11/24/2017 0 Comments Example Of A High Protein DietProtein - Wikipedia. Proteins ( or ) are large biomolecules, or macromolecules, consisting of one or more long chains of amino acidresidues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, responding to stimuli, and transporting molecules from one location to another. Proteins differ from one another primarily in their sequence of amino acids, which is dictated by the nucleotide sequence of their genes, and which usually results in protein folding into a specific three- dimensional structure that determines its activity. A linear chain of amino acid residues is called a polypeptide. A protein contains at least one long polypeptide.
Short polypeptides, containing less than 2. The individual amino acid residues are bonded together by peptide bonds and adjacent amino acid residues. The sequence of amino acid residues in a protein is defined by the sequence of a gene, which is encoded in the genetic code. In general, the genetic code specifies 2. Shortly after or even during synthesis, the residues in a protein are often chemically modified by post- translational modification, which alters the physical and chemical properties, folding, stability, activity, and ultimately, the function of the proteins. Sometimes proteins have non- peptide groups attached, which can be called prosthetic groups or cofactors. Proteins can also work together to achieve a particular function, and they often associate to form stable protein complexes. Once formed, proteins only exist for a certain period of time and are then degraded and recycled by the cell's machinery through the process of protein turnover. A protein's lifespan is measured in terms of its half- life and covers a wide range. They can exist for minutes or years with an average lifespan of 1–2 days in mammalian cells. Abnormal or misfolded proteins are degraded more rapidly either due to being targeted for destruction or due to being unstable. Like other biological macromolecules such as polysaccharides and nucleic acids, proteins are essential parts of organisms and participate in virtually every process within cells. Many proteins are enzymes that catalyse biochemical reactions and are vital to metabolism. Proteins also have structural or mechanical functions, such as actin and myosin in muscle and the proteins in the cytoskeleton, which form a system of scaffolding that maintains cell shape. ![]() On a healthy high protein fiber diet plan it’s vitally important to eat only healthy fats. Besides the nutritional reasons, all fat is high in calories. Planning meals is easy. ![]() Other proteins are important in cell signaling, immune responses, cell adhesion, and the cell cycle. In animals, proteins are needed in the diet to provide the essential amino acids that cannot be synthesized. Digestion breaks the proteins down for use in the metabolism. Proteins may be purified from other cellular components using a variety of techniques such as ultracentrifugation, precipitation, electrophoresis, and chromatography; the advent of genetic engineering has made possible a number of methods to facilitate purification. Methods commonly used to study protein structure and function include immunohistochemistry, site- directed mutagenesis, X- ray crystallography, nuclear magnetic resonance and mass spectrometry. Biochemistry. Chemical structure of the peptide bond (bottom) and the three- dimensional structure of a peptide bond between an alanine and an adjacent amino acid (top/inset)Most proteins consist of linear polymers built from series of up to 2. L- . All proteinogenic amino acids possess common structural features, including an . Only proline differs from this basic structure as it contains an unusual ring to the N- end amine group, which forces the CO–NH amide moiety into a fixed conformation. Once linked in the protein chain, an individual amino acid is called a residue, and the linked series of carbon, nitrogen, and oxygen atoms are known as the main chain or protein backbone. The other two dihedral angles in the peptide bond determine the local shape assumed by the protein backbone. Protein is generally used to refer to the complete biological molecule in a stable conformation, whereas peptide is generally reserved for a short amino acid oligomers often lacking a stable three- dimensional structure. However, the boundary between the two is not well defined and usually lies near 2. Smaller bacteria, such as Mycoplasma or spirochetes contain fewer molecules, namely on the order of 5. By contrast, eukaryotic cells are larger and thus contain much more protein. For instance, yeast cells were estimated to contain about 5. For instance, of the 2. Eukaryotes, bacteria, Archaea and viruses have on average 1. Each protein has its own unique amino acid sequence that is specified by the nucleotide sequence of the gene encoding this protein. ![]() The genetic code is a set of three- nucleotide sets called codons and each three- nucleotide combination designates an amino acid, for example AUG (adenine- uracil- guanine) is the code for methionine. Because DNA