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The ChemicalLevel of

Organization2.1-2.3August 8, 2012August 9, 2012

AgendaGeneral

HousekeepingReview Chapter 2

2.1 2.3

Research Paper

2.2

Assignments

Overview Process

Review• Are the ribs superficial to the lungs? How do you

know?• In which cavity is the thymus located?• Locate the nine abdominopelvic regions on yourself

and list some of the organs found in each– Use four strips of tape to mark yourself

• Which forms of medical imagery would be used toshow a blockage of an artery of the heart?

Chapter 2: The ChemicalLevel of Organization• 2.1 How Matter is Organized

• 2.2 Chemical Bonds

• 2.3 Chemical Reactions

• 2.4 Inorganic Compounds & Solutions

• 2.5 Organic Compounds

The Big Idea• Chemistry and Homeostasis

– Maintaining the proper assortment andquantity of thousands of different chemicalsin your body, and monitoring the interactionsof these chemicals with one another, are twoimportant aspects of homeostasis

2.1 How Matter is Organized• Objectives

– Identify the main chemical elements of thehuman body

– Describe the structures of atoms, ions,molecules, free radicals, and compounds

Chemical Elements• Matter exists in three states

– Solid•Compact, definite shape and volume

–Bones and teeth– Liquid

•Definite volume, shape of their container–Blood plasma

– Gas•No definite shape or volume

–Oxygen and carbon dioxide

How Matter is Organized• All forms of matter are composed of chemical

elements which are substances that cannot be splitinto simpler substances by ordinary chemical means

• Elements are given letter abbreviations calledchemical symbols

• Major Elements constitute about 96% of thebody’s mass

– O, C, H, N

• Lesser Elements contribute about 3.6% of thebody’s mass

– Ca, P, K, S, Na, Cl, Mg, Fe

• Trace elements are elements in our bodies,present in tiny amounts and account for theremaining 0.4% of the body’s mass

– Several trace elements have importantfunctions in the body

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Structure of Atoms• Units of matter of all chemical elements are called

atoms.

• An element is a quantity of matter composed ofatoms of the same type.

• Atoms contain three types of subatomic particles

• Electrons (e-) are very small and light (mass about1/2000th that of proton or neutron), oftenrepresented as orbiting around the nucleus

• In reality, they are found in a “cloud” of probabilitysurrounding the nucleus

• Protons (p+) and neutrons (n0) form the nucleusof an atom

– Protons are large, positively-charged particles

•The number of protons in the nucleus(called the atomic number) determines theelement

• Neutrons are the second largest particle thatmake-up the nucleus of atoms

– Unlike protons, neutrons have no charge

– They do add mass, however, and determine thevariety, or “isotope” of a certain element

•Isotopes are atoms of an element that havedifferent numbers of neutrons

•Carbon-12 vs. Carbon-14, which has 2 extraneutrons in nucleus

• Radioactive isotopes are unstable and their nucleidecay into stable configurations

– As they decay, the isotopes emit radiation andin the process, often transform into differentelements

•C-14 decays into N-14

– The half-life of an isotope is the time requiredfor half of the radioactive atoms in a sample ofthat isotope to decay into a more stable form

•Half-life of C-14 is about 5730 years

•Half-life of I-131 is 8 days

• Mass is measured as a dalton(atomic mass unit)

• Certain numbers are used todescribe different properties ofelements

- Atomic number is the number ofprotons in an atom

- Mass number is the sum ofprotons and neutrons in an atom

- Atomic mass (atomic weight) isthe average mass of all naturallyoccurring isotopes

Elements in the Human Body Ions• Atoms that have given up or gained an electron in

their outer electron shell (also called the valenceshell)

– Written with its chemical symbol and (+) or (–)

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Molecules• Molecules are formed when

atoms share electrons• Written as a molecular formula showing the

number of atoms of each element (H2O)

• The oxygen gas in the atmosphere we breathis really not oxygen the atom, but a pair ofoxygen atoms linked together into an oxygenmolecule (O2)

Compounds• A substance that contains atoms of two or

more different elements

– Most of the atoms in the body are joinedinto compounds

•H2O

•NaCl

•O2 is not a compound. Why?

Free Radicals• Is an electrically charged atom or group of atoms with

an unpaired electron in its outermost shell• They are unstable and highly reactive

– They can become stable by giving up an electron ortaking an electron from another molecule, oftenbreaking apart important body molecules

• Antioxidants are substances that inactivate oxygen-derived free radicals

2.2 Chemical Bonds• Objectives

– Describe how valence electrons formchemical bonds

– Distinguish among ionic, covalent, andhydrogen bonds

• The atoms of a molecule are held together by forcesof attraction called chemical bonds

• The likelihood that an atom will form a chemicalbond with another atom depends on the number ofelectrons in its outermost or valence shell

• Atoms will interact in ways that produce a chemicallystable arrangement of eight valence electrons in eachatom (Octet Rule)

Ionic Bonds• Ions form when an atom loses or gains a valence

electron• Positively and negatively charged ions are attracted to

one another• Cations are positively charged ions that have given up

one or more electrons (they are electron donors)• Anions are negatively charged ions that have picked

up one or more electrons that another atom has lost(they are electron acceptors)

• Ionic compounds that break apart into positive andnegative ions in solution are called electrolytes

Covalent Bonds• Formed by the atoms of molecules sharing one,

two, or three pairs of their valence electrons

• Covalent bonds are the strongest chemical bonds

• Single, double, or triple covalent bonds are formedby sharing one, two, or three pairs of electrons,respectively

• Covalent bonds may be nonpolar or polar

• In a nonpolar covalent bond, atoms share theelectrons equally

– Nonpolar covalent bonds are the mostcommon types of covalent bonds

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• Polar covalent bonds are formed by the unequalsharing of electrons between atoms

