Biological Molecules

1. Biological Molecules

2. Biological Molecules • Life is carbon-based chemistry • Hydrolysis and Synthesis of Biological Molecules • Carbohydrates • Lipids • Proteins • Nucleic Acids

3. Life is carbon-based chemistry • Organic is used to describe molecules that have a carbon skeleton and some additional hydrogen atoms • Life is composed of organic molecules • Inorganic molecules include carbon dioxide, water and all other non-carbon molecules

4. Life is carbon-based chemistry • The tremendous diversity of organic molecules is due to the diverse functional groups that attach themselves to common carbon skeletons: • Hydrogen (-H) • Hydroxyl (-OH) • Carboxyl (-COOH) • Amino (-NH2) • Phosphate (-H2PO4) • Methyl (-CH3)

5. Hydrolysis and Synthesis of Biological Molecules • Small organic molecules are used as subunits to synthesize longer molecules • The individual subunits are called monomers • The longer molecules are called polymers

6. Hydrolysis and Synthesis of Biological Molecules • Monomers are linked to monomers in a chemical process called dehydration synthesis • The –H group is removed from one monomer and the –OH group is removed from the second monomer • The two monomers join by forming a covalent bond • The –H group and –OH group bond to form a water molecule

8. Hydrolysis and Synthesis of Biological Molecules • Polymers are disassembled into monomers through a process called hydrolysis • The polymer splits into monomers • A water molecule splits and releases a –H group and a –OH group • The –H group and –OH group bond to the monomers to complete their structure

10. Carbohydrates • Contain carbon, hydrogen and oxygen in the constant ratio of 1:2:1 • Carbohydrates are “hydrates of carbon” • C1H201 or CH20 • All carbohydrates are either small, simple sugars or polymers of these simple sugars

11. Carbohydrates

12. Lipids • Lipids contain large regions of H and C atoms joined by non-polar covalent bonds • Non-polar regions are hydrophobic • Lipids are not soluble in water • Three major groups of lipids • (1) oils, fats and waxes • (2) phospholipids • (3) steroids

13. Oils, Fat and Waxes • Contain only C, H and O atoms • Composed of one or more fatty acids subunits attached to a glycerol subunit • Are straight chains: do not have ring structures • Function as source of energy

14. Oils, Fat and Waxes • Fatty acid chains that have no C=C double bonds are said to be saturated with H atoms • Fatty acid chains that have C=C double bonds are said to be unsaturated with H atoms • Saturated fatty acid chains are straight • Unsaturated fatty acid chains are kinked

15. Oils, Fat and Waxes • Oils are liquid at room temperature because they are unsaturated → kinks • Waxes are solid at room temperature because they are saturated → straight

16. Phospholipids • Similar to structure of fats, waxes and oils except one of the three fatty acid chains is replaced by a phosphate group containing a polar functional group • The two fatty acid chains are hydrophobic • The phosphate head (being polar) is hydrophilic • Function as basic component of membranes

17. Steroids • Composed of four rings of carbon fused with various functional groups • Steroids are synthesized from cholesterol • Function as hormones and components of animal cell membranes

18. Proteins • Proteins are polymers of amino acid subunits • The bond between amino acid subunits is called a peptide bond (formed by dehydration synthesis) • Diversity of proteins is due to diversity of amino acids and the diverse ways amino acids arrange themselves • Proteins function as enzymes, structural components, transport proteins, energy storage, cross-membrane transport, and hormones

19. Proteins • Amino acids are composed of a central C atom bonded to four different functional groups: • (1) amino group (-NH2) • (2) carboxylic acid group (-COOH) • (3) hydrogen group (-H) • (4) variable group (-R)

20. Proteins • The –R group creates the diversity of amino acids • Some -R groups are small, others large • Some –R groups are hydrophobic, others hydrophilic • The type of –R group directly affects the structure of the protein

21. Proteins • Proteins have four levels of structure • (1) Primary Structure: sequence of amino acids in the linear protein polymer • (2) Secondary Structure: simple repeating pattern created by hydrogen bonding between amino acid subunits • Secondary structure can be either a helix or pleated sheet

22. Proteins • (3) Tertiary Structure: complex 3 dimensional shape formed by folding over of secondary structure • Tertiary structure is due to disulfide bridging between neighbouring cysteine amino acids; size of –R group; hydrophobic/hydrophilic interactions

23. Proteins • (4) Quaternary Structure: due to joining together of smaller proteins in order to form a larger protein complex

24. Nucleic Acids • Nucleic acids are polymers of nucleotide subunits • Nucleotides are composed of three components themselves: • (1) a five C sugar (ribose/deoxyribose) • (2) a phosphate group • (3) a N containing base

25. Nucleic Acids • It is the diversity in N containing bases that creates diversity in nucleotides • It is the diversity in sugars that adds to the diversity of nucleic acids

26. Nucleotides

27. Nucleic Acids • Nucleic acids function primarily as the molecules of heredity and the blueprint for protein synthesis (DNA and RNA) • Nucleic acids also act as intracellular messengers (cAMP), coenzymes and energy carrier molecules (ATP)