Chemistry of Life: Basic Elements, Molecules, and Reactions

1. Chapter 2 Chemistry of Life

2. Outline • Basic Chemistry • Atoms • Molecules and Compounds • Chemical Reactions • Properties of Water • Acids and Bases • Macromolecules • ATP

3. Basic Chemistry • There are 92 naturally-occurring elements. • Over 90% of human body is composed of four elements. (CHON) • Carbon. • Hydrogen. • Oxygen. • Nitrogen.

4. Atoms • An atom is the smallest unit of matter that retains an element’s physical and chemical properties. • Positively-charged protons and neutral neutrons are located in the nucleus. • Negatively-charged electrons orbit the nucleus in shells.

5. Atoms • An element’s atomic number is designated by its number of protons. • An element’s atomic weight is designated by its protons and neutrons.

6. Elements and Atoms

7. Molecules and Compounds • A molecule and compound is a group of atoms bonded together.

8. Ionic Reactions • During an ionic reaction, atoms give up or take on an electron to stabilize their outer shells of the atom. • Ions are particles that carry a positive (+) or negative (-) charge. • The attraction between oppositely charged sodium ions and chloride ions forms an ionic bond.

9. Ionic “electron stripping” Reaction

10. Covalent “electron sharing” Reactions • In covalent reactions, atoms share electrons in covalent bonds instead of losing or gaining them. • A single bond is formed when atoms share a single pair of electrons. • A double bond is formed when atoms share two pairs of electrons. • A triple bond is formed when atoms share three pairs of electrons.

11. Covalent Reactions

12. Water and Living Things and a Third type of bond- Hydrogen bond • The electrons in water spend more time circling the larger oxygen atom than the smaller hydrogen atom. • Water is a polar molecule with the oxygen end being slightly negative and the hydrogen end being slightly positive. • A hydrogen bond occurs when a covalently bonded hydrogen is positive and is attracted to a negatively charged atom.

13. Hydrogen Bonding between Water Molecules

14. Some Properties of Water • liquid at room temperature. • solvent for polar molecules. • cohesive. • temperature rises and falls slowly.

16. Acids and Bases • Acids break down in water and release hydrogen ions (H+). • Bases/alkaline take up hydrogen ions (H+) or release hydroxide ions (OH-). • Buffers help keep the pH within normal limits by taking up excess hydrogen ions or hydroxide ions.

17. Water can break down to form Ions (atoms with a + or – charge)

18. pH Scale • The pH scale measures acidity or alkalinity of a solution. • Neutral = 7. • Acidic < 7. • Basic > 7. • Logarithmic Scale.

19. Log scale

20. The pH Scale

21. Molecules of Life • Four categories of molecules are unique to cells. • Carbohydrates. • Lipids. • Proteins. • Nucleic Acids. • Macromolecules are synthesized by a dehydration reaction, and degraded by a hydrolysis reaction.

22. pg.24a

24. Synthesis of larger product (macromolecule)

25. Breakdown of Molecule to simpler subunits

26. Carbohydrates • Carbohydrates function for quick and short-term energy storage. • Monosaccharide (simple sugar). • Glucose. • Disaccharide. • Fructose.

27. Complex Carbohydrates • Polysaccharides. • Starch (plants). • Glycogen (animals). • Cellulose (plant cell walls).

28. Glucose molecule in various forms

29. A Disacharride

30. Plant Polysaccharide

31. Animal polysaccharide

32. Lipids • Lipids contain more energy per gram than any other biological molecule. • Do not dissolve in water. • Absence of polar groups. • Fats. • Animal origin, solid at room temperature. • Oils. • Plant origin, liquid at room temperature.

33. Synthesis and breakdown of Fat

34. Phospholipids and Steroids • Phospholipids contain a phosphate head and fatty acid tails. • Polar head and non-polar tails. • Soluble in water. • Steroids are lipids with a backbone of four fused carbon rings. • Estrogen and testosterone.

35. Another Example of a lipid

36. Cell membrane

37. Other lipid examples

38. Fig. 2.15bb

39. Emulsyfier • Bile salts • Tween

40. Emulsyfication

41. Proteins • Proteins are macromolecules with amino acid subunits. • An amino acid has a central carbon atom bonded to a hydrogen and three groups. • Peptide bond - Any bond joining two amino acids. • Polypeptide - Single amino acid chain.

42. Building block of proteins

43. Fig. 2.16a

44. Peptide bond- bond between two amino acids

45. Levels of Protein Organization • Primary Structure. • Linear sequence of amino acids. • Secondary Structure. • Polypeptide takes on orientation in space. • Tertiary Structure. • Final three-dimensional shape. • Quaternary Structure. • Proteins with more than one polypeptide.

47. Nucleic Acids • Nucleic acids are huge macromolecules composed of nucleotides. • A nucleotide is constructed of a phosphate, a pentose sugar, and a nitrogenous base. • Deoxyribonucleic acid (DNA). • Double-stranded helix. • Ribonucleic acid (RNA). • Single stranded.

48. Building block of an Nucleic Acid- A Nucleotide

49. DNA Structure

50. (ATP) Adenosine Triphosphate • ATP is the primary cellular energy carrier. • Energy currency of cells. • Breaks down to adenosine diphosphate (ADP) and a molecule of inorganic phosphate, releasing energy to drive cellular metabolism.