Chemistry in Biology

Element – a pure substance that can’t be broken down into a simpler form of matter * see THE PERIODIC TABLE of ELEMENTS *

• ATOM -The simplest particle of an element that retains the properties of that element

Sub-atomic particle

Charge

Proton +1

Neutron 0

Electron -1

In Nucleus →

In Nucleus →

Elements Found in Living Things

• Carbon (C) 18.5%• Hydrogen (H) 9.5%• Oxygen (O) 65%• Nitrogen (N) 3.3%• Phosphorus (P) 1.0%• Sulfur (S) 0.3%

Others… K, Ca, Na

• Compound – A substance containing atoms of 2 or more elements bonded together

Covalent Bond → electrons are shared

Ionic Bond → electrons are transferred

BONDING

COVALENT BOND

IONIC BOND

WATERRemember: Electrons are shared in a covalent bond

*** But not necessarily shared evenly

• A molecule is said to be POLAR if it has an uneven charge distribution like this

Characteristics of POLAR Compounds:

• Hydrogen Bonding• Attraction (“polar likes polar”)• Temperature Moderation• Water’s Surface Tension

SOLUTIONS• A mixture of 2 or more substances• Uniformly distributed • SOLUTE dissolved into a SOLVENT• CONCENTRATION – a measurement of the amount

of solute dissolved in a fixed amount of solvent

• A solution is saturated when no more solute can dissolve

• AQUEOUS SOLUTION – a solution in which water is the solvent

*** THINK ABOUT LIVING SYSTEMS *** (your body cells!)

Potential of Hydrogen• A water molecule can break up (dissociate)

2 H20 ↔ H30+ + OH-

(Hydronium ion) + (hydroxide ion)

• ACID SOLUTION – hydronium ions outnumber hydroxide ions• BASE SOLUTION – hydroxide ions outnumber hydronium ions

(a.k.a. alkaline solution)

pH scale

acidic neutral basic]____________________________________________[0 7 14

stomach acid Urine Water Intestinal Fluid

Organic Compounds

• Carbon can make 4 bonds • Organic compounds have a carbon backbone

STRUCTURE:• Monomer – single, simple structural unit• Polymer – repeated, linked chain of monomers

Condensation Reaction – • Forms polymers; water molecule is given off in the process

Hydrolysis Reaction –• Breaks polymers; water molecule is used in the process

GLUCOSE

Condensation (dehydration synthesis)

Hydrolysis

ENERGY TRANSFER Reactants → Products

• BUT: Not all reactions were created equalExergonic/Exothermic –• A chemical reaction that results in a

release of energy Endergonic/Endothermic –• A chemical reaction that results in an

absorption of energyActivation Energy - • The energy needed to start a reaction

CATALYST - • A substance that reduces the

activation energy of a reaction

ENZYME - • Acts as a catalyst in a living system• Usually a protein

ENERGY CURRENCY The energy currency for the cell is a molecule called …Adenosine Triphosphate (ATP)

A = Adenosine ATP = A ~ P ~ P ~ P

P = Phosphate ADP = A ~ P ~ P

~ = chemical bond AMP = A ~ P

Breaking of a bond (~) in ATP releases energy (EXERGONIC)

A~P~P~P → A~P~P + P + ENERGY

Making of a bond (~) in ATP“bottles up” energy for later use(requires energy input)

A~P~P + P + ENERGY → A~P~P~P