid 3. Pro amines – soluble in 70-80% 80% ethanol bu butt insoluble in water and absolute ethanol; arginine-rich arginine 4. Histones – soluble in salt solution 5. Scleroproteins – insoluble in water or salt solution; rich in glycine, alanine, praline Biological Functions of Proteins Proteins have varied functions. As major components off enzymes, they cat as organic catalysts in different kinds of chemical reactions. Aside from enzymes, the regulatory function of proteins may be exercised by acting as hormones. One such hormone is insulin, necessary for the proper cellular absorption of glucose. Some proteins serve as food reserves especially for the growing embryo. Examples of such proteins are ovalbumin of egg white, casein of milk, gliadin of wheat seeds and zein, the se4ed protein of corn. Another group of proteins has the ability to bind and transport specific molecules via the blood. This is exemplified by hemoglobin in the red blood cells which transports oxygen from the lungs to the tissues and carbon dioxide from the tissues to the lungs. Proteins may have protective or defensive function as in the case of immunoglobulins or antibodies. Thrombin and fibrinogen are necessary for blood clotting to protect the body against excessive loss of blood. Other types of protein serve as structural materials of cells and tissues. Actin and myosin in muscle cells are necessary for contraction. Fibrous proteins like collagen, elastin and keratin are important constituents of connective tissues. All these functions are characterized by specificity, a particular enzyme catalyzes the reaction of specific substrates; antibodies are specific for certain antigens; the structural proteins are characteristic for a given cell or tissue; hormones activate only specific cells or organs; and transport proteins carry only specific molecules. Its three-dimensional conformation gives each type of protein its biological activity and its conformation in turn, is determined by the specific kind, number, and sequence of amino acids in the polypeptide chain.