The Molecules of Life

1. The Molecules of Life Chapter 3

2. Polymers Are Built of Monomers • Organic moleculesare formed by living organisms. • Carbon-based core • The core has attached groups of atoms called functionalgroups. • The functional groups confer specific chemical properties on the organic molecules.

3. Five principal functional groups Group Structural Formula Ball-and- Stick Model Found In Hydroxyl Carbohydrates OH O H Carbonyl Lipids C O C O O O C C Carboxyl Proteins O H OH H H Amino Proteins N N H H O– O– O– P Phosphate DNA, ATP O P O– O O O

4. Macromolecules • The building materials of the body are known as macromoleculesbecause they can be very large. • There are four types of macromolecules: • Proteins • Nucleic acids • Carbohydrates • Lipids

5. Macromolecules • Large macromolecules are actually assembled from many similar small components, called monomers. • The assembled chain of monomers is known as a polymer.

6. Dehydration Synthesis • All polymers are assembled the same way. • A covalent bond is formed by removing a hydroxyl group (OH) from one subunit and a hydrogen (H) from another subunit.

7. Dehydration Synthesis H2O • Because this amounts to the removal of a molecule of water (H2O), this process of linking together two subunits to form a polymer is called dehydration synthesis. HO H HO H Energy H HO

8. Hydrolysis • The process of disassembling polymers into component monomers is essentially the reverse of dehydration synthesis. • A molecule of water is added to break the covalent bond between the monomers. • This process is known as hydrolysis. H2O H HO Energy H HO HO H

9. Proteins • Proteins are complex macromolecules that are polymers of many subunits called amino acids.

10. Proteins Amino acid Amino acid H R H R • The covalent bond linking two amino acids together is called a peptide bond. • The assembled polymer is called a polypeptide. H N C C H N C C OH OH H O H O H2O Polypeptide chain H H R R H N C C N C C OH H O H O

11. Proteins • Amino acids are small molecules with a simple basic structure, a carbon atom to which three groups are added: • an amino group (—NH2) • a carboxyl group (—COOH) • a functional group (R) • The functional group gives amino acids their chemical identity. • There are 20 different types of amino acids.

12. Proteins • Protein structure is complex. • The order of the amino acids that form the polypeptide is important. • The sequence of the amino acids affects how the protein folds together.

13. Proteins • The way that a polypeptide folds to form the protein determines the protein’s function. • Some proteins are comprised of more than one polypeptide.

14. Proteins Primary structure Amino acids H N • There are four general levels of protein structure: • Primary • Secondary • Tertiary • Quaternary C Secondary structure C N N C C O C O H C H N C C N O O C H H C N N C C O C O H H C β-pleated sheet N C C O N O C α-helix C O Tertiary structure Quaternary structure

15. Proteins Primary structure Amino acids • Primary structure—the sequence of amino acids in the polypeptide chain. • Determines all other levels of protein structure.

16. Proteins H Secondary structure N C • Secondary structureforms because regions of the polypeptide that are nonpolar are forced together; hydrogen bonds can form between different parts of the chain. • The folded structure may resemble coils, helices, or sheets. C N N C C O C O H C H N C C N O O C H H C N N C C O C O H H C β-pleated sheet N C C O N O C α-helix C O

17. Proteins • Tertiary structure—the final 3-D shape of the protein. • The final twists and folds that lead to this shape are the result of polarity differences in regions of the polypeptide. Tertiary structure

18. Proteins • Quaternary structure—the spatial arrangement of proteins comprised of more than one polypeptide chain. Quaternary structure

19. Proteins Folded protein • The shape of a protein affects its function. • Changes to the environment of the protein may cause it to unfold or denature. • Increased temperature or lower pH affects hydrogen bonding, which is involved in the folding process. • A denatured protein is inactive. Denaturation Denatured protein

20. Proteins Active-site cleft • Enzymes are globular proteins that have a special 3-D shape that fits precisely with another chemical. • They cause the chemical that they fit with to undergo a reaction. • This process of enhancing a chemical reaction is called catalysis.

21. Nucleic Acids • Nucleic acidsare very long polymers that store information. • Comprised of monomers called nucleotides. • Each nucleotide has 3 parts: • a five-carbon sugar • a phosphate group • an organic nitrogen-containing base

22. Nucleic Acids Nitrogenous bases Structure of nucleotide Nitrogenous base • There are five different types of nucleotides. • Information is encoded in the nucleic acid by different sequences of these nucleotides. NH2 O NH2 6 7 N 5 C C N N N C C H N N 1 H C H C Phosphate group 8 NH2 C C C H C 2 N N N N 4 N N O H H 3 9 –O CH2 P O Adenine Guanine 5 O– O O NH2 O C C C 4 1 H3C H C N H C N H C H N H C C O H C C O 3 2 C H O C OH in RNA N N N OH R H H H H in DNA Sugar Cytosine Thymine (DNA only) Uracil (RNA only) (b) (a)

23. Nucleic Acids • There are two types of nucleic acids: • Deoxyribonucleic acid (DNA) • Ribonucleic acid (RNA) • RNA is similar to DNA except that • it uses uracil instead of thymine • it is comprised of just one strand • it has a ribose sugar O P Sugar-phosphate “backbone” O O C P P G O P O G C P O Hydrogen bonds between nitrogenous bases P T O A P O Phosphodiester bond P C O G O P P A T O O P OH

24. Nucleic Acids • The structure of DNA is a double helix because: • There are only two base pairs possible • Adenine (A) pairs with thymine (T) • Cytosine (C) pairs with Guanine (G) • Properly aligned hydrogen bonds hold each base pair together. • A sugar-phosphate backbone comprised of phosphodiester bonds gives support.

25. A and C cannot properly align to form hydrogen bonds. A C G and T cannot properly align to form hydrogen bonds. G T A and T can align to form two hydrogen bonds. A T G and C can align to form three hydrogen bonds. G C

26. Nucleic Acids • The structure of DNA helps it to function. • The hydrogen bonds of the base pairs can be broken to unzip the DNA so that information can be copied. • Each strand of DNA is a mirror image so that the DNA contains two copies of the information. • Having two copies means that the information can be accurately copied and passed to the next generation.

27. Carbohydrates • Carbohydratesare monomers that make up the structural framework of cells and play a critical role in energy storage. • A carbohydrate is any molecule that contains the elements C, H, and O in a 1:2:1 ratio.

28. Carbohydrates • The sizes of carbohydrates varies: • Simple carbohydrates—consist of one or two monomers. • Complex carbohydrates—are long polymers.

29. Carbohydrates • Simple carbohydrates are small. • Monosaccharidesconsist of only one monomer subunit. • An example is the sugar glucose(C6H12O6). • Disaccharidesconsist of two monosaccharides. • An example is the sugar sucrose, which is formed by joining together glucoseand fructose.

30. Carbohydrates • Complex carbohydratesare long polymer chains. • Because they contain many C-H bonds, these carbohydrates are good for storing energy. • These bond types are the ones most often broken by organisms to obtain energy. • The long chains are called polysaccharides.

31. Carbohydrates • Plants and animals store energy in polysaccharide chains formed from glucose. • Plants form starch. • Animals form glycogen. • Some polysaccharides are structural and resistant to digestion by enzymes. • Plants form cellulosecell walls. • Some animals form chitinfor exoskeletons.

32. Lipids • Lipids—fats and other molecules that are not soluble in water. • Lipids are nonpolar molecules. • There are many different types of lipids. • fats • oils • steroids • rubber • waxes • pigments

33. Lipids • Fats are converted from glucose for long-term energy storage. • Fats have two subunits • 1. fatty acids • 2. glycerol • Fatty acids are chains of C and H atoms, known as hydrocarbons. • The chain ends in a carboxyl (—COOH) group.

34. Saturated and unsaturated fats O H H H H H H H H H C H H C O C C C C C C C C H H H H H H H H Because there are 3 fatty acids attached to a glycerol, another name for a fat is triglyceride O H H H H H H H H H C O C H C C C C C C C C H H H H H H H H O H H H H H H H H H C O C C C C C C C C C H H H H H H H H H H Glycerol backbone Fatty acids (a) Fat molecule (triacylglycerol)

35. Lipids • Fatty acids have different chemical properties due to the number of hydrogens that are attached to the non-carboxyl carbons • If the maximum number of hydrogens are attached, then the fat is said to be saturated. • If there are fewer than the maximum attached, then the fat is said to be unsaturated.

36. Saturated and unsaturated fats H H H H C C C C H H (b) Hard fat (saturated): Fatty acids with single bonds between all carbon pairs (c) Oil (unsaturated): Fatty acids that contain double bonds between one or more pairs of carbon atoms

37. Phospholipids • Biological membranes involve lipids. • Phospholipidsmake up the two layers of the membrane. • Cholesterolis embedded within the membrane. Outside of cell Carbohydrate chains Cell membrane Membrane proteins Phospholipid Cholesterol Inside of cell