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November Molecules of life, Proteins.docx

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Natural Science
NATS 1610
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Living Body-Molecules of Life, Proteins -proteins are the most diverse biological molecules with many roles • Catalysts-enzyme: regulate metabolism by selectively accelerating chemical reactions • Structural: mechanical support for cells and tissues (cytoskeleton, collagen, etc) • Receptors: binding molecules to or inside cells • Regulatory: adjust cell activity (many hormones) • Movement and transport: movement of cells and cell parts (muscle contraction), transport of substances • Protection defense: assists in immune responses and other bodily defenses (antibodies destroy bacteria and viruses -Proteins are polymers of amino acids connected in a specific sequence • Polymers are amino acids are called polypeptides o Polypeptides must undergo structural changes to become functional proteins • 20 natural amino acids (AA) 8 essential amino acids (must be ingested) • Specific backbone (-N-C-C-N-C-C-) • Giant macromolecules (e.g. Haemoglobin in red blood cells) -Amino acid structure: 5 components 1. Central carbon atom 2. Hydrogen atom 3. Amino group: NH2 or NH3+ 4. Carboxylic group: COOH or COO- 5. R-group(side chain) a. Differences in r groups produce the 20 different amino acids b. Each with own unique characteristics c. Due to presence of specific functional groups -Differences between AA-due to differences in their R-groups- different properties -One group of amino acids has non-polar r groups, making them Hydrophobic (no oxygen in their R group) -one group of amino acids has polar R groups, making them hydrophilic (oxygen part of their R groups) -last group of amino acids includes those with functional groups that are charges (ionized) at cellular pH • Notice the presence of additional carboxylic or amino groups in R groups -Amino acids are joined together by Dehydration reactions and degraded by hydrolysis reactions • During dehydration: removing a hydroxyl group from the carboxyl end (acidic end) of one amino acid and a hydrogen from the amino group of another amino acid (forming water in the process) o A difference here- No oxygen bridge formation  Instead the resulting covalent bond is a peptide bond  Repeating the process over and over creates a long polypeptide chain • Peptide bond formation can also occur when the amino acids are in ionized state -a proteins function depends on its specific conformation (3 dimensional structures) • A functional protein consists of one or more polypeptides precisely twisted, folded, and coiled into a unique shape • The order of amino acids determines the three dimensional conformation • Protein structure enables it is recognize and bi
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