Molecules of Life

1. Molecules of Life Chapter 3 Part 1

2. Organic Molecules • All molecules of life are built with carbon atoms • We correctly call carbon the signature atom of life and living forms, past and present • We can use different models to highlight different aspects of the same molecule

3. 3.1 Carbon – The Stuff of Life • Organicmolecules are complex molecules of life, built on a framework of carbon atoms – all the biological macromolecules below have a carbon backbone – the first two are rigid; proteins are uniquely flexible, and nucleic acids make up the DNA and RNA of heredity • Carbohydrates • Lipids • Proteins • Nucleic acids

4. Carbon – The Stuff of Life • Carbon atoms can be assembled and remodeled into many organic compounds – carbon: • Can bond with one, two, three, or four atoms (maximum of four because four electrons are present in the carbon outer valence shell) • Can form polar or nonpolar bonds • Can form chains or rings

5. Three Models of a Hemoglobin Molecule It’s a protein and you can see the twists and coils and flex shapes.

6. 3.2 From Structure to Function • The function of organic molecules in biological systems begins with their structure • The building blocks of carbohydrates, lipids, proteins, and nucleic acids bond together in different arrangements to form different kinds of complex molecules to actually perform needed functions and work

7. Functional Groups Are The Difference • Hydrocarbon • An organic molecule that consists only of hydrogen and carbon atoms • Most biological molecules have at least one functional group (A cluster of atoms that imparts specific chemical properties to a molecule ex. polarity, acidity, ETOH, etc.)

8. Common Functional GroupsFound In Biological Molecules

9. Effects of Functional Groups: Sex Hormones Note similarity of sex hormones above that result in female and male below

10. What Cells Do With Organic Compounds • Metabolism • Activities by which cells acquire and use energy to construct, rearrange, and split organic molecules (must have energy to do this work) • Allows cells to live, grow, and reproduce • Requires enzymes (proteins that greatly increase the speed of reactions) • Remember that released energy must be used and/or captured or it escapes as heat

11. How Cells Form Large Molecules • Condensation • Covalent bonding of two or more molecules to form a larger molecule by subtracting O from one molecule and OH from the adjoining molecule • Water forms as a product to this joining • Hydrolysis • The reverse of condensation – put HOH back • Cleavage reactions split larger molecules into the smaller ones that originally formed them • Water is split

12. What Cells Do With Organic Compounds • Monomers (mono means single) • Single molecules used as subunits to build larger molecules (polymers) • Polymers (poly means more than one) • Larger molecules that are chains of monomers • May be split and used for energy • Polymer example: starch is many glucose units joined together by condensation bonds

13. What Cells Do With Organic Compounds

14. Condensation and Hydrolysis Illustrated

15. 3.1-3.2 Key Concepts:Structure Dictates Function • We define cells partly by their capacity to build complex carbohydrates and lipids, proteins, and nucleic acids • All of these organic compounds have functional groups attached to a backbone of carbon atoms

16. Carbohydrates • Carbohydrates • Organic molecules that consist of carbon, hydrogen, and oxygen in a 1:2:1 ratio; example glucose, a simple sugar, is C6H12O6 • Monosaccharides (mono=one) – ex. glucose • Three types of carbohydrates in living systems • Oligosaccharides (oligo=few) – ex. sucrose • Polysaccharides (poly=many) – ex. starch

17. Simple Sugars • Monosaccharides (one sugar unit) are simple carbohydrates • Used as an energy source or structure • Backbones of 5 or 6 carbons • Example: glucose is a 6-carbon sugar with red numbers showing carbon locations

18. Short-Chain Carbohydrates • Oligosaccharides • Short chains of monosaccharides • Example: sucrose, a disaccharide (two sugars)

19. More Complex Carbohydrates • Polysaccharides • Straight or branched chains of many sugar monomers joined by condensation bonds • The most common polysaccharides are cellulose, starch, and glycogen • All consist of joined glucose monomers • Each has a different pattern of covalent bonding, and different chemical properties and strength

20. Cellulose, Starch, and Glycogen Note that cellulose gains strength over starch by “side bar” reinforcing

21. Chitin – A Carbohydrate Of Strength • Chitin – (a hard, durable carbohydrate) • A nitrogen-containing polysaccharide that strengthens hard parts of animals such as crabs, and cell walls of fungi

22. 3.3 Key Concepts:Carbohydrate Characteristics • Carbohydrates are the most abundant biological molecules • They function as energy reservoirs and structural materials • Different types of complex carbohydrates are built from the same subunits of simple sugars, bonded in different patterns

23. 3.4 Greasy, Oily – Must Be A Lipid • Lipids function as the body’s major energy reservoir, and as the structural foundation of cell membranes • Lipids • Fatty, oily, or waxy organic compounds that are insoluble in water – need a nonpolar solvent

24. Fatty Acids In Lipids • Many lipids incorporate fatty acids • Simple organic compounds with a carboxyl group joined to a backbone of 4 to 36 carbon atoms • Essential fatty acids are not made by the body and must come from food • Omega-3 and omega-6 fatty acids are examples of essential fatty acids

25. Fatty Acid Examples • Are saturated, monounsaturated, or polyunsaturated on basis of their bonds • Saturated – no d-bond • Mono – one d-bond • Poly – multi d-bonds • Double bonds can attach other atoms

26. Characteristics Of Fats • Fats • Lipids with one, two, or three fatty acid “tails” attached to glycerol • Triglycerides • Neutral fats with three fatty acids attached to glycerol • The most abundant energy source in vertebrates • Concentrated in adipose tissues (for insulation and cushioning)

27. Triglyceride Examples

28. Saturated and Unsaturated Fats • Saturated fats (animal fats) • Fatty acids with only single covalent bonds • Pack tightly; are solid at room temperature • Unsaturated fats (vegetable oils) • Fatty acids with one or more double bonds • Kinked; are liquid at room temperature

29. Trans Fats Should Be Avoided • Trans fats • Partially hydrogenated vegetable oils formed by a chemical hydrogenation process • Restaurants often use as have longer usage life • Double bond straightens the molecule • Pack tightly; solid at room temperature • Worth avoiding for good health based upon current knowledge of effects in human body

30. Phospholipids • Phospholipids • Molecules with a polar head containing a phosphate and two nonpolar fatty acid tails • Heads are hydrophilic, tails are hydrophobic • The most abundant lipid in cell membranes • Note that cell membrane is a double layer with the hydrophilic heads pointing “out” while hydrophobic tails point “in”

31. Phospholipid Structure of Cell Membrane

32. c Cell membrane section greatly magnified Fig. 3-13c, p. 43

33. Waxes – Nature’s Waterproofing • Waxes • Complex mixtures with long fatty-acid tails bonded to long-chain alcohols or carbon rings • Protective, water-repellant covering, many uses

34. Cholesterol And Other Steroids • Steroids • Lipids with a rigid backbone of four carbon rings and no fatty-acid tails • Cholesterol – an important steroid in humans • Component of eukaryotic cell membranes • Remodeled into bile salts, vitamin D, and steroid hormones (estrogens and testosterone) • Excessive cholesterol can be bad for health

35. 3.4 Key Concepts:Lipids In General • Lipids function as energy reservoirs and waterproofing or lubricating substances • Some are remodeled into other substances • Lipids are the main structural components of cell membranes

36. Molecules of Life Chapter 3 Part 2

37. 3.5 Proteins – Diversity In Structure and Function Gives Many Uses • Proteins are the most diverse biological molecules (examples: there are structural, nutritious, enzyme, transport, communication, and defense proteins) • Cells build thousands of different proteins by stringing together amino acids according to the directions found in the DNA • Key is the flexibility of proteins allowing them to perform many functions in the organism

38. Proteins And Amino Acids • Protein • An organic compound composed of one or more chains of amino acids joined by peptide bonds • Amino acid • A small organic compound with an amine group (—NH3+), a carboxyl group (—COO-, the acid), and one or more variable groups (R group) • It is the R group that makes each of the 20 naturally occuring amino acids different

39. Amino Acid Structure Examples R above is functional group; valine is example of amino acid

40. Polypeptides From Amino Acids • Protein synthesis involves the formation of chain of joined amino acids (also called a polypeptide) • Polypeptide • A chain of amino acids bonded together by peptide bonds in a condensation reaction between the amine group of one amino acid and the carboxyl group of another amino acid • Remember: the condensation bond is made by extracting water from the two amino acids and thus linking them together

41. Peptide Bond Formation Example

42. Protein Structure (Primary & Secondary) • Primary structure • The unique amino acid sequence of a protein (just the list of amino acids contained in protein) • Secondary structure • The polypeptide chain can fold and it forms hydrogen bonds between the amino acids

43. Protein Structure (Tertiary & Quaternary) • Tertiary structure (more complex) • A secondary structure is compacted into structurally stable units called domains • Forms a functional protein • Quaternary structure (most complex) • Some proteins consist of two or more folded polypeptide chains in close association • Example: hemoglobin

44. Protein Structure Examples

45. 3.6 Why Is Protein Structure So Important? • When a protein’s structure goes awry, so does its function (example: fried egg white – cannot return it to unfried condition) • A really scary example is the brain prion that is involved in “mad cow disease” and similar cases in which the normal protein structure of the prion becomes distorted and literally starts destruction of the surrounding tissue.

46. Just One Wrong Amino Acid… • Hemoglobin contains four globin chains, each with an iron-containing heme group that binds oxygen and carries it to body cells • In sickle cell anemia, a DNA mutation changes a single amino acid in a beta chain, which changes the shape of the hemoglobin molecule, causing it to clump and deform red blood cells

47. Molecular Basis of Sickle Cell Anemia

48. Glutamic acid carries a negative charge; valine carries no charge. This difference changes the protein so it behaves differently. At low oxygen levels, HbS molecules stick together and form rod-shaped clumps that distort normally rounded red blood cells into sickle shapes. (A sickle is a farm tool that has a crescent-shaped blade.) sickled cell Phenotypic Basis Of Sickle Cell Anemia normal cell Fig. 3-19c, p. 47

49. Proteins Undone – Denaturation Proteins function only as long as they maintain their correct three-dimensional shape • Heat, changes in pH, salts, and detergents can disrupt the hydrogen bonds that maintain a protein’s shape • When a protein loses its shape and no longer functions, it is denatured; a breakfast egg with the “white” set around the yolk is a familiar example of denatured protein

50. 3.5-3.6 Key Concepts:Proteins In General • Structurally and functionally, proteins are the most diverse molecules of life • They include enzymes, structural materials, and transporters • A protein’s function arises directly from its structure