the nature and importance of biomacromolecules in the chemistry of the
cell:
– synthesis of biomacromolecules through the condensation reaction
– lipids and their sub-units; the role of lipids in the plasma membrane
– examples of polysaccharides and their glucose monomer
– structure and function of DNA and RNA, their monomers, and
complementary base pairing
- the nature of the proteome; the functional diversity of proteins; the
structure of proteins in terms of primary, secondary, tertiary and
quaternary levels of organisation
All of these organic molecules always contain the
elements Carbon (C), Hydrogen (H) and Oxygen (O).
Proteins also contain Nitrogen (N) and sometimes
sulfur (S). Nucleic acids have C, H, O, N and
Phosphorus (P).
Condensation Reaction
A condensation reaction is a chemical reaction in
which two molecules or moieties (functional groups)
combine to form a single molecule, together with the
loss of a small molecule. When this small molecule is
water, it is known as a dehydration reaction; other
possible small molecules lost include hydrogen chloride
(HCl), methanol (CH3OH)or acetic acid (CH3CO2H).
The condensation of two amino acids to form a peptide bond (red) with the
expulsion of water (blue).
The major classes of organic compounds are:
Carbohydrates
Proteins
Lipids
Nucleic acids.
What is the basic unit for each of these organic
molecules?
How do the units combine to form complex molecules?
Where is each kind of molecule found in the cell?
What are the functions of the molecules?
Each of the above compounds are complex
macromolecules called polymers which are made up of
smaller sub-units called monomers.
Carbohydrates
This class of compounds uses only carbon, oxygen, and
hydrogen and are called carbohydrates
Below are some examples of carbohydrates ( Sugars, starch,
cellulose and glycogen):
• Glycogen is a complex polysaccharide created in animals for
the purpose of storing chemical energy. The small black
granules (dots) are glycogen.
• Starch is the long term energy storage molecule for most
plants.
Carbohydrates
 Monosaccharides (one unit) