Chapter 2

1. Chapter 2 Are We Alone in the Universe?Water, Biochemistry, and Cells 0

2. 2.1 What Does Life Require? A Definition of Life There is no simple definition of life. Instead there is a list of characteristics. 1. movement 2. responsiveness 3. growth 4. reproduction 5. respiration 6. digestion 7. absorption 8. circulation 9. excretion

3. 2.1 What Does Life Require? A Definition of Life But, all Earth organisms… have a common set of biological molecules are composed of cells can maintain homeostasis can evolve require liquid water

4. Life: Levels of Organization • Atoms • Molecules • Macromolecules • Organelles • Cells • Tissues • Organs • Organ systems • Organism

5. 2.1 What Does Life Require? Elements: fundamental forms of matter Atoms: the smallest units of an element Atoms are composed of Protons (positive charge) and neutrons in the nucleus of the atom Electrons (negative charge) are found in an “electron cloud” Ions are atoms with an electrical charge.

6. Atom = smallest unit of an element that still retains the chemical & physical properties of that element i.e. really, really, really tiny thing! -composed of: protons = one positive charge, 1 atomic mass unit electrons = one negative charge, no mass neutrons = no charge, 1 atomic mass unit

7. Periodic Table of Elements -elements are grouped on a Periodic Table of Elements -the elements are grouped according to physical and chemical characteristics -on the chart each element is associated with a letter, an atomic number & an atomic mass IA IIA IIIA IVA VA VIA VIIA VIII

8. Li 7 3 atomic symbol atomic mass (weight) e.g. # protons (e-) = 6 # pr+6 + #No 6 = 12 C 12 6 atomic number e.g. # protons (e-) = 3 # pr+3 + #No 4 = 7 Atomic mass = number of protons + neutrons Atomic number = number of protons when the element is electrically neutral ** when neutral, the number of protons and electrons are equal

10. Atoms and Disease: Cystic Fibrosis Cystic fibrosis is the most common lethal genetic disease in the United States one out of every 2,500 people of European descent loss of three NT’s from a gene coding for a transporter of chloride ions results in the loss of one amino acid within the protein sequence of the transporter diffusion of chloride ions out of epithelial cells is blocked results in the thickening of the extracellular fluid outside epithelial cells symptoms include mucus buildup in some internal organs (blocks passages), pancreatic damage (build up of digestive enzymes) and abnormal absorption of nutrients in the small intestine average life span in US – 37.4 yrs average life span in Canada – 47.7 yrs

11. 12C13C14C pr+: 6 6 6 e-: 6 6 6 No: 6 7 8** radioactive Isotope: • all atoms of an element have the same number of protons but may differ in number of neutrons • the number of protons defines what the element is • e.g. 6 protons = carbon and only carbon • isotopes are two atoms of an element that differ in number of neutrons • in nature an element is a mixture of its isotopes

12. Radioactive isotope uses: 1. carbon dating - 14C 2. radioactive imaging - e.g. PET scanning -use of FDG – radioactive glucose tracer -18F radioactive isotope (2-fluoro-deoxy-glucose) 3. radiotherapy in cancer treatment - 60Co Cancerous throat tissue

13. Radioactive Iodine: -Iodine-131 -high doses specifically enter and kill thyroid tissues -lower doses are more dangerous and not used

14. Radioactivity • the protons and neutrons are held together in the nucleus by a kind of nuclear “glue” • when the number of neutrons increase – the nucleus becomes unstable • the breakup of the nucleus releases particles with energy in the form of radioactivity • also known as radioactive decay • three different kind of particles released – each with different energy levels • alpha (helium atom), beta and gamma • the decay can eventually change the # protons – transform one atom into another 12C13C14C pr+: 6 6 6 e-: 6 6 6 No: 6 7 8** radioactive

15. Molecules of Life: • the chemicals used in metabolic reactions or those that are produced by them can be classified into 2 groups: 1. Inorganic 2. Organic

16. Organic Chemistry All life on Earth is based on organic chemistry: the chemistry of the complex carbon containing molecules. organic molecules must contain: oxygen, hydrogen and carbon Carbon makes up most of the mass of living organisms. Carbon: a molecular TinkerToy Can bond to 4 different atoms at once Carbon can make hydrocarbons Simple organic molecules Carbon can make macromolecules

17. Chemical bonds are dependent on the atom’s electron configuration. Electrons are arranged in energy levels or electron shells 1st electron shell holds up to 2 electrons made of a subshell called the s orbital 2nd and 3rd electron shells holds up to 8 electrons each each are made up two subshells called the s and p orbitals 4th shell holds up to 18 electrons made up of s, p and d orbitals The outer shell that holds electrons is called the valence shell First shell Second shell y x z 1s orbital 2s orbital Three 2p orbitals (b) Separate electron orbitals 1s, 2s, and 2p orbitals (c) Superimposed electron orbitals How do you make a molecule? Bonding and Electron Configurations

18. First shell Neon, with two filled Shells (10 electrons) Second shell (a) Electron distribution diagram How do you make a molecule? Bonding and Electron Configurations • The Bohr Model: Bed check for electrons • forming bonds depends on how are electrons organized around the nucleus of an atom • Nils Bohr proposed electrons orbit around the atom’s nucleus in specific energy levels or orbits (shells) • 1st shell – closest to the nucleus only holds 2 electrons • 2nd shell can hold 8 • 3rd holds 18 – only 8 are involved in bonding reactions • 4th holds 18 – only 8 are involved in bonding reactions

19. an atom will always try to complete its outermost shell • basis for bonding reactions

20. VIII I Helium 2He Hydrogen 1H Electron distribution diagram First shell II III IV V VI VII Lithium 3Li Beryllium 4Be Boron 5B Nitrogen 7N Fluorine 9F Oxygen 8O Carbon 6C Neon 10Ne Second shell Sodium 11Na Magnesium 12Mg Aluminum 13Al Sulfur 16S Argon 18Ar Silicon 14Si Chlorine 17Cl Phosphorus 15P Third shell • the periodic table of the elementstells you the electron distribution for each element • by its row and column position • 1st row – valence electrons in the first electron shell • 2nd row – valence electrons in the second electron shell • 1st column – 1 valence electron • 3rd column – 3 valence electrons

21. How do you make a molecule? Bonding and Electron Configurations • atoms with incomplete valence shells can share or transfer valence electrons with certain other atoms to form molecules • molecule - particle formed by the union of more than one atom • e.g. same kind of atom - O2 • e.g. different types of atoms - H20 • formed by held by attractions called chemical bonds • two types of chemical bonds

22. Ionic bonds: occurs when there is a transfer of electrons between atoms sodium atom has 1 valence electron chloride has 7 valence electrons chloride “steals” sodium’s electron to become a more negatively charged ion sodium loses its electron to become a more positively charged ion Molecular Bonds: Covalent and Ionic

23. Molecular Bonds: Covalent and Ionic Covalent bonds: stronger bond from sharing electrons usually forms when a valence shell needs to lose or gain more than 3 electrons Single bonds indicate sharing of one pair of electrons Double bonds share two pairs of electrons

24. Polar and Non-Polar Covalent Bonds • in a nonpolar covalent bond - the atoms share their electron equally • in a polar covalent bond - one atom is more electronegative • the atoms do not share the electron equally • unequal sharing of electrons causes a partial positive or negative charge for each atom or molecule • annotated with the greek letter delta

25. Polar and Non-Polar Covalent Bonds • oxygen is very electronegative – creates polar bonds • so does nitrogen (N) – O H H + + H2O

26. Requirements for Life: 1. water 2. food 3. oxygen 4. heat 5. pressure

27. Animation: Chemistry and Water Right-click slide / select “Play”

28. 2.1 What Does Life Require? WATER The Properties of Water Molecule: two or more atoms held together by chemical bonds Water molecule: two hydrogen atoms bonded to one oxygen atom Water is a good solvent (helps chemical reactions). Solute: what is being dissolved in the solvent Solution: solutes added to a solvent – O H H + + H2O

29. 2.1 What Does Life Require? The Properties of Water Water is a polar molecule: Oxygen side is slightly negative because it is more electronegative than hydrogen Hydrogen side is slightly positive When molecules have no charges, they are nonpolar.

30. Hydrogen bond: the weak attraction between the hydrogen atom of one water molecule and the oxygen atom of another The Properties of Water

31. Water can dissolve salts and hydrophilic(water–loving) molecules because it is polar. Nonpolar molecules such as oil are hydrophobic (water-fearing) and do not easily dissolve in water The Properties of Water

32. Water facilitates chemical reactions Solutes in the mixture are called reactants End result of the chemical reaction are called products Water molecules tend to stick together: cohesion Water moderates temperature The Properties of Water

33. Water can dissolve acids and bases and liberate their ions acid = proton (H+) donor e.g. HCl  the H+ ion is donated base = proton (H+) acceptor can also be considered an OH- acceptor e.g. NaOH when acids and bases are mixed together – water an a salt is produced HCl + NaOH  NaCl and H2O The Properties of Water

34. The pH scale is a measure of the relative amounts of acids and bases in a solution. pH greater than 7 = basic pH lower than 7 = acidic Pure water = 7 – neutral pH 7 means 10-7 moles of H+ ions/liter of solution pH 10 means 10-10 moles of H+ ions/liter pH 4 means 10-4 moles of H+ ions/liter of solution The Properties of Water

35. Which of the following would not be considered an element? oxygen iron water nitrogen

36. Which of the following would not be considered an element? oxygen iron water nitrogen

37. An atom’s atomic number refers to its _________. electrons nucleus protons neutrons

38. An atom’s atomic number refers to its _________. electrons nucleus protons neutrons

39. What type of bond occurs when electrons are transferred between atoms? covalent bonds hydrogen bonds ionic bonds double bonds

40. What type of bond occurs when electrons are transferred between atoms? covalent bonds hydrogen bonds ionic bonds double bonds

41. Glucose and sucrose are both examples of which category of macromolecules? polysaccharides proteins nucleic acids lipids

42. Glucose and sucrose are both examples of which category of macromolecules? polysaccharides proteins nucleic acids lipids