Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapter 2 The Chemical Basis of Life

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Nature’s Chemical Language The rattlebox moth –Produces chemicals important for mating and defense

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The compound produced during mating –Allows the moths to communicate using chemicals Thomas Eisner of Cornell University –Has studied this process in rattlebox moths

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Chemicals play many more roles in life than signaling –Making up our bodies, those of other organisms, and the physical environment

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings ELEMENTS, ATOMS, AND MOLECULES 2.1 Living organisms are composed of about 25 chemical elements About 25 different chemical elements –Are essential to life

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Carbon, hydrogen, oxygen, and nitrogen –Make up the bulk of living matter Table 2.1

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Trace elements –Are essential to life, but occur in minute amounts

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 2.2: Trace elements are common additives to food and water Dietary deficiencies in trace elements –Can cause various physiological conditions Figure 2.2A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Trace elements are essential to human health –And may be added to food or water Figure 2.2B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Fundamental Building Blocks Matter - all materials that occupy space & have mass Matter is composed of atoms Atom – simplest form of matter not divisible into simpler substances composed of protons, neutrons, & electrons Element – atoms that differ in numbers of protons, neutron & electrons

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Models of atoms

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 2.3 Elements can combine to form compounds Chemical elements –Combine in fixed ratios to form compounds Sodium Chlorine Sodium Chloride Figure 2.3

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 2.4 Atoms consist of protons, neutrons, and electrons The smallest particle of matter that still retains the properties of an element is an atom

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Subatomic Particles An atom is made up of protons and neutrons –Located in a central nucleus The nucleus is surrounded by electrons –Arranged in electron shells Figure 2.4A + + –– + – Protons Neutrons Electrons Mass number = e – Electron cloud Nucleus

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Differences in Elements Atoms of each element –Are distinguished by a specific number of protons Figure 2.4B + – Protons Neutrons Electrons Mass number = e – Nucleus Electron cloud

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Atomic number – number of protons Mass number – number of protons & neutrons Isotopes – variant forms of an element that differ in mass number Atomic weight – average of the mass numbers of all of the element’s isotopic forms

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Isotopes The number of neutrons in an atom may vary –Variant forms of an element are called isotopes –Some isotopes are radioactive Table 2.4

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 2.5 Radioactive isotopes can help or harm us Radioactive isotopes are useful as tracers –For monitoring the fate of atoms in living organisms

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Basic Research Biologists often use radioactive tracers –To follow molecules as they undergo chemical changes in an organism

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Medical Diagnosis Radioactive tracers are often used for diagnosis –In combination with sophisticated imaging instruments Figure 2.5AFigure 2.5B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Dangers Radioactive isotopes have many beneficial uses –But uncontrolled exposure to them can harm living organisms

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 2.6 Electron arrangement determines the chemical properties of an atom Electrons in an atom –Are arranged in shells, which may contain different numbers of electrons Hydrogen (H) Atomic number = 1 Electron Carbon (C) Atomic number = 6 Nitrogen (N) Atomic number = 7 Oxygen (O) Atomic number = 8 Outermost electron shell (can hold 8 electrons) First electron shell (can hold 2 electrons) Figure 2.6

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Atoms whose shells are not full –Tend to interact with other atoms and gain, lose, or share electrons These interactions –Form chemical bonds

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Molecules & Bonds Molecule – distinct chemical substance that results from the combination of two or more atoms Elements can combine to form compounds. A.Compounds contain two or more atoms in a fixed ratio. B.Different combinations of atoms determine the unique properties of each compound. Chemical bonds – when 2 or more atoms share, donate or accept electrons. 3 types: covalent, ionic, & hydrogen

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 3 Types of Chemical Bonds Covalent bonds – electrons are shared among atoms polar covalent bonds– unequal sharing nonpolar covalent bonds– equal sharing Ionic bonds – electrons are transferred to one atom forming positively charged cations & negatively charged anions Hydrogen bonds – weak bonds between hydrogen & other atoms

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 2.7 Ionic bonds are attractions between ions of opposite charge When atoms gain or lose electrons –Charged atoms called ions are created Transfer of electron Na Sodium atom Cl Chlorine atom Na + Sodium ion Cl – Chloride ion Sodium chloride (NaCl) Na Cl Na + – – – Figure 2.7A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings An electrical attraction between ions with opposite charges –Results in an ionic bond

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Sodium and chloride ions –Bond to form sodium chloride, common table salt Na + Cl – Figure 2.7B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 2.8 Covalent bonds join atoms into molecules through electron sharing In covalent bonds –Two atoms share one or more pairs of outer shell electrons, forming molecules

