Sunday , January 29 2023

Biochemistry

Bacteria: External Structures

Bacteria cells

Structures External to the Cell Wall Among the possible structures external to the prokaryotic cell wall are the glycocalyx, flagella, axial filaments, fimbriae, and pili. Glycocalyx Many prokaryotes secrete on their surface a substance called glycocalyx. Glycocalyx (meaning sugar coat) is the general term used for substances that surround cells. …

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Protein Folding & Its Pathways

Protein Folding

Protein Folding Studies of protein stability and renaturation suggest that protein folding is directed largely by the residues that occupy the interior of the folded protein. But how does a protein fold to its native conformation? One might guess that this process occurs through the protein’s random exploration of all …

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Protein: Tertiary Structures

tertiary structures of Protein.

The tertiary structure of a protein describes the folding of its secondary structural elements and specifies the positions of each atom in the protein, including those of its side chains. This information is deposited in a database and is readily available via the Internet, which allows the tertiary structures of …

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Protein: Secondary Structures

Secondary Structures of Protein

Protein secondary structure includes the regular polypeptide folding patterns such as helices, sheets, and turns. However, before we discuss these basic structural elements, we must consider the geometric properties of peptide groups, which underlie all higher order structures. The Planar Peptide Group Limits Polypeptide Conformations A polypeptide is a polymer …

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Protein Misfolding: The Origin of Some Diseases

Protein Misfolding

Many Diseases Are Caused by Protein Misfolding Most proteins in the body maintain their native conformations or, if they become partially denatured, are either renatured through the auspices of molecular chaperones or are proteolytically degraded. However, at least 35 different—and usually fatal—human diseases are associated with the extracellular deposition of …

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Protein Folding: Molecular Chaperones

Protein Folding

Molecular Chaperones Assist Protein Folding Proteins begin to fold as they are being synthesized, so the renaturation of a denatured protein in vitro may not entirely mimic the folding of a protein in vivo. In addition, proteins fold in vivo in the presence of extremely high concentrations of other proteins …

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Protein & Its Dynamism

Protein Dynamics

Proteins Are Dynamic The static way that protein structures are usually portrayed may leave the false impression that proteins have fixed and rigid structures. In fact, proteins are flexible and rapidly fluctuating molecules whose structural mobilities are functionally significant. Groups ranging in size from individual side chains to entire domains …

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Protein Stability & Its Factors

Protein Stability & Its Factors

Incredible as it may seem, thermodynamic measurements indicate that native proteins are only marginally stable under physiological conditions. The free energy required to denature them is ∼0.4 kJ ∙ mol−1 per amino acid residue, so a fully folded 100-residue protein is only about 40 kJ ∙ mol−1 more stable than …

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Microorganisms & Human Welfare

Microorganisms & Human Welfare

Microorganisms & Human Welfare As mentioned earlier, only a minority of all microorganisms are pathogenic. Microbes that cause food spoilage—such as soft spots on fruits and vegetables, decomposition of meats, and rancidity of fats and oils— are also a minority. The vast majority of microbes benefit humans, other animals, and …

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Amino Acids: Structures

The analyses of a vast number of proteins from almost every conceivable source have shown that all proteins are composed of 20 “standard” amino acids. Not every protein contains all 20 types of amino acids, but most proteins contain most, if not all, of the 20 types. The common amino …

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