Proteins are composed of amino acids and play many essential roles in the body. They have four levels of structure: primary, secondary, tertiary, and quaternary. The primary structure is the amino acid sequence, secondary involves hydrogen bonding into shapes like alpha helices and beta sheets, tertiary is the 3D folding of these structures, and quaternary involves the assembly of multiple protein subunits. Proteins serve as enzymes, hormones, antibodies, and structures. They undergo synthesis from amino acids and breakdown through catabolism. Disorders can occur if amino acid metabolism is disrupted.

1. PROTEINS

2. Proteinsare biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form in a biologically functional way.

3. HistoryProteins were first described by the Dutch chemist Gerardus Johannes Mulder and named by the Swedish chemist Jöns Jacob Berzelius in 1838. Early nutritional scientists such as the German Carl von Voit believed that protein was the most important nutrient for maintaining the structure of the body, because it was generally believed that "flesh makes flesh.“The central role of proteins as enzymes in living organisms was however not fully appreciated until 1926, when James B. Sumner showed that the enzyme urease was in fact a protein. The first protein to be sequenced was insulin, by Frederick Sanger, who won the Nobel Prize for this achievement in 1958. The first protein structures to be solved were hemoglobin and myoglobin, by Max Perutz and Sir John Cowdery Kendrew, respectively, in 1958. The three-dimensional structures of both proteins were first determined by X-ray diffraction analysis; Perutz and Kendrew shared the 1962 Nobel Prize in Chemistry for these discoveries.

4. Protein StructureAn α-amino acid. The CαH atom is omitted in the diagram.CO-R-N ruleBond angles for ψ and ωTwo amino acids

5. Levels of Protein StructurePrimary StructureThe primary structure refers to amino acid sequence of the polypeptide chain. The primary structure is held together by covalent or peptide bonds, which are made during the process ofprotein biosynthesis or translation. The two ends of the polypeptide chain are referred to as the carboxyl terminus (C-terminus) and the amino terminus (N-terminus) based on the nature of the free group on each extremity. Counting of residues always starts at the N-terminal end (NH2-group), which is the end where the amino group is not involved in a peptide bond. Secondary StructureSecondary structure refers to highly regular local sub-structures.These secondary structures are defined by patterns of hydrogen bonds between the main-chain peptide groups. They have a regular geometry, being constrained to specific values of the dihedral angles ψ and φ on the Ramachandran plot. Both the alpha helix and the beta-sheet represent a way of saturating all the hydrogen bond donors and acceptors in the peptide backbone.

6. Levels of Protein StructureTertiary StructureTertiary structure refers to three-dimensional structure of a single protein molecule. The alpha-helices and beta-sheets are folded into a compact globule. The folding is driven by the non-specific hydrophobic interactions (the burial of hydrophobic residues from water), but the structure is stable only when the parts of a protein domain are locked into place by specific tertiary interactions, such as salt bridges, hydrogen bonds, and the tight packing of side chains and disulfide bonds. The disulfide bonds are extremely rare in cytosolic proteins, since the cytosol is generally a reducing environment.Quaternary StructureQuaternary structure is a larger assembly of several protein molecules or polypeptide chains, usually called subunits in this context. The quaternary structure is stabilized by the same non-covalent interactions and disulfide bonds as the tertiary structure. Complexes of two or more polypeptides (i.e. multiple subunits) are called multimers.

7. Functions of proteinAntibodiesHormonal Proteinsare specialized proteins involved in defending the body from antigens (foreign invaders). One way antibodies destroy antigens is by immobilizing them so that they can be destroyed by white blood cells. are messenger proteins which help to coordinate certain bodily activities. Examples include insulin, oxytocin, and somatotropin. Insulin regulates glucose metabolism by controlling the blood-sugar concentration. Oxytocin stimulates contractions in females during childbirth. Somatotropin is a growth hormone that stimulates protein production in muscle cells. Contractile Proteinare responsible for movement. Examples include actin and myosin. These proteins are involved in muscle contraction and movement. Structural ProteinsEnzymesare fibrous and stringy and provide support. Examples include keratin, collagen, and elastin. Keratins strengthen protective coverings such as hair, quills, feathers, horns, and beaks. Collagens and elastin provide support for connective tissues such as tendons and ligaments.are proteins that facilitate biochemical reactions. They are often referred to as catalysts because they speed up chemical reactions. Examples include the enzymes lactase and pepsin. Lactase breaks down the sugar lactose found in milk. Pepsin is a digestive enzyme that works in the stomach to break down proteins in food.

8. Functions of proteinStorage Proteinsstore amino acids. Examples include ovalbumin and casein. Ovalbumin is found in egg whites and casein is a milk-based protein.Transport Proteinsare carrier proteins which move molecules from one place to another around the body. Examples include hemoglobin and cytochromes. Hemoglobin transports oxygen through the blood. Cytochromes operate in the electron transport chain as electron carrier proteins.

9. ProteinmetabolismProtein metabolism denotes the various biochemical processes responsible for the synthesis of proteins and amino acids, and the breakdown of proteins (and other large molecules, too) by catabolism.Protein anabolismis the process by which protein are formed from amino acids (aka anabolic amino acid synthesis).

10. Protein catabolismis the process by which proteins are broken down to their amino acids. This is also called proteolysis.Proteins contain carbon, hydrogen, oxygen, nitrogen , and sometimes other atoms. They form the cellular structural elements, are biochemical catalysts, and are important regulators of gene expression . Nitrogen is essential to the formation of twenty different amino acids, the building blocks of all body cells. Amino acids are characterized by the presence of a terminal carboxyl group and an amino group in the alpha position, and they are connected by peptide bonds.Digestion breaks protein down to amino acids. If amino acids are in excess of the body's biological requirements, they are metabolized to glycogen or fat and subsequently used for energy metabolism. If amino acids are to be used for energy their carbon skeletons are converted to acetyl CoA, which enters the Krebs cycle for oxidation, producing ATP. The final products of protein catabolism include carbon dioxide, water, ATP, urea, and ammonia.Vitamin B 6 is involved in the metabolism (especially catabolism) of amino acids, as a cofactor in transamination reactions that transfer the nitrogen from one keto acid (an acid containing a keto group [-CO-] in addition to the acid group) to another. This is the last step in the synthesis of nonessential amino acids and the first step in amino acid catabolism. Transamination converts amino acids to L-glutamate, which undergoes oxidative deamination to form ammonia, used for the synthesis of urea. Urea is transferred through the blood to the kidneys and excreted in the urine.

11. The glucose-alanine cycle is the main pathway by which amino groups from muscle amino acids are transported to the liver for conversion to glucose. The liver is the main site of catabolism for all essential amino acids, except the branched-chain amino acids, which are catabolized mainly by muscle and the kidneys. Plasma amino-acid levels are affected by dietary carbohydrate through the action of insulin, which lowers plasma amino-acid levels (particularly the branched-chain amino acids) by promoting their entry into the muscle.Body proteins are broken down when dietary supply of energy is inadequate during illness or prolonged starvation. The proteins in the liver are utilized in preference to those of other tissues such as the brain. The gluconeogenesis pathway is present only in liver cells and in certain kidney cells.Disorders of amino acid metabolism include phenylketonuria , albinism, alkaptonuria, type 1 tyrosinaemia, nonketotic hyperglycinaemia, histidinaemia, homocystinuria, and maple syrup urine disease.

12. Protein Synthesisis the process in which cells build proteins. The term is sometimes used to refer only to protein translation but more often it refers to a multi-step process, beginning with amino acid synthesis and transcription of nuclear DNA into messenger RNA, which is then used as input to translation.

13. Protein Synthesis Presentation

14. Protein Rich-FoodsBeansAs mentioned before, one half cup of beans contains as much protein as a 3 oz steak! Beans are a cheap, easy solution to just about any meal. Try black beans in a taco for lunch or a side of lima beans with your dinner.EggsOne egg contains 6 grams of protein. Eggs also contain many vital vitamins and minerals and all of the essential amino acids. An egg over-easy is a great breakfast or try a poached egg with spinach for dinner.SeafoodDairySeafood is a great way to get healthy, high quality protein. Fishes such as salmon contain Omega-3 Fatty Acids, which is great for the heart and brain. Try salmon with brown rice and kale for an extremely healthy, protein charged dinner.Milk, cheese, and yogurt are all protein rich foods. Milk contains about 6.3 grams of high quality protein! Dairy products also contain calcium, which is great for strong bones and teeth. Add milk or yogurt to a smoothie and have some cubes of cheddar cheese as a snack- cheddar contains 25 grams of protein for every 100 grams.

15. Protein Rich-FoodsPoultryLean white meats such as turkey or chicken (without the skin) are high in protein low fat foods. Either a turkey sandwich or a chicken salad would be a perfect lunch to get you through the rest of the day without being hungry.SoySoy is a great form of protein for vegans or vegetarians. Studies have shown that 25 grams of soy protein can reduce the risk of heart disease. Try edamame beans as a pre-dinner snack or a glass of soy milk in the morning with breakfast.BeefA lean cut of beef is an excellent source of high quality protein. Beef contains about 25 grams of protein and has zinc, iron, and vitamin B12. Try a lean cut of beef with crisp iceberg salad or oven roasted potatoes.

16. As 40% of the body’s dry matter is protein, so, after water, protein is the 2nd most important nutrient for the human body.Around 60% of the human body constitutes water & 40% is dry matter. This makes water the most essential nutrient for the human body.The word Protein has originated from the Greek word "Porto's" which means to come first.Only water is more important than proteins, as just a 8% deficit in your body’s water store could lead to serious eventualitiesif your body loses more than 14% of its Protein store, it could lead to severe health consequences.IMPORTANTFACTSSevere depletion of protein can lead to –• Loss of muscle mass causing physical weakness.• Fatigue• A weakened immune system.AsktheAbOuTpRoTeIneGiu!NS

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