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The Structure and Function of Large Biological Molecules Monomers – small organic, used for building blocks of polymers, connects w condensation reaction (dehydration synthesis) Polymers – long chains of monomers, w many identical or similar blocks linked by covalent bonds. Macormolecules – giant molecules. 2 or more polymers bonded together. (ex: smallest to largest… amino acid à peptide à polypeptide à protein) Reactions:Dehydration synthesis (condensation reaction): make polymers. Monomers à polymers. A+B =AB + H2O -dehydration removes a water molecule, forming a new bond Hydrolysis: breaks down polymers. Polymers à monomers. AB + H2O = A+B -hydrolysis adds a water molecule, breaking a bond PROTEINSAccounts for 50% dry weight of cells.Contains: C, H, O, N, S Protein functions (and examples)-enzymes: selective acceleration of chemical reactions (lactase in digestion)-defense: protection against disease (antibodies in immune response)-storage: storage of amino acids (milk protein for baby mammals – casein)-transport: transport of substances (hemoglobin transports oxygen in the blood)-hormones: coordinating an organisms activities (insulin in blood sugar regulation)-receptors: response of cells to chemical stimuli (nerve signaling)-movement: moving (motor proteins responsible for muscle contraction)-structure: support (collagen and elastin in connective tissue) There are 4 levels of protein structure:1. Primary: amino acid sequence. There are 20 different amino acids. Peptide bonds link AAsa. Amino acid: each has an amino group (-NH2), an acid group (-COOH), an H group, and a unique R group (side chain). The R group gives it distinctive properties (hydrophobic, hydrophilic, ionic (acid/base))b. Peptide bonds form between the amino and carboxyl groups, forming the backbone of the protein so that each peptide has an N-terminus and a C-terminus.c. The side chains hang off the backbone2. Secondary: gains 3D shape (folds, coils) by H-bonding. Alpha helix, beta pleated sheet.a. Basic principles of protein folding: i. Hydrophobic AA buried in the interior of the protein (hydrophobic interactions) ii. Hydrophilic AA exposed on surface of the protein (H-bonds) iii. Acid + basic AA form salt bridges (ionic bonds) iv. Cysteines can form disulfide bonds3. Tertiary: bonding between side chains of AA. H-bonds, ionic, disulfides, van der Waals interactions.4. Quarternary: 2 or more peptides bond together. SUMMARY: AAs -- polypeptides -- protein sequence -- folding/shape -- end form Chaperonins – molecules that assist in the proper folding of proteins Protein structure and function are sensitive to chemical and physical conditions.-unfolds or denatures if pH and temp are not optimal-change in structure = change in function variations within proteins provide a wider range of functions (i.e. different types of hemoglobin, MHC proteins) NUCLEIC ACIDSFunction: store hereditary information DNA: double-stranded helix. N-bases A, G, C, T. stores hereditary info. Longer/larger. Sugar = deoxyriboseRNA: single-stranded helix. N-bases A, G, C, U. carry info from DNA to ribosomes. tRNA, rRNA, mRNA, RNAi. Sugar = ribose Nucleotides: monomer of DNA/RNANucleotide = sugar + phosphate + nitrogen base -sugars: deoxyribose (DNA), ribose RNA)-nitrogenous bases: pyrimidines: cytosine, thymine (DNA), uracil (RNA) purines: adanine, guanine information flow in a cell: DNA à RNA à protein CARBOHYDRATESFuel and building materialInclude simple sugars (fructose) and polymers (starch)Ratio of 1 carbon to 2 hydrogen to 1 oxygen (1 C : 2 H : 1 O) or CH2OMonosaccharide à disaccharide à polysaccharideMonosaccharides = monomers (glucose, ribose)Polysaccharides: -storage (plants-starch, animals-glycogen) -structure (plants-cellulose, srthropods-chitin) cellulose vs. starchthere are 2 forms of glucose: alpha glucose and beta glucose -starch = alpha glucose monomers -cellulose = beta glucose monomers LIPIDS--Fats (triglycerides): store energy. Glycerol + 3 fatty acids.Can be saturated (saturated with H. present in animals. Solid at room temp. butter/lard), unsaturated or polyunsaturated (have some C=C, resulting in kinks. Present in plants. Liquid at room temp. olive oil)--Steriods: cholesterol and hormones--Phospholipids: lipid bilayer of cell membrane. Hydrophilic head, hydrophobic tails. Where hydrophobic/hydrophilic interactions make a phospholipid bilayer.
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