CHAPTER 6: THE CHEMISTRY OF
LIFE
▸WHAT YOU WILL LEARN:
▸1. You will relate the structure of an atom to how it
interacts with other atoms.
▸2. You will explain how water is important to life.
▸3. You will compare the role of carbon compounds in
organisms.
▪WHY IT’S IMPORTANT:
▸Living organisms are made of simple elements as
well as complex carbon compounds. With an
understanding of these elements and compounds,
you will be able to relate them to how living
organisms function.
6.1 Atoms and their Interactions
Both living and nonliving things are composed of the
same basic building blocks called Atoms
▪ I. Elements
▪ Substance that can’t be broken down into simpler
chemical substances.
▪ 90 naturally occurring elements
▪ A. Natural elements in living things
▪
Only about 25 of the Natural occurring
elements are essential to living organisms.
▪ Four out of the 90 make up 96% of a human
▸(1) Carbon
▸(2) Hydrogen
▸(3) Oxygen
▸(4) Nitrogen
▪B. Trace Elements
▸Elements found in living things in very small amounts
▸Plants obtain trace elements by absorption
▸Animals get their trace elements by eating.
Chemical Reactions
Chemical reactions occur when bonds are formed or broken
All the chemical reactions in an organism are referred to as
Metabolism – breaking down and building up
▪A. Writing chemical equations
▸ Reactants – undergo chemical reactions H + O
▸ Products – substances formed by chemical reactions
H2O,Table sugar C12H22O11, glucose C6H12O6
Mixtures and Solutions
A mixture is a combination of substances in which the
individual components retain their own properties
Sand/Sugar
A solution is a mixture in which one or more substances
(solute) are distributed evenly in another (solvent) Kool–Aid
▪ A. Acids and Bases
▸Chemical reactions can occur only when conditions
are right.
▸Temperature
▸Energy
▸ pH
▪ The pH is measure of how acid or basic a solution is.
Scale
0
7
14
Acid
Neutral
Base
H+
0H-
6.2 Water and Diffusion
▪ I. Water and its Importance
▸Most life processes can occur only when molecules and
ions are free to move and collide with one another
▸Water allows movement.
▸A. Water is polar
A polar molecule is a molecule with
unequal distribution of charge.
OH+
H+
▸
Water attracts to water
▪ Hydrogen bonds - attractions between
hydrogen and oxygen
▪
Capillary action
▪B. Water resists temperature changes
Water is like an insulator, helps maintain a steady environment
▪C. Water expands when it freezes
Ice on ponds
Ice breaking rocks
II. Diffusion
Particles of matter are in constant motion, colliding
with each other.
▪A. Early observation: Brownian motion
Brown – pollen grain in water
Dye particles
▪B. The process of Diffusion
▸The net movement of particles from area of high
concentration to areas of low concentration.
▪ Slow process because it relies on random
molecular motion.
▪
Key factors: Concentration
Temperature
Pressure
▪ C. Diffusion in living systems
▸The differsnce in concentrations of a substance across
space is called Concentration Gradients.
▸Diffusion is one way cells move things in and out of
the cell (air/blood)
6.3 Life Substances
“you are what you eat”
▪I. Role of Carbon in
Organisms
▸Single bond shares 1 pair of
electrons
▸Double bond shares 2 pairs of
electrons
▸Triple bond shares 3 pairs of
electrons
Carbon--because of its 4 outer electrons can form:
Straight chains
Branched chains
Rings
Compounds that have the same simple formula (what and
how much) but different structures are Isomers
▪ A. Molecular Chains
▸Carbon compounds vary in size from two carbons to
thousands
▸A polymer is a large molecule formed when many
smaller molecules bond together.
▪ Condensation - water is removed from two smaller
molecules that have H+ and an OH-
▪ Hydrolysis - Polymers are broken apart by the
insertion of a water molecule
▪B. The Structure of Carbohydrates
▸Contain C H O 2H to 1O
▸Monosaccharides – simple sugar
▸( glucose and fructose)
▸Disaccharide – two monosaccharide linked together.
( sucrose)
▸Polysaccharide – polymers composed of many
monosaccharides. ( starch, glycogen, and cellulose )
▪C. The structure of Lipids
▸Contain C H O called fats and oils
▸Used for energy storage, insulation and protective
coatings.
▪ D. The structure of Proteins
▸Contain C H O N
▸Basic building blocks of protein are amino acids.
▸20 common amino acids
▸Peptide bonds hold amino acids together to form
proteins
▪ E. The structure of Nucleic acids
▸Consist of Carbon, Hydrogen, Oxygen, and Nitrogen
Made of smaller units called NUCLEOTIDES
▸A Nucleotide has three groups of molecules:
▸
Five carbon sugar
▸ A phosphate group
▸ A base