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Biochemistry VI

Biochemistry VI. Proteins & Enzymes. Proteins. Large, complex organic molecules Made of smaller monomers: Amino Acids Categories of proteins: Structural Proteins Storage Proteins Transport Proteins Defensive Proteins Enzymes. Structural Proteins.

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Biochemistry VI

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  1. Biochemistry VI Proteins & Enzymes

  2. Proteins • Large, complex organic molecules • Made of smaller monomers: Amino Acids • Categories of proteins: • Structural Proteins • Storage Proteins • Transport Proteins • Defensive Proteins • Enzymes

  3. Structural Proteins • Used to provide structure and support for certain parts of organisms • Examples: • Keratin in hair/horns of animals • Collagen in connective tissues • Silk in spider webs

  4. Storage Proteins • Used to store other molecules for later use • Examples: • Casein in milk • Ovalbumin in egg whites • Zein in corn seeds

  5. Transport Proteins • Used to assist in the transport of molecules into and out of a cell or other membrane • Examples: • Hemoglobin (O2 carrier) in red blood cells • Integral membrane proteins

  6. Defensive Proteins • Used to protect cells and organisms against foreign substances or life forms • Examples: • Antibodies • Cell surface recognition proteins • Poisons made by plants, insects, snakes, etc.

  7. Enzymes • Regulate the rate of chemical reactions • Examples: • DNA polymerase and helicase • Lactase • Peroxidase • Sucrase

  8. Amino Acids • The building blocks of proteins • 20 total amino acids • Some can be synthesized by humans, others must be consumed • Carbon w/ 4 groups: • Amine • Carboxyl (acid) • Hydrogen • R group (varies)

  9. Amino Acid R Groups • R Groups determine the physical and chemical properties of the protein • They can be polar, nonpolar, acidic, or basic (importance?) • They can also be used for the attachment of other inorganic groups that are essential for the functioning of the protein • Heme group on hemoglobin bonds to Fe2+ • Other organic co-enzymes from our diet (vitamins)

  10. Putting Amino Acids Together • To build a protein, the amino acids must be connected by peptide bonds • Peptide bonds connect the amine group of one amino acid to the carboxyl group of the next • This bond is caused by a dehydration reaction • A chain of connected amino acids is called a polypeptide

  11. Where Do A.A.s Come From? • Many foods contain amino acids in the form of protein • When we digest protein, we recycle the amino acids and re-assemble them into our proteins

  12. Types of Amino Acids

  13. Structure of a Protein • The code in the DNA recipe is a sequence of A’s, T’s, C’s and G’s • The corresponding RNA copy of the recipe contains this code, which is read in 3’s • AUG, GGC, CUA, AAU, GCC, etc… • Every 3 letter combination translates into 1 specific amino acid • The chain of amino acids has a specific sequence

  14. Structure of Protein • Primary Structure • A unique sequence of amino acids in a polypeptide chain • Secondary Structure • Repeated folds and coils of a polypeptide chain • Tertiary Structure • Irregular contortions from bonding of the side chains of the various amino acids • Quaternary Structure • overall protein structure that results from the aggregation of tertiary subunits

  15. Fibrous Proteins • Found only in animals • Rod or wire-like shapes • Usually structural/storage • Water insoluble (hydrophobic R-groups) • Common in connective tissues, tendons, bone matrix, and muscle fiber • Examples: keratins, collagens, elastins

  16. Globular Proteins • Soluble in aqueous solutions (water) • Apolar amino acids are oriented toward the center of the globe-like structure • Used as enzymes, messengers (hormones), transporters • Examples: hemoglobin, immunoglobulins, insulin

  17. Website Animation • http://www.learner.org/channel/courses/biology/units/proteo/images.html • http://www.johnkyrk.com/aminoacid.html

  18. Enzymes • Enzymes speed up metabolic reactions • Enzymes: catalytic proteins • Catalyst: reduces the activation energy • Activation energy (Ea): energy required to start a reaction

  19. Enzymes • Substrate: reactant an enzyme works on • Active site: pocket where substrate is worked on • Induced fit: brings chemical groups into positions that enhance their ability to work between the enzyme and substrate • Effects of temperature and pH: enzymes have an optimal temperature and pH they work within • Metabolic pathways consist of chains or cycles of enzymes

  20. Induced-Fit Model

  21. Enzymes • Cofactors: helpers bound into active site • Coenzyme: an organic cofactor • Competitive inhibitors: block the active site • Non-competitive inhibitors: bind to another part of the enzyme, inhibiting work • Allosteric site: receptor site away from the active site, where other molecules regulate activity

  22. Enzymes • Feedback (end-product) Inhibition: metabolic pathway is switched off by its end product

  23. Website Animations • http://www.phschool.com/science/biology_place/labbench/lab2/images/indfit.gif

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