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BIOMOLECULES
Substances found in living
organism
5%
30%
65%
Water
Biomolecules
Mineral salts
Listening activity
Listen and try to write down as many words as possible, above
all the names of the four biomolecules.
Then, answer the questions.
https://youtu.be/hl9PtmbsAZg
Transcript
Biomolecules are the main components of our body and of the body of all living organisms.
They are complex molecules, very complex in some cases, but they are part of our everyday life although most of us are not
aware of this. In fact, together with vitamins and minerals, they are the basis of our nutrition.
Carbohydrates, for example, contain sugar and polysaccharides. Sugars are compounds that can be found in fruit, but also
in milk and many other kinds of food. Generally they are easily recognized by their sweet taste.
Polysaccharides are not sweet, though they are made of sugars. However, they are the basis of nutrition for most human
beings. They are the basic components of all such foods such as wheat, potatoes, corn, rice, but also pasta, bread and
polenta. They can be found in many other kinds of foods for example legumes like beans, chickpeas, lentils and the like.
Lipids are fatty acid substances such as the seasonings like oil and butter, but they can be found in high quantities in some
kinds of meat, in eggs and in several vegetables such as avocado.
They work mostly as reserve substances as they are very rich in energy.
Proteins are perhaps the most varied and complex class of biomolecules. This is why several foods contain an amount of them,
but in our diet the food which is rich in proteins are meat, eggs, fish and their by-products such as ham and salami.
Among vegetables, legumes are an important source of proteins.
The last class of biomolecules is that of nucleic acids. These include RNA and the well-known DNA.
All cell contain an amount of DNA because, as you probably know, it works as hereditary memory.
Each cells has its own quantity of DNA though this is not stored in a specific part of a living organism so, it is not
particulalry important as an elementary source. In spite of that, all living beings contain it.
Questions
1. What are biomolecules?
2. Why biomolecules are important together with vitamins and minerals?
3. Which are the four biomolecules mentioned in the track?
4. Which is the only biomolecule that is not important as a nutritional source?
5. In which food can we found sugar and how can we recognize it?
6. Polysaccharides are the basic component of which foods?
7. Which is the main function of lipids?
8. Which is the most varied and complex class of biomolecules?
9. Which biomolecules can we found in legumes?
10. What is the function of DNA?
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With the exception of the lipids, these biological molecules are polymers (poly,
“many”; mer, “unit”) constructed by the covalent bonding of smaller molecules
called monomers.
MONOMERS
condensation
idrolysis
POLYMER
Polymers are formed from monomers by a series of condensation reactions that result in the
formation of covalent bonds between monomers.
A molecule of water is released with each covalent bond formed and energy is added to the
system.
MONOMERS
condensation
idrolysis
POLYMERS
The reverse of a condensation reaction is a hydrolysis reaction (hydro, “water”; lysis, “break”).
Hydrolysis reactions result in the breakdown of polymers into their component monomers.
Water reacts with the covalent bonds that link the polymer together. Hydrolysis releases
energy.
MONOMERS
condensation
idrolysis
POLYMERS
How the macromolecules function and interact with other molecules
depends on the properties of certain chemical groups in their
monomers, the functional groups.
Each functional group has specific chemical properties, and when it is
attached to a larger molecule, it confers those properties on the larger
molecule. Because macromolecules are so large, they contain many
different functional groups such as:
https://www.youtube.com/watch?v=H8WJ2KENlK0
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Carbohydrates usually have the general formula Cn(H2O)n which
makes them appear as hydrates of carbon.
BIOCHEMICAL ROLES
• they are a source of energy ready to use or of
stored energy that can be released in a form
usable by organisms;
• they serve as carbon skeletons that can be
rearranged to form new molecules.
CATEGORIES OF CARBOHYDRATE DEFINED
BY THE NUMBER OF MONOMERS
• Monosaccharides;
• Disaccharides;
• Oligosaccharides;
• Polysaccharides.
simple sugars
complex sugars
Monosaccharides
(mono, “one”; saccharide, “sugar”)
They are the monomers from which the larger carbohydrates are constructed.
