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BIO 1010 Chapter 2 - Chemistry Why study chemistry? Corpse flower.

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1 BIO 1010 Chapter 2 - Chemistry Why study chemistry? Corpse flower

2 Devil’s Gardens Why are there 800 year old stands of only lemon trees in the middle of the Amazon rain forest?

3 Some Basic Chemistry  Take any biological system apart, and you eventually end up at the chemical level.  Chemical reactions are always occurring in the human body and our environment.

4 Figure Organisms Biosphere Ecosystems Populations Communities Organ Systems and Organs Tissues Cells Organelles Molecules and Atoms Nucleus Atom

5 Are Chemicals Bad or Good for you?  Misconceptions and Concerns about chemicals  Appreciation for chemical nature of our bodies and our world  Potential harms and benefits

6 Several chemicals are added to food for a variety of reasons –Help preserve it –Make it more nutritious –Make it look better

7 Matter: Elements and Compounds  Matter is anything that occupies space and has mass.  Matter is found on Earth in three physical states:  solid,  liquid, and  gas. © 2013 Pearson Education, Inc.

8  Matter is composed of chemical elements.  An element is a substance that cannot be broken down into other substances by chemical reactions.  There are 92 naturally occurring elements on Earth.  All of the elements are listed in the periodic table. Matter: Elements and Compounds © 2013 Pearson Education, Inc.

9 Elements & Atoms Element: a substance that can neither be broken down nor converted to another substance by chemical reactions. Pure substance that contains only one type of atom

10 Figure 2.1a Atomic number (number of protons) Mass number (number of protons plus neutrons) Element symbol 12 6 C He Ne SeBr Cl F Ar Kr Xe O N C B S P Si Al I Ge AsGa TeSbSnIn Mn Cr Po At RnPbBiTI Co FeV Cu Ni Zn TmYb Lu Ho ErDy Be Li Mg Na K ScCaTi MoNbRuTcPdRh Ag Y Sr RbZr H Cd LaBa TaHfOs Re IrW AuPt HgCs Bh Sg Mt Hs Rg Ds Cn Fr Ac Ra Rf Db MdNo Lr Es FmCfAm Cm Bk NpPuU EuGd Tb Pm Sm Nd Pa Pr Th Ce

11 Figure 2.1b Thermometers, dental fillings and batteries Mercury in the air settles into water. It can pass through the food chain and build up in fish, shellfish and animals that eat fish. Exposure to high levels can damage the brain and kidneys. Can damage the kidneys and the nervous system, and interfere with development of the brain in the very young children Mercury

12 Figure 2.1c Deficiencies of copper can cause premature hair graying, sterility and premature wrinkling of the skin.

13 Figure 2.1d Affects nearly all system: Hearing loss, kidney problems, lower IQ, children are more vulnerable because they tend to place things in their mouths. Houses built before ‘78, present toys, pipes, faucets Lead

14  Twenty-five elements are essential to people.  Four elements make up about 96% of the weight of most cells:  oxygen,  carbon,  hydrogen, and  nitrogen. Matter: Elements and Compounds © 2013 Pearson Education, Inc.

15 ELEMENTS, ATOMS, AND MOLECULES What is matter? There are 92 chemical elements in nature Life requires 25 essential elements; some are called trace elements.

16 Figure 2.2 Oxygen (O): 65.0% Carbon (C): 18.5% Calcium (Ca): 1.5% Magnesium (Mg): 0.1% Chlorine (Cl): 0.2% Sodium (Na): 0.2% Sulfur (S): 0.3% Potassium (K): 0.4% Phosphorus (P): 1.0% Hydrogen (H): 9.5% Nitrogen (N): 3.3% Trace elements: less than 0.01% Iron (Fe) Iodine (I) Fluorine (F) Copper (Cu) Cobalt (Co) Chromium (Cr) Boron (B) Zinc (Zn) Vanadium (V) Tin (Sn) Silicon (Si) Selenium (Se) Molybdenum (Mo) Manganese (Mn)

17  Trace elements are  required in only very small amounts and  essential for life.  An iodine deficiency causes goiter.  Fluorine  is added to dental products and drinking water and  helps to maintain healthy bones and teeth. Matter: Elements and Compounds © 2013 Pearson Education, Inc.

18 Trace elements are common additives to food and water –Without iron, your body cannot transport oxygen –An iodine deficiency prevents production of thyroid hormones, resulting in goiter -Deficiencies of copper can cause premature hair graying, sterility and premature wrinkling of the skin.

19 Figure 2.3

20  Elements can combine to form compounds.  Compounds are substances that contain two or more elements in a fixed ratio.  Common compounds include  NaCl (table salt) and  H 2 O (water). Matter: Elements and Compounds © 2013 Pearson Education, Inc.

21 Sodium Chloride (Kitchen salt) Chlorine (poisonous gas) Sodium (metal) + Compound—a substance consisting of two or more different elements combined in a fixed ratio

22 Atoms  Each element consists of one kind of atom.  An atom is the smallest unit of matter that still retains the properties of an element. © 2013 Pearson Education, Inc.

23 Electron cloud Protons 2e – Nucleus Electrons Mass number = 4 Neutrons Atoms consist of protons, neutrons, and electrons Electrons are kept in orbit by the attraction between the negatively charged electrons and positively charged protons Atomic number: 2 (number of protons) Mass number: 4 (sum of the number of protons and neutrons in its nucleus

24 The Structure of Atoms  Atoms are composed of subatomic particles.  A proton is positively charged.  An electron is negatively charged.  A neutron is electrically neutral.  Most atoms have protons and neutrons packed tightly into the nucleus.  The nucleus is the atom’s central core.  Electrons orbit the nucleus. © 2013 Pearson Education, Inc.

25 Atomic Number C 12 Mass number (atomic weight) ( # Protons + # Neutrons) 6 Atomic Number (# of Protons in an atom) Atomic Symbol (Carbon) The atomic number determines which element it is. # protons = atomic number # electrons = atomic number (in an uncharged atom) # neutrons = mass number – atomic number

26  Elements differ in the number of subatomic particles in their atoms.  The number of protons, the atomic number, determines which element it is.  Mass is a measure of the amount of material in an object.  An atom’s mass number is the sum of the number of protons and neutrons in its nucleus. The Structure of Atoms © 2013 Pearson Education, Inc.

27 Isotopes  Isotopes are alternate mass forms of an element.  Isotopes  have the same number of protons and electrons but  differ in their number of neutrons. © 2013 Pearson Education, Inc.

28 Atomic Weight (Mass Number) May Vary Isotope: a variant form of an atom with same number of protons but different numbers of neutrons Naturally occurring carbon 99%~1%Minute quantities Stable isotopes Radioactive: the nucleus decays

29 Atomic number: Mass number:

30 Table 2.1

31  The nucleus of a radioactive isotope decays spontaneously, giving off particles and energy.  Radioactive isotopes have many uses in research and medicine.  They can be used to determine the fate of atoms in living organisms.  They are used in PET scans to diagnose heart disorders and some cancers. Isotopes © 2013 Pearson Education, Inc.

32 Radioisotopes in Medicine & Research when radioactive compounds are used in metabolic processes, they act as radioactive tracers An imaging instrument that uses positron- emission tomography (PET) detects the location of injected radioactive materials Normal Alzheimer’s

33  C isotope studies can be used to identify areas with histories of vegetation change  How the Maya were able to sustain such large populations is still a question today. Use of Carbon Isotopes in Determining Ancient Maya Land Use  Jungle: C 3 Plants  Discriminate more against CO 2 containing 13 C isotope  Maize: C 4 Plants

34 Why is the energy emitted in radioactive decay hazardous?.

35 Radioactive Isotopes Can Harm  Uncontrolled exposure to radioactive isotopes can harm living organisms by damaging DNA.  The 1986 Chernobyl nuclear accident released large amounts of radioactive isotopes.  Naturally occurring radon gas may cause lung cancer.

36 Electron arrangement determines the chemical properties of an atom  Only electrons are involved in chemical activity  Electrons occur in energy levels called electron shells The number of electrons in the outermost shell determines the chemical properties of an atom

37 Electron Arrangement and the Chemical Properties of Atoms  Electrons orbit the nucleus of an atom in specific electron shells.  The farther an electron is from the nucleus, the greater its energy.  The number of electrons in the outermost shell determines the chemical properties of an atom. © 2013 Pearson Education, Inc.

38 The number of electrons in the valence shell (outermost shell) determines the chemical properties of the atom Elements whose outer shells contain unfilled orbitals are chemically reactive When all the orbitals are filled, the element is inactive (inert)

39  An uncharged atom of gold has an atomic number of 79 and a mass number of 197. This atom has _________ protons, _______ neutrons, and __________ electrons.  a. 79 …118 …79  b. 118 …79 …118  c. 276 …118 …79  d. 79 …276 …79

40  The most abundant element found in the human body by weight is _________.  a. oxygen  b. carbon  c. fluorine  d. hydrogen

41  Isotopes of atoms differ in their number of __________.  a. neutrons  b. electrons  c. protons  d. atomic nuclei

42 Intro to Atoms, Ions etc

43 Chemical Bonding and Molecules  Chemical reactions enable atoms to give up or acquire electrons, completing their outer shells.  Chemical reactions usually result in atoms  staying close together and  being held together by attractions called chemical bonds. © 2013 Pearson Education, Inc.

44 Na Sodium atom Transfer of electron Cl Chlorine atom Ionic bonds are attractions between ions of opposite charge The octet rule: atoms are most stable when their outer most energy shells are either full or empty Ions: atoms electrically charged as a result of gaining or losing electrons Complete transfer of electrons. Attraction between ions of opposite charge

45 Na Sodium atom Transfer of electron Cl Chlorine atom Na + Sodium ion Cl – Chloride ion Sodium chloride (NaCl) + – Na + Cl –

46 Covalent bonds join atoms into molecules through electron sharing A covalent bond results when atoms share outer-shell electrons –A molecule is formed when atoms are held together by covalent bonds

47 Covalent Bonds The number of covalent bonds an atom can form is equal to the number of additional electrons it needs to fill its valence shell –A single bond forms when two electrons are shared between two atoms –A double bond forms when four electrons are shared between two atoms –A triple bond forms when ______ electrons are shared between two atoms

48 Electrons are Unequally Shared in Polar Covalent Bonds Fig 2.8 Oxygen draws shared electrons towards itself Oxygen becomes “a little” negative Hydrogens become “a little” positive Results in Hydrogen Bonds between neighboring molecules Water molecule Polar molecule: opposite charges on opposite ends Weak electrical attractions

49 Hydrogen bond Water molecules are electrically attracted to oppositely charged regions on neighboring molecules Because the positively charged region is always a hydrogen atom, the bond is called a hydrogen bond Hydrogen bonds are weak bonds important in the chemistry of life

50 TypeChemical basisStrengthExample Covalent bondsAtoms share electron pairs StrongHydrocarbons, methane Ionic bondsAtoms donate one or more electrons to other atom of opposite charge ModerateSodium chloride Sodium iodide Hydrogen bondsAtoms with partial negative charge attract hydrogen atoms WeakWater, DNA Chemical bonds and attractive forces


52 WATER AND LIFE  Life on Earth began in water and evolved there for 3 billion years.  Modern life remains tied to water.  Your cells are composed of 70–95% water.  The abundance of water is a major reason Earth is habitable. © 2013 Pearson Education, Inc.

