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Unit 3:CELLS
Cellular Energy
Carbon Compounds
Objective
• What are the functions of each
group of organic compounds?
Interest Grabber
Section 2-3
Life’s backbone
• Most of the compounds that make up living
things contain carbon. In fact, carbon makes
up the basic structure, or “backbone,” of these
compounds. Each atom of carbon has four
electrons in its outer energy level, which
makes it possible for each carbon atom to
form four bonds with other atoms.
• As a result, carbon atoms can form long
chains. A huge number of different carbon
compounds exist. Each compound has a
different structure. For example, carbon chains
can be straight or branching. Also, other kinds
of atoms can be attached to the carbon chain.
Methane
Acetylene
Butadiene
Benzene
Isooctane
Macromolecules “giant molecules”
• Formed by a process called
polymerization
Monomers
• Smaller units
Polymers
• Linked up monomers
Carbohydrates
• Compounds made up of carbon,
hydrogen, and oxygen atoms
usually in a ratio of 1:2:1
• Main source of energy
• The monomers of starch are
sugars
• Single sugar molecules are called
monosaccharides
• The large macromolecules
formed from monosaccharides
are known as polysaccharides
Starch
Glucose
Lipids
• Made mostly from carbon and
hydrogen atoms
• Used to store energy
Lipid
Fatty Acids
Glycerol
Proteins
• Macromolecules that contain
nitrogen as well as carbon,
hydrogen, and oxygen
• Proteins are polymers of
molecules called amino acids
Amino Acids
Carboxyl group
General structure
Alanine
Serine
• More than 20 different amino
acids, can join to any other amino
acid
• The instructions for arranging
amino acids into many different
proteins are stored in DNA
• Each protein has a specific role
• The shape of proteins can be very
important
Proteins
Amino
Acids
Nucleic Acids
• Macromolecules containing hydrogen,
oxygen, nitrogen, carbon, and
phosphorus
Double
Helix
Nucleotides
• Consists of 3 parts: 5-carbon sugar,
phosphate group and nitrogen base
Nitrogen Base
Phosphate
group
5-Carbon Sugar
2 kinds of nucleic acids
• RNA (ribonucleic acids) –
contains sugar ribose
• DNA (deoxyribonucleic acid) –
contains sugar deoxyribose
Homework
1. Name four groups of organic compounds
found in living things
2. Describe at least one function of each
group of organic compounds
3. Compare the structures and
functions of lipids and starches
Chemical Reactions and
Enzymes
Objectives
• What happens to chemical bonds
during chemical reactions?
• How do energy changes affect
whether a chemical reaction will
occur?
• Why are enzymes important to
living things?
The Big Idea
• Living things are made up of
chemical compounds
• Everything that happens to an
organism is based on chemical
reactions
Chemical Reactions
• A process that changes or
transforms one set of chemicals
into another
Reactants
• Elements or compounds that
enter into a reaction
Products
• Elements or compounds
produced by a chemical reaction
Example Reaction: Getting
rid of carbon dioxide
• In the blood
CO2 + H20  H2CO3 (carbonic acid)
• In the lungs
H2CO3  CO2 + H2O
Released as you
breathe
Energy in reactions
Energy-Absorbing Reaction
Energy-Releasing Reaction
Activation
energy
Products
Activation energy
Reactants
Reactants
Products
Activation Energy
• The energy that is needed to get
a reaction started
Enzymes
• Some chemical reactions are too
slow or have activation energies
that are too high to make them
practical for living tissue
• These chemical reactions are
made possible by catalysts
Catalyst
• Substance that speeds up the
rate of chemical reactions
• Work by lowering a reactions
activation energy
Enzyme
•
•
•
•
•
Biological catalysts
Speed up reactions in cells
Very specific
Named for the reaction is catylzes
Enzyme names always end in ase
Reaction pathway
without enzyme
Activation energy
without enzyme
Reactants
Reaction pathway
with enzyme
Activation
energy
with enzyme
Products
Substrates
• The reactants of enzyme
catalyzed reactions
• The active site of the enzyme and
the substrate have
complementary shapes
• Fit like a lock and key
Enzyme Action
Enzyme – substrate complex
ADP
Enzyme
(hexokinase)
Glucose
Substrates
Products
ATP
Glucose-6phosphate
Products
are released
Active site
Enzyme-substrate
complex
Substrates
are converted
into products
Substrates
bind to
enzyme
Regulation of Enzyme Activity
• Enzymes are affected by any
variable that affects chemical
reactions
1. pH
2. Temperature
3. Concentration
of enzyme
Homework
1. What happens to chemical bonds
during chemical reactions
2. Describe the role of energy in
chemical reactions
3. What are enzymes, and how are
they important to living things?
4. Describe how enzymes work,
including the role of the enzyme
substrate complex
5. A change in pH can change the
protein. How might a change in pH
affect the function of an enzyme such
as hexokinase (hint: think about the
analogy of the lock and key)