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Molecules can be represented in many ways Table 2.8

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2.9 Unequal electron sharing creates polar molecules A molecule is nonpolar –When its covalently bonded atoms share electrons equally

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings In a polar covalent bond –Electrons are shared unequally between atoms, creating a polar molecule (–) (+) O H H Figure 2.9

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Solution – a mixture of one or more substances called solutes, dispersed in a dissolving medium called a solvent Solutes – Na+ & Cl - Solvent – H 2 O

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2.10 Hydrogen bonds are weak bonds important in the chemistry of life The charged regions on water molecules –Are attracted to the oppositely charged regions on nearby molecules

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings This attraction forms weak bonds –Called hydrogen bonds Hydrogen bond (+) H H (–) O Figure 2.10

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings WATER’S LIFE-SUPPORTING PROPERTIES 2.11 Hydrogen bonds make liquid water cohesive Due to hydrogen bonding –Water molecules can move from a plant’s roots to its leaves

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Insects can walk on water due to surface tension –Created by cohesive water molecules Figure 2.11

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 2.12 Water’s hydrogen bonds moderate temperature Water’s ability to store heat –Moderates body temperature and climate

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings It takes a lot of energy to disrupt hydrogen bonds –So water is able to absorb a great deal of heat energy without a large increase in temperature As water cools –A slight drop in temperature releases a large amount of heat

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings A water molecule takes energy with it when it evaporates –Leading to evaporative cooling Figure 2.12

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 2.13 Ice is less dense than liquid water Hydrogen bonds hold molecules in ice –Farther apart than in liquid water Liquid water Hydrogen bonds constantly break and re-form Ice Hydrogen bonds are stable Hydrogen bond Figure 2.13

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Ice is therefore less dense than liquid water –Which causes it to float Floating ice –Protects lakes and oceans from freezing solid

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 2.14 Water is the solvent of life Polar or charged solutes –Dissolve when water molecules surround them, forming aqueous solutions + – – – – – – – – – – Na + + Cl – Ion in solution Salt crystal Cl – Figure 2.14

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 2.15 The chemistry of life is sensitive to acidic and basic conditions A compound that releases H + ions in solution is an acid –And one that accepts H + ions in solution is a base Acidity is measured on the pH scale –From 0 (most acidic) to 14 (most basic)

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The pH scale Basic solution Oven cleaner Acidic solution Neutral solution pH scale Lemon juice, gastric juice Grapefruit juice, soft drink Tomato juice Human urine Pure water Human blood Seawater Milk of magnesia Household ammonia Household bleach Increasingly ACIDIC (Higher concentration of H + ) NEUTRAL [H + ]=[OH – ] H+H+ H+H+ H+H+ OH – H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ Increasingly BASIC (Lower concentration of H + ) OH – H+H Figure 2.15

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings The pH of most cells –Is kept close to 7 (neutral) by buffers Buffers are substances that resist pH change

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CONNECTION 2.16: Acid precipitation threatens the environment Some ecosystems are threatened by acid precipitation Acid precipitation is formed when air pollutants from burning fossil fuels –Combine with water vapor in the air to form sulfuric and nitric acids

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings These acids –Can kill trees and damage buildings Figure 2.16AFigure 2.16B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings CHEMICAL REACTIONS 2.17 Chemical reactions change the composition of matter In a chemical reaction –Reactants interact, atoms rearrange, and products result 2 H 2 O2O2 2 H 2 O Figure 2.17A

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Living cells carry out thousands of chemical reactions –That rearrange matter in significant ways CH 3 H2CH2C C CHC C C C CH 2 CH 3 C CH 2 H2CH2C CH CH 3 CH C C C C CH 3 O2O2 4H CH C C C OH H H CH 3 C C H2CH2C C CH 2 H2CH2C CH 3 Vitamin A (2 molecules) Beta-carotene 2 Figure 2.17B

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings PowerPoint Lectures for Biology: Concepts and Connections, Fifth Edition – Campbell, Reece, Taylor, and Simon Lectures by Chris Romero Chapter 2 The Chemical Basis of Life

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 1.Which four chemical elements are most abundant in living matter? 2.Why are sodium chloride and vitamin A both classified as compounds? 3.Why are radioactive isotopes useful as tracers in research and medical testing? 4.Sodium has an atomic number of 11. How many electron shells does it have and how many electrons are in its outer shell?

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 1.What holds together the atoms in table salt? 2.What is wrong with the chemical structure H- C=C-H? 3.What allows neighboring water molecules to bond to each? What is the bond and how does it work?

