Chapter 2: Chemistry of Life

Building Blocks of MatterThe basic unit of matter is the atom

◦Atoms are made of subatomic particles: protons (+), electrons (-), and neutrons

◦Protons and neutrons reside in the nucleus

◦Electrons move around in orbitals outside of the nucleus

Atoms of the same element but with different neutrons are isotopes◦Carbon-12, Carbon-13, Radioactive

Carbon-14

Building Blocks of MatterTwo or more elements can combine to

form compounds (H2O)

◦Ionic bonds hold a compound together by a transfer of an electron leading to charged elements (NaCl)

◦Covalent bonds involve sharing of electrons between elements (H2O)

Building Blocks of LifeElement – Substance that can’t be

broken down into simpler chemical substances.

Carbon - the element of life as it can combine with other elements and with itself to form long complex structures. It must have 4 bonds.

MacromoleculesMacromolecules – big molecules

Monomers – small subunits (building blocks) of large molecules, ex. Glucose is the monomer of starch, a polymer

Polymer- made of many molecules, ex. proteins, nucleic acids

CarbohydratesMain source of energy for living

organisms (glucose)Organisms store energy as complex

carbohydrates called starches

CarbohydratesMonosaccharide – single sugar.

Polysaccharide – large molecules formed from monosaccharides.

LipidsComposed predominately of

carbon and hydrogen atoms (limited oxygen)

Includes fats, oils, waxes, steroids

Composed of glycerol and fatty acids

Lipids

Nucleic AcidsComposed of monomers called

nucleotides◦Composed of 5-C sugar, phosphate

group, and a nitrogenous base◦Joined together to form nucleic acids:

ribonucleic acid (RNA) and deoxyribonucleic acid (DNA)

Store and transmit hereditary (genetic) information

Nucleic Acids

ProteinsContain nitrogen, carbon, oxygen, and

hydrogenMonomer: amino acids20 different amino acids are found in

nature, leads to significant diversity in proteins

ProteinsProteins are the doers of life

◦Controls rates of reactions◦Regulate cells processes◦Form bones and cells◦Transport substances into and out of

cells

Proteins

Organic MacromoleculesCompound Subunit(s) Elements Function ExamplesCarbohydrates 

Glucose or sugar

C, H, O Main energy source

Structure 

glucose, starch, cellulose, glycogen

Lipids(fats & oils)

Glycerol and 3 fatty acids

C, H, O Energy storage Protective

coverings

Phospholipids, steroids

Proteins 

Amino acids

C,H,O,N, & usu. S

Muscles/bones/ structure

Control reaction rates

Regulation Transport

substances Fight disease

Insulin, enzymes, hemoglobin, muscle fibers

Nucleic acids 

Nucleotides C, H, O, N, P

Store and transmit genetic information

DNA, RNA

Chemical ReactionsChemical reactions involve the

breaking of bonds in reactants and the formation of new bonds in products◦Those entering the reaction are

reactants◦Products are produced by the

reaction

Chemical ReactionsEquations must balance. Atoms are not

created or destroyed, just rearranged.

Example: 2H2 + O2 2H2O

Reactants are on the left and enter into the reaction.

Products are on the right and result from the reaction.

Metabolism – All of the chemical reactions that occur within an organism.

Energy in Reactions2H2 + O2 2H2O

◦Occurs naturally, releasing energy◦The reverse reaction: 2H2O 2H2 +

O2 requires so much energy it rarely occurs

Chemical ReactionsActivation energy – energy needed to get a

reaction started.Catalyst – substance that speeds up the rate

of a chemical reaction.

Enzymes – proteins that speed up chemical reactions because they lower the activation energy. Enzymes provide a site where reactants can be brought together. (This reduces the energy needed for the reaction, called activation energy).

Substrate – the reactant(s) the enzymes fit.

Enzymes

Enzymes

EnzymesEnzymes can be affected by any

variable that affects chemical reactions including temperature and pH

Enzyme activity are regulated by cells often by turning them on or off

Characteristics of EnzymesSpecific (a special shape; use induced

fit)ReusableNot consumed (used) in the reactionAffected by factors such as pH and

temperature.

Enzymes are specific because they are proteins made by folding into a 3-D shape (linked to their function).

Properties of WaterAlthough water is neutral, it does have

polarity◦Water molecule is polar because of

uneven distribution of electrons◦The oxygen end has a slight negative

charge◦The hydrogen end has slight positive

charge

Properties of WaterDue to its polarity, water can

hydrogen bond with itself (attract itself)◦Weaker than ionic bonding (NaCl)◦Cohesion is attraction of molecules

of same substance (beads of water)◦Adhesion is attraction of molecules

of different substances (water and graduated cylinder)

Properties of WaterWater is not always pure, it is often

found as a mixture (material composed of two or more elements or compounds that are not chemically combined)◦If the materials are evenly

distributed it is called a solution◦The substance that is dissolved is

the solute◦The substance that dissolves is the

solvent

Properties of WaterWhen material does not dissolve a

suspension is formed◦Example: blood cells and water◦The movement of the water keeps

the small particles suspended

Acids and BasespH – A measure of how acidic or basic a

solution is. Scale is 0 to 14. Below 7 is acidic. Above 7 is basic. 7 is neutral

Acidic solutions have higher concentration of H+ ions than pure water (pH 7)

Basic solutions have a lower concentration of H+ ions than pure water

Buffers – prevent sharp, sudden changes in pH

Acids and Bases

Acids and Bases