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Molecules of Life

Molecules of Life. Chapter 2 Part 1. 2.1 Impacts/Issues Fear of Frying. All living things consist of the same kinds of molecules, but small differences in the ways they are put together have big effects on health

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Molecules of Life

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  1. Molecules of Life Chapter 2 Part 1

  2. 2.1 Impacts/IssuesFear of Frying • All living things consist of the same kinds of molecules, but small differences in the ways they are put together have big effects on health • Artificial trans fats found in manufactured and fast foods raise cholesterol and increase risk of atherosclerosis, heart attack, and diabetes

  3. Video: Fear of frying

  4. Fear of Frying • Trans fats are made by adding hydrogen atoms to liquid vegetable oils

  5. trans fatty acid Fig. 2-1, p. 20

  6. 2.2 Start With Atoms • All substances consist of atoms • Atom • Fundamental building-block particle of matter • Life’s unique characteristics start with the properties of different atoms

  7. Subatomic Particles and Their Charge • Atoms consist of electrons moving around a nucleus of protons and neutrons • Electron (e-) • Negatively charged subatomic particle that occupies orbitals around the atomic nucleus • Charge • Electrical property of some subatomic particles • Opposite charges attract; like charges repel

  8. Subatomic Particles in the Nucleus • Nucleus • Core of an atom, occupied by protons and neutrons • Proton (p+) • Positively charged subatomic particle found in the nucleus of all atoms • Neutron • Uncharged subatomic particle found in the atomic nucleus

  9. An Atom

  10. an atom Fig. 2-2a, p. 21

  11. Elements: Different Types of Atoms • Atoms differ in numbers of subatomic particles • Element • A pure substance that consists only of atoms with the same number of protons • Atomic number • Number of protons in the atomic nucleus • Determines the element

  12. Elements in Living Things • The proportions of different elements differ between living and nonliving things • Some atoms, such as carbon, are found in greater proportions in molecules made only by living things – the molecules of life

  13. Same Elements, Different Forms • Isotopes • Forms of an element that differ in the number of neutrons their atoms carry • Changes the mass number, but not the charge • Mass number • Total number of protons and neutrons in the nucleus of an element’s atoms

  14. Radioactive Isotopes • Radioisotope • Isotope with an unstable nucleus, such as carbon 14 (14C) • Radioactive decay • Process by which atoms of a radioisotope spontaneously emit energy and subatomic particles when their nucleus disintegrates

  15. Carbon 14: A Radioisotope • Most carbon atoms have 6 protons and 6 neutrons (12C) • Carbon 14 (14C) is a radioisotope with six protons and eight neutrons • When 14C decays, one neutron splits into a proton and an electron, and the atom becomes a different element – nitrogen 14 (14N)

  16. Radioactive Tracers • Researchers introduce radioisotope tracers into living organisms to study the way they move through a system • Tracers • Molecules with a detectable substance attached, often a radioisotope • Used in research and clinical testing

  17. Why Electrons Matter • Electrons travel around the nucleus in different orbitals (shells) – atoms with vacancies in their outer shells tend to interact with other atoms • Atoms get rid of vacancies by gaining or losing electrons, or sharing electrons with other atoms • Shell model • Model of electron distribution in an atom

  18. Shell Models

  19. Fig. 2-3 (top), p. 22

  20. Fig. 2-3 (a-c), p. 22

  21. 1 1 proton 2 1 electron first shell hydrogen (H) helium (He) 8 10 6 second shell carbon (C) oxygen (O) neon (Ne) 11 17 18 third shell sodium (Na) chlorine (Cl) argon (Ar) Fig. 2-3 (a-c), p. 22

  22. A) The first shell corresponds to the first energy level, and it can hold up to 2 electrons. Hydrogen has one proton, so it has one vacancy. A helium atom has 2 protons, and no vacancies. The number of protons in each shell model is shown. 2 1 1 proton 1 electron first shell hydrogen (H) helium (He) B) The second shell corresponds to the second energy level, and it can hold up to 8 electrons. Carbon has 6 protons, so its first shell is full. Its second shell has 4 electrons, and four vacancies. Oxygen has 8 protons and two vacancies. Neon has 10 protons and no vacancies. 8 10 6 second shell carbon (C) oxygen (O) neon (Ne) 11 17 18 C) The third shell, which corresponds to the third energy level, can hold up to 8 electrons, for a total of 18. A sodium atom has 11 protons, so its first two shells are full; the third shell has one electron. Thus, sodium has seven vacancies. Chlorine has 17 protons and one vacancy. Argon has 18 protons and no vacancies. third shell sodium (Na) chlorine (Cl) argon (Ar) Stepped Art Fig. 2-3 (a-c), p. 22

  23. Animation: Shell models of common elements

  24. Ions • The negative charge of an electron balances the positive charge of a proton in the nucleus • Changing the number of electrons may fill its outer shell, but changes the charge of the atom • Ion • Atom that carries a charge because it has an unequal number of protons and electrons

  25. Ion Formation

  26. electron gain Chlorine atom 17p+ 17 17e– charge: 0 Chloride ion 17 17p+ 18e– charge: –1 Sodium atom electron loss 11p+ 11 11e– charge: 0 Sodium ion 11 11p+ 10e– charge: +1 Fig. 2-4, p. 23

  27. Fig. 2-4a, p. 23

  28. electron gain Chlorine atom 17p+ 17 17e– charge: 0 Chloride ion 17p+ 17 18e– charge: –1 Fig. 2-4a, p. 23

  29. Fig. 2-4b, p. 23

  30. electron loss Sodium atom 11p+ 11 11e– charge: 0 Sodium ion 11 11p+ 10e– charge: +1 Fig. 2-4b, p. 23

  31. electron gain Chlorine atom 17p+ 17 17e– charge: 0 Chloride ion 17 17p+ 18e– charge: –1 Sodium atom electron loss 11p+ 11 11e– charge: 0 Sodium ion 11 11p+ 10e– charge: +1 Stepped Art Fig. 2-4, p. 23

  32. Animation: How atoms bond

  33. Animation: PET scan

  34. Animation: The shell model of electron distribution

  35. Animation: Subatomic particles

  36. Animation: Atomic number, mass number

  37. Animation: Electron arrangements in atoms

  38. Animation: Isotopes of hydrogen

  39. Video: ABC News: Nuclear Energy

  40. Animation: Electron distribution

  41. 2.3 From Atoms to Molecules • Atoms can also fill their vacancies by sharing electrons with other atoms • A chemical bond forms when the electrons of two atoms interact • Chemical bond • An attractive force that arises between two atoms when their electrons interact

  42. From Atoms to Molecules • Molecule • Group of two or more atoms joined by chemical bonds • Compound • Type of molecule that has atoms of more than one element

  43. Referring to a Molecule

  44. Same Materials, Different Results

  45. Animation: Building blocks of life

  46. Ionic Bonds and Covalent Bonds • Depending on the atoms, a chemical bond may be ionic or covalent • Ionic bond • A strong mutual attraction formed between ions of opposite charge • Covalent bond • Two atoms sharing a pair of electrons

  47. An Ionic Bond: Sodium Chloride

  48. ionic bond 11 17 sodium ion (Na+) chloride ion (Cl–) p. 24

  49. Covalent Bonds • Molecular hydrogen (H—H) and molecular oxygen (O=O)

  50. 1 1 molecular hydrogen (H2) 8 8 molecular oxygen (O2) p. 24

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