Structure of Food Components and Colloidal Interactions in Food Systems - Article Example

FOOD HYGIENE AND NUTRITION Student name: Class name: Instructor’s name: School name: Date: Introduction Starch, triacylglycerols and a protein are the major components of food in the body. Starch is a component of food and a polymer of carbohydrates. Starch is made up of units of glucose. Glycoside bonds join together the glucose units of starch forming a polymer of carbohydrate. Glucose is a polysaccharide which many plants use to store their energy. Starch is the major component of food and common in diets of humans. Staple foods like wheat, maize, potatoes, cassava and rice contain starch in large quantities. In plants, molecules of starch arrange themselves in semi-crystalline structure. When heated, starch dissolves in water. When heated, starch’s semi-crystalline granules first swell and then burst losing their original semi-crystalline structure and its amylase molecules begin leaching out from the granule. This leads to formation of a network hence holding the water and raising the viscosity of the mixture. (Vance 2002). Triacylglycerol is made up of 3 fatty acids and glycerol. The 3 fatty acids and glycerol combine to form an ester called triacylglycerol. Triacyglycerol is the major component of vegetable fats and humans’ and animals’ body fats. Skin oils of humans also contain this food component. Blood also contains this food component where it plays a crucial role of adipose fats’ bidirectional transference. We have unsaturated and saturated triacylglycerol. Saturated ones are found in sites where carbon atoms bond with hydrogen atoms. The melting point of the saturated fats is higher and at room temperature, they are solid. There exist double bonds between carbon atoms, but not all, in the case for unsaturated fats. Existence of double bonds reduces the number of hydrogen bonds required for the bonding resulting to lower melting point for unsaturated fats. At room temperature, unsaturated fats are in liquid state (Berg 2007). Proteins, being macromolecules exhibit four levels, which are different, of structure: primary, secondary, tertiary and quaternary. To study the quaternary structure, you must fist understand the other three structures, that is, the primary, secondary and the tertiary structures. Beginning with primary structure which has about 20 standard L-alpha-amino acids which are different, cells use the amino acids for construction of protein. Amino acids contain a carboxyl group which is acidic and amino group which is basic. This nature makes the amino acids to form long chains by joining together with peptide bonds between the molecules. The amide bonds exist between any two different –NH2 and –COOH of the amino acids. 50 and below amino acids form sequences that are known as peptides. Polypeptide and proteins are used in cases of longer sequences. The number of molecules in proteins is not fixed since they can have more than one polypeptide molecules. C-terminus or a carboxyl terminus is the name given to the ends of protein or peptide sequence if they have a carboxyl group which is free. N-terminus or amino-terminus is used to describe the cases where the sequence ends with a group of free alpha-amino. The substituent in the amino acids side chains makes them to differ in structure. There are different physical, structural and chemical properties conferred by these side chains to the most final protein or peptide (Holm & Rosenstrom, 2010). Classification of amino acids into basic, acidic or neutral depends upon the substitutes of their side chains. 20 amino acids are usually required to synthesis various proteins in the body of humans but only 10 can also be used in the synthesis. The remaining amino acids, 10 in number, are termed as essential and they are only gained from the diet. DNA encodes the sequence of protein’s amino acids. Protein synthesis follows serial steps referred to as transcription and translation. Transcription involves construction of complimentary messenger strand of RNA using DNA strand while translation involves the guidance of the complimentary messenger strand of RNA to synthesis the amino acids chain of the protein sequence. Phosphorylation and glycosylation modifications which often occur after translation are essential for protein’s biological functions. While the protein’s primary structure s made up of the sequence of the amino acids, the proteins biological or chemical properties depend much on the tertiary or three-dimensional structures (Holm & Rosenstrom, 2010). Peptides’ or protein’s strands or stretches have different characteristics of conformation’s local structure also known as secondary structure which is dependent on a type of bonding called hydrogen bonding. Β-sheet and α-helix are the secondary structure’s main types. Α-helix strand is coiled on the right hand side. The amino acid groups’ substitutes of the side chain extend outwards in α-helix strand. Hydrogen bonds exists between C=O and oxygen of every peptide bond within the strand and the group of N-H belonging to the peptide bond and hydrogen for all the amino acids below the group in the strand of helix. This structure is made especially stable by the hydrogen bonds. Beside the groups of N-H, amino acids side-chain substitutes are fitted. Β-sheet has hydrogen bonds between its strands instead of within its strands. The sheet conformation has pairs made of strands which lie side by side. In one strand of hydrogen, carbonyl oxygen is bonded with the adjacent strand’s amino hydrogen. Depending on whether the directions of the strands are opposite or the same, the strands can either be anti-parallel or parallel. The more the hydrogen bonds are well aligned, the more stable is the β-sheet hence the anti-parallel one is the most stable (Zhang 2008) Tertiary structure is the overall shape, three-dimensional, of a complete protein molecule. To achieve a state of low energy or maximum stability, the protein molecule has to twist or bend in a certain way. The protein’s shape, three-dimensional, depends on the forces of the forces generated by its molecules while gaining the maximum stability to achieve low energy state hence the shape can be random or irregular. Non-polar amino acidic strands like phenylalanine, neutral hydrophobic side-chains and isoleucine are buried on protein molecules’ interior to protect them from physiologic conditions such as aqueous medium. Hydrophobic interactions are formed between isoleucine, leucine, valine and alanine alkyl groups while tyrosine and phenylalanine aromatic groups stuck together often. Since the side-chains of basic and acidic amino acids are hydrophilic, they are exposed generally on the proteins’ surface (Hayne, & Xue, 2015). Disulphide bridges formed by oxidation of cysteine’s sulfhydryl group play a crucial role in stabilizing the tertiary structure of the proteins hence bonding covalently the protein chain’s different parts. There may also be hydrogen bonds between non-similar side-chain groups. The protein tertiary structure is also stabilized by the salt bridges which are interactions of ions between negatively and positively charged amino acidic side-chain’s sites. Many proteins have many polypeptide chains which are often called protein subunits. Quaternary structure of protein therefore depends on the interactions of these different protein subunits with one another and their arrangements to form larger protein complex. Salt bridges, disulfide bridges and hydrogen bonding interactions stabilize the protein’s complex final shape (Hayne, & Xue, 2015). Protein denaturation involves possible destruction and disruption of both tertiary and secondary structures. Primary structure remains unchanged after the denaturation process since the reactions are weak and cannot break peptide bonds in the primary structure. Protein denaturation uncoils α-helix and β-sheets into a shape which is random. Disruption of the secondary and the tertiary structures’ bonding interactions results to protein denaturation. Denaturation can be caused by variety of conditions and reagents. Protein coagulation or precipitations are commonly observed protein denaturation processes (Jaremko, Jeremko, Kim, Cho, Schwieters, Giller, Becker, & Zweckstetter, 2013). Temperature changes disrupt the interactions between non-polar hydrophobias and hydrogen bonds. This occurs simply because, high temperatures increases the molecules’ kinetic energy vibrating the molecules more violently and rapidly hence disrupting the bonds. For example, while cooking an egg, its proteins are denatured and coagulated. Other foods which are rich in protein are also cooked so that its proteins are denatured making work easier for digestive enzymes in the body. Medical instruments and supplies contain protein bacteria which have to be sterilized before use to avoid transferring the bacteria to another person. To sterilize them, they are heated hence denaturing the proteins in the bacteria (Jaremko, Jeremko, Kim, Cho, Schwieters, Giller, Becker, & Zweckstetter, 2013 Conclusion A mixture whereby, one substance is suspended over another is called a colloid. The substance which is dispersed is termed as colloid while the word colloidal suspension is used when the overall mixture is unambiguous. In colloidal system where one amount of electrolyte is low, a conventional theory of double layer cannot be used in describing the interactions of electrons among the particles. Counter ions’ contributions which are derived from the colloidal particles are proposed. This results to a potential of colloid-colloid pair which differs from the present colloidal particles’ volume fraction in the system (Gonzalez 2016) Reference Berg, J (2007). Biochemistry. Sixth edition. New York: W.H. Freeman. Gonzalez, M (2016). Effective electrostatic interactions among charged thermo-responsive micro gels immersed in a simple electrolyte. Journal of chemical physics. Jaremko, M, Jeremko, L, Kim, H, Cho, M, Schwieters, C, Giller, K, Becker, S & Zweckstetter, M (2013). Cold denaturation of a protein dimmer monitored at atomic resolution. Natural chemistry biology 9(4): 264-70 Hayne, D & Xue, B (2015). ‘’Super domain in the protein structure hierarchy: the case of PTP-C2’’.Protein science. 24: 874-82 Zhang, Y (2008). ‘’ Progress and challenges in protein structure prediction’’. Curriculum of opinion structural biology. 18(3): 342-348 Holm, L & Rosenstrom, P (2010). ‘’ Dali server: conservation mapping in 3D’’ Nucleic Acids Research. 38(web server issue): W545-9 Vance, J & Vance, D (2002). Biochemistry of lipids, lipoproteins and membranes. Amsterdam: Elsevier Read More