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings 1.In plants, water in thin tubes within the trunk is pulled upward by evaporation from leaves. What keeps the water molecules at the bottom of the tree moving? 2.Explain the popular adage “It’s not the heat, it’s the humidity.” 3.Explain how freezing of water can crack boulders. 4.What is the relationship between fossil fuel consumption and acid rain?

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Concept Check In order to understand the chemical basis of inheritance, one must understand the molecular structure of DNA. This is an example of the application of __________ to the study of biology ? emergent properties the cell theory reductionism philosophy

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Answer In order to understand the chemical basis of inheritance, one must understand the molecular structure of DNA. This is an example of the application of __________ to the study of biology ? reductionism

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Concept Check The reactive properties or chemical behavior of an atom mostly depend on the number of the electrons in each electron shell of the atom. the neutrons found in the nucleus. the filled electron shells. the electrons in the outer electron shell of the atom.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Answer The reactive properties or chemical behavior of an atom mostly depend on the number of the electrons in the outer electron shell of the atom.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Concept Check Water molecules form hydrogen bonds because the water molecule is polar. the oxygen molecule is positively charged. the water molecule forms a tetrahedron. the hydrogen atoms are negatively charged.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Answer Water molecules form hydrogen bonds because the water molecule is polar.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Interpreting Data This is the general equation for photosynthesis—the process of capturing sunlight energy and converting it to chemical energy. Which of the following are the reactants of this reaction? C 6 H 12 O 6 and O 2. CO 2 and H 2 O.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Answer This is the general equation for photosynthesis—the process of capturing sunlight energy and converting it to chemical energy. Which of the following are the reactants of this reaction ? CO 2 and H 2 O.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Interpreting Data Earth’s oceans are immense. Small floating plants called phytoplankton contribute to ocean productivity. As ocean productivity (the rate of photosynthesis) goes up what would you predict would happen to global carbon dioxide levels? CO 2 levels should also go up. CO 2 levels should go down CO 2 levels should remain constant.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Answer Earth’s oceans are immense. Small floating plants called phytoplankton contribute to ocean productivity. As ocean productivity (the rate of photosynthesis) goes up what would you predict would happen to global carbon dioxide levels? CO 2 levels should go down

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Interpreting Data Ironically, the world’s oceans throughout the tropics are not very productive. (these oceans do not capture much sunlight through the process of photosynthesis.) On the other hand some of the most productive ocean are the Arctic and Antarctic. What might be limiting production in the tropical oceans? Low temperature. Low sunlight. Low nutrients. High nutrients.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Answer Ironically, the world’s oceans throughout the tropics are not very productive. (these oceans do not capture much sunlight through the process of photosynthesis.) On the other hand some of the most productive ocean are the Arctic and Antarctic. What might be limiting production in the tropical oceans? Low nutrients.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Interpreting Data – Iron is the fourth most common element (by weight) in the Earth’s crust. – Iron is an essential trace element for all living organisms. – Ocean waters, particularly the Southern Ocean have very minute amounts of iron. – The Iron hypothesis states that Iron availability limits ocean productivity.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Interpreting Data These are the results of a laboratory experiment to test the effect of trace nutrients on the productivity of Pacific Ocean water. After 6 days which nutrient had the greatest effect on productivity? Iron. Manganese. Copper. Zinc. Adapted from Coale, Kenneth H Effects of Iron, Manganese, Copper and Zinc Enrichments on Productivity and Biomass in the Subarctic Pacific. Limnology and Oceanography. 36:

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Answer These are the results of a laboratory experiment to test the effect of trace nutrients on the productivity of Pacific Ocean water. After 6 days which nutrient had the greatest effect on productivity? Iron. Adapted from Coale, Kenneth H Effects of Iron, Manganese, Copper and Zinc Enrichments on Productivity and Biomass in the Subarctic Pacific. Limnology and Oceanography. 36:

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Interpreting Data Some have suggested that fertilizing the oceans with iron might be a possible solution to the increasing carbon dioxide levels in the atmosphere. Iron’s function as a trace nutrient in phytoplankton possibly affecting the atmosphere and possibly global climate is a good example of ? The stability of atoms. The unity of life on earth. Emergent properties.

Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings Answer Some have suggested that fertilizing the oceans with iron might be a possible solution to the increasing carbon dioxide levels in the atmosphere. Iron’s function as a trace nutrient in phytoplankton possibly affecting the atmosphere and possibly global climate is a good example of ? Emergent properties.