2: Chemistry of Life

Compound

Made of atoms of 2 or more different elements combined at fixed ratio; table salt in 1:1 ratio NaCl

Compound’s Properties

Depends on its atoms + how they’re bonded together; formic acid’s O attracts H’s elecectrons that releases H+ making it an acid

Protons

# determines atom’s identity/atomic #, single positive electrical charge with mass of 1.7×10^-24g in nucleus

Neutrons

Subatomic particle with no electrical charge with mass of 1.7×10^-24g in nucleus

Element’s Mass #

Sum of protons + neutrons in nucleus, atomic mass approximated using this #

Electrons

Single negative electrical charge with mass of 1/2000th of neutron/proton, moves around nucleus

Electron Distribution

Determines its ability to form bonds/chemical behavior, oxygen has space for 2 more electrons so can form 2 bonds, left-right sequence of elements in each row corresponds to sequential addition of electrons + protons

Electron Energy Levels

Electrons of an atom differ in amounts of potential energy based on distance from nucleus, change in potential energy of electrons can occur only in steps of fixed amounts

Electron Shells

Each has characteristic average distance + energy level

Valence Electrons

Outermost energy shell, atoms interact to “complete” valence shells

Orbital

3D space where electron’s found 90% of time

Isotopes

Two atoms on element with same # of protons but different neutrons, Carbon-12 6 protons/electrons/neutrons, Carbon-13 6 protons/7neutrons/6electrons, Carbon-14 6 protons/8 neutrons/6 electrons

Radioactive Isotopes

Decay spontaneously, give off particles + energy

Radiometric Dating

Parent isotope decays into daughter as fixed rate, ½ life of isotope; measure ration of different isotopes + calculate how many ½ lives have pass since fossil/rock formed

Radioactive Tracers

Diagnostic tools used to track specific atoms through metabolic processes in combination with sophisticated imaging instruments; positron emission tomography (PET) scans detect + monitor cancers

Dalton

1=1 atomic mass unit

Matter

Anything that takes up space + has mass, biotic + abiotic factors, living things made up on non-living components

Atoms

Smallest unit of an element that contains all characteristics of element, building blocks of matter

Element

Any substance that can’t be broken down to any other substance by chemical reactions

Elements in Humans

Oxygen, carbon, hydrogen, nitrogen, calcium, phosphorus, potassium, sulfur, sodium, chlorine, magnesium

Essential Elements

Chemical element required for organisms’ existence

Trace Elements

Required for life, minute quantities; Fe, I

Chemical Bonds

Atoms with incomplete valence shells share/transfer valence electrons with other atoms, held by attractions, covalent bond, ionic bond, hydrogen bond, hydrophobic bond, hydrophobic bond, Van der Waals attraction

Covalent Bond

Sharing pair of valence electrons

Ionic Bond

Attraction of opposite electrical charges, called salts, found in nature as crystals, stable dry, dissolve in water

Table Salt

NaCl, not a molecule, formula for ionic compound indicates ration of elements in crystal salt

Hydrogen bond

Sharing of a H atom

Hydrophobic Interaction

Forcing hydrophobic substance together in presence of polar substance

Van der Waals Attraction

Weak attractions between atoms due to oppositely polarized electron clouds

Covalent Bond

Sharing of pair of valence electrons by 2 atoms, shared electrons count as part of each atom’s valence shell

Molecules

Consist of 2 or more atoms held together by covalent bonds, can be single/double/triple, smallest units of compounds that retain characteristics of compound

Electronegativity

Atom’s attraction for electrons in electron bond, more means stronger pull of electrons

Non-Polar Covalent Bonds

Atoms share electron equally, same element, 2 different atoms of same electronegativity

Polar Covalent Bonds

1 atom has more electronegative, atoms don’t share electron equally, partial positive/negative charge for each atom/molecule

Molecular Form

Determined by positions of atoms’ orbitals, determines function, in covalent bonds s + p orbitals hybridize to create specific molecular shapes

Similar Shape

Similar effects, determines how biological molecules recognize + respond to 1 another, opiates + naturally produced endorphins have similar effects because similar shapes + bind same receptors in brain

Chemical Reactions

Alter bonds, make + break chemical bonds, reactants starting molecules, products resulting molecules

Reaction Influencers

Temperature, concentration of reactions + products, catalysts

Temperature

Heating reactants increase reaction rates as reactants collide with 1 another more often

Concentration of Reactants + Products

Proceed faster when more reactants available for collisions, accumulation of product slows/reverses reactions

Catalysts

Substance that increases reaction rates, enzymes catalyze most reactions needed for life by bringing reactants into close proximity

Reversibility

All chemical reactions theoretically reversible, products of forward reaction become reactants for reverse reaction

Chemical Equilibrium

Reached when forward + reverse reactions occur at same rate, relative concentrations of reactants + products don’t change