Pentoses
five-carbon sugars
• ribose
• deoxyribose
One oxygen atom is missing from carbon 2 in
deoxyribose (de-, “absent”).
The absence of this oxygen atom is an important
distinction between RNA and DNA.
Hexoses
six-carbon sugars
• glucose
• fructose
• galactose
Disaccharides
(di, “two”)
They are constructed from two monosaccharides that are covalently
bonded together by condensation reactions that form glycosidic
linkages.
Disaccharides
(di, “two”)
Sucrose
Glc + Fru
Maltose
Glc + Glc
Lactose
Glc + Gal
Oligosaccharides
(oligo, “several”)
They are made up of several (3–20) monosaccharides.
They are often covalently bonded to proteins and lipids on the outer cell
surface, where they serve as recognition signals. The different human blood
groups (for example, the ABO blood types) get their specificities from
oligosaccharide chains.
Polysaccharides
(poly, “many”)
They are polymers made up of hundreds or thousands of
monosaccharides. In contrast to proteins, polysaccharides are not
necessarily linear chains of monomers.
Polysaccharides
(poly, “many”)
They are all polysaccharides of glucose, but they have a different
molecular structure.
Cellulose
Starch
Glycogen
Polysaccharides
(poly, “many”)
Polysaccharides in cells.
Starch
(vegetal)
Cellulose
(vegetal)
Glycogen
(animal)
Starch is the principal energy
storage compound of plants. Large
starch aggregates called starch
grains can be observed in the
storage tissues of plant seeds.
Glycogen is a water-insoluble, highly branched
polymer of glucose. It is used to store glucose
in the liver and muscles and is thus an energy
storage compound for animals, as starch is for
plants. Both glycogen and starch are readily
hydrolyzed into glucose monomers, which in
turn can be broken down to liberate their
stored energy.
Like starch and glycogen, cellulose is a
polysaccharide of glucose. As the predominant
component of plant cell walls, cellulose is an
excellent structural material and it is by far the most
abundant organic compound on Earth. Starch is
easily degraded by the actions of enzymes.
Cellulose, however, is chemically more stable and
we can’t digest it.
There is a fourth polysaccharide called chitin that is a polymer
of glucose, too.
It is a characteristic component of:
• the cell walls of fungi
• the exoskeletons of arthropods such as crustaceans (e.g.,
crabs, lobsters and shrimps) and insects.
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PROTEINS
Proteins have very diverse roles, only two (energy storage and
information storage) are not usually performed by them.
PROTEINS
All proteins are polymers made up of 20 aminoacids in
different proportions and sequences.
Proteins range in size from small ones such as insulin, which has
51 amino acids to huge molecules such as the muscle proteins,
with thousands of aminoacids.
Primary structure of insulin
PROTEINS
Proteins consist of one or more polypeptide chains—
unbranched (linear) polymers of covalently linked amino acids.
Each chain folds into a particular three-dimensional shape
that depends on the sequence of amino acids present in the
chain.
AMINO ACIDS STRUCTURE
Each amino acid has both a carboxyl functional group and an
amino functional group attached to the same carbon atom.
Also attached to the carbon atom are a hydrogen atom and a
side chain, or R group.
PROTEINS
The R groups of amino acids contain functional groups that are important in
determining the 3D structure and thus the function of the protein.
The 20 amino acids found in living organisms are grouped and distinguished by
their side chains.
Nine of them are
essential amino acids
because they cannot
be synthesized by the
organism, and thus
must be supplied in its
diet.
CONDENSATION REACTION
When amino acids polymerize, the carboxyl and amino groups attached to the
carbon atom are the reactive groups. The carboxyl group of one amino acid
reacts with the amino group of another, undergoing a condensation reaction that
forms a peptide linkage (also called a peptide bond).
LEVELS of PROTEIN ORGANISATION
LEVELS of PROTEIN ORGANISATION
For example, Hemoglobin consist of four
folded polypeptide chain that assemble
themselves into a quaternary structure.