53 Water’s Life-Supporting Properties  The polarity of water molecules and the hydrogen bonding that results explain most of water’s life- supporting properties.  Water molecules stick together.  Water has a strong resistance to change in temperature.  Frozen water floats.  Water is a common solvent for life. © 2013 Pearson Education, Inc.

54 Biology and Society: More Precious than Gold  A drought is  a period of abnormally dry weather that changes the environment and  one of the most devastating disasters. © 2013 Pearson Education, Inc.

55 Figs 2.12, 2.13 Surface Tension Capillary Action Cohesion: attraction between molecules (water= hydrogen bonds) Hydrogen bonds give water a high surface tension

56  Droughts can cause  severe crop damage,  shortages of drinking water,  dust storms,  famine,  habitat loss, and  mass migration. Biology and Society: More Precious than Gold © 2013 Pearson Education, Inc.

57  Throughout human history, droughts have helped wipe out societies and even whole civilizations.  Droughts are catastrophic because life cannot exist without water. Biology and Society: More Precious than Gold © 2013 Pearson Education, Inc.

58 Water resistance to temperature change stabilizes ocean temperatures. Evaporative cooling: when a substance evaporates, the surface of the liquid remaining behind cools down

59 Water’s hydrogen bonds moderate temperature Because of hydrogen bonding, water has a greater ability to resist temperature change than other liquids. The efficiency of evaporative cooling is affected by humidity.

60 Water Expands When Frozen Fig 2.15 Fewer molecules than an equal volume of liquid

61 What is a solution? Example What is a solvent? Example What is an aqueous solution? What is a solute? Example

62 Ionic bond between Na + and Cl - holds ions together in a solid crystal Dissolve in water: The chloride anion (-) attracts the (+) pole of water The sodium cation (+) attracts the (-) pole of water Dissolved ions cannot re- associate into a solid Water is a polar solvent: A polar molecule has opposite charges on opposite ends

63 Ion in solution Salt crystal Water is the solvent of life

64 Fig 2.17 Ionization of Water: Water dissociates hydrogen ions H+ hydroxide ions OH- Bases: release OH - (or accept H + ): decrease [H + ] Sodium Hydroxide  Na + & OH - Acids: release H+ (or accept OH-): increase [H+] Hydrochloric acid: HCl  H+ & Cl- (in your stomach) The chemistry of life is sensitive to acidic and basic conditions

65 Figure 2.17a OH − HH HH Basic solution OH − HH HH HH HH HH HH HH HH HH HH Neutral solution Acidic solution

66 The pH Scale A pH scale (pH = potential of hydrogen) is used to describe whether a solution is acidic or basic. –pH ranges from 0 (most acidic) to 14 (most basic) –A solution that is neither acidic or basic is neutral (pH = 7)

67 Acid rain Water reacting with pollutants (SO2, NO) pH 2-3 Normal rain: pH 5.6

68 Buffers minimize changes in pH Buffers Act as H + reservoirs Take up H + ions when they are abundant, release them when they are scarce. Keep proton concentration steady. A buffer that maintains pH 7: accepts protons if pH is < 7, releases protons if pH is > 7

69 The Carbonic-Acid-Bicarbonate Buffer in Blood When we exercise, we increase the H + concentration in our blood stream:  [H + ] increases  Blood pH decreases  Our blood contains a buffering system

70 Chemical reactions make and break bonds, changing the composition of matter  You learned that the structure of atoms and molecules determines the way they behave –Remember that atoms combine to form molecules –Hydrogen and oxygen can react to form water 2 H 2 O2O2 2 H 2 O Reactants Product

71 You should now be able to 1.Describe the importance of chemical elements to living organisms 2.Explain the formation of compounds 3.Describe the structure of an atom 4.Distinguish between ionic, hydrogen, and covalent bonds 5.Define a chemical reaction and explain how it changes the composition of matter 6.List and define the life-supporting properties of water 7.Explain the pH scale and the formation of acid and base solutions Copyright © 2009 Pearson Education, Inc.

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