Chapter 6
The Chemistry of Life
Elements
n
Everything that
has mass is made of substances called elements
n
Elements are the
different types of atoms
n
You can’t break
them down any further without changing their chemical properties
Elements in Life
n
Big 6 in Life
(not necessarily humans): CHNOPS
n
Carbon, Hydrogen,
Nitrogen, Oxygen,
Phosphorus, Sulfur
n
Trace elements
Atoms
n
An atom is the
smallest particle of an element that has the characteristics of that element
n
The “basic
building blocks of all matter”
n
Atom of gold to
the right
Structure of at Atom
n
Nucleus – center of atom
n
Contains protons
(positively charged particles)
n
And neutrons
(neutrally charged particles)
n
Each element has a distinct number of protons
(the atomic number)
n
Electrons are negatively charged particles that
“orbit” the nucleus
n
Electron clouds
Bohr Model of Atom
n
Simplified way of
showing how electrons orbit the nucleus of an atom
n
2 electrons in
first shell
n
8 electrons in
each subsequent shell
Isotopes
n
Isotopes are
atoms of the same element that have different numbers of neutrons
n
Unstable isotopes
break down to more stable ones and give off radiation
n
Useful
in radioactive dating, atomic bonds, etc.
Compounds & Bonding
n
A compound is a
substance that is composed of atoms of two or more different elements that are
chemically combined
n
Covalent bonds
form when atoms share electrons
n
Stronger bonds
Ionic Bonds
n
Ions are charged
particles
n
They either lose
or gain electrons
n
Ionic bonds are
formed when ions of opposite charges are attracted to each other
Chemical Reactions
n
Chemical
reactions occur when bonds are formed or broken, forming new substances
n
Metabolism refers
to all of the chemical reactions that occur within an organism
Writing Chemical Equations
n
Reactants undergo
chemical reactions and are generally written on the left
n
Products are
substances formed from chemical reactions and are generally written on the
right
n
An arrow
indicates which way the reaction flows (can be a 2-way arrow)
Mixtures & Solutions
n
A mixture is a
combination of substances in which the individual components retain their own
properties
n
i.e. – stirring
sand and sugar together
n
A solution is a
mixture in which one or more substances (solutes) are distributed evenly in
another substance (solvent)
n
i.e. – sugar
dissolving in water & Kool-Aid
Acids & Bases
n
An acid is any substance that forms hydrogen
ions (H+) in water
n
Has a pH below 7
n
A base is any substance that forms hydroxide
ions (OH-) in water
n
Has a pH above 7
Water
n
Life occurs where
water exists
n
Makes up 70-95%
of most organisms
n
Water is polar
n
Polar molecules
have an unequal distribution of charge
n
On atom in the
covalent bond “hogs” the electrons and becomes more negative
n
The other atom
becomes more positive
n
Hydrogen bonds
form between water molecules
n
Weak bond between
two polar molecules
Properties of Water
n
Capillary action
- water an creep up thin tubes
n
Due to polarity
& surface tension
n
Allows water to
go up xylem in plants without using energy
n
Water resists
changes in temperature
n
Helps maintain
homeostasis
Properties of Water
n
Water expands
when it freezes
n
Most things get
more dense
n
Allows ice to
float, to break up rocks into soil
Brownian Motion
n
1827, Scottish scientist Robert Brown looked at
pollen grains in water under a microscope
n
He noticed that they were constantly moving
n
He was observing that all atoms and molecules
randomly move
Diffusion
n
The net movement of particles from an area of
higher concentration to an area of lower concentration
n
Occurs due to Brownian Motion
n
Diffusion is slow
n
Can be sped up by
n
Increased Concentration
n
Increased Temperature
n
Increased pressure
Diffusion
n
Equilibrium is met when there is continuous
movement but no overall concentration change
n
Diffusion occurs into and out of cells
constantly
Carbon
n
Single Bond – two
atoms share one pair of electrons
n
Double Bond – two
atoms share 2 pairs
n
Triple Bond – two
atoms share 3 pair
n
Every organic
molecule has carbon
n
Carbon is unique
because it has 4 “empty spots” in it’s outer shell and can share an electron
with up to 4 other atoms
Biomolecules
n
Biomolecules are large organic compounds
n
Polymers are
large molecules formed when many smaller molecules bond together
n
The Main Ones
n
Carbohydrates
n
Lipids
n
Proteins
n
Nucleic acids
Carbohydrates
n
Biomolecule composed of carbon, hydrogen, and oxygen in a ration
of about 2 hydrogen atoms and 1 oxygen atom for every carbon
n
Monosaccharide
n
Simplest
carbohydrate – a simple sugar
n
Glucose &
fructose
n
Disaccharide
n
Combine two monosaccharides
n
Glucose +
fructose = sucrose
Carbohydrates
n
Polysaccharides
n
Polymers composed of many monosaccharides
n
Glycogen – storage form in animals
n
Starch – storage form in plants
n
Cellulose – Cell walls & structual
support
Lipids
n
Large biomolecules that are made mostly of carbon and hydrogen
with a small amount of oxygen
n
Include fats,
oils, waxes and steroids
n
Fatty acids are
common lipids
n
Fatty acids
linked with glycerol
n
Can be saturated
(all single bonds – more solid)
n
Monounsaturated
(one double bond)
n
Polyunsaturated
(multiple double bonds – more liquid)
Lipids
n YOU NEED FAT!
n Lipids store energy, insulate, provide protective
coverings
n Steroids are “messengers”
Proteins
n A large, complex polymer composed of carbon, hydrogen,
oxygen, nitrogen and sometimes sulfur
n Provide structure for tissues and organs
n Carry out cell metabolism
Structure of Proteins
n
Amino acids are
the building blocks (monomers) of proteins
n
There are 20
common amino acids
n
Amino acids are
joined by peptide bonds
n
Water is removed
n
There are many
“levels” to a protein formation
n
Different turns,
twists, etc in the protein can change it’s function
Proteins – Enzymes
n
Enzymes are proteins
that function as a catalyst
n
Speed up the rate
of a chemical reaction
n
Essential
to make reactions go fast enough to keep organisms alive.
Nucleic Acids
n
Complex biomolecule
that stores cellular information in the formation of a code
n
Polymers of nucleotides
n
Used to store and transfer information
Nucleic Acids
n DNA – double stranded
n Contains “master code” for an organism
n RNA – single stranded
n Carries information to help make proteins