Chapter 2: Chemistry Comes Alive (pt 1)

Energy

capacity to do work or put matter into motion

Types of Energy

Kinetic - energy in action

Potential - stored energy

Chemical Energy

stored in bonds of chemical substances

Electrical energy

results from movement of charged particles

Mechanical energy

directly involved in moving matter

Radiant or electromagnetic energy

travels in waves (ex. visible light, ultraviolet light, x-rays)

Major Elements of Human Body

CHON - 96.1% of body mass

Lesser Elements of Human Body

Ca, P, K, S, Na, Cl, Mg, I, Fe - 3.9%

Trace Elements of Human Body

Cr, Cu, F, Mn, Si, Zn

When atoms gain electrons…

the atoms become negatively charged

Chemical Bonds

Electrons can occupy up to 7 electron shells around nucleus

Electrons in valance shell…

have most potential energy and are chemically reactive electrons

Octect rule

have 8 electrons in valence shell except for first shell (has 2 electrons)

Chemically inert elements

outermost energy level complete

Chemically reactive elements

outermost energy level incomplete

Covalent bonds

electrons are shared between atoms

Types of Chemical Bonds

iconic, covalent, hydrogen

Iconic Bonds

• Attraction of opposite charges

• anion - negative, cation - positive charged

• Complete transfer of electrons

• Shape: crystal lattice

Bond Types

C (single bond), O (double bond), N (triple bond)

Nonpolar Covalent

electrons shared equally

CO2 properties

• shape: linear and symmetrical

• non polar

• O=C=O

Atoms tend to be electronegative if…

it lacks only 1-2 electrons in the valence shell

Polar Covalent Bonds

Unequal sharing of electrons (positive and negative end)

Electronegative

• strong electron-attracting ability

• atoms with only 6-7 VE

Electropositive

Atoms with only 1-2 VE (ex. H)

Hydrogen Bonds

• attractive force between H and EN atom of another molecule (opposite charge attractions)

• common between dipoles (ex. water)

• acts as intramolecular bonds

Patterns of Chemical Reactions

synthesis, decomposition, exchange

Synthesis Reactions

• Molecules combine to form large molecule

• anabolic

• bond formation

• A + B → AB

• endergonic

• ex. amino acids to form proteins

Decomposition Reactions

• Molecules break down into small molecules

• catabolic

• breaking bonds

• AB → A + B

• exergonic

• ex. glycogen broken down into glucose

Exchange Reactions

• Displacement Reaction

• Involve both synthesis and decomposition

• Bonds made and broken

• AB + C → AC + B

• ex. ATP transfer glucose to form glucose-phosphate

Oxidation-Reduction (Redox) Reaction

• decomposition and exchange reactions

• electron donors (lose electrons = oxidized)

• electron acceptors (receive electrons = reduced)

• Ex. C6H12O6 → 6CO2 + 6H2O + ATP

  • glucose oxidized, oxygen molecule is reduced

Energy Flow in Chemical Reactions

• exergonic: release of energy

  • products have less potential energy than reactants

  • catabolic and oxidative rxns

• endergonic: absorption of energy

  • products have more potential energy than reactants

  • anabolic rxns

Reversible Reactions

• all chem rxns theoretically reversible

• A + B → AB → A + B

Irreversible Reactions

due to energy requirements and removal of products

Affects Rate of Chemical Reactions

• temperature

• concentration of reactant

• decreased particle size

• catalysts (enzymes are biological catalysts)