biochem summer midterm lesson 3

• Proteins


  Composed of amino acids linked by peptide bonds
• Peptide bonding


  A dehydration process (removal of water)
• Proteins


  • Organic compounds composed of C, H, O and N
  • High molecular weight

  
• Importance of proteins


  • Enzymes
  • Antibodies
  • Transport proteins
  • Regulatory proteins
  • Structural proteins
  • Movement
  • Maintenance of oncotic pressure
  • Cell adhesion
  • Receptor, channels, and pumps
  • Packing of DNA suril cell division
• Enzymes


  Proteins that speed up chemical processes; catalyze the rate of chemical reactions without being consumed in the process
• Enzymes


  • Amylase - breaks down carbohydrates
  • Pepsin and trypsin - breaks down proteins
  • Lipase - breaks down triglycerides (lipids)
• Antibodies


  Also known as immunoglobulins, protective proteins generated and presented in the immunity system against antigens
• Transport proteins


  • Transferrin - transports Fe
  • Ceruloplasmin - transport Cu
  • Hemoglobin - transport O, gives red pigment in blood, in RBC
  • Myoglobin - transport O in muscles
  • Lipoproteins - transport lipids
• Regulatory proteins


  • Insulin - control blood sugar level, produced by pancreas
  • Leptin - control appetite, produced by adipocytes
• Structural proteins


  • Keratin in skin; provide roughness; protection from friction (stratified squamous keratinized) and microorganisms
  • Collagen in skin
• Movement


  • Myosin and actin - small proteins in muscles
• Albumin


  Responsible for oncotic pressure
• Cell adhesion


  • Tight junction
  • Desmosomes
  • Staphylococcal scalded skin syndrome
• Insulin receptors


  Made up of proteins, thus glucose enters the cells with insulin to produce ATP to lessen sugar levels
• Histones


  Protein that wraps DNA into condensed units
• Chiral carbon


  Carbon atoms that are attached to four different substituents
• All amino acids contain chiral carbon EXCEPT glycine (the side chain is another H)
• Amino acid positive-charge


  If it is in immersed in acidic pH because amino group accepts H+
• Amino acid negative-charge


  If it is in immersed in alkaline pH because carboxylic acid group loses H+
• Zwitterions


  Ions possessing both + and - electrical charges, mostly electrically neutral (net charge is 0), contain positive and negative charges within the same molecule and can act as both an acid and a base in a chemical reaction
• Isoelectric point


  The pH at which the amino acid has no net electrical charge
• Groups of amino acids

  • Hydrophobic amino acids
  • Hydrophilic amino acids

  
• Hydrophobic amino acids


  "Water-fearing" - non polar, generally found in the interior of proteins

  
• Hydrophobic amino acids


  • Glycine, alanine, valine, leucine, isoleucine, methylthionine (sulod si S), phenylalanine, tryptophan, proline

  
• Hydrophilic amino acids


  "Water-loving" - polar, attracted to polar water molecules, often outside/surfaces of proteins

  
• Classes of hydrophilic amino acids at pH 7.0

  • Polar neutral amino acids
  • Negatively charged amino acids
  • Positively charged amino acids

  
• Polar neutral amino acids

  Have R-side chains that are not charged but can interact with water, has only -OH or -SH group at the outer part of the proteins

  
• Negatively charged amino acids

  Have ionized carboxyl (NOT HYDROXYL) group in their side chain, may extra carboxyl (COO-), negative, at pH 7 has a charge of -1

  
• Positively charged amino acids


  May extra amino group, at pH 7 has a charge of +1

  
• Peptide bonds


  Formed between amino group if first amino acid and carboxylic acid group of 2nd amino acid with release of WATER, a dehydration process, covalent bond - STRONG bond

  
• Dipeptide


  The molecule formed by condensing two amino acids
• Primary structure of proteins

  Amino acid sequence of the protein chain, results from the covalent bonding between the amino acids in the chain (peptide bonds), are translations of information contained in genes in the ribosomes

  
• Secondary structure of proteins

  Refers to local folded structures that form within a polypeptide due to interactions between atoms of the backbone, arises from the H-bonds formed between atoms of the polypeptide backbone
• Alpha helix


  The C=O (carbonyl) of one amino acid is H bonded to the amino H (N-H) of an amino acid that is four down the chain, the pattern of bonding pulls the polypeptide chain into a helical structure that resembles a curled ribbon, with each turn of the helix containing 3.6 amino acids

  
• Beta-pleated sheet


  Form when two or more segments of a polypeptide chain line-up next to each other, forming a sheet-like structure held together by H-bonds, the strands may be parallel or antiparallel
• Tertiary structure of proteins

  Primarily due to interactions between the R groups of the amino acids that make up the protein, formed by hydrophobic bonds, hydrogen bonds, disulfide bonds, and ionic bonds

  
• Quaternary structure of proteins


  The association of several protein chains or subunits into a closely packed arrangement, each of the subunits has its own primary, secondary and tertiary structure, held together by the same types of bonds that contribute to tertiary structure
• Denaturation of proteins


  Loss of the protein's function due to structural change in the protein caused by some chemical or physical factor such as high temperature or unfavorable pH, the folded protein (the tertiary structure) unfolds, unravels
• Electrophoresis


  Results based on charge (more negative charges, the faster) and size (smaller the size, the faster), if cathode (negative) is in the loob ng box, use acid on the blood serum (to activate positive-charged proteins) for the blood serum to move, if anode (positive) is in the loob ng box, use alkaline (to activate negative-charged proteins) for the blood serum to move
• Classification of proteins


  • Simple proteins
  • Conjugated proteins
  • Essential amino acids
  • Nonessential amino acids
  • Complete proteins
  • Incomplete proteins