Biological ReactionsPage 32

Reactions • The major classes of macromolecules consist of carbohydrates, proteins,

nucleic acids and lipids.• Most macromolecules are polymers (a large unit composed of smaller

subunits).• Chemical reactions are necessary to bring subunits together or break

them apart.• Other reactions are used in various biological processes to maintain

proper biological function.

Acid-Base Reactions• Acids – increase concentration of hydrogen ions in solution• Base – increase concentration of hydroxide ions in solution• Neutralization reactions: acid and base react to form a salt and water.• Body must maintain a certain pH in order for reactions to occur. Eg. If the

blood is too acidic or basic, illness and even death, results.• Buffers – maintain pH levels by releasing/taking up hydrogen ions. Eg.

Carbonic acid and hydrogen carbonate ion buffer system.

Oxidation-Reduction Reactions

• Based on transfer of electrons between molecules• Oxidized – losing electrons (becoming more positive)• Reduced – gaining electrons (becoming more negative).• When one molecule is oxidized, another must be reduced – reactions

always occur together! REDOX!!• Combustion is a form of redox.

– The hydrocarbon is oxidized to become carbon dioxide (loses electrons via hydrogen)

– The oxygen is reduced to become water (gains electrons via hydrogen).

Condensation Reaction• Creates a covalent bond between 2 subunits.• H is removed from one subunit and – OH is removed from the other.• Water is formed and energy is absorbed.• It is an anabolic reaction because a large molecule is built from smaller

subunits.

Breaking apart - Hydrolysis

• Catabolic reactions break larger molecules into individual parts.• It is the reverse of a condensation reaction.• Water is used to break the covalent bond• H is provided to one subunit and –OH to the other.• Energy is released.• Enzymes are used to make these reactions occur efficiently.• http://science.nhmccd.edu/biol/dehydrat/dehydrat.html

Internet Resources• http://library.thinkquest.org/C006669/data/Biol/carbon_2.htm• http://www.zerobio.com/functional.htm

Questions• Page 36: #25-30