Powerpoint Templates Chapter 2: Chemistry of Life

I. Matter – anything that has mass and takes up space A.Atoms – small particles that make up all matter & cannot be broken down chemically 1.Nucleus – positively charged core Protons (+) Neutrons (neutral) 2.Electron Cloud – region where electrons (-) orbit around the nucleus

3.Atomic # = # protons = # electrons 4.Mass # = protons + neutrons 5.Atomic Mass = mass of atom (in Daltons) ≈ mass # # of Protons = # of Neutrons = # of Electrons = Atomic Number = Mass Number = Atomic Mass =

Diagram of an Atom

6.Isotopes – atoms that have a different number of neutrons Neutrons have mass, so isotopes are heavier than their normal atom Identified by atomic mass Carbon 12 (normal) Carbon 13 (isotope) Have same number of electrons, so isotopes have the same properties Radioactive isotopes break down over time

B.Elements – substance made of atoms that have the same number of protons 1.Ex: Each atom of the element Carbon (C) has 6 protons 2.90% of the mass living things is made of only 4 elements: oxygen, carbon, hydrogen, nitrogen

Checkpoint In a neutral atom the # of protons is equal to the # of Different # of protons gives different Different # of neutrons gives an

II. Chemical Bonds A.Valence Electrons – electrons in the outermost level of the electron cloud 1.The innermost level can only hold 2 electrons. 2.Levels further out hold 8 electrons. 3.Atoms tend to combine with each other so that the outer level will have 8 electrons.

B.Chemical Bonds – the force that holds atoms together 1.Form because atoms become stable when they have 8 electrons (or full levels) in the valence (outer) level. 2.Compound – substance made of atoms of 2 or more different elements, and has different properties from those of the atoms. 3.Ex: water, H 2 O: 2 hydrogen atoms and 1 oxygen atom

C.Types of Bonds 1.Covalent Bonds – atoms sharing electrons Molecule – atoms held together by covalent bonds Ex: Carbon Dioxide CO 2 2.Ionic Bonds - one atom transfers electrons to another Results in positive & negative charged atom = ion Ions of opposite charge are attracted to each other, and this attraction is the ionic bond. Ex: Sodium Chloride NaCl

3.Hydrogen Bonds – bond between molecules (holds water together) 4.Van der Waals bond – weakest of bonds (bonds between Gecko’s foot & the molecules of a wall)

III. Water A.Polarity 1.In some covalent bonds, electrons are attracted more strongly to one atom than another. 2.One end of the molecule will then be partially positive, & the other end will be partially negative. These molecules are polar. 3.Ex: water!

B.Hydrogen bonds (H-bonds) 1.When bonded to O 2, N 2, or F, a hydrogen has a partial positive charge nearly as great as a proton. 2.This hydrogen is then attracted to the negative region of polar molecules, forming hydrogen bonds.

C.Properties of Water – most result because water forms hydrogen bonds with itself 1.Polarity 2.Density = Ice Floats – solid water is less dense than liquid water (h-bonds)

3.Water absorbs & retains heat – large bodies of water keep Earth’s temp. regulated; water maintains organisms’ internal body temp. High Heat of Vaporization: water absorbs a lot of energy before it evaporates High Specific Heat: water absorbs a lot of energy before its temperature is raised

4.Cohesion – h-bonds hold water molecules together 5.Adhesion – water sticks to other polar substances both cohesion and adhesion allow water to move upward through roots and stems of plants

D.Mixtures – 2 or more elements or compounds mixed together physically, not chemically E.2 Types of Mixtures: 1.Solutions – one or more substances mixed evenly in another substance Solute – substance that is dissolved (salt) Solvent – substance that does the dissolving (water) 2.Suspension – material don’t dissolve

E.Acids & Bases 1.Dissociation – a molecule breaks into its ions H 2 O ↔ H + + OH - H + = hydronium ion OH - = hydroxide ion 2.Acid – solution with more hydronium ions HCl = hydrochloric acid 3.Base – solution with more hydroxide ions NaOH = sodium hydroxide

4.pH scale – measures the concentration of hydronium ions; is logarithmic, so each step is 10 times more acidic or basic pH of 0-6 is acidic pH of 7 is neutral pH of 8-14 is basic or alkaline o pH of 1 is 10 times more acidic than pH of 2 o pH of 14 is 100 times more basic than pH of 12 5.Buffers – chemicals that neutralize acids and bases

IV. Energy & Metabolism A.Energy – ability to do work 1.Comes in multiple forms – light, heat, chemical, mechanical, electrical, nuclear 2.Free energy – energy in a system (our bodies) that is available to do work

B.Chemical Reactions – bonds between atoms are broken, and new ones form Ex: CO 2 + H 2 O  H 2 CO 3 Reactants  Products (# reactant atoms = # of product atoms) 1.Energy in Reactions Exergonic Reactions – reactions that release free energy (feel hot) Endergonic Reactions – reactions that absorb energy (feel cold) Activation Energy – energy needed to start (or activate) a chemical reaction

C.Biological Reactions 1.Reactions in living things require large amounts of activation energy. 2.Catalysts are chemicals that lower the amount of activation energy needed. 3.Enzymes are biological catalysts!

D.Enyzme Activity – reactions depend on a physical fit between an enzyme’s active site and its specific substrate (Lock and Key) 1.Two substrates bind to an enzyme’s active site, like a key into a lock. 2.Enzyme’s shape changes slightly, breaking bonds in each substrate. 3.New bonds form, creating new product(s).