Examine the structure and function of proteins - Essay Example

? The structure and function of proteins Proteins are amino acids’ polymers, which are covalently bonded through peptide bonds forming a chain (Box et al, 2005). In and outside cells, proteins have several functions including acting as transporters to ferry molecuules and ions across membranes, structural roles for instance cytoskeleton, acting as hormones, and catalyzing other biological body reactions (He J et al., 2005). Biotechnology entails understanding, exploiting, and modifying proteins for useful purposes. In order to accomplish this, one needs to understand various fuctions of proteins and their structure. The focus of this paper is to summarize various structures of proteins, various funcions of protein molecule in the cell, the link between molecular structure of proteins and their function, and how proteins as a whole contribute to health and/or disease. Studies conducted in this field have shown that there are four categories of protein structure. These are the primary structure, secondary structure, tertiary structure, and quaternary structure. The amino acids are made up of a backbone section which is available in the different types of amino acids, together with a side chain for each residue (Nelson, L. & Cox, M. 2008). Since the carbon atom remains bound to the four categories, one isomer would happen in the biological protein. In this case, the molecules would be chiral. Glycine fails to be chiral due to the fact that it has a side chain that is an atom of hydrogen. The amino acids are bonded by a covalent bond chain which are referred to as the peptide bonds (Brown EC et al. 2004). Whenever the chain is short, such a chain is called a peptide. The chains that are long are referred to as proteins or polypeptides. In many cases, the peptide bonding is established in between the one amino acid carboxyl group together with the amino group. The bonding of peptides happens in the reactions of condensation, which involve the loss of a molecule of water. Primary structure of proteins. The primary structure proteins is the amino acid polypeptide chain sequence. The basic structure is combined together using the covalent bonding just like the case of the peptide bonds, which are often established in the translation process of proteins. The two ends of a polypeptides are referred to as the C-terminus. In this, the carboxyl terminus, and the N-terminus are the amino terminus (Mahn K et al. 2005). In order to count the residues, one would begin at the N-terminus, which involves the terminus where the group of amino acid fails to be involved in the peptide boding (Nelson, L. & Cox, M. 2008). This type of structure is identified by the corresponding gene to the protein molecule. A particular nucleotide sequence in DNA is normally shifted to the mRNA that is interpreted by ribosome in a process referred to as translation (Mahn K et al. 2005). In this case, the protein sequence is specific to the particular protein, and identifies the structure and the roles of the protein molecule. Protein sequence could be determined through tandem spectrometry tandem mass, and Ednan degradation (Nelson, L. & Cox, M. 2008). In most cases, it is always interpreted directly from the gene sequence through the utility of the genetic code. The post-translational modifications including the formation of disulfide, glycosylation, is considered as a section of the primary structure hence cannot be identified from the specific gene. For instance Insulin has fifty one amino acids classified in two chains, one having thirty one amino acids, and the other one having twenty amino acids (Mahn K et al. 2005). The primary structure is displayed in diagram 1. Diagram 1. Secondary structure. This is the second structure of proteins displaying the regular local sub-structures. The two categories of secondary structure include the betastrand, and the alpha helix (Nelson, L. & Cox, M. 2008). These structures are normally identified by the hydrogen bonding pattern between the key chains of peptide groups (Lukaczer D et al. 2006). They poses a smooth geometry that is constrained to particular values of dihedral angles on the plot of Ramachandran. The beta-sheet and the alpha helix are a representation of a saturation of all the hydrogen donor bonds together with the peptide backbone acceptors. Some sections of the protein would be ordered but fail to come up with a regular structure. These structures should not be confused with the randomized coils because they are the unfolded polypeptides with no fixed three dimensional structure. The secondary structure of protein is displayed in diagram 2. Diagram 