2.3: CarbonBased Molecules
Carbon-based
molecules are the
foundation of life.
Bonding Properties of Carbon
• Carbon forms covalent bonds with up to
four other atoms, including other carbon
atoms.
1
3, 4
2
Structure of carbon-based
molecules…
• Three general types:
1. straight chain
H H Cl H H
| | | | |
H - C- C - C - C - C - H
| | | | |
H H H H H
3-chloropentane
Structure of carbon-based
molecules…
• Three general types:
2. Branched chain
Structure of carbon-based
molecules…
• Three general types:
3. Ring
• Many carbon-based molecules are made of
many small subunits bonded together.
– Monomers are the individual subunits.
– Polymers are made of many monomers.
Four Types of CarbonBased Molecules
Carbohydrates
Lipids
Proteins
Nucleic Acids
ALL four are found in LIVING things.
Carbohydrates
• Organic molecules
made of the elements
carbon, hydrogen, and
oxygen (CHO)
• Includes sugars and
starches
• Pasta, bread, and fruit
are high in
carbohydrates
Structure of Carbohydrates
• Monomer
• Monosaccharides
– “saccharide” means
sugar
– simple sugars
– Glucose, galactose,
fructose
Structure of Carbohydrates
• Disaccharide
• Two
monosaccharide
molecules bonded
together
• Sucrose, or table
sugar, made of one
glucose and one
fructose molecule
Structure of Carbohydrates
• Polymer
• Polysaccharides
– Chains of
monosaccharides
– starches,
cellulose, and
glycogen
Function of Carbohydrates
• Can be broken down to
provide energy for cells.
– Glucose-main source of energy
for cells, product of
photosynthesis
• Provide us with energy
– Sugar rush then crash
• Some carbohydrates are part
of cell structure.
– Cellulose-makes up the cell wall
of plant cells
LIPIDS
• Organic molecules made
of the elements carbon,
hydrogen, and oxygen
(CHO)
• Nonpolar molecules
–Do not dissolve in water
• Include fats, oils,
cholesterol, and wax
Structure of Lipids
• Fatty acids bonded to
glycerol.
– Glycerol-3 hydroxyl
groups
– Fatty acids-long carbon
chains
 Two different types of
fatty acids found in
fats and oils:
oSaturated fatty acids
oUnsaturated fatty
acids
Two Types of Fatty Acids
Functions of Lipids
• Used for long term energy
storage
• Make up cell membranes
– Phospholipid bilayer
• Used to make hormones
– Testosterone (males) & estrogen
(females)
• Insulate and waterproof
organisms
– Cutin-waxy substance that
coats leaves of plants to
help prevent water loss
Lipid Polymer-Phospholipid
• Consists of glycerol,
two fatty acids
(nonpolar tails) and
a phosphate group
(polar head of
molecule)
• Makes up ALL cell
membranes
Lipid Polymer-Triglycerides
• Consists of glycerol and
three fatty acids
• Type of fat found in your
blood.
– Your body uses them for
energy.
• You need some
triglycerides for good
health.
– But high triglycerides can
raise your risk of heart
disease and may be a sign
of metabolic syndrome
Nucleic Acids
• EXTREMELY long
carbon-based
molecules made of
carbon, hydrogen,
oxygen, nitrogen,
and phosphorus
(CHONP)
Structure of Nucleic Acids
• Monomer
A phosphate group
– Nucleotide
• made of a five-carbon
sugar, phosphate
group, and a nitrogen
base.
• 5 kinds: Adenine,
Thymine, Cytosine,
Guanine, & Uracil
• Polymers
– DNA-Deoxyribonuleic
Acid
– RNA-Ribonucleic Acid
deoxyribose (sugar)
nitrogen-containing
molecule,
called a base
Function of Nucleic Acids
• DNA stores genetic
information
• RNA builds proteins
using information from
DNA
DNA
RNA
Proteins
• Large organic molecules
made of carbon,
hydrogen, oxygen, and
nitrogen (CHON)
• Essential to all life
• Foods high in proteins:
– Poultry, fish, eggs,
beans, nuts, peanut
butter, milk
Structure of Proteins
• Monomer
– Amino acid
• Contain an amino group and
a carboxyl group
• Interact to give a protein its
shape and function
• Peptide bonds form
between amino acids to
form chains
• Organisms use 20 different
amino acids to build
proteins
– Your body makes 12,
others come from food
you eat
Structure of Proteins
• Polymer
– Protein
– Also called polypeptide
• Each protein has a
different arrangement of
amino acids
• Incorrect amino acid
sequence and/or
arrangement changes
the protein’s structure
and function
Function of Proteins
• Building and connecting materials of living
things
– Collagen-forms bones, tendons, ligaments, and
cartilage
• Take part in chemical reactions and transport
materials
– Hormones, antibodies, and enzymes
Function of Proteins
• Longer-lasting energy source than
carbohydrates because broken down more
slowly
• Involved in eyesight, digestion, etc. as well
2.5: Enzymes
Enzymes are catalysts for chemical reactions in
living things.
Chemical Reactions
• Substances are
changed into different
substances by
breaking and forming
chemical bonds
– Reactants are changed to form
products
• Cell growth,
reproduction,
interaction with the
environment, and
response to stimuli
are the result of a
chemical reaction
Reactants  Products
Catalysts
• Lowers activation energy
• Speed up chemical reactions
Activation Energy
• Energy that needs to be absorbed for
a chemical reaction to start
–Energy reactants need in order to react
• Break bonds and form new ones
Rate of Chemical Reactions
• Biochemical reactions must occur at certain
speeds, or rates, in order to be useful.
• Rate of a reaction depends on:
– Temperature
– Concentration of the chemicals
– Surface area
Enzymes as Catalysts
• Enzymes are proteins
• Makes reactions that happen in cells possible
– Lower activation energy and speed up reaction
rate
• Without enzymes, many reactions would not
happen
– Others would occur too slowly for the organism to
survive
• Enzyme will not be used up or changed during
the reaction
Structure of Enzymes
• Gives reactants a site where
they can come together to
react
substrates
(reactants)
– Substrates-reactants affected
by enzyme
• Substrates bind to the active
site
• Shape of substrate and active
site are complimentary, or
opposite
– Fit together like a lock and key
enzyme
Substrates bind to an
enzyme at certain places
called active sites.
Lock and Key Model
Illustrates how enzymes function
Substrates bind to an
enzyme at certain places
called active sites.
The enzyme brings
substrates together and
weakens their bonds.
The catalyzed reaction forms
a product that is released
from the enzyme.
Structure of Enzymes
• Allows only certain reactants to bind to the
enzyme
– An organism may have thousands of different
enzymes
– Each is specific to one chemical reaction
• An enzyme’s function depends on its
structure.
Functions of Enzymes
• Energy-releasing enzymes power cell
functions
• Enzymes in nerve cells produce
neurotransmitters to carry impulses from
nerves to muscles
• Muscle cells have enzymes that are triggered
in response to the neurotransmitters
Functions of Enzymes
• Blood contains enzyme carbonic anhydrase
– Catalyzes reaction in your blood where carbon
dioxide combines with water to form carbonic acid
– Makes reaction one million times faster so that
carbon dioxide does not build up in your blood,
which could be fatal
• Enzyme lipase in the pancrease
– Speeds up digestion of lipids
Functions of Enzymes
• Disruptions in homeostasis can
prevent enzymes from functioning.
– Enzymes function best in a small range of
conditions.
– Changes in temperature and pH can break
hydrogen bonds.
– Destroyed at temperatures above 50˚C
– Work best at pH of 7