Chapter 2

Chapter 2

Chapter 2 Chemistry of Life GreenChem.jpg Section 1 Vocabulary Pretest Positively charged particle A. Matter Mass Element Atom Nucleus B. C. D.

E. F. G. Proton Neutron Atomic H. Number I. Mass Number Simplest particle of an element Central region of an atom Anything that has mass and takes up space Quantity of matter Neutral particle Represents the number of

protons in an atom Substances that cannot be broken down chemically into simpler kinds of matter Total number of protons and neutrons in an atom J. Electron Orbital Isotope Compound Chemical K. L. M. N. bond

Covalent bond O. Molecule P. Ion Q. Ionic bond R. Atoms of the same element that have a different number of neutrons Negatively charged particles Area around an atom where electrons are found Two or more elements chemically joined together Atom or molecule with an electrical charge Attractive force that holds atoms together Simplest part of a substance that

retains the properties of the substance Type of bond in which one or more pairs of electrons are shared Type of bond in which electrons are transferred creating ions that attract each other Answers Matter Mass E Element Atom B Nucleus

Proton D H Electron Orbital L Isotope J Compound M Chemical bond O

Covalent bond Q C A Neutron F Atomic Number G Mass Number

I Molecule Ion N Ionic bond K P R Chemistry of Life

Chemistry is important to biologists because all of the life activities in our cells that keep us alive are the result of chemical reactions. The elements that make up living things and how they interact with each other is essential to life. AAAAAAAAAAM/k-35m-oBuQU/s320/chemical_bases1.jpg Matter Matter

is anything that has mass and takes up space. Everything in the universe is made of matter. Mass is the quantity of matter in an object. Weight is the force produced by gravity acting on mass What changes on the moonyour mass or your weight??? Why??? So, would my jeans that are too small on Earth fit me on the moon?? Elements and Atoms Elements are substances that cannot be broken down chemically into simpler kinds of matter. The Periodic Table lists over 100 known

elements. About 30 of these are important to living things. Check the Chart: Can you identify any of the 30??? carbon_atom.gif Heres the List!!! AluminumAl Arsenic Boron Bromine Manganese As B Br

Cadmium Cd Calcium Ca Carbon C Chlorine Cl Chromium Cr Cobalt Co Copper Cu Flourine F Germanium Ge Hydrogen H Iodine I Iron Fe Magnesium Mg Mn Molybdenum Mo Nickel Ni Nitrogen N Oxygen

O Phosphorus P PotassiumK Selenium Se Silicon Si Sodium Na Sulfur S Tin Sn Titanium Ti Tungsten W Vanadium V Zinc Zn The four most common elements in living cells are HONC Honk Hydrogen makes up 59% of living cells. A lot of it is found in the form of water.

Oxygen makes up 24% of living cells. It is essential for the process of cellular respiration and is also found in water. Nitrogen makes up 4% of living cells. It is a key element needed for growth. Carbon makes up 11% of living cells. It is the element of life All organic compounds contain carbon. Atoms An atoms is the simplest particle of an element that retains all of the properties of that element. Parts of an atom: Nucleus center of the atom. It contains two subatomic particles: Protons positively charged

particles Neutrons particles with no charge. Electrons negatively charged particles that orbit the nucleus 146474201/atom.jpg The atomic number is the number of protons in an atom The atomic mass is the number of protons plus the number of neutrons. The number of electrons in an atom is the same as the number or protons giving it a net charge of zero.

Isotopes Atoms of the same element always have the same number of protons. However, they may have a different number of neutrons. Isotopes atoms of the same element with different number of neutrons. This gives them a different atomic mass. Average Atomic Mass is the average of all of the isotopes of that Carbon Isotopes C12C14.GIF Carbon is really a mixture of isotopes. Carbon 12, Carbon 13 and

Carbon 14. Its average atomic mass is 12.0107 Elements like Carbon can be used in radiometric dating. Scientists have calculated how long it takes Carbon 14 to change into Carbon 13 and Carbon 12. By measuring the amount of each isotope in a sample, they can then date how long it has been decaying. Unstable isotopes are called radioisotopes. They are unstable because their nucleus is too big. Models of Atoms bohr_atom.gif Bohr Model Models of Atoms

Electron Cloud Model carbon_atom.gif Orbitals Notice in the Bohr model, electrons are seen in energy levels called shells consisting of orbitals around the nucleus. Orbital threedimensional region around a nucleus. Electrons in orbitals that

are farther away from the nucleus have greater energy than those that are closer to the nucleus. The maximum number of electrons that can occupy a specific energy level can be found using the formula: 2n2 Thus: Energy Level 1 2 3 4 5 6 Shell Letter Electron Capacity K

2 L 8 M 18 N 32 O 50 P 72 The electrons fill the shells according to the following formula: 1st shell holds 2 electrons 2nd shell holds 8 electrons 3rd shell holds 8 electrons 4th shell holds 18 electrons

5th shell holds 18 electrons 6th shell holds 32 electrons Compounds Compounds atoms of two or more elements joined by chemical bonds. Examples: H2O NaCl C6H12O6 Electron Cloud model Stick modelmodels Three below show a water Bohr model molecule Water1.gif

Chemical Bonds Chemical bonds are attractive forces that hold atoms together. Bonds are determined by the number and arrangement of electrons in the outer orbital of an atom. bond.gif Stable Elements Atoms prefer to be chemically stable. This happens when their highest energy level is filled with its maximum number of electrons.