2. Tertiary structures. This is the third of proteins and involves the three dimension structure of triple, double, and single bonding of the molecule of protein. The beta pleated and alpha-helixes sheets are normally folded to form a global structure (Lukaczer D et al. 2006). The global structure, in this case, is considered to be compact. This type of folding is directed by the hydrophobic interactions, which are considered to be non-specific. The structure is only stable whenever the protein sections domain is locked in place by particular tertiary interaction like those of hydrogen bonds, side chains of tight packs, salt bridges, and disulfide bonds (Nelson, L. & Cox, M. 2008). In many cases, the disulfide bonding appears to be rare for the cytosolic molecules of protein as the cytosol involves a reducing environment. The tertiary structure is displayed in diagram 3. Diagram 3. Quaternary protein structure. Quaternary structure involves a three-dimensional structure for three multi-protein subunit, and the manner in which the sub-unit links together. This structure experiences is stabilized by the interactions of the non-covalent disulfide bonds. More than two polypeptides complexes are referred to as the multimers (Kovacs-Nolan J et al. 2005). Particularly, this would be referred to as a dimer, whenever it is made up of two subunits. It can be referred to as a trimer whenever it is made up of three subunits. A tetramer occurs when there exist four sub-units.. In many cases, the subunits would relate to each other through symmetry operations like the case of a 2-fold axis inside a dimer (Nelson, L. & Cox, M. 2008). Other multimers that have identical subunits are identified using the ‘homo’ prefix, and those established from many subunits would be identified by the ‘hetero’ prefix. Diagram 4 represents the quaternary protein structure. Diagram 4. Function of proteins in the cell. Proteins are vital molecules in the cells of living organisms. They take part in all functions of the cell. Some are involved in the structural support whereas others are involved in providing defense against foreign bodies, and bodily movement (Kovacs-Nolan J et al. 2005). The protein molecule vary in terms of their function and structure. They have three dimensional shapes, and are made from a set of twenty amino acids. To start with the antibodies, this is specialized proteins that take part in protecting the body from antigens (McVeigh BL et al. 2006). They move through the blood stream and used by the system of immunity in identifying and providing defense against viruses, bacteria, and foreign bodies. The antibodies immunize the antigens, to allow the white blood cells to destroy them. The contractile proteins have a vital function in movement (McVeigh BL et al. 2006). For instance, the myosin, and actin are involved in the movement and contraction of the muscles. The enzymes involve the protein molecule that enhances the biochemical reactions. These proteins are called catalysts since they have a key role in speeding up the chemical reactions. For instance, the lactase enzyme is responsible in breaking down the lactose in the milk. In addition, pepsin involves another digestive enzyme which is responsible in breaking down the protein found in the food (Lukaczer D et al. 2006). The hormonal proteins involve the messenger proteins that help in coordinating some specific activities of the body. For example, insulin is used in regulating the metabolism of glucose through controlling the concentration of blood sugar. Structural proteins are stingy and fibrous form of protein which is responsible in giving out support (Kovacs-Nolan J et al. 2005). A good example is the Keratin that strengthens the protecting coverings like quills, hair, horns, feathers, and beaks. The storage proteins such as the ovalbumin, are responsible in storing the amino acids. The transport proteins like the hemoglobin are the protein carrier that moves molecules from one part of the body to another (Mahn K et al. 2005). In this regard, the protein molecule is an end product of a process of decoding, which begins with the cellular DNA information. In the cell, protein function as work horses. They constitute the motor, and structural elements within the cell, which function as catalysts for all biochemical reactions which happen in the cells of living organisms (McVeigh BL et al. 2006). All the genes inside the cellular DNA have a code for the different unique structure of protein. These proteins are not only assembled through different sequences of amino acid, but also held together by other bondings and folded to form the three-dimensional structures (Jenkins DJ et