FUNCTIONS
• Enzymes  catalyze (speed up) biochemical reactions
• Structural proteins  provide physical stability such as collagen
FUNCTIONS
• Signaling proteins hormones that control physiological processes such as
insulin
• Defensive proteins  recognize and respond to nonself substances such as
antibodies
FUNCTIONS
• Membrane transporters  regulate
passage of substances across cellular
membranes
• Transport proteins  bind and carry
substances within the organism such
as hemoglobin that carry oxygen
FUNCTIONS
• Movement function  actin and myosin for example, are
involved in muscle contraction
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LIPIDS
Lipids—colloquially called fats—are hydrocarbons that are insoluble in
water because of their hydrophobic chains.
They are not polymers in a strict chemical sense.
CLASSIFICATION
SIMPLE LIPIDS
fats and oil
COMPLEX LIPIDS
Es. phospholipids
OTHERS
carotenoids,
steroids,
vitamins,
waxes
SIMPLE LIPIDS
Chemically, fats and oils are called triglycerides.
Triglycerides that are:
• solid at room temperature (around 20°C) are called fats;
• liquid at room temperature are called oils.
SIMPLE LIPIDS
Triglycerides are composed of two types of building blocks:
fatty acids and glycerol.
SIMPLE LIPIDS
Glycerol is a small molecule with three hydroxyl (—OH) groups (thus it is an
alcohol).
A fatty acid is made up of a long hydrocarbon chain and a carboxyl group (—
COOH), so it is a molecule with a hydrophilic end and a long hydrophobic tail.
The technical term for this is amphipathic.
A triglyceride contains three fatty acid molecules and one molecule of glycerol.
SIMPLE LIPIDS
Synthesis of a triglyceride involves three condensation (dehydration) reactions.
In each reaction, the carboxyl group of a fatty acid bonds with a hydroxyl group
of glycerol, resulting in a covalent bond called an ester linkage and the release of
a water molecule.
SIMPLE LIPIDS
The three fatty acids in a triglyceride molecule need not all have the
same hydrocarbon chain length or structure; some may be saturated
fatty acids, whereas others may be unsaturated.
In saturated fatty acids, all the
bonds between the carbon atoms
in the hydrocarbon chain are
single. These fatty acid molecules
are straight, and they pack
together tightly.
SIMPLE LIPIDS
The triglycerides of animal fats tend to have many long-chain
saturated fatty acids packed tightly together; these fats are usually
solids at room temperature and have high melting points.
SIMPLE LIPIDS
In unsaturated fatty acids, the
hydrocarbon chain contains one or
more double bonds. Linoleic acid is
an example of a polyunsaturated
fatty acid that has two double bonds
causing kinks in the molecule that
prevent
the
unsaturated
fat
molecules from packing together
tightly.
The kinks are important in
determining the fluidity and melting
point of lipids.
SIMPLE LIPIDS
The triglycerides of plants, such as corn oil, tend to have short or
unsaturated fatty acids. Because of their kinks, these fatty acids pack
together poorly and have low melting points, and these triglycerides
are usually liquids at room temperature.
SIMPLE LIPIDS
Fatty acids are excellent storehouses for chemical energy:
when the C—H bond is broken, it releases energy that an
organism can use for its own purposes, such as movement or
building up other complex molecules.
PHOSPHOLIPIDS
Phospholipids contain fatty acids bound to glycerol by ester linkages. In
phospholipids, however, a phosphate-containing compound replaces one of the
fatty acids.
The fatty acids are
hydrophobic and tend
to avoid water while the
phosphate
functional
group is hydrophilic; for
this the phospholipid is
an amphipathic molecule.
PHOSPHOLIPIDS
PHOSPHOLIPIDS
In an aqueous environment, phospholipids line up in such a way that
the hydrophobic “tails” pack tightly together and the phosphatecontaining “heads” face outward.
The phospholipids thus form a
bilayer.
Biological membranes have this
kind of phospholipid bilayer
structure.