contains four nucleotides, the total number of possible codons is 6. Most organisms then process the pre- m. RNA (also known as a primary transcript) using various forms of Post- transcriptional modification to form the mature m. RNA, which is then used as a template for protein synthesis by the ribosome. In prokaryotes the m. RNA may either be used as soon as it is produced, or be bound by a ribosome after having moved away from the nucleoid. In contrast, eukaryotes make m. RNA in the cell nucleus and then translocate it across the nuclear membrane into the cytoplasm, where protein synthesis then takes place. The rate of protein synthesis is higher in prokaryotes than eukaryotes and can reach up to 2. The m. RNA is loaded onto the ribosome and is read three nucleotides at a time by matching each codon to its base pairinganticodon located on a transfer RNA molecule, which carries the amino acid corresponding to the codon it recognizes. The enzyme aminoacyl t. RNA synthetase . The growing polypeptide is often termed the nascent chain. Proteins are always biosynthesized from N- terminus to C- terminus. The average size of protein increases from Archaea, Bacteria to Eukaryote (2. Da respecitvely) due bigger number of protein domains constituting proteins in higher organisms. Chemical synthesis is inefficient for polypeptides longer than about 3. Most chemical synthesis methods proceed from C- terminus to N- terminus, opposite the biological reaction. A single protein subunit is highlighted. Chaperonins assist protein folding. Left: All- atom representation colored by atom type. Middle: Simplified representation illustrating the backbone conformation, colored by secondary structure. Right: Solvent- accessible surface representation colored by residue type (acidic residues red, basic residues blue, polar residues green, nonpolar residues white). Most proteins fold into unique 3- dimensional structures. The shape into which a protein naturally folds is known as its native conformation. A protein is a polyamide. Secondary structure: regularly repeating local structures stabilized by hydrogen bonds. The most common examples are the . Because secondary structures are local, many regions of different secondary structure can be present in the same protein molecule. Tertiary structure: the overall shape of a single protein molecule; the spatial relationship of the secondary structures to one another. Tertiary structure is generally stabilized by nonlocal interactions, most commonly the formation of a hydrophobic core, but also through salt bridges, hydrogen bonds, disulfide bonds, and even posttranslational modifications. The tertiary structure is what controls the basic function of the protein. Quaternary structure: the structure formed by several protein molecules (polypeptide chains), usually called protein subunits in this context, which function as a single protein complex. Proteins are not entirely rigid molecules. In addition to these levels of structure, proteins may shift between several related structures while they perform their functions. In the context of these functional rearrangements, these tertiary or quaternary structures are usually referred to as . Such changes are often induced by the binding of a substrate molecule to an enzyme's active site, or the physical region of the protein that participates in chemical catalysis. In solution proteins also undergo variation in structure through thermal vibration and the collision with other molecules. Almost all globular proteins are soluble and many are enzymes. Fibrous proteins are often structural, such as collagen, the major component of connective tissue, or keratin, the protein component of hair and nails. Membrane proteins often serve as receptors or provide channels for polar or charged molecules to pass through the cell membrane. Common experimental methods of structure determination include X- ray crystallography and NMR spectroscopy, both of which can produce information at atomic resolution. However, NMR experiments are able to provide information from which a subset of distances between pairs of atoms can be estimated, and the final possible conformations for a protein are determined by solving a distance geometry problem. Dual polarisation interferometry is a quantitative analytical method for measuring the overall protein conformation and conformational changes due to interactions or other stimulus. Circular dichroism is another laboratory technique for determining internal . Cryoelectron microscopy is used to produce lower- resolution structural information about very large protein complexes, including assembled viruses. Further, the set of solved structures is biased toward proteins that can be easily subjected to the conditions required in X- ray crystallography, one of the major structure determination methods. In particular, globular proteins are comparatively easy to crystallize in preparation for X- ray crystallography. Membrane proteins, by contrast, are difficult to crystallize and are underrepresented in the PDB.
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