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Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece.

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Presentation on theme: "Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece."— Presentation transcript:

1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings PowerPoint Lectures for Biology, Seventh Edition Neil Campbell and Jane Reece Lectures by Chris Romero Chapter 2 The Chemical Context of Life

2 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Overview: Chemical Foundations of Biology Biology is a ___________science Living organisms are subject to basic laws of _____________________ One example is the bombardier beetle, which uses chemistry to defend itself

3 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

4 Concept 2.1: Matter consists of chemical elements in pure form and in combinations called compounds Organisms are composed of matter Matter is anything that ______________________ Matter is made up of elements

5 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Elements and Compounds An element is a substance that ____________________________________ ____________________________________ A compound is a substance consisting of ____________________________________

6 LE 2-2 SodiumChlorineSodium chloride

7 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Essential Elements of Life About 25 of the 92 elements are essential to life Carbon, _________, oxygen, and ________ make up 96% of living matter Most of the remaining 4% consists of calcium, phosphorus, potassium, and sulfur __________ are those required by an organism in minute quantities

8 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

9 LE 2-3 Nitrogen deficiencyIodine deficiency

10 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 2.2: An elements properties depend on the structure of its atoms Each element consists of unique atoms An atom is the smallest unit of matter that still retains the properties of an element

11 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Subatomic Particles Atoms are composed of subatomic particles Relevant subatomic particles include: – Neutrons (no electrical charge) – Protons (positive charge) – Electrons (negative charge) _______________ form the atomic nucleus ________ form a cloud around the nucleus

12 LE 2-4 Nucleus Electrons Cloud of negative charge (2 electrons)

13 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Atomic Number and Atomic Mass Atoms of the various elements differ in number of subatomic particles An elements atomic number is the number of protons An elements mass number is the sum of protons plus neutrons in the nucleus Atomic mass, the atoms total mass, can be approximated by the mass number

14 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Isotopes Atoms of an element have the same number of protons but may differ in number of neutrons Isotopes are two atoms of an element that differ in number of ________ Most isotopes are stable, but some are radioactive, ____________________________

15 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Some applications of radioactive isotopes in biological research: – D____________________ – T______________________________________ _______________________ – D_____________________________________ ______________________________________

16 LE 2-5a Ingredients including radioactive tracer (bright blue) Incubators Human cells DNA (old and new) 123 456 789 10°C 25°C 40°C 15°C 30°C 45°C 20°C 35°C 50°C TECHNIQUE

17 LE 2-5b

18 LE 2-5c Optimum temperature for DNA synthesis RESULTS Counts per minute (x 1,000) 30 20 10 0 20304050 Temperature (°C)

19 LE 2-6 Cancerous throat tissue

20 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings The Energy Levels of Electrons Energy is the capacity to cause change Potential energy is the energy that matter has because of its L____________________ The electrons of an atom differ in their amounts of P________________ An electrons state of potential energy is called its E_______________________

21 LE 2-7a A ball bouncing down a flight of stairs provides an analogy for energy levels of electrons.

22 LE 2-7b Third energy level (shell) Second energy level (shell) First energy level (shell) Atomic nucleus Energy absorbed Energy lost

23 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Electron Configuration and Chemical Properties The C_____________ of an atom is determined by the distribution of electrons in electron shells The periodic table of the elements shows the electron distribution for each element

24 LE 2-8 First shell Hydrogen 1 H Lithium 3 Li Second shell Third shell Sodium 11 Na Beryllium 4 Be Magnesium 12 Mg Boron 5 B Aluminum 12 Al Silicon 14 Si Carbon 6 C Nitrogen 7 N Phosphorus 15 P Oxygen 8 O Sulfur 16 S Chlorine 17 Cl Fluorine 9 F Neon 10 Ne Argon 18 Ar Helium 2 He Atomic number Element symbol Electron-shell diagram Atomic mass 2 He 4.00

25 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Valence electrons are those in the O_______________________________ The chemical behavior of an atom is mostly determined by the valence electrons

26 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Electron Orbitals An O_________ is the three-dimensional space where an electron is found 90% of the time Each electron shell consists of a specific number of O_____________

27 LE 2-9 Electron orbitals Electron-shell diagrams 1s orbital2s orbitalThree 2p orbitals1s, 2s, and 2p orbitals First shell (maximum 2 electrons) Second shell (maximum 8 electrons) Neon, with two filled shells (10 electrons) x z y

28 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 2.3: The formation and function of molecules depend on chemical bonding between atoms Atoms with incomplete valence shells can share or transfer valence electrons with certain other atoms These interactions usually result in atoms S_______________, held by attractions called chemical bonds