OTHERS
The carotenoids are plants or animal pigments that traps light energy
in leaves during photosynthesis. In humans, they are precursor of
Vitamin A which is required for vision.
Carotenoids are responsible for the colors of carrots, tomatoes,
pumpkins, egg yolks, butter and autumn leaves.
OTHERS
The steroids are a family of organic compounds with multiple rings of
carbons. The steroid cholesterol is an important constituent of
membranes, helping maintain membrane integrity.
Sex hormones are derived from cholesterol such as testosterone.
OTHERS
Vitamins are small molecules that are not synthesized by the human body and so
must be acquired from the diet. For example, vitamin A is formed from the βcarotene found in orange and yellow vegetables.
In humans, a deficiency of vitamin A leads to night blindness, which is a
diagnostic symptom for the deficiency. Vitamins D, E, and K are also lipids.
OTHERS
Waxes are produced by birds
and mammals as a waterproof
coating that help them retain
water and exclude pathogens.
The shiny leaves of plants
such as holly, familiar during
winter holidays, also have waxy
coatings.
Bees make their honeycombs
out of wax.
BIOLOGICAL FUNCTIONS
To sum up, they play a number of roles in living
organisms:
• Fats and oils store energy;
• Phospholipids play important structural roles in cell
membranes;
• Carotenoids and chlorophylls help plants capture
light energy
BIOLOGICAL FUNCTIONS
• Steroids play regulatory roles as
hormones and vitamins;
• Fat in animal bodies serves as
thermal insulation;
• Oil or wax on the surfaces of skin,
fur, feathers, and leaves repels
water and prevents excessive
evaporation
of
water
from
terrestrial animals and plants.
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NUCLEIC ACIDS
Nucleic acids are polymers specialized for the storage, transmission,
and use of genetic information.
CHEMICAL STRUCTURE
Nucleic acids are polymers composed of monomers called nucleotides.
A nucleotide consists of three components.
P: phosphate group
B: nitrogen-containing base
Z: pentose sugar (ribose or deoxyribose)
The pentose sugar deoxyribose differs from the ribose by the
absence of one oxygen atom.
CHEMICAL STRUCTURE
There are 5 types of nitrogen-containing base:
During the formation of a nucleic acid, a
condensation reaction occurs between a
pentose sugar and the phosphate on the
next nucleotide.
DNA molecules in humans contain
hundreds of millions of nucleotides.
https://webiebook.scuola.zanichelli.it/fro
m-biochemistry-tobiotechnology/frombiochemistry-tobiotechnology-1/z43544v14-c00-01/z43544v14-p-00-01-05
There are two types of nucleic acids
DNA
deoxyribonucleic acid
RNA
ribonucleic acid
DIFFERENCES between DNA and RNA
SUGAR: in DNA, the pentose sugar is deoxyribose, which differs
from the ribose found in RNA by the absence of one oxygen atom.
BASES: four bases are found in DNA, A, C, G and T. RNA is
also made up of four different monomers, but its nucleotides include
U instead of T.
STRAND STRUCTURE: RNA is generally single-stranded
while DNA is double-stranded
STRUCTURE of DNA
DNA
consists
of
two
separate
polynucleotide strands of the same length
that are held together by hydrogen bonds
between base pairs: thymine and adenine
always pair (T-A) and cytosine and
guanine always pair (C-G).
the two polynucleotide strands form a
“ladder” that twists into a double helix .
The key differences among DNA
molecules are their different nucleotide
base sequences.
DIFFERENCES in FUNCTION
DNA is a purely informational molecule that encodes hereditary information and passes it
from generation to generation.
During cell division and reproduction, information flows from existing DNA to the newly
formed DNA in a new cell or organism.
In the non-reproductive activities of the cell, information flows from DNA to RNA to
proteins. The information encoded in DNA is used to specify the amino acid sequences of
proteins using RNA as an intermediary. This process is called gene expression.
The central dogma of
molecular biology is
an explanation of the
flow of genetic
information within a
biological system