1. 1 The Chemical Building Blocks of Life Chapter 3

2. 2 Biological Molecules The framework of biological molecules consists of carbon bonded to other carbon molecules, or other types of atoms. – Hydrocarbons consist of carbon and hydrogen.  Covalent bonds store considerable energy.  Make good fuels

3. 3 Biological Molecules Functional groups – specific groups of atoms attached to carbon backbones  retain definite chemical properties Macromolecules. – proteins – nucleic acids – lipids – carbohydrates

4. 4 Hydroxyl Carbonyl Carboxyl Amino Sulfhydryl Phosphate Methyl Acetic acid Functional Group Structural Formula Example Acetaldehyde Alanine  -mercaptoethanol Glycerol phosphate Pyruvate H S P O–O– O O H C H H OH O C H H N C O Ethanol C H H CH H H OH CH H H C O H CH 3 O H CCHON H CH H H HC O C H HH SHC H CH OH H C HH OC H P O C O C O H HC H O–O– O–O– O–O– O–O–

5. 5 Macromolecules Macromolecules are often polymers. – long molecule built by linking together small, similar subunits  Dehydration synthesis removes OH and H during synthesis of a new molecule.  Hydrolysis breaks a covalent bond by adding OH and H.

6. 6

7. 7 Proteins - C, H, O, N, S A.Amino acids B.Peptide bonds C.Polypeptide chains H - N - C - C - OH OH H Amine Group Acid Group R H

8. 8 Protein Function

9. 9 Amino Acids contain an amino group (-NH 2 ), a carboxyl group (-COOH) and a hydrogen atom, all bonded to a central carbon atom – twenty common amino acids grouped into five classes based on side groups  nonpolar amino acids  polar uncharged amino acids  charged amino acids  aromatic amino acids  special-function amino acids

10. 10 Amino Acids Peptide bond links two amino acids. – A protein is composed of one or more long chains of amino acids linked by peptide bonds (polypeptides).

11. 11 Alanine (Ala) Leucine (Leu) Isoleucine (Ile) Phenylalanine (Phe) Tryptophan (Trp) Tyrosine (Tyr) Glutamine (Gln) Asparagine (Asn) Threonine (Thr) Serine (Ser) Glycine (Gly) Glutamic acid (Glu) Aspartic acid (Asp Histidine (His) Lysine (Lys) Arginine (Arg) Charged Polar uncharged Nonpolar NONAROMATICAROMATIC Valine (Val) CH 3 CC HO CH CC HO CC HO CC HO H C CCCC HO NH C CC HO OH H C CC HO CC HO C NH 2 O CH 2 CCO–O– HO OH C CC HO O H CC HO CC HO C O CC HO NH C CC HO CC HO C N HC NH + CH H CC HO C O CH 3 CH 2 NH 2 CH 3 CH 2 NH 2 H3N+H3N+ H3N+H3N+ H3N+H3N+ H3N+H3N+ H3N+H3N+ H3N+H3N+ O–O– O–O– O–O– O–O– O–O– H3N+H3N+ H3N+H3N+ H3N+H3N+ H3N+H3N+ H3N+H3N+ O–O– O–O– O–O– O–O– O–O– O–O– O–O– CH 2 NH 2 + NH 3 + O–O– HO H3N+H3N+ H3N+H3N+ H3N+H3N+ H3N+H3N+ H3N+H3N+ H3N+H3N+ O–O– O–O– O–O– O–O– O–O–

12. 12 Protein Structure  The shape of proteins is extremely important and can determine the function  Water’s tendency to hydrophobically exclude nonpolar molecules literally shoves the nonpolar portions of the protein to the interior Many shapes  Primary – the specific amino acid sequences  Secondary – formed by hydrogen bonding  Alpha helix – coils  Beta pleated sheet - foldbacks  motifs - folds or creases  supersecondary structure

13. 13 NNN H H H H HH H C CC CC CNCCNC C C O O O OHH OHH R R RR RR Motifs Primary structure 1 2 3  helix  turn  motif  motif  pleated sheet Secondary structure

14. 14 Protein Structure  Tertiary - final folded shape of globular protein (3-dimensional shape) based on bonding of side groups  Domains – independent functional units of the protein 100–200 amino acids long - encoded by a specific DNA sequence (exon)  Quaternary - forms when two or more polypeptide chains associate to form a functional protein

15. 15 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 4 5 6 Tertiary structure Domains Quaternary structure Domain 3 Domain 2 Domain 1

16. 16 Chaperone Proteins Chaperone proteins are special proteins which help new proteins fold correctly. – Chaperone deficiencies may play a role in facilitating certain diseases.

17. 17 Unfolding Proteins Denaturation refers to the process of changing a protein’s shape. – usually rendered biologically inactive  pH  temperature  Ionic concentration - salt-curing and pickling used to preserve food

18. 18 Nucleic Acids - C, H, O, N, P Deoxyribonucleic Acid (DNA) – Encodes information used to assemble proteins. Ribonucleic Acid (RNA) – Reads DNA-encoded information to direct protein synthesis.

19. 19 Nucleic Acid Structure Nucleic acids are composed of long polymers of repeating subunits, nucleotides. – five-carbon sugar – Phosphate group – nitrogenous base  Purines double ringed  adenine and guanine  Pyrimidines – single ringed  cytosine, thymine, and uracil

20. 20 5959 3939 P P P P OH 5-carbon sugar Nitrogenous base Phosphate group Phosphodiester bonds Adenine O O O O Guanine C C N N N C H N C CH O H Cytosine (both DNA and RNA) Thymine (DNA only) Uracil (RNA only) HCC N C H N C NH 2 N N CH O C C N C H N C H H OC C N C H N C O H H3CH3C H O CC N C H N C O H H H PURINESPURINES PYRIMIDINESPYRIMIDINES

21. 21 Nucleic Acid Structure DNA exists as double-stranded molecules. – double helix – complementary base pairing  Chargaff’s rule  hydrogen bonding RNA exists as a single stand. – contains ribose instead of deoxyribose – contains uracil in place of thymine

22. 22 Structure of DNA

23. 23 Lipids Lipids are loosely defined as groups of molecules that are insoluble in water. – fats and oils Phospholipids form the core of all biological membranes. – composed of three subunits  Glycerol - backbone  fatty acid – long tail  phosphate group – head  Polar head - hydrophilic  Nonpolar tail - hydrophobic

24. 24 Phospholipids form membranes micelle

25. 25 Fats and Other Lipids Fats consist a of glycerol molecule with three attached fatty acids (triglyceride / triglycerol). – Saturated fats - all internal carbon atoms are bonded to at least two hydrogen atoms – maximum # of H – Unsaturated fats - at least one double bond between successive carbon atoms  Polyunsaturated - contains more than one double bond  usually liquid at room temperature

26. 26 Fats as Energy Storage Molecules Fats, on average, yield about 9 kcal per gram versus 4 kcal per gram for carbohydrates. – Animal fats are saturated while most plant fats are unsaturated.  Consumption of excess carbohydrates leads to conversion into starch, glycogen, or fats for future use.

27. 27 Carbohydrates Carbohydrates are loosely defined as molecules that contain carbon, hydrogen, and oxygen in a 1:2:1 ratio. – monosaccharides - simple sugars

28. 28 – disaccharides - two monosaccharides joined by a covalent bond H2OH2O

29. 29 – polysaccharides - macromolecules made of monosaccharide subunits  isomers - alternative forms of the same substance – Many C 6 H 12 0 6

30. 30 Carbohydrate Transport and Storage Transport disaccharides – Humans transport glucose as a simple monosaccharide. – Plants transform glucose into a disaccharide transport form. Storage polysaccharides – plant polysaccharides formed from glucose – starches  most is amylopectin – Animal starch is glycogen

31. 31 Structural Carbohydrates Cellulose - plants – alpha form or beta form of ring Chitin - arthropods and fungi  modified form of cellulose