1. Chemical Level of Organization Chapter 2 Atoms, Molecules and Bonds

2. What Are Atoms? Smallest particles that retain properties of an element, smallest particle of a substance Made up of subatomic particles: –Protons (+) –Electrons (-) –Neutrons (0) no charge)

3. Elements Fundamental forms of matter Can’t be broken apart by normal means 92 occur naturally on Earth

4. Most Common Elements in Living Organisms Oxygen Hydrogen Carbon Nitrogen P and S

5. Representing the Hydrogen Atom Shell modelBall model Electron density cloud

6. Atomic Number and Mass # = Number of protons All atoms of an element have the same atomic number Mass= # of P + # on N 1.0079 ----- Atomic Mass H element symbol 1 --- Atomic number

7. Mass Number Number of protons + Number of neutrons Isotopes vary in mass number # of protons = # of electrons

8. Isotopes Atoms of an element with different numbers of neutrons (different mass numbers) Carbon 12 has 6 protons, 6 neutrons Carbon 14 has 6 protons, 8 neutrons

9. What Determines whether Atoms Will Interact? The number and arrangement of their electrons

10. Electrons Carry a negative charge Repel one another Are attracted to protons in the nucleus Move in orbitals - volumes of space that surround the nucleus

11. Shell Model First shell –Lowest energy –Holds 1 orbital with up to 2 electrons Second shell –4 orbitals hold up to 8 electrons

12. Chemical Bonds, Molecules, & Compounds Bond is union between electron structures of atoms Atoms bond to form molecules Molecules may contain atoms of only one element - O 2 Molecules of compounds contain more than one element - H 2 O Compound= +/- atoms

13. Important Bonds in Biological Molecules Ionic Bonds Covalent Bonds Hydrogen Bonds

14. Ionic Bonding One atom loses electrons, becomes positively charged ion Another atom gains these electrons, becomes negatively charged ion Charge difference attracts the two ions to each other

15. Formation of NaCl Sodium atom (Na) –Outer shell has one electron Chlorine atom (Cl) –Outer shell has seven electrons Na transfers electron to Cl forming Na + and Cl - Ions remain together as NaCl

16. Covalent Bonding Atoms share a pair or pairs of electrons to fill outermost shell Single covalent bond Double covalent bond Triple covalent bond

17. Polar Covalent Bonds Number of protons in nuclei of participating atoms is not equal Electrons spend more time near nucleus with most protons Water - Electrons more attracted to O nucleus than to H nuclei

18. Hydrogen Bonding Molecule held together by polar covalent bonds has no net charge However, atoms of the molecule carry different charges Atom in one polar covalent molecule can be attracted to oppositely charged atom in another such molecule

19. Examples of Hydrogen Bonds hydrogen bond water molecule ammonia molecule

20. Water Is a Polar Covalent Molecule Molecule has no net charge Oxygen end has a slight negative charge Hydrogen end has a slight positive charge ++ H H O

21. Organic Compounds Hydrogen and other elements covalently bonded to carbon ** The Biomolecules Carbohydrates Lipids Proteins Nucleic Acids

22. Carbohydrates Monosaccharides (simple sugars) Oligosaccharides (short-chain carbohydrates) Polysaccharides (complex carbohydrates)

23. Monosaccharides Simplest carbohydrates Most are sweet tasting, water soluble Most have 5- or 6-carbon backbone Glucose (6 C)Fructose (6 C) Ribose (5 C)Deoxyribose (5 C)

24. Polysaccharides Straight or branched chains of many sugar monomers Most common are composed entirely of glucose –Cellulose –Starch (such as amylose) –Glycogen

25. Glycogen Sugar storage form in animals Large stores in muscle and liver cells When blood sugar decreases, liver cells degrade glycogen, release glucose

26. Lipids Most include fatty acids –Fats –Phospholipids –Waxes Sterols and their derivatives have no fatty acids Tend to be insoluble in water

27. Fats Fatty acid(s) attached to glycerol Triglycerides are most common Carboxyl group (-COOH) at one end Carbon backbone (up to 36 C atoms) –Saturated - Single bonds between carbons –Unsaturated - One or more double bonds

28. Sterols and Derivatives No fatty acids Rigid backbone of four fused-together carbon rings Cholesterol - most common type in animals

29. Properties of Amino Acids Determined by the “R group” Amino acids may be: –Non-polar –Uncharged, polar –Positively charged, polar –Negatively charged, polar

30. Protein Synthesis Protein is a chain of amino acids linked by peptide bonds Peptide bond –Type of covalent bond –Links amino group of one amino acid with carboxyl group of next –Forms through condensation reaction

31. Protein Shapes Fibrous proteins –Polypeptide chains arranged as strands or sheets Globular proteins –Polypeptide chains folded into compact, rounded shapes

32. Primary Structure & Protein Shape Primary structure influences shape in two main ways: –Allows hydrogen bonds to form between different amino acids along length of chain –Puts R groups in positions that allow them to interact

33. Secondary Structure Hydrogen bonds form between different parts of polypeptide chain These bonds give rise to coiled or extended pattern Helix or pleated sheet

34. Tertiary Structure Folding as a result of interactions between R groups

35. Quaternary Structure Some proteins are made up of more than one polypeptide chain

36. Polypeptides with Attached Organic Compounds Lipoproteins –Proteins combined with cholesterol, triglycerides, phospholipids Glycoproteins –Proteins combined with oligosaccharides

37. Nucleotide Structure Sugar –Ribose or deoxyribose At least one phosphate group Base –Nitrogen-containing –Single or double ring structure

38. Nucleic Acids Composed of nucleotides Single- or double-stranded Sugar-phosphate backbone

39. DNA Double-stranded Consists of four types of nucleotides A bound to T C bound to G

40. RNA Usually single strands Four types of nucleotides Unlike DNA, contains the base uracil in place of thymine Three types are key players in protein synthesis