BIO

• Proteins


  Polymers of amino acids<|>Most versatile macromolecules in living systems and serve crucial functions in essentially all biological processes<|>They function as catalysts<|>They transport and store other molecules such as oxygen<|>They provide mechanical support and immune protection<|>They generate movement, they transmit nerve impulses, and they control growth and differentiation
• Properties that enable proteins to participate in a wide range of functions


  • Proteins contain a wide range of functional groups
  • Proteins can interact with one another and with other biological macromolecules to form complex assemblies
  • Some proteins are quite rigid, whereas others display flexibility
• Functions of proteins


  • Digestive enzymes
  • Transport
  • Structural
  • Hormones
  • Defense
  • Contractile
  • Storage
• Digestive enzymes


  Help in digestion of food by catabolizing nutrients into monomeric units
• Transport proteins


  Carry substances in the blood or lymph throughout the body
• Structural proteins


  Construct different structures, like the cytoskeleton
• Hormones


  Chemical-signaling molecules that act to control or regulate specific physiological processes, including growth, development, metabolism, and reproduction
• Defense proteins


  Protect the body from foreign pathogens
• Contractile proteins


  Effect muscle contraction
• Storage proteins


  Provide nourishment in early development of the embryo and the seedling
• Common types of proteins

  • Enzymes
  • Hormones
  • Amino acids
• Enzymes


  Catalysts in biochemical reactions (like digestion) and are usually complex or conjugated proteins<|>Help in breakdown, rearrangement, or synthesis reactions<|>Catabolic enzymes - Enzymes that breakdown their substrates<|>Anabolic enzymes - Enzymes that build more complex molecules from their substrates<|>Catalytic enzymes - Enzymes that affect the rate of reaction
• Hormones


  Chemical-signaling molecules, usually small proteins or steroids, secreted by endocrine cells that act to control or regulate specific physiological processes, including growth, development, metabolism, and reproduction
• Amino acids


  Building blocks of proteins<|>Consist of a central carbon atom, also known as the alpha (a) carbon, bonded to an amino group (NH2), a carboxyl group (COOH), and to a hydrogen atom<|>The R group determines the identity of the amino acid
• Zwitterion


  A molecule that has both negative and positive charges
• Amino acids have chiral center, optical activity is observed, except for glycine which is achiral
• Amino acids are amphoteric
• There are 20 known amino acids
• Amino acids naturally occur in L form
• Essential amino acids


  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
  • Phenylalanine
  • Threonine
  • Tryptophan
  • Valine
• Non-essential amino acids


  • Alanine
  • Arginine
  • Asparagine
  • Aspartic acid
  • Cysteine
  • Glutamic acid
  • Glutamine
  • Glycine
  • Proline
  • Serine
  • Tyrosine
• Peptide bond


  Dehydration synthesis reaction, condensation reaction<|>Each amino acid is attached to another amino acid by a covalent bond<|>Peptide bonds are formed when the amine group of one amino acid binds with the carbonyl carbon of another amino acid, releasing a molecule of water
• The products formed by such linkages are called peptides
• Levels of protein structure

  • Primary structure
  • Secondary structure
  • Tertiary structure
  • Quaternary structure
• Primary structure


  Describes the order or sequence of the amino acids in a polypeptide chain
• Secondary structure


  The polypeptide backbone can fold into periodic structures<|>The folded structure is stabilized by hydrogen bonding<|>The backbone can change direction by making reverse turns or loops<|>Has 2 types of folding: alpha (a) helix and the beta (ß) pleated sheets
• Alpha helix


  The polypeptide chain is coiled tightly in the fashion of a spring<|>The "backbone" of the peptide forms the inner part of the coil while the side chains extend outward from the coil<|>The helix is stabilized by hydrogen bonds between the >N-H of one amino acid and the >C=O on the 4th amino acid away from it<|>Every helical turn in an alpha helix has 3.6 amino acid residues
• Beta pleated sheet


  Individual protein chains are aligned side-by-side with every other protein chain aligned in an opposite direction<|>The protein chains are held together by intermolecular hydrogen bonding, that is hydrogen bonding between amide groups of two separate chains
• Tertiary structure


  The overall three-dimensional structure of a polypeptide<|>The tertiary structure is primarily due to interactions between the R groups of the amino acids that make up the protein<|>R group interactions that contribute to tertiary structure include hydrophobic interactions, ionic bonding, hydrogen bonding and disulfide linkages
• Quaternary structure


  Describes the interactions of the subunits in an oligomeric protein<|>Stabilized by both covalent and non-covalent bonds (interchain) - various interactions, including hydrogen-bonding, disulfide-bridges and salt bridges
• Insulin


  Has a combination of hydrogen bonds and disulfide bonds that cause it to be mostly clumped into a ball shape
• Types of protein shape

  • Fibrous proteins
  • Globular proteins
• Fibrous proteins


  Long, rod-like forming fibers<|>Insoluble in water
• Fibrous proteins


  • α-Keratin
  • Collagen
  • Elastin
  • Silk fibroin
• α-Keratin


  Bundles of helical polypeptides twisted together<|>Found in hair, wool, skin, horns and fingernails
• Collagen


  Most abundant proteins in vertebrates<|>Synthesized by connective tissue cells<|>Essential components of all connective tissues such as cartilage, tendons, ligaments and skin
• Elastin


  Structural protein that gives elasticity to the body's tissues and organs<|>Found predominantly in the walls of arteries, intestines, skin and other elastic tissues<|>Highly hydrophobic: composed primarily of Alanine, Valine, Leucine and Glycine
• Silk fibroin


  Protein found in silk<|>Silk can be produced by insects and spiders<|>Fibroin is considered to be β-keratin (the polypeptide chains are arranged in anti-parallel β-pleated sheet conformations)<|>Consists of amino acid residues with small R-groups (i.e. glycine and serine)
• Globular proteins


  Spherical in shape<|>Soluble in water<|>Functions as enzymes, hormones, membrane transporters and receptors, immunoglobulins or antibodies, storage proteins
• Myoglobin


  Found in high concentration in skeletal and cardiac muscles (responsible for the red color)<|>Diving mammals such as whales have high myoglobin concentrations in muscles<|>Serves as a reservoir of oxygen within muscle cells<|>Facilitates diffusion of oxygen in metabolically active cells