CHAPTER 5
Biological compounds play
an important role in life
processes
•Most molecules of a cell are
carbon based
•These “biomolecules”backbones of carbon atoms
bonded to one another – called
“organic molecules”, can be
gigantic in size
•Carbon+hydrogen –
“hydrocarbons”-methane
(CH³)-in natural gas
•Functional group – group of atoms
within a molecule that interacts in a
predictable way
•Carbon skeleton + attached
functional group determines the
properties of an organic molecule
•Hydroxyl group – hydrophilic:
attracts water molecules
•Hydrophobic water avoiding
molecules
•Monomer - Small building block of a larger
molecule
•Polymer – straight chain of monomers, about
a total of 50 in number
 Carbohydrates
 Lipids
 Proteins
 Nucleic Acids
Protein that makes up a spider’s web
•Dehydration Reaction or Dehydration Synthesis –
two monomers bond to each other, making a polymer
chain longer, The Hydroxyl group(OH) of one
monomer reacts with the Hydrogen(H) atom from
another monomer.The reaction releases a water
molecule.
•Hydrolysis - Cells break bonds between monomers
by adding water to them
•Water (hydro) is used to break down( lysis ) a
molecule
Inorganic compounds
no carbon
exception carbon dioxide,
calcium
carbonate,
examples - water,
salts
•CARBOHYDRATES – “energy source”
Organic compound made up of 1
carbon :2 hydrogen:1 Oxygen
Molecular formula CH2O
Glucose
Ring shaped carbon skeleton
•Monosaccharide – simple sugars
with 1 sugar unit : glucose(main
fuel supply for cells), fructose
•Disaccharide – “double sugar”:
sucrose
•Polysaccharide – long
polymer chains,complex
carbohydrates : starch
•Glycogen – animal cells,
stored in liver
•Cellulose – plant cell walls
•LIPIDS (FATS) – Three carbon backbone called “glycerol”
attached to 3 “fatty acids”which contain long hydrocarbon chains
Some solid at room temperature Oils – liquid at room temperature
•Function – stores energy, cushions organs, insulation
•“Saturated fat” – all three fatty acid chains contain the maximum
possible number of hydrogen atoms : animal fats,butter,lard
•“Unsaturated fat” – less than the maximum number of hydrogen
atoms in one or more of it’s fatty acid chains : corn oil, olive oil
Cholesterol
animal products like
butter and meat
buildup of deposits
that narrow arteries
;leads to heart
attacks and strokes
•Steroids – lipid
molecule in which the
carbon skeleton forms
four fused rings. While
all steroids have the
core of 4 rings, they
differ in the kinds and
locations of functional
groups
•Circulate in the body
as chemical signals
Nucleic Acids
carbon, hydrogen,
oxygen, phosphorous,
nitrogen
DNA(Deoxyribonucleic
Acid)- transmits genetic
information that is
passed from one
generation to the nextdouble helix
RNA (Ribonucleic Acid)
structure
long chains of repeating
units called NUCLEOTIDE
(a) 5 carbon sugar deoxyribose
(b) phosphate group
© nitrogenous base adenine=thymine;
cytosine=guanine
Structure of RNA
single strand
each nucleotide
(a) 5 carbon sugar - ribose
(b) phosphate group
© nitrogenous bases - adenine=uracil ;
cytosine=guanine
•PROTEIN from the Greek word meaning “first place”suggests the importance of this class of polymers.
•Each one has a unique 3-dimensional structure that
corresponds to a specific function
•Responsible for
the day to day
function of
organisms
•Example –
hair,fur,muscles
control chemical
reactions in the
cell
Texture of animals coat
Powerful muscles
Food value
in nuts
•Protein is a polymer constructed from a set of 20
kinds of monomers called “amino acids”
•Each amino acid consists of a central carbon atom
bonded to 4 partners : amino group, carboxyl
group,hydrogen atom
•4th group is a “side group” or “R-group” is
responsible for the particular chemical properties of
each amino acid.
hydrocarbon
•Cells create proteins by
linking amino acids together
in a chain called a
“polypeptide”
•Each link is created by the
dehydration reaction
between the amino group of
one amino acid and the
carboxyl group of the next
amino acid in the chain.
•Proteins are composed of
one or more polypeptide
chains ,usually at least 100
amino acids in length
•Protein Shape – a functional
protein consists of one or
more polypeptides precisely
twisted, folded,and coiled
into a unique shape
•Influenced by the
surrounding environment
•Unfavorable change in the
environment
(pH,temperature) can cause
the protein to unravel.This is
called “denaturation”
•The chemical reactions within a cell requires “activation
energy”(start-up energy)
•Provided indirectly by “catalysts”(compounds that speed
up a chemical reaction without themselves changing)
•“Enzymes” or “organic catalysts” are specialized
proteins example - maltase acts on maltose
Enzymes lowers
the energy
requirement
barrier so that
the reaction can
proceed at
normal cell
temperatures
Enzyme action - Lock and key
on surface of the protein is the active
site
substrate molecule fits the active site
forms a temporary enzyme-substrate
complex - Lock and Key mechanism
Induced Fit Mold
enzyme, not with rigid shape, changes
slightly so that the it can fit snugly
around the substrate
Factors affecting the Rate of Enzyme
reaction
small amount of enzyme for large
amounts of substrate
rate of reaction dependent on
enzyme:substrate concentration
coenzymes may be required sometimes
allow optimal
reactions at normal
temperature-36*
works best at certain
pH -7
ex. Pepsin in
stomach acts only
when HCL is present