Chapter 2
Chemical level of structural organization… Lowest level of body organization Atoms build molecules and form matter Atoms and molecules release and store energy in chemical reactions

Chemistry Science of structure and interactions of matter All body activities are chemical in nature
Energy for life ATP Atom A + Atom B A-B
Can make ATP from glucose element element chemical bond
Catabolism: Need to break chemical bond to use energy (ATP)
Anabolism: making the bond

Matter: occupies space and has mass in 1 of 3 states… Solids: bones & teeth Liquids: blood plasma Gases: oxygen, carbon dioxide
Chemical Elements (designated by letters) Building block of matter, can’t be subdivided by ordinary chemical means *major ones in the body (96%) are Oxygen, Carbon, Hydrogen, and Nitrogen Others (3.8%) are Ca, P, K, S, Na, Cl, Mg, Fe Trace elements (0.2%) are 14 other elements

Structure of Atoms…
Atoms: building blocks of element
Subatomic particles; proton (+ charge), neutron (uncharged), electron (-charge)
Atomic Structure… Atomic core or nucleus – protons and neutrons Electron shells – moving could of electrons around nucleus Element is electrically neutral with equal number of protons and electrons
*As long as the proton number stays the same it is safe, if it changes it is harmful

Differences among atoms…
Atomic number Number of protons in nucleus (same for all atoms of 1 element)
Mass number Sum of an atom’s protons and neutrons
Isotopes (atoms of same element may have different numbers of neutrons, thus different mass numbers
Atomic mass (also called atomic weight) Average mass of all its naturally occurring isotopes measured in unit called a Dalton

Ions, molecules and compounds…
Ions
Atom that has a + or – charge due to the loss or gaining of electrons + ion: cation - ion: anion
*Molecules
Two or more atoms that share electron;
*Compounds
Molecule that contains two or more different elements:
Free radical Electrically charged atom or group of atoms with unpaired electron in outermost shell Unstable and highly reactive with other molecules in body Usually result of oxidation which involves oxygen
**All compounds are molecules but not all molecules are compounds**
Chemical bonds…
Forces that hold atoms together in molecules and compounds
Octet rule Predicts how atoms will interact based on the number of electron in valence shell (outermost) Electron distribution in valence shell determines kind of bond that will form Atom is chemically stable if valence shell is full, holding 8 electrons Atoms will interact to gain 8 electrons by… Emptying partially filled valence shell….+ charge ionic bond Filling valence shell with donated electron…-charge ionic bond Sharing electrons with another atom…covalent bond (strongest bond)
Ionic bonds
Ions (charged) Formed when atoms loose or gain 1 or more valence electrons Cation (Na+, K+, Ca2) positively charged ion that lost electron(s) Anion (Cl-) negatively charged ion that gained electron(s) Ionic bond Attraction between oppositely charged atoms Ionic compounds are normally solid, often crystals Forms electrolytes when break apart in solutions
*electrolytes: anything that breaks down into charged portions
Covalent bonds
Formed between atoms that share a pair of valence electrons to fulfill octet rule rather than gain or lose electron
Most common kind of bond in the body
Bond strength depends upon number of electron pairs shared: single, double or triple bonds; ex: ATP
Types…
Non polar covalent bonds: atoms share electron equally; form lipids/ no charge/ hates water
Polar covalent bonds: atoms share electrons unequally; 1 nucleus attracting electron more strongly than other results in partial + and – charge; H2O is polar/ H2O likes anything polar/protein and carbs
Hydrogen bonds
Specific type of covalent bond between H and other atoms
Partial +