Chemistry of Life/ Carbon
Compounds
Chapter 10, Lessons 1 & 2
Elements of Life
• Biomass is the total mass of all living
matter on Earth, which is made up mostly
of the elements sulfur, phosphorus,
oxygen, nitrogen, carbon, and hydrogen
(SPONCH)
– 96% of which is hydrogen, oxygen, nitrogen,
carbon (HONC)
• Living organisms obtain these elements
from their environments.
Cycles in Life
• All of the elements essential to life flow
through food webs that are part of natural
cycles.
• The carbon cycle describes how carbon
moves from the atmosphere into plants
(where it is used to provide energy) , into
animals that eat plants, and into the
environment as waste from animals.
Carbon Cycle
• Plants obtain carbon from atmospheric
carbon dioxide to make sugar molecules to
store energy.
• Animals eat the plants or other animals to
obtain carbon.
• Carbon dioxide is a waste product of
breathing.
• When fossil fuels are burned, they release
carbon dioxide into the atmosphere.
Carbon Cycle (cont’d)
Nitrogen cycle
• Plants cannot use atmospheric nitrogen.
• Bacteria in the soil ‘fix’ nitrogen, changing
it to a form that plants can take up through
their roots.
• Plants use the nitrogen for building cells.
• Animals eat the plants and nitrogen is
passed on.
• Nitrogen is also passed on when one
animal eats another.
Nitrogen Cycle (cont’d)
• The cycle is complete when decomposers
break down dead organisms and return
the nitrogen to the soil.
Phosphorus Cycle
• Natural processes break down rocks
containing phosphorus.
• Plants absorb phosphorus through
their roots.
• Consumers obtain phosphorus by eating
plants or animals that have eaten plants.
Water and Living Organisms
• In addition to the elements that make up living
tissue, living organisms cannot survive without the
compound water.
• Essentially, all of life’s processes occur in a water
mixture.
– The fluid properties of water allow blood to flow and
carry substances through the body. The liquid
portion of blood, called plasma, is 90% water.
– Water requires more heat than other liquids to
change temperature, which protects living organisms
from temperature changes.
– Solid water is less dense than liquid water. Ice,
therefore, floats on liquid water and provides a
protective layer for organisms living in water.
Polar Molecule
• Water is a polar molecule, which makes it
an excellent solvent for other polar
molecules necessary for living organisms.
– A polar molecule is a molecule that has a
positive end and a negative end because of an
unequal sharing of electrons between its
molecules.
– A nonpolar molecule is a molecule that shares
electrons equally and does not have oppositely
charged ends.
Polar Molecule (cont’d)
• Individual water
molecules act like
magnets.
• The positive end
attracts the negative
end of other water
molecules.
• This weak bonding is
known as hydrogen
bonding.
Life-Sustaining Properties of
Water
Organic Compounds
• An organic compound is one of a large
group of compounds that always contain
carbon.
• Most of the compounds in living cells are
organic compounds, but not all carbon
compounds are organic compounds.
Carbon Bonding
• Carbon has atomic
number 6 = 4 valence
electrons.
• Carbon can bond to
itself and other
elements in many
different ways
(chain, branched,
ring).
• Carbon can always
make up to 4 bonds.
• Carbon is unusual
because it can form
double and triple
covalent bonds.
Hydrocarbons
• Molecules that contain only carbon and
hydrogen atoms are called hydrocarbons.
• They are flammable and burn easily –
used for fuels.
• Isomers – different arrangement of a
formula. *Butane (C4H10) *Isobutane
(C4H10)
Butane
Isobutane
Hydrocarbons- Saturated vs.
Unsaturated
• Saturated CH have all
single bonds and are
saturated with
hydrogens. (names
end in –ane)
• Unsaturated CH
contain double or
triple bonds and fewer
hydrogens. (names
end in –ene or –yne)
Ethene
Substituted Hydrocarbons
• A functional group is a group of atoms
that replace a hydrogen atom in organic
compounds.
– A functional group changes the properties of an
organic compound from the original
hydrocarbon on which it is based.
• Organic compounds that contain a
functional group are called substituted
hydrocarbons.
Hydroxyl Group
• A hydroxyl group contains an oxygen atom
and a hydrogen atom covalently bonded to
one another (-OH).
• A hydrocarbon substituted with a hydroxyl
group is called an alcohol
• Nonpolar hydrocarbons do not dissolve in
water, but by adding a hydroxyl group,
water-soluble compounds are formed.
Carboxyl Group
• Carboxylic acids contain the carboxyl
group, –COOH, where the carbon is
double-bonded to one of the oxygen
atoms.
– Aspirin is a carboxylic acid, as is lactic acid.
Amino Group
• Amino groups contain a nitrogen atom and
two hydrogen atoms, –NH2.
• Compounds that contain the amino group
are called amines.
– Many amines, such as histamine and thiamine,
end with the suffix –amine.
Amino Acids and Proteins
• Substituted hydrocarbons with both an
amino functional group and a carboxylic
functional group are called amino acids.
– An amino acid is a member of a class of
organic compounds that are the basic building
blocks of proteins.
– Twenty common amino acids are used in your
body to create different protein molecules.
Human cells can create 11 of the 20 common
amino acids, but you must get the other nine
common amino acids from the foods you eat.
Shapes of Molecules
• Models can be used to
understand the
shapes of molecules.
• The three-dimensional
shapes of molecules
help explain the
properties of the
compounds that
consist of those
molecules.
• Tetrahedral molecules
are shaped like
pyramids.
Shapes of Molecules (cont’d)
• Planar molecules are flat like sheets
of paper.
Shapes of Molecules (cont’d)
• Linear molecules are arranged in a line.
Lesson Review Questions
1) Which is one of the six
elements that make up
most of Earth’s biomass?
A
helium
B
iron
C
nitrogen
D
sodium
Lesson Review Questions
2) Water is a polar molecule
because ____.
A it has a negative charge
B it has a covalent bond
with unequal sharing
of the electrons
C it has a positive charge
D it has an ionic bond
Lesson Review Questions
3) Where do plants obtain nitrogen
for cellular activities?
A from the air
B from decaying organisms
C from animal waste
D from nitrogen-fixing
bacteria in the soil
Lesson Review Questions
4) Which of the following
is the amino group?
A
–OH
B
–NH2
C
–COOH
D
CH4
Lesson Review Questions
5) Which type of molecule is like
a flat piece of paper?
A planar
B linear
C cubic
D tetrahedral
Lesson Review Questions
6) How many possible covalent
bonds can carbon form?
A one
B two
C three
D four