Chemistry of Life
Key Elements
• Element: composed of only one kind of atom;
cannot be broken down to a simpler structure.
• Six elements make up 99% of all living tissue –
sulfur, phosphorus, oxygen, nitrogen, carbon,
and hydrogen (SPONCH).
• Carbon is most important because one carbon
atom can make covalent bonds (e- are shared)
with 4 other atoms; carbon is in ALL living
things.
• Organic: contains carbon; Inorganic: no carbon
present (ex- water).
Carbohydrates
• Carbohydrates store energy. The starch
in a potato is a good example. They also
act as structural components, such as the
cellulose that makes a celery stalk stringy
or the chitin that composes the outer
skeleton of a beetle.
carbohydrates
Lipids
• Lipids perform a variety of functions. Fats
store energy. Cell membranes are made
of a type of structural lipid. Sex hormones,
such as testosterone and estrogen, are
made of lipids. The pigment chlorophyll,
which is important in photosynthesis, is a
lipid.
lipids
Proteins
• Proteins are what the cell uses to
translate the information in DNA into cell
products. Proteins act as enzymes, which
are important in making chemical
reactions happen in cells. There are also
structural proteins. Hair and cartilage are
good examples.
proteins
Nucleic Acids
• Nucleic acids include DNA, which carries
genetic information, and RNA, which
translates that information into proteins.
• DNA (deoxyribonucleic acid) directs cell
activities and contains the sugar
deoxyribose.
• RNA (ribonucleic acid) is involved in
protein synthesis and contains the sugar
ribose.
nucleic acids
Cell Composition
•
•
•
•
•
Water – 70%
Proteins – 15%
Fats – 10%
DNA and other materials – 4%
Carbohydrates – 1%
Section 1 Review (p 71 – 72)
• Answer numbers 2-4 in Multiple Choice.
• Answer 1 – 3 in Short Answer.
• Answer 1 – 3 in Fill in the Blanks.
Cellular Respiration
Energy and Chemical Bonds
• Two types of bonds – ionic (electrons are lost or gained
giving an atom a charge; opposite charges attract; metal
and nonmetal); covalent (electrons are shared between
atoms; nonmetal and nonmetal).
• The stronger the bond, the more energy it contains.
• When bonds are broken in the mitochondria, the energy
they contain is released and becomes “free”, or useable,
energy.
• Of the energy used, about 60% is lost as heat, making
respiration about 40% efficient.
ATP (adenosine triphosphate)
• Molecule that serves as chemical energy supply
for all cells.
• Made of adenine, ribose (sugar), and 3
phosphates. Covalent bonds between
phosphate groups contain much energy.
• After ATP breaks down, ADP is formed and
combines with a free phosphate to form a new
ATP molecule. Each ATP molecule is recycled
this way 2000-3000 times per day.
Obtaining Cellular Energy
• Photosynthesis
The process of converting
CO2, H2O, and light energy
into O2 and high energy
sugar molecules.
There are 2 basic stages:
light-dependent and lightindependent reactions (the
Calvin Cycle).
Light-Dependent Reactions
• Happens inside a
chloroplast.
• Plastids engage
in photosynthesis
and store the food
produced.
• Pigments absorb
light.
6H20 + 6CO2 → C6H12O6 + 6O2
• The end products of light-dependent
reactions are ATP, oxygen, and NADPH
(NADP+ is an electron acceptor).
• The ATP and NADPH will be used in the
light-independent reactions, and the
oxygen will be released into the
atmosphere.
Light-Independent Reactions
• Also called carbon fixation reactions.
• Uses the ATP formed in the lightdependent reactions as an energy source.
• Carbon (from CO2) combines with NADPH
to form glucose.
• This glucose can be used as food to enter
cellular respiration or can be converted to
other carbohydrate products (sucrose or
starch).
Cellular Respiration
• The process of breaking down food molecules to
release energy.
• There two types – aerobic and anaerobic.
• Aerobic respiration requires oxygen to proceed;
anaerobic happens without oxygen.
• Energy released by cellular respiration is used to
produce ATP.
• The three phases of cellular respiration are
glycolysis, Kreb’s cycle, & electron
transport.
C6H12O6 + 6O2 → 6CO2 + 6H20 + ENERGY
• The respiration reaction is the opposite of
photosynthesis.
• Respiration occurs in the cells of ALL
organisms.
• Enzymes ARE NOT used.
• The process starts with one molecule of
glucose.
Anaerobic Respiration
• C6H12O6 → 2C2H5OH + 2CO2 + energy
• Takes place WITHOUT oxygen present.
• Also called FERMENTATION.
• Produces ETHANOL (ethyl alcohol) and
lactic acid.
• CO2 released is why bread rises and beer
has bubbles.
Chemosynthesis
• The process by which
inorganic materials are
broken down and energy
released.
• Only happens with
bacteria that live around
thermal vents on the
ocean floor or near
volcanic vents like at
Yellowstone National Park.
Comparing Photosynthesis,
Respiration, and
Chemosynthesis
HAND-OUT
For remainder of class…
• READ pages 74 -76, Catalysts and
Enzymes; Food Energy.
• Take THOROUGH notes.
• Chapter 3 REVIEW, pages 85 – 86.
a. 1 – 18 Multiple Choice
• TURN IN FOR CREDIT