proteins

• Primary structure refers to the linear sequence of amino acids in a protein.
• Secondary structure is formed by hydrogen bonds between different parts of the polypeptide chain, resulting in regular repeating patterns such as alpha helices or beta sheets.
• The hydrophobic effect drives the folding process as hydrophobic amino acids cluster together to minimize their contact with water.
• Quaternary structure occurs when multiple polypeptides come together to form complex structures like hemoglobin.
• Tertiary structure involves interactions between side chains on adjacent residues within a single polypeptide chain, leading to compact globular shapes with specific functions.
• Protein folding is influenced by factors such as hydrophobic interactions, disulfide bonds, and ionic interactions.
• Tertiary structure involves interactions between side chains (R groups) of amino acids within one polypeptide chain, leading to compact globular structures.
• Hydrophilic regions are exposed to the solvent while hydrophobic regions are buried inside the protein.
• Disulfide bridges can stabilize tertiary structure through covalent bond formation between sulfur atoms from two cysteine residues.
• There are 20 AAs that normally occur in proteins, of which 10 are essential.
• Abundant elements in the chemical elements of life include Carbon, Hydrogen, Oxygen, Nitrogen, Phosphorus, and Sulfur.
• Trace elements in the chemical elements of life include Copper, Iodine, Iron, Manganese, Molybdenum, Selenium, and Zinc.
• Essential elements in the chemical elements of life include Chlorine, Fluorine, Sodium, and Potassium.
• Quaternary structures are proteins with more than 1 polypeptide, known as oligomers.
• Vitamin C is required for hydroxyproline residue formation.
• A quaternary structure is the organization and arrangement of polypeptides (subunits) in a protein, with forces holding the subunits together similar to those in tertiary structure determination.
• There are other amino acid residues present in collagen, e.g.
• Protein folding is the process by which a newly synthesized polypeptide molecule changes its shape to reach the final stable and functional tertiary structure.
• Disulfide bridges are covalent linkages between cysteine residues within or between polypeptide chains, common in extracellular proteins, and prevention of protein unfolding.
• Grass pollen protein has a "sandwich" structure of the β-sheets with hydrophobic residues.
• Collagen is a structural protein in connective tissues and a fibrous protein.
• An electron micrograph shows thousands of collagen molecules aligned to form collagen fibers.
• A collagen molecule is a triple helix of 3 polypeptide chains, with hydroxyproline residues formed from proline residues after the polypeptide is synthesized.
• Proteins have hydrophobic cores, with some being highly hydrophobic, moderately hydrophobic, or charged.
• Tertiary structures of proteins include the 3-D shape of a protein, which includes regular and irregular secondary structure, and the overall folding of the peptide backbone.
• Loops are longer strands of amino acid residues linking beta-strands and alpha-helices.
• α-Helix is a right-handed helical structure with H-bonding within the polypeptide backbone.
• Disulfide bridges (covalent linkages) are formed between cysteine residues after protein folding.
• Turns are a few amino acid residues (usually 1 proline) causing an abrupt change in direction, common in anti-parallel beta-sheets.
• Parallel β-sheets have amide hydrogen and carbonyl oxygen atoms aligned in the same direction, while antiparallel β-sheets have amide hydrogen and carbonyl oxygen atoms aligned in opposite directions.
• α-Helix is a structure where each carbonyl oxygen (residue n) forms a H-bond with the amide hydrogen of the fourth residue further toward the C-terminus (n+4 residue).
• Secondary structures of proteins include α-helix, β-strands, and β-sheets.
• β-Sheets are formed by hydrogen bonding between amide hydrogen and carbonyl oxygen in adjacent strands.
• Tertiary structures are stabilized by non-covalent interactions between side chains of amino acid residues which may be very far away in the primary sequence.
• At pH = pK2, concentration of Form II is equal to concentration of Form III.
• Protein conversion factors for the Kjeldahl method are different for food items with proteins having higher percentages of these amino acids.
• At pH = pK1, concentration of Form I is equal to concentration of Form II.
• Free amino acids have at least two ionizable groups: α-carboxyl group and α-amino group.
• Melamine, which is 67% N by mass, is used in plastic production and as a protein adulterant in milk products.
• Collagen fibers are insoluble fibers with tremendous tensile strength, stronger than steel on a per-weight basis, stabilized by hydrogen bonding and covalent cross-links.