The Structure and Function of Macromolecules

1. The Structure and Function of Macromolecules

2. Organic Molecules • Organic molecules are molecules that contain the element carbon (C) • They also frequently contain the elements hydrogen (H) and oxygen (O).

3. Solubility in Water • When organic molecules encounter water, some dissolve and some do not. • When a solvent (water) contains a solute (organic molecule) and the solute dissolves, we would say that a solution has been formed. • Not all organic molecules are soluble in water.

4. Macromolecules • Macromolecules are large organic molecules used by the body for most bodily functions in animals and plants. • Most macromolecules are made of smaller units called “monomers” which when joined, form “polymers”. • Most importantly, it is the molecule’s shape that determines its function and its shape is determined by chemical bonding of elements.

5. Monomers • Are small molecules that may become chemically bonded to other monomers to form a polymer. • Monomers can be joined together to form polymers. • As you will see, water is the main ingredient in forming polymers. • Monomers and polymers are very important and an organism’s body is constantly breaking and building polymers.

6. Polymers (macromolecules) • Polymer Defined • Polymers are large molecules that include carbohydrates, proteins, and nucleic acids. • Polymers consist of many similar or identical monomer building blocks linked by covalent bonds.

7. Polymer Formation • Monomers are connected by a reaction in which two molecules are covalently bonded to each other through a loss of water. • This is called dehydration synthesis because the molecule lost is water. • To make a polymer, this reaction is repeated and monomers are added one by one in a chain.

9. Polymer Disassembling • Polymers are disassembled into monomers by hydrolysis, where the bonds of joined monomers are broken by the addition of water molecules.

10. Polymer Diversity • Depending on the type of cell, each cell can have up to thousands of monomers. • There are only 50-60 types of monomers which are assembled in an infinitesimal number of ways.

11. There are 4 Types of Macromolecules • Carbohydrates • Lipids • Proteins • Nucleic Acids

12. Carbohydrates • Include sugars, starch and cellulose • The monomers of carbohydrates are called monosaccharides • Usually have a CnH2nOn type of formula. • Glucose (C6H12O6) is a more common monosaccharide.

13. In water, the structure of sugar forms a ring.

14. Polymers of Carbohydrates • Disaccharides are polymers of carbohydrate that consists of two monosaccharides joined by a covalent bond. • The covalent bond formed between two monosaccharides by dehydration synthesis. • Two glucose monosaccharides joined together form a disaccharide called “maltose”. • One glucose and a fructose joined together make “sucrose” (table sugar)

16. Polymers of Carbohydrates • Polysaccharides are polymers with a few hundred to a few thousand monosaccharides joined by covalent bonds. • Can be branched or straight. • Some polysaccharides serve as storage material in animal muscles and liver (glycogen), others serve as building structural materials for cells (cellulose).

17. 4. Cell Usage of Carbohydrates • Cell Usage • Monosaccharides are major nutrients for cells. • In a process called cell respiration, cells extract energy contained in glucose molecules. • Plant cells also make carbohydrates through photosynthesis.

18. Storage Polysaccharides • Starch • A storage polysaccharide of plants, is a polymer consisting entirely of glucose monomers. • Starch is stored as granules within plant cells (like rice and potatoes). • Starch is stored energy.

19. Glycogen • Human stored polysaccharide, a polymer of glucose that is extensively branched • Stored in liver and muscle cells. • Your body needs glycogen all the time so the fuel source is short lived and must be replenished daily.

20. Cellulose • Used for structure in plant cell walls.

21. 2. Chitin • A structural polysaccharide carbohydrate used by arthropods in exoskeletons. • Chitin is similar to cellulose except that it has a nitrogen containing appendage (P. 68)

22. II. Lipids • Macromolecules that do not include polymers. • Lipids are hydrophobic. • Based on the molecular structure of mainly hydrocarbons. • Lipid Families: • Fats • Oils • Waxes • Phospholipids • Steroids

23. Fats • Are not polymers but are assembled through dehydration synthesis. • They are constructed from 2 types of small molecules: glycerol and fatty acids. • Fats separate from water because the water molecules would rather H bond to each other than with the fat.

24. Making Fat • 3 fatty acids each join 1 one glycerol. • The 3 fatty acids can be the same or different.

25. Fatty Acids • Vary in length and in the number and location of double bonds. • Saturated and unsaturated fats refer to the structure of the chains of the fatty acids • If there are no double bonds between carbon atoms, then as many hydrogen atoms that can fit are bonded to them. • Thus, the molecule is saturated with hydrogen. • An unsaturated fatty acid has one or more double bonds formed by the removal of hydrogen atoms from the chain. Wherever the double bond occurs, the chain will have a bend to it. • Most animal fats are saturated, and solid at room T. • Fats from plants or fish are generally unsaturated, are liquid at room T, and are commonly oils. The bends in the molecule prevent the molecules from stacking and being solid at room T.

26. Uses for fat • Fats have incredible energy storing ability. One gram of fat stores more than twice the amount of polysaccharides. • For plants, their energy mostly comes from starches because plants are stationary. But animals go places and need to have energy reserves in their body. • Fats also help cushion vital bodily organs.

27. 2. Phospholipids • Have only 2 fatty acid tails rather than 3. • Phospholipids have parts that are hydrophobic (hydrogen tails) and hydrophilic (phosphate head). • When phospholipids encounter water, they self-assemble in clusters, oriented so that the hydrophilic heads point outward and the hydrophobic tails are shielded inward. • This phospholipid bi-layer forms a boundary between the cell and its external environment; becoming major components of cell membranes.

29. Steroids • Lipids with a skeleton of carbon with 4 fused carbon rings. • Cholesterol is a steroid and is a common component of cell membranes and is also the site where other steroids are synthesized. • Testosterone and estrogen are also steroids secreted from your body.

30. Proteins

31. Protein Characteristics • Proteins are macromolecules that are made by the decoding of genes located on an organisms DNA. • Compose about 50% of all of the dry weight of most cells and play a part in most everything organisms do. • Storage, structure, transport, signaling, movement, etc • Enzymes (special proteins) regulate metabolism by accelerating chemical reactions. • Humans alone have 10’s of thousands of proteins, each with a specific function. • They are the most sophisticated molecules known. • The monomers of proteins are called amino acids and all proteins are made from the same 20 piece set of amino acids. • Polymers of amino acids are called polypeptides.

32. 20 Amino Acids

33. Polypeptides • Polypeptides are the polymers of proteins. • Each amino acid monomer is joined by a “peptide bond”. • Proteins have different layers of structure. • The primary layer is the order of the amino acids. • The secondary through tertiary layers determine the shape of the polypeptide and this happens by chemical bonding along the length of the chain.

35. 4 Levels of Protein Structure • Level 1: Primary Structure • Its unique sequence of amino acids • Example: Lysozyme (129 amino acids long); one of the 20 amino acids resides on each link of the 129 link long chain. • The primary structure is the order of the letters like a very long word). Derived from inherited genetic information.

36. Secondary structure • Coils or folds in the primary structure that contribute the proteins overall conformation. • Result of H bonding at regular intervals along the PP backbone.

38. Tertiary Structure • Superimposed on the secondary structure and consists of irregular contortions from interaction between side chains (R Groups) of the various amino acids. • The irregular folding of tertiary structure results from interactions among the R groups of amino acids. Acidic and basic R groups ionize, and these positively and negatively charged groups may form ionic bonds.

39. Quaternary Structure • Results from the combination of two or more polypeptide subunits. • Quaternary structure is stabilized by the same sorts of attractions that stabilize tertiary structure. • Hemoglobin, the red oxygen-carrying protein of blood, is an example of a protein with quaternary structure. It consists of two kinds of polypeptide chains. Two of each-- a total of four chains-- make up each hemoglobin molecule. • The specific function of the protein arises from the architecture of the molecule through each structure.

41. Protein Shape • A change in pH, salinity, etc may cause the protein to unravel in a process called denaturing. • The misshapen denatured protein is biologically inactive, but if returned to the proper environmental abiotic conditions, it could return to its previous shape.

42. Nucleic Acids • Nucleic Acids are “informational polymers” since they carry the genetic code of life. • Types: • Deoxyribonucleic (DNA) • Provides directions for its own replication • All proteins and enzymes are made from DNA. • Ribonucleic (RNA) • Single strand of nucleotides instead of 2 that are found in DNA • Contain a sugar called ribose rather that deoxyribose (found in DNA) • While DNA contains A,C and G nitrogen bases, RNA contains uracil (U) and no Thymine. Uracil is complementary with adenine whenever RNA base-pairs with another nucleic acid.

43. DNA • Inherited genetic material (from the parents) • The DNA molecule is very long and consists of hundreds or thousands of genes. • Remember that a gene is a segment of DNA that codes a particular protein or RNA molecule. • DNA function • When a cell divides, DNA molecules are passed on from one cell to the next • Encoded in the DNA structure are genes that programs all of the cellular activities • DNA does not give commands directly to the cell just as this computer alone cannot print out this page. • Proteins are needed to carry out the cell functions and are synthesized through DNA transcription and translation.

44. Monomers and Polymers of Nucleic Acids • Nucleic Acid Strands (nucleotides) • Are polymers composed of monomers called nucleotides • Each nucleotide is composed of 3 parts: a nitrogen base, a pentose sugar, and a phosphate group • Nitrogenous Bases • These include cytosine (C), Thymine (T), Uracil (U in RNA), Adenine (A) and Guanine (G)

45. The Pentose (5 carbon) sugar • The sugar is connected to the nitrogenous base. There are 2 kinds: • Ribose: found in the nucleotides of RNA • Deoxyribose: found in the nucleotides of DNA • Phosphate Group • Attached to the the sugar. • Nucleic Acid Polymers (polynucleotide) • Nucleotides are joined by covalent bonds called phosphodiester linkages between the phosphate of one nucleotide and the sugar of the next. • This bonding results in a backbone of a repeating pattern of sugar-phosphate units. • The nitrogen base units project from the backbone • The sequences of bases along the RNA or DNA polymer is unique for each gene. • Because genes are hundreds or thousands of nucleotides long, the number of base sequences are limitless.

47. The gene’s meaning to each cell is encoded in its specific sequence of 4 letter nitrogenous bases • AGGTAACTT means one thing to a cell while the sequence CGCTTTAC means another • The linear order of the bases in a gene specifies the amino acid sequence of a protein (sort of like coded instructions), which in turn specifies the protein’s 3-D conformation, which specifies the protein’s function to the organism. • “Genes are like stories from chromosome chapters, paragraphs are called codons, and each written word is composed of letters called bases”

48. Inheritance based on DNA replication • Form and function • DNA is shaped as a double polynucleotide helix and RNA only consists of one polynucleotide • In DNA, the 2 sugar-phosphate backbones are connected by “bridges” of complimentary nitrogen base pairs • Each base pair is held together by H bonds • One DNA strand contains many genes, each a particular segment on the strand. • Certain bases pair with others • AT, GC • One strand compliments the other so that: AGGTCCG (strand 1) TCCAGGC (strand 2) • This complimentary feature allows for precise replication of genes.

49. Replication • In cell division, each of the 2 DNA strands serve as a template to order nucleotides into a new complimentary strand. • The result is 2 identical copies of the original double strand which are then distributed to daughter cells • The structure of DNA accounts for its function in transmitting genetic information whenever a cell replicates.