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Chemistry 100 Chapter 25

Chemistry 100 Chapter 25. Biochemistry. Chiral Molecules. Molecules that have non-superimposable mirror images – chiral molecules Enantiomers Distinguish using the R and S configuration. Chiral Molecules. Enantiomers. Physical properties are generally identical

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Chemistry 100 Chapter 25

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  1. Chemistry 100 Chapter 25 Biochemistry

  2. Chiral Molecules • Molecules that have non-superimposable mirror images – chiral molecules • Enantiomers • Distinguish using the R and S configuration

  3. Chiral Molecules

  4. Enantiomers Physical properties are generally identical Chemical properties are different only in a chiral environment. Mixture of two enantiomers in equal proportions – racemic mixture. Some molecules have more than one chiral centre!

  5. Biochemistry • Biomolecules – large and hard to synthesize in the laboratory. • Built up from smaller molecules present in the biosphere – largeentropy cost!! • Biologically active polymers – biopolymers. • Proteins • Polysaccharides • Nucleic Acids

  6. Amino Acids and Proteins • Amino Acids • Contain the –NH2 group and the COOH group. • Building block of proteins. • Proteins are macromolecules present in all cells. • Physiological pH – present as zwitterions.

  7. Common Amino Acids

  8. The Amino Acids About 20 common amino acids used to synthesize proteins in biological systems. These amino acids differ with respect to the R group attached to the  carbon. The -carbon on all amino acids except glycine is chiral.

  9. Amino Acid Enantiomers Two enantiomeric forms of amino acids D (dextrorotary) L (levorotary) L-amino acids are used to synthesize proteins in living systems.

  10. Polypeptides and Proteins Proteins – polyamides. The amino acid residues are linked via peptide bonds. Condensation reaction of amino acids produces peptide sequences.

  11. Polypeptides • Polypeptides are formed when a large number of amino acids are linked together via peptide bonds. • Masses are less than 10 000. • Proteins – linear polypeptides with a molecular weight between 6000 and 50 million amu’s.

  12. Protein Structure The arrangement or sequence of amino acids along a protein chain Primary structure. The regular arrangement of segments along the protein chain Secondary structure.

  13. The -Helix A common secondary structure type. Hydrogen bonds and other intermolecular forces hold the helix in place. Another common type of protein structure is the -pleated sheet.

  14. Tertiary Structure • The three dimensional structure of the protein. • Two broad categories • Globular proteins – mainly water soluble. • Fibrous Proteins – water-insoluble. • Enzymes – protein catalysts. • Largely due to their tertiary structure. • Extremely specific with regard to what reactions they catalyze.

  15. Carbohydrates Have the general formula Cn(H2O)n The simple sugars glucose and fructose are the basic building units of many carbohydrates. These sugar molecules can make rings.

  16. Polysaccharides Disaccharides like table sugar (sucrose) consists of two rings joined together. When many rings join we get starch or cellulose. The difference is in how the rings are joined. We can digest starch but not cellulose.

  17. Simple Sugars Two common carbohydrates Glucose (an aldehyde sugar or aldose). Fructose (a ketone sugar or ketose). Glucose is the most common carbohydrate.

  18. Ring Closing Carbohydrates, containing both aldehyde and alcohol functional groups, can form rings. These 6-membered rings are not planar.

  19.  and  Glucose Glucose can form two different six-membered rings, -glucose, and -glucose. A small difference that can have important biological consequences!!

  20. Mono- and Disaccharaides Glucose and fructose are both examples of monosaccharides, or simple sugars. Two monosaccharides can condense to form a disaccharide. Sucrose (table sugar). Lactose (milk sugar).

  21. Polysaccharides Consist of multiple monosaccharides linked together. Starch, glycogen, and cellulose are important polysaccharides, and are all made of repeating glucose units.

  22. Nucleic Acids • Nucleic acids carry genetic information. • DNA – deoxyribonucleic acid • Molecular mass between 6 – 16 million amu! • RNA - ribonucleic acid • Molecular mass between 20 – 40 thousand amu! • Nucleic Acids are made up of monomers called nucleotides.

  23. Nucleotides A nucleotide consists of three parts. A phosphoric acid unit A five carbon sugar. DNA – deoxyribose. RNA – ribose. H3PO4

  24. Nucleic Acids that Make Up Nucleotides There are five bases found in DNA and in RNA

  25. A Nucleotide The arrangement of the three components in a nucleotide. Nucleic acids are formed by the condensation of nucleotides.

  26. Nucleic Acids A nucleic acid strand is formed by successive condensation of nucleotides.

  27. DNA DNA consists of two deoxyribonucleic acid strands wound together in a double helix.

  28. Base Pairings • The structure of the double helix is supported by base pairs that optimize hydrogen bonding. • The structures guanine/cytosine and adenine/thymine make them ideal hydrogen bonding partners. • Two hydrogen bonds form between A and T. • Three H-bonds form between C and G.

  29. Replication A schematic representation of DNA replication. The double helix unwinds by separation of the base pairs Each half serves as a template for the synthesis of a new strand.

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