29 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Covalent Bonds A covalent bond is the S____________ of valence electrons by two atoms In a covalent bond, the shared electrons count as part of E____________________

30 LE 2-10 Hydrogen atoms (2 H) Hydrogen molecule (H 2 )

31 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings A ________ consists of two or more ______ held together by covalent bonds A single covalent bond, or single bond, is the sharing of one pair of valence electrons A double covalent bond, or double bond, is the sharing of two pairs of valence electrons Covalent bonds can form between atoms of the same element or atoms of different elements Animation: Covalent Bonds Animation: Covalent Bonds

32 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

33 LE 2-11b Oxygen (O 2 ) Name (molecular formula) Electron- shell diagram Structural formula Space- filling model

34 LE 2-11c Water (H 2 O) Name (molecular formula) Electron- shell diagram Structural formula Space- filling model

35 LE 2-11d Methane (CH 4 ) Name (molecular formula) Electron- shell diagram Structural formula Space- filling model

36 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings _________________ is an atoms attraction for the electrons in a covalent bond The more ______________ an atom, the more strongly it pulls shared electrons toward itself

37 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings In a __________________, the atoms share the electron equally In a __________________, one atom is more electronegative, and the atoms do not share the electron equally

38 LE 2-12 H O H H2OH2O + + –

39 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Ionic Bonds Atoms sometimes strip electrons from their bonding partners An example is the transfer of an electron from sodium to chlorine After the transfer of an electron, both atoms have charges A charged atom (or molecule) is called an ________

40 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings An anion is a negatively charged ion A cation is a positively charged ion An ionic bond is an attraction between an anion and a cation Animation: Ionic Bonds Animation: Ionic Bonds

41 LE 2-13 Na Sodium atom (an uncharged atom) Cl Chlorine atom (an uncharged atom) Na + Sodium ion (a cation) Cl – Chlorine ion (an anion) Sodium chloride (NaCl)

42 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Compounds formed by ionic bonds are called ionic compounds, or S__________ Salts, such as sodium chloride (table salt), are often found in nature as C_________

43 LE 2-14 Na + Cl –

44 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Weak Chemical Bonds Most of the strongest bonds in organisms are ____________ that form a cells molecules Weak chemical bonds, such as _______________ bonds and hydrogen bonds, are also important Weak chemical bonds reinforce shapes of large molecules and help molecules adhere to each other

45 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Hydrogen Bonds A hydrogen bond forms when a hydrogen atom covalently bonded to one electronegative atom is also attracted to another electronegative atom In living cells, the electronegative partners are usually O_________ or N________ atoms

46 LE 2-15 – Water (H 2 O) Ammonia (NH 3 ) Hydrogen bond + + – + + +

47 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Van der Waals Interactions Molecules or atoms that are very close together can be attracted by fleeting charge differences These weak attractions are called v___________________ interactions Collectively, such interactions can be strong, as between molecules of a geckos toe hairs and a wall surface

48 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

49 Molecular Shape and Function A molecules shape is usually very important to its function A molecules shape is determined by the positions of its atoms valence orbitals In a covalent bond, the ____________ orbitals may hybridize, creating specific molecular shapes

50 LE 2-16a s orbital z x y Three p orbitals Four hybrid orbitals Tetrahedron Hybridization of orbitals

51 LE 2-16b Space-filling model Ball-and-stick model Hybrid-orbital model (with ball-and-stick model superimposed) Unbonded electron pair Water (H 2 O) Methane (CH 4 ) Molecular shape models 104.5°

52 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Biological molecules recognize and interact with each other with a specificity based on molecular s____________ Molecules with similar s________ can have similar biological effects

53 LE 2-17a Natural endorphin Morphine Carbon Hydrogen Nitrogen Sulfur Oxygen Structures of endorphin and morphine

54 LE 2-17b Natural endorphin Morphine Brain cell Endorphin receptors Binding to endorphin receptors

55 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Concept 2.4: Chemical reactions make and break chemical bonds Chemical reactions lead to new arrangements of atoms The starting molecules of a chemical reaction are called r___________ The final molecules of a chemical reaction are called p__________

56 LE 2-UN44 ReactantsReactionProducts 2 H 2 OO2O2 2 H 2

57 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Photosynthesis is an important chemical reaction In photosynthesis, sunlight powers the conversion of CO 2 and H 2 0 to glucose _______________________

58 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings

59 Some chemical reactions go to completion: All reactants are converted to products Most chemical reactions are reversible: Products of the forward reaction become reactants for the reverse reaction Chemical equilibrium is reached when the forward and reverse reaction rates are equal


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