• Polar covalent bonds are extremely importantbecause the all-important water molecule makesuse of this bond

• In water, oxygen attracts the hydrogen electronsmore strongly, making oxygen slightlyelectronegative as indicated by the negativeGreek delta sign

Hydrogen Bonds• Are weak interactions (approximately 5% as strong

as covalent bonds) between hydrogen andadjacent electronegative atoms like oxygen orsulfur

• Result from attraction of oppositely charged partsof molecules—they should not be confused withcovalent bonding to hydrogen which involvesactual sharing of electrons

• Hydrogen bonds are useful in establishing linksbetween molecules or between distant parts of avery large molecule.– Large 3-D molecules (like proteins) are often held

together by a great many hydrogen bonds• In water, hydrogen bonding provides considerable

cohesion which creates a very high surface tension– A measure of difficulty of stretching or breaking

the surface of a liquid

2.3 Chemical Reactions• Objectives

– Define a chemical reaction

– Describe the various forms of energy

– Compare exergonic and endergonic chemicalreactions

– Describe the role of activation energy andcatalysts in chemical reactions

– Describe synthesis, decomposition, exchange,and reversible reactions

• Chemical reactions occur when electrons in thevalence shell are shared or transferred

– Old bonds are broken in the reactants and newbonds are formed in the product(s)

• Metabolism is the “sum of all the chemicalreactions in the body”

• Law of Conservation of Mass

– The total mass of reactants equals the totalmass of the products

Energy• Energy (the capacity to do work) is transferred in a

chemical reaction

• Kinetic Energy is the energy of matter in motion

• Potential Energy is energy stored by matter - due toan object’s position in space, or stored in chemicalbonds (Chemical Energy)

• Law of Conservation of Energy

– Energy can be neither created nor destroyed, itcan be converted from one form to another

• An exergonic reaction releases energy (usually inthe form of heat during catabolism of food) bybreaking a bond with more energy than the onebeing formed

• An endergonic reaction requires that energy beadded, usually from a molecule called ATP, toform a bond

• Activation Energyis the energyrequired to breakchemical bonds inthe reactantmolecules so areaction can start

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• Chemical concentration and temperatureinfluence the chance that a collision will occur andcause a chemical reaction

– The more particles of matter present in aconfined space, the greater the chance thatthey will collide

– As temperature rises, particles of matter movemore rapidly increasing the chance of collisionsbetween particles

Catalysts• Factors that cause a collision (and a chemical reaction

to take place) include the temperature and theconcentration of the reactants, and the presence orabsence of a catalyst

• Catalysts are chemical compounds that speed upchemical reactions by lowering the activation energyneeded for a reaction to occur

• Catalysts are neither consumed nor produced in thereaction– They are used over-and-over again, often several

million times per second

• In a chemical reaction, a catalyst helps to properlyorient the colliding particles of matter so that areaction can occur at a lower collision speed

• A catalyst does not alter the difference inpotential energy between the reactants andproducts (it only lowers the amount of energyneeded to get the reaction started)

Types of Chemical Reactions• Synthesis Reactions• Anabolism- A + B ➙ AB- Two or more atoms, ions, or molecules

combining to form a new, larger molecule- Usually endergonic because they absorb more

energy than they release

N2 + 3H2 2NH3

• Decomposition Reactions• Catabolism- AB ➙ A + B- Large molecule breaks down into smaller atoms,

ions, or molecules

- Usually exergonic because they release moreenergy than they absorb

2H2O2 2H2O + O2

• Exchange Reactions

- AB + CD ➙ AD + CB- The ions in both compounds have

“switched” partners

HCl + NaHCO3 H2CO3 +NaCl

• Reversible Reactions- AB ↔ A + B- Products can revert back to the original

reactants

- Some reactions are only reversible underspecial conditions

- Many reversible reactions in the body requirespecific enzymes to guide the reaction inopposite directions

• Oxidation-Reduction Reactions– Involves the transfer of electrons between atoms

and molecules– Oxidation: the loss of electrons, and in the process

the oxidized substance releases energy– Reduction: the gain of electrons, and in the

process the reduced substance gains energy– Reactions are parallel; when one substance is

oxidized, another is reduced at the same time– Involved the in the break down of food molecules

to produce energy

Clinical Connections• Harmful and Beneficial Effects of Radiation

– Some radioactive isotopes release radiation that can breakapart molecules, producing tissue damage and/or causingdifferent types of cancer• Radon-222, produced during the break down or uranium,

may seep out of the soil and accumulate in buildings. It hasbeen linked to cases of lung cancer

– Other radioisotopes can be used as tracers to follow themovement of certain substances through the body

• Thallium-201 is used to monitor blood flow through theheart during exercise stress tests

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• Free Radicals & Antioxidants

– Sources include exposure to UV radiation, x-rays, and somereactions that occur during normal metabolic processes

– Certain harmful substances, such as carbon tetrachloride can giverise to free radicals when they are metabolized in the body

– Linked to cancer, athrosclerosis, Alzheimer’s, emphysema,diabetes, cataracts, and arthritis (among other disorders anddiseases)

– Antioxidants, substances that inactivate oxygen-derived freeradicals, is thought to slow the pace of damage caused by freeradicals.

• Dietary antioxidants include selenium, zinc, beta-carotene, andvitamins C and E

• Red, blue, and purple fruits and vegetables also contain highlevels of antioxidants

Assignments• Finish Chapter 1 Review WS

• Begin Chapter 2 Review WS• Read Sections 2.4 - 2.5

• Choose five pieces of technology used inscience and brainstorms improvements youwould like to see made to it

• Terminology Quiz next class (1.5)