B1.2 - Proteins

• Proteins are used for fluid balance
• Proteins are used as acid-base balances
• Proteins are used as channels and pumps and for transport
• Proteins are used for enzymes, hormones, signaling molecules, and antibodies
• Proteins are polypeptides, which are chains of amino acids
• Amino acids are composed of a carbon core, an amino group, an R - group, and a carboxyl group
• There are 20 different amino acids
• Essential amino acids are amino acids that the human body cannot synthesize on its own, meaning they must be obtained through diet.
• Essential amino acids help with protein synthesis, enzyme function, and hormone production.
• When polypeptide is about 20 amino acid residues long, it is generally agreed to have become a protein.
• Peptide linkage: covalent bonding of the amino group of one amino acid to the carboxyl group of another (with the loss of a molecule of water).
• A further condensation reaction between the dipeptide and another amino acid results in a tripeptide.
• Proteins in our food are broken down by protease and turned into amino acids
• Non - essential amino acids can be made through other amino acids
• Branched - chain amino acids are essential for exercise and muscle metabolism
• Changing pH will alter the charge on proteins. This alters their solubility and may change their shape.
• Proteins (including enzymes) can become denatured by too much of a rise in temperature and change in pH
• Proteins usually can't change back to original shape once denatured
• structure of an enzyme may spontaneously reform when the optimum pH is restored, but exposure to strong acids or alkalis usually denatures enzymes irreversibly.
• Isoelectric point is the specific pH that each protein has when it carries no net electrical charge. Change in the pH can alter the charge.
• When temperature is increased, enzymes and proteins move faster leading to more frequent collisions
• At low temps, proteins can experience cold denaturation, where the protein structure becomes less stable
• acidic amino acids: having additional carboxyl groups and basic amino acids have additional amino groups
• amino acids with hydrophilic properties (soluble): have polar or charged R-groups and amino acids with hydrophobic properties (insoluble): have non-polar R-groups
• Primary protein structure: determines shape of protein and is a chain of amino acids
• Secondary structure occurs when the protein chain folds into helices or sheets
• The tertiary structure is the formation or overall three-dimensional shape of a protein which is formed by hydrogen bonding and has a folding pattern
• Quaternary structure: Where two or more polypeptides are combined (via intermolecular forces) to form a larger protein.
• Primary structure only has peptide bonds
• Secondary structure can either be alpha helices or beta sheets and are held together through hydrogen bonds and peptide bonds
• Tertiary Structure: protein takes a 3D shape as helices and sheets fold further into a specific shape which is stabilized by different interactions, such as hydrogen bonds, ionic bonds, disulfide bonds, and peptide bonds.
• Quaternary Structure: when two or more protein chains come together to form a larger, functional protein and has hydrogen bonds, ionic bonds, disulfide bonds and peptide bonds.
• Globular proteins: shaped like a globe (circular), har irregular and wide range of R - groups, and is generally soluble in water (amphipathic)
• Fibrous proteins: long strands, repetitive with limited range of R - groups, and is insoluble in water
• Integral proteins: proteins that move from one side of a membrane to the other side.
• Conjugated protein: a combination of protein and non-protein prosthetic group. (A protein that has a non-protein part (like a metal, vitamin, or sugar) attached to it, which helps it function.)