These stable elements are known as the Noble Gases or Inert Elements. They do not react with other elements under normal conditions. They are found on the far right-hand side of the Periodic Table. Other elements are not stable, so they react with other atoms to become more stable. In other words, they are trying to fill their outer energy level. This is how most chemical bonds are formed. bond.gif Types of Chemical Bonds

Covalent Bonds two atoms share one or more pairs of electrons. Examples: H2 H2O 31704423/image.gif q=tbn:aztc6Xoa_4SzTM:http:// pics/h_h_bond.gif&t=1 Carbon has the ability to form multiple covalent bonds and is therefore vital to living organisms. Carbon has 4 electrons in its outer shell. The shell can hold 8. Carbon needs 4 more electrons to become stable. This can result in big biological

molecules based around chains of carbon atoms. Covalent.png q=tbn:ANd9GcTDsTGWMhdl6_3izM7K7RCw6b5ueLWXpacSg91FXY8Tt6PoObw&t=1& usg=__fkitOKpfQ768Lo6SF7eDzZ0qobs= Many complex biological molecules will be formed using double and triple covalent bonds. Double share 2 pair of electrons Triple share 3 pair of electrons Ethane Ethylene Acetylene

Ionic Bonds bonds based on attracted positive and negative charges on atoms These charges are created when an atom either loses an electron (creating a positive charge) or gains an electron (creating a negative charge). Atoms with an electrical charge are called ions. *Sodium transfers an electron to chlorine making both atoms Example: NaCl q=tbn:ANd9GcTi4aS8FuhFvBMUYICvST23b1BVvDia3jearqkPXhvhGpqHfU&t=1&usg=__xXMBkGXtvo0ysKw8eUcanNOrUSs= more stable. *Sodium now has a positive charge and is called a sodium ion Na+

*Chlorine now has a negative charg because of the extra electron and is called a chlorine ion Cl*Opposite charges attract and bond these two together creating sodium chloride NaCl (table salt) Section 2 Vocabulary Pretest Energy

Chemical Reaction Reactant Product Metabolism Activation Energy Catalyst Enzyme Redox Reactions Oxidation Reaction Reduction Reaction A. B. C. D.

E. F. G. H. I. J. K. Substances on the left-hand side of a chemical equation All of the chemical reactions that occur in an organism Ability to do work A protein or RNA molecule that speeds up a reaction Substances on the right-hand side of a chemical equation Occurs anytime one or more substances change into different substances Amount of energy needed to start a

chemical reaction Any substance that reduces the amount of activation energy needed in a chemical reaction Reactant loses electrons Reactant gains electrons General term for reactions where electrons are transferred between atoms Answers Energy C Chemical Reaction F ReactantA Product E Metabolism B Activation Energy G Catalyst H Enzyme D Redox Reactions K

Oxidation Reaction I Reduction Reaction J Energy Energy the ability to do work The forms of energy important to living things include: Chemical energy Thermal energy Electrical energy Mechanical energy Living things can convert one form of energy into another. EnergyTransformations.gif States of Matter Three states of matter describe the motion and spacing between atoms or molecules of a substance. They are: Solid maintains a fixed volume and shape Liquid maintains a fixed volume but takes the shape of its container Gas takes the shape and volume of its container %20of%20Matter.gif Thermal energy must be added to cause a substance to change state Energy and Chemical Reactions Chemical reactions occur when one or more substances change to produce one or more new substances. Chemical equations show what happens during the reaction Reactants on left 6CO2 + 6 H2O Products on right C6H12O6 + 6O2

Reaction Speed Most reactions need the addition of energy before they will begin. Activation Energy energy required for a reaction to begin Catalyst substances that speed up chemical reactions by lowering the activation energy required. Enzymes are common catalysts in living things They remain unchanged throughout the reaction. activationenergy1.gif

Endothermic and Exothermic Reactions Endothermic reactions result in a net absorption of energy Exothermic reactions results in the net release of energy Oxidation Reduction Reactions Also called Redox Reactions Reactions in which electrons are transferred between atoms

Oxidation reaction a reactant loses electrons resulting in a positive charge ExampleNa loses an electron to become more stable creating a sodium ion (Na+) Reduction reaction a reactant gains electrons resulting in a negative charge ExampleChlorine gains an electron to become more stable creating a chlorine ion (Cl-) The two always occur together. One reactant gives up what the other needs. Section 3 Vocabulary Pretest Polar Hydrogen Bond Cohesion Adhesion

Capillarity Solution Solute Solvent Concentration A. Attractive force between two particles of different substances B. A dissolved substance Substance in which something else is dissolved C. D. E. F.

