CHAPTER 2 Essential Chemistry for Biology Figures 2 1 2 7 PowerPoint Lecture Slides for Essential Biology Second Edition Essential Biology with Physiology Neil Campbell Jane Reece and Eric Simon Presentation prepared by Chris C Romero Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Because of surface tension some insects can walk on water Water molecules stick to each other by cohesion which results from hydrogen bonding The iron in a multivitamin pill is the same element as the iron in a train or ship Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings BIOLOGY AND SOCIETY FLUORIDE IN THE WATER There has been a sharp decline in tooth decay in the last few decades Fluoride containing chemicals have been added to drinking water and dental products The use of fluoride in drinking water illustrates the point that organisms are chemical systems Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 1 TRACING LIFE DOWN TO THE CHEMICAL LEVEL Biology includes the study of life at many levels In order to understand life we will start at the macroscopic level the ecosystem and work our way down to the microscopic level of cells Cells consist of enormous numbers of chemicals that give the cell the properties we recognize as life Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Ecosystem African savanna Community All organisms in savanna Organism Zebra Population Herd of zebras Organ system Circulatory system Organ Heart Cell Heart muscle cell Tissue Heart muscle tissue Molecule DNA Atom Oxygen atom Figure 2 1 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Ecosystem Community Population ex all humans in city all termites in class Individual Organism Organ Systems ex respiratory reproductive circulatory Organs ex lungs ovaries heart Tissue ex connective nervous muscular Cells ex neuron sarcomere epithelial Organelles ex nucleus chloroplast mitochondria Macromolecules ex DNA RNA cellulose lipids Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 2 SOME BASIC CHEMISTRY Take any biological system apart and you eventually end up at the chemical level Cells ex Prokaryotic Eukaryotic Macromolecules ex DNA RNA fat Molecules ex H2O HCl H2SO4 Atoms ex C H O N Iodine C carbon Subatomic particles within nucleus neutron proton around nucleus electrons Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Matter Elements and Compounds Matter is anything that occupies space and has mass Matter is found on the Earth in 3 physical states Solid Liquid Gas Plasma Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Matter is composed of chemical elements Elements are substances that cannot be broken down into other substances There are 92 naturally occurring elements on Earth Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 3 All the elements are listed in the periodic table Atomic number Element symbol Mass number Figure 2 2 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Twenty five elements are essential to life Four of these make up about 96 of the weight of the human body C H O N Trace elements occur in smaller amounts Figure 2 3 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Trace elements are essential for life An iodine deficiency causes goiter Figure 2 4 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 4 Elements can combine to form compounds These are substances that contain two or more elements in a fixed ratio Example NaCl salt Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 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 Nucleus a b Cloud of negative charge 2 electrons 2 Protons 2 Neutrons 2 Electrons Figure 2 5 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 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 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 5 Most atoms have protons and neutrons packed tightly into the nucleus The nucleus is the atom s central core The electrons orbit the nucleus Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Elements differ in the number of subatomic particles in their atoms The number of protons the atomic number determines which element it is An atom s mass number is the sum of the number of protons and neutrons Mass is a measure of the amount of matter in an object protons and neutrons each have an atomic mass unit of 1 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Isotopes Isotopes are alternate mass forms of an element They have the same number of protons and electrons But they have a different number of neutrons p 23 Table 2 1 p 23 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 6 Radioactive isotopes The nucleus decays giving off particles and energy Radioactive isotopes have many uses in research and medicine Example PET scans Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings a Hearing words Seeing words Speaking words Generating words b Figure 2 6 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Uncontrolled exposure to radioactive isotopes can harm living organisms by damaging DNA Example the 1999 Tokaimura nuclear accident Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings 7 Electron Arrangement and the Chemical Properties of Atoms Electrons determine how an atom behaves when it encounters other atoms Electrons orbit the nucleus of an atom in specific electron shells The number of electrons in the outermost shell determines the chemical properties of an atom Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Atoms of the four elements most abundant in life First electron shell can hold 2 electrons Outermost electron shell can hold 8 electrons Electron Hydrogen H Atomic number 1 Carbon C Atomic number 6 Nitrogen N Atomic number 7 Oxygen O Atomic number 8 Figure 2 7 Copyright 2004 Pearson Education Inc publishing as Benjamin Cummings Chemical Bonding and Molecules Chemical reactions enable atoms to give up or acquire electrons in order to complete their outer shells These interactions usually result in atoms staying close together The