al. 2006). The folding of different shapes depends on the linear sequence of amino acid of the protein. Sources of protein. Protein molecules are derived from the diet that is consumed by a living organism. An appropriate protein combination depends on the access, region of the world, types of amino acids, cost, and nutritional balance. Some diets have high amino acids, but their digestibility and the anti-nutritional factor in these foods make them be of limited value to the nutrition of humans. The protein obtained from plants contribute more that sixty percent of whatever protein that is needed by the body. The diets obtained from animals has about seventy percent of protein sources. In this case, foods like fish, meat, and eggs, are great sources of complete protein (Kovacs-Nolan J et al. 2005). In addition, milk together with the milk derived foods are equally good protein sources. Cereals, and whole grain are a source of protein which has limited amino acid threonine, that could be found in other meats, and vegetarian sources. Some examples of diets and cereal protein sources with a concentration above seven percent could be found in oats, buckwheat, rye, maize, millet, wheat, bulgar, spaghetti, quinoa, and amaranth. The vegetarian protein sourced include seeds, legumes, nuts, and fruits (Nelson, L. & Cox, M. 2008). Protein in health and disease. Protein is an important nutrient in the diet of a living organism. The absence of protein in the diet can play a number of roles in proving health issues such as low blood pressure, edema, and heart problems. Malnutrition is a disease that result due to the absence of the required amount of protein in one's diet (Jenkins DJ et al. 2006). Diseases such as marasmus, and kwashiorkor occur as a result of insufficient protein in the diet. This condition leads to the wasting away of the tissues thus leading to the development and growth issues. On the other hand, not getting the required level of proteins could trigger disease like liver cirrhosis, and muscle shrinking. Other patients have been reported to suffer from congenital protein C or S deficiency, that can lead to problems with the clotting of blood. A good number of individuals who failed to include protein in their diet have developed thrombosis. The quantity of protein that is needed in a diet of an individual is greatly determined by the general intake of energy for the essential amino acids, and nitrogen, body composition, and weight, growth rate of an individual, individual energy, physical activity, intake of carbohydrate, and the existence of an illness (Nelson, L. & Cox, M. 2008). The requirement of protein would also increase depending on the exertion, physical activity, and the enhanced muscle mass. During childhood, protein requirements are higher as a result of development and growth. There is also a high demand of proteins during pregnancy and breastfeeding so as to nourish the baby. Whenever enough protein is not taken in, the body would utilize the protein in the muscle to satisfy the energy demands, resulting in the wasting of the muscle for some time. When an individual takes in enough proteins, the muscles would be able to operate normally. References. Box, w., Hill, S., & DiSilvestro, RA., 2005. The Soy intake plus moderated weighting resistance exercise: effects on serum concentration of lipids peroxide in young adults women. Journal Sports Med Phys Fitness, 45(4):524-8.  Brown EC et al., 2004. The Soy against whey protein bar: effects on exercises training impacts on mean body mass and the antioxidant status. Nutr J, 8;3:22.  He J et al., 2005. The effects of soybean proteins on blood pressure: a random, control trial. Ann Intern Medical, 5;143 (1) :1-9.  Jenkins DJ et al., 2006. Assessment of long-term effect of a diet portfolio on cholesterol-lowering food in hypercholesterolemia. Am J Clin Nutr; 83(3):582-91.  Kovacs-Nolan J et al., 2005. Advancement in the values of egg and eggs component for human health. Journal Agric Food Chemical, 2;53(22):8421-31. Lukaczer D et al., 2006. Effecta of a lowering the glycemic index diets with soy proteins and phytosterol on CVD risk factor in postmenopausal women. Nutrition, 22(2):104-13.  Mahn K et al., 2005. The dietary soy isoflavone induces increase in antioxidant and eNOS genes expression leadding to improvement in endothelial functions and reduced pressure of blood in vivo. FASEB J, 19(12):1755-7.  McVeigh BL et al., 2006. Effects of soy proteins varying in isoflavones content in serum lipid in healthy young men. Am J Clin Nutr, 83(2):244-51.  Nelson, L., & Cox, M., 2008. Lehninger, Principles of Biochemistry, fifth edition. New York: Freeman & Co. Read More