G. H. I. Molecule with opposite charges on opposite ends Attractive force that holds molecules of a single substance together Rise of the surface of a liquid when in contact with a solid Mixture in which substances are uniformly distributed in another substance Amount of solute dissolved in a fixed amount of solution Force of attraction between positive hydrogen molecules and other atoms or molecules with a negative charge Saturated

Solution Aqueous Solution Hydroxide Ion Hydronium Ion Acid Base pH scale Buffer J. K. L. M. N. O. P.

Q. OH- ion H3O+ ion Chemicals that neutralize either an acid or a base Measures how acidic or basic a substance is Solution in which water is the solvent Solution in which no more solute can be dissolved A solution that contains more hydroxide ions than hydronium ions A solution that contains more hydronium ions than hydroxide ions.

Answers: Polar D Hydrogen Bond I Cohesion E Adhesion A Capillarity F Solution G Solute B Solvent C Concentration H Saturated Solution

O Aqueous Solution N Hydroxide Ion J Hydronium Ion K Acid Q Base P pH Scale M Buffer L Water and Solutions Waters chemical structure is

important in its vital role in life. %20molecule.jpg %20water%20color.jpg Each water molecule has two hydrogen atoms covalently bonded to one oxygen atom. The hydrogen and the oxygen share electrons The electrons are not shared equally. Oxygen pulls harder on the electrons resulting in

one side of the water molecule having a partial negative charge and the other a partial positive charge image15.gif A molecule, like water, with opposite charges on opposite ends is said to be a polar compound. The covalent bonds holding it together are called polar

covalent bonds. Being polar allows water to dissolve many other substances such as: Other polar substances like sugars Ionic substances like salts (see below) Some proteins Water cannot dissolve nonpolar substances, such as oil oilwater1.jpg Hydrogen Bonding Hydrogen

bonds occur between a hydrogen molecule with a partial positive charge and another atom or molecule with a partial negative charge They allow water to cling to itself hydrogen_bonding_c_la_784.jpg Hydrogen bonds break and reform continuously. The number of hydrogen bonds depends on the state of water Solid all molecules are hydrogen bonded and do not break Liquid equal number of bonds are broken and reformed Gas minimal hydrogen bonds exist

Hydrogen Bonds sunk the Titanic!!! Why?? Because ice floats!! Ice floats because water is less dense as a solid. This is due to hydrogen bonds In liquid water, hydrogen bonds pull water molecules together, resulting in a compact, dense structure As ice, water is arranged in a rigid lattice structure with large holes in it. Thus, in a given volume of ice there are less water molecules than in the same volume of water---making it less dense. rjo0628l.jpg

Water Ice The density of ice has an impact on living things: Water freezes from the top down Ice on the top of ponds and lakes insulates the water below from the cold air which allows fish and other creatures to survive under the icy surface. 25_1.gif Hydrogen

bonding in water is responsible for: Cohesion attractive force that holds molecules of a single substance together Ex: water moves up from roots to leaves Surface Tension cohesive forces of water pull surface molecules down, creating a thin skin on the surface Ex: water-strider can walk on water Adhesion attractive forces between two particles of different substances Ex: water sticks to glass Capillarity rise of the surface of a liquid when in contact with a solid Ex: water moves through small tubes in plants

Hydrogen bonds are also responsible for the high heat capacity of water Water can absorb or release a large amount of energy as heat Hydrogen bonds break and reform with great frequency in water Energy is absorbed to break hydrogen bonds Energy is released as heat when hydrogen bonds form This impacts living things in several ways: Earths oceans stabilize global temperatures Living cells can maintain even temperatures despite temperature changes in the environment Evaporative cooling from water prevents overheating in many living things Solutions

Solution mixture in which one or more substances are uniformly distributed in another substance. Solute dissolved substance Solvent substance in which the solute is dissolved Concentration amount of solute dissolved in a fixed amount of solution Saturated Solution no more solute can be dissolved Aqueous Solutions Aqueous Solutions solutions in which water is the solvent. Vital to all living things Examples: The ocean is an aqueous solution

Plants get nutrients from aqueous solutions in moist soil Cells depend on inter and extra cellular aqueous solutions for most chemical reactions to occur Suspensions and Colloids Suspension mixture in which particles spread through a liquid or a gas but settle over time. Ex: Blood Colloid mixtures in which particles do not settle out over time Ex: Milk Colloid in liquid formsol Ex: Cytosol Colloid in semisolid formgel Ex:

Cytoplasm Ionization of Water Water molecules can collide and break each other apart H2O H+ + OH- OH- is known as the hydroxide ion Free H+ ions react with water molecules: H + + H 2O H3O+ H3O+ is known as the hydronium ion Acids and Bases Acid solution in which the number

of hydronium ions is greater than the number of hydroxide ions They have a value below 7 on the pH scale. Base solution in which the number of hydroxide ions is greater than the number of hydronium ions (Alkaline) They have a value above 7 on the pH scale Buffers Living things must be able to control pH Buffers chemical substances that neutralize small amounts of either an acid or a base

Living things need complex buffer systems to balance the pH levels of fluids within their bodies. Blood Plasma 7.5 Gastric Acid 3.0 Mothers Milk 7.5 Saliva 7.3 1.0 6.6 6.5

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