Proteins

• Proteins originate from the Greek word “proteios” which means “primary.”
• Proteins are the primary building blocks of cell assembly.
• proteins are the most abundant and diverse biomolecule constituting more than half of the cell’s dry mass
• All processes in the cell are mediated by proteins including gene expression
• Function: Selective acceleration of chemical processes

  Enzymatic proteins
• Function: Protection against disease

  Defensive Proteins
• Function: Storage of Amino Acids

  Storage proteins
• Function: Transport of substances

  Transport proteins
• Function: Coordination of an organism's activities

  Hormonal proteins
• Function: Response of cell to chemical stimuli

  Receptor protein
• Function: Movement

  Contractile and motor proteins
• Function: Support

  Structural proteins
• proteins are made up of simple monomeric subunits which are amino acids
• Amino acids are organic molecules that has a general structure comprised of an amino group (NH2), a carboxyl group (COOH), a side chain (R group) and a hydrogen (H) atom which are individually bonded to an asymmetric carbon (α carbon) atom in the center
• Amino acids can be categorized based on their tendency to interact with water or polarity
• An amino acid can be also classified as basic or acidic depending on the charge of their side chains due to the presence of an amino or a carboxyl group, respectively
• Polypeptides are polymers of amino acids.
• polypeptides are formed when any of the 20 amino acids combine to form a long linear chain connected by peptide bonds, a covalent bond, as a result of dehydration reactions
• The primary structure is characterized by a linear chain of amino acids
• if the primary structure is altered, the shape and function of a protein would be affected.
• Two common folding patterns are present in certain segments of the polypeptide chain and in different proteins. They are collectively termed as the secondary structure.
• secondary structures are formed as a result of hydrogen bonds between the partially positively-charged hydrogen atom attached to nitrogen (N–H group) and the partially negatively-charged oxygen attached to the carbon atom (C=O group) in the polypeptide backbone
• The α helix structure is characterized by repeated coils resembling a spiral staircase held in shape by hydrogen bonds every fourth amino acid
• β pleated sheet is formed when hydrogen bonds connect two or more segments of the polypeptide chain that lies side by side, either parallel or anti-parallel to each other giving rise to a very rigid structure
• the tertiary structure, or the three-dimensional conformation of the entire polypeptide chain stabilized by side chains interactions of the amino acids giving it its overall unique shape
• hydrophobic and van der Waals interaction

  between nonpolar side chains
• hydrogen bonds

  between polar side chains
• ionic bonds

  between oppositely charged side chains
• disulfide bridges

  between sulfhydryl (-SH) groups of cysteine
• Quaternary structure arises from a complex or aggregation of two or more polypeptide subunits.
• only some proteins exhibit quaternary structure such as collagen, which is a fibrous protein, and hemoglobin, a type of globular protein.
• protein structure is also affected by the physical and chemical conditions of the environment such as pH, temperature, and salt concentration.
• where the folded proteins unfold causing it to lose its function

  denaturation
• Enzymes is a large class of proteins that function in catalyzing or speeding up chemical reactions.
• They mediate almost all the biochemical processes taking place in the cells of the body for the other proteins to also fully carry out their functions

  Enzymes
• Enzymes bind to ligands called substrates converting them rapidly into different chemically modified molecules called products while remaining unchanged during the entire process.
• Enymes will lose their catalytic activity if they are denatured
• Enzymes are naturally produced in the body
• Digestive enzymes particularly amylase, lipase, and protease are hydrolases.
• Amylase catalyzes the breakdown of starch into sugars.