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Nucleotides, Hydrolysis, and Proteins. nucleotide. Hydrolysis This is a type of reaction in which a macromolecule is broken down into smaller molecules. It is the reverse of condensation. Proteins. Composed of Amino Acids

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slide3
Hydrolysis
  • This is a type of reaction in which a macromolecule is broken down into smaller molecules.
  • It is the reverse of condensation.
proteins
Proteins
  • Composed of Amino Acids
    • Consist of a Carboxyl group, an amine group, and a variable (“R” group)
    • The R group is the defining group for the 20 different types of amino acids
  • Polypeptide chains are put together using Dehydration Synthesis.
proteins1
Proteins
  • When two amino acids are added together, they are always joined in the same way.
  • The carboxyl group of one amino acid is connected to the amine group of the other amino acid.
  • This bond is called a peptide bond
proteins2
Proteins
  • Importance of proteins
  • enzymes (chemical reactions)
  • hormones
  • storage (egg whites of birds, reptiles; seeds)
  • transport (hemoglobin)
  • contractile (muscle)
proteins3
Proteins
  • protective (antibodies)
  • membrane proteins (receptors, membrane transport, antigens)
  • structural
  • toxins (botulism, diphtheria)
proteins4
Proteins
  • Each protein has a unique shape.
  • This shape (form) determines how the protein functions.
  • 4 levels of protein structure
    • Primary
    • Secondary
    • Tertiary
    • Quaternary (Not all proteins)
proteins5
Proteins
  • Primary Structure – refers to the order of the amino acids in the polypeptide chain
    • A change in 1 amino acid can have drastic consequences. Ex. Sickle Cell Anemia
  • Secondary Structure – results from hydrogen bonding within the polypeptide molecule.
proteins6
Proteins
  • 2 types of secondary structure:
    • Alpha helix
    • Beta pleated sheet
  • Proteins exhibiting these structures are called fibrous proteins
    • Wool, claws, beaks, collagen, ligaments
proteins7
Proteins
  • Tertiary Structure – 3-D shape of a protein
    • Determines the specificity
  • Factors that affect the tertiary structure:
    • H-Bonding between R groups
    • Ionic bonding between R groups
    • Hydrophobic interactions
    • Van der Waals interactions
    • Disulfide bonds between cysteine
proteins8
Proteins
  • Quaternary Structure
    • Proteins that consist of more than one polypeptide chain
    • Ex. Hemoglobin – Alpha + Beta
form vs function
Form vs. Function
  • It is not understood how proteins spontaneously fold into unique shapes.
  • Proteins interact with each other to control cellular processes.
  • The shape of a protein determines its function.
enzymes
Enzymes
  • Enzymes are globular proteins
    • Exhibit tertiary structure
  • Lower the activation energy of a reaction
  • Enzymes are substrate specific
    • An enzyme will on work on a specific substrate.
  • Enzymes are not used and remain unchanged during a chemical rxn.
induced fit model
Induced-Fit Model
  • As a substrate enters the active site, it causes a slight change in the shape of the enzyme. This change in the shape of the enzyme causes the substrate to fit better.
enzymes1
Enzymes
  • Named based on their substrate.
  • Name ends in “-ase”
    • Ex. Lactase, Sucrase, Ligase, Helicase
  • Catalyze reactions in both directions
    • Ex. Sucrase helps to break down and form Sucrose
  • Often require cofactors (inorganic) or coenzymes (vitamins)
enzymes2
Enzymes
  • Enzymes are not only substrate specific but are temperature and pH specific.
  • When the temp. or pH is too high/low, an enzyme will begin to denature.
  • Ex. Gastric enzymes are effective at a low pH (~2)
inhibition of enzymes
Inhibition of Enzymes
  • Competitive Inhibition
    • Occurs when a compound resembles the normal substrate for an enzyme
inhibition of enzymes1
Inhibition of Enzymes
  • These competitive inhibitors reduce the productivity of the enzyme.
  • Prevents the substrate form combining with the enzyme.
  • Can be reversible or irreversible.
inhibition of enzymes2
Inhibition of Enzymes
  • Non-competitive inhibition
    • Enzymes contains more than 1 active site
    • Substrates do not resemble each other
    • When one substrate binds to one active site, the other substrate cannot bind to the enzyme
    • Concentration of the substrates has a large effect on which one binds to the enzyme
inhibition of enzymes3
Inhibition of Enzymes
  • Allosteric inhibition
    • Involves 2 active sites
      • 1 substrate
      • 1 inhibitor
    • Enzyme ocscillates between two conformations
    • When the inhibitor binds, the enzyme becomes inactive.
allosteric inhibition
Allosteric Inhibition
  • Example – phosphofructokinase (PFK)
    • Found in glycolysis
    • Inhibited by ATP, which is a product of glycolysis
    • Example of Feedback inhibition
      • Pathway is switched off by its end-product