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Organic Compounds
Organic Compounds and biomolecules
Carbon is the Basic Element of Biomolecules
The chemical compounds associated to life processes are known as organic compounds. Among
the organic compounds, the most known belong to four categories:
1- CARBOHYDRATES
2- LIPIDS
3- PROTEINS
4- NUCLEIC ACIDS
Organic Compounds and biomolecules
Carbon is the Basic Element of Biomolecules
A single bacterial cell may contain up to 5000
different biomolecules, plants and animals even
more.
All the organisms in the side picture use a different
carbohydrate as structural molecule.
This variety of biomolecules is given by the
complex chemistry of carbon
Organic Compounds and biomolecules
Carbon is the Basic Element of Biomolecules
Carbon needs four electrons to complete its outer electronic shell. Hence
every single carbon can share electrons with as many as four other atoms
like in the octane molecule.
●
●- C
●-
●Furthermore the carbon-carbon bond is a covalent and stable bond, so it
can form very long and strong carbon chains.
Organic Compounds and biomolecules
Carbon is the Basic Element of Biomolecules
The great variety of biomolecules is given
by the functional groups that confer
typical features to the molecules.
F u n c t i o n a l g r o u p s a r e s p e c i fi c
combinations of atoms that always
react in the same way.
A single functional group can change
the chemical properties of the
whole organic molecule
Organic Compounds and biomolecules
Carbon is the Basic Element of Biomolecules
Macromolecules are large molecules (polymers)
composed by molecular subunits (monomers) linked
together.
MACROMOLECULES
Category
Example
Subunit(s)
Carbohydrates*
Sugar
Monosaccharide
Lipids
Fats
Glycerol and fatty acids
Proteins*
Polypeptide
Amino acids
Nucleic acids*
DNA or RNA
Nucleotide
*The biggest macromolecules are polymers, large molecules composed of
repeating structural units (monomers), normally connected by covalent bonds
Organic Compounds and biomolecules
Carbon is the Basic Element of Biomolecules
In the synthesis of a polymer, cells use enzymes to
attach monomers to one another such as wagons to a train.
This reaction is named dehydration as a molecule of
water is freed.
Organic Compounds and biomolecules
Carbon is the Basic Element of Biomolecules
The opposite reaction is the degradation of a
polymer. During this process, called hydrolysis, a
molecule of water is used to separate the two molecules.
CARBOHYDRATES
Almost all organisms use carbohydrates as sources of energy. In addition, some carbohydrates
serve as structural materials.
Carbohydrates are molecules composed of Carbon (C), Hydrogen (H) and Oxygen (O). The
ratio of hydrogen atoms to oxygen atoms is 2:1. In few words for every two H there is
an atom of O.
Simple carbohydrates, commonly known as sugars, can be monosaccharides if they are
composed of a single molecule, disaccharides if composed of two molecules, polysaccharides
if they are composed of several monosaccharides.
CARBOHYDRATES MONOSACCHARIDES
The most important carbohydrate is the glucose and is a monosaccharide with the molecular formula
C6H12O6. Glucose is the final product of the photosynthesis and is metabolized by the animals to release its
energy (during the respiration).
Glucose
Photosynthesis reaction
Sun light
6CO2 + 6H2O
Carbon dioxide
Water
C6H12O6 + 6O2
Glucose
Oxygen
CARBOHYDRATES DISACCHARIDES
There are 3 important disaccharides in living organisms.
Maltose is a combination of two glucose units covalently linked.
Sucrose (also known as saccarose) is the common table sugar and is found in plants. It is formed by
linking the two monosaccharides glucose and fructose.
Lactose is composed of glucose and another monosaccharide, the galactose. Lactose is a kind of
sugar produced in the milk.
Maltose
Sucrose
Glucose
Glucose
Glucose
Lactose
Glucose
Galactose
Fructose
CARBOHYDRATES POLYSACCHARIDES
Starches are among the most important polysaccharides. They represent a sugar reserve in
plants and are composed of hundreds and hundreds molecules of glucose, linked to one another.
Much of the world’s human population satisfies its energy needs with the starches contained in rice,
wheat and potatoes.
Glycogen is the main sugar reserve in animals and as the starch is composed of hundreds
molecules of glucose, but bonded in different ways.
Cellulose is used primarily as structural carbohydrate in plants (cell wall). It is composed
of glucose units. The cellulose chain can be decomposed only by a few species of microorganisms.
Wood is composed of dead cellulose (lignin). Cotton and paper are commercial products of
cellulose.
Chitin is a substance consisting of polysaccharides as the cellulose and forming the major
constituent in the exoskeleton of insects and the cell walls of fungi.
CARBOHYDRATES
Monosaccharides
(Cn(H2O)n)
Disaccharides
Polysaccharides
Glucose: sugar with 6 atoms of Sucrose: common table sugar, is Starch: supply sugar contained in
composed of one molecule of glucose plants
Carbons (C6H12O6)
and one of fructose. Is the
carbohydrate contained into plants.
Fructose: sugar produced in fruits Lactose: composed of glucose and C e l l u l o s e : s t r u c t u r e s u g a r
with similar formula as glucose
galactose, is the sugar contained in the contained in plants
milk
Glycogen: supply sugar contained in
animals and fungi.
Chitin: structure sugar contained in
some animals.
LIPIDS
Lipids are organic molecules composed of Carbon, Hydrogen and Oxygen with the ratio Hydrogen
atoms to Oxygen much higher than in carbohydrates, (this is why lipids contains more energy
than carbohydrates).
The most important molecules of lipids are the fats. Fats are composed of a glycerol
molecule (that contains hydroxyl group -OH), and one, two or three units of fatty acid tales (a
long chain of Carbon atoms with a carboxyl group -COOH)
LIPIDS
Lipids provide energy storage and protection and are insoluble in
water as they are nonpolar molecules.
A fat, or an oil, forms through the dehydration reaction of the
functional groups of the glycerol (-OH) and the fatty acids (COOH).
LIPIDS
Some fatty acids have one or more double bonds in their molecules and are
so called unsaturated fats.
Other fatty acids have no double bond and are called saturated fats.
In most human health diets, the consumption of unsaturated fats is preferred to the
saturated ones.
Fats do not dissolve in water and are lighter than aqueous solutions. This is why fats as oil tend to lay
on the surface of the water.
Plants often store fats in their seeds, animals store fats in large, clear globules in the cells of adipose
tissue. Lipids in adipose tissue contain much concentrated energy. Hence, they serve as a reserve
energy supply to the organisms.
LIPIDS
Phospholipids are a cell membrane component and are composed of two
fatty acids bound to glycerol. A phosphate group replaces the third
fatty acid.
Phosphate group is the hydrophilic (polar)
“head” while the fatty acid chains are
hydrophobic (nonpolar).
The cell membrane is composed of a
double layer of phospholipids.
LIPIDS
Steroids, as cholesterol, are lipids that
serve as a cell membrane component
but they also have a hor mo nal
function (i.e. testosterone).
Wa x e s a r e s o li d at a m b i e nt
temperature and are insoluble in
water.
For their properties waxes are used to
prevent water loss in plants and assist
in skin and fur maintenance in animals.
PROTEINS
Among the most complex of all organic compounds, proteins are composed of amino acids.
Proteins are the most abundant and versatile biomolecules. Their functions in animals include:
1.Support: as keratin (in hair and fingernails) and collagen (in ligaments and tendons)
2.Metabolisms: as the enzymes (a particular enzyme catalyzes a specific reaction).
3.Transport: carrier proteins embedded in the plasma membrane allow substances to enter
or exit cells
PROTEINS
Amino acids are molecules that contain Carbon, Hydrogen, Oxygen and Nitrogen atoms. Some
amino acids also contain Sulfur atoms, Phosphorous or other trace elements as Iron and Copper.
Many proteins are immense in size and extremely complex. However all proteins are composed of long
chains of relatively simple amino acids.
group -NH2
group -COOH
There are 21 kinds of amino acids.
Each amino acid (see on the left picture) has:
an amino group (-NH2)
a carboxyl group (-COOH)
a group of atoms called -R group (radical group).
group -R
PROTEINS
The 21 different amino acids differ
depending on the nature of the -R group.
PROTEINS
Amino acids combine together to form proteins.
Small proteins are often called peptides and are
composed following 4 consecutive structures:
Primary, Secondary, Tertiary and Quaternary.
All living things depend on proteins for their
existences.
Proteins are the major molecules from
which the living org a nisms a re
constructed.
NUCLEIC ACID
Every living species manufactures proteins unique to that species. The information for synthesizing the
unique protein is located in the nucleus of the cell. The so-called genetic code (DNA) specifies the
amino acid sequence in proteins trough a process called transcription
NUCLEIC ACIDS
Nucleic acids are biological molecules essential for life, and include DNA (deoxyribonucleic acid) and
RNA (ribonucleic acid). Together with proteins, nucleic acids make up the most important and
complex macromolecules. Found in abundance in all living things, they have function in encoding,
transmitting and expressing genetic information.
Nucleic acids are now known to be found in
all life forms, including bacteria, archaea,
mitochondria, chloroplasts, viruses and viroids.
All living cells and organelles contain both
DNA and RNA, while viruses contain either
DNA or RNA
NUCLEIC ACIDS
The basic component of biological nucleic acids is the nucleotide.
Nucleotides are composed of:
a nucleobase (nitrogenous base): Purines and Pyrimidines
a five-C sugar (either ribose or 2'-deoxyribose, with formula)
one to three phosphate groups.
Nucleotide structure
Phosphate
group
Sugar
Nucleobases
NUCLEIC ACIDS
In DNA, the purine bases are adenine (A) and guanine (G), while the pyrimidines are thymine (T) and
cytosine (C).
RNA uses uracil (U) in place of thymine
Living organisms have two important nucleic acids. One
type is deoxyribonucleic acid (DNA), the other one is
ribonucleic acid (RNA).
DNA is found primarily in the nucleus of cells, and is the
deposit of the genetic information.
RNA is found in both nucleus and cytoplasm and is
responsible, in eukaryotic cells, for transporting the
genetic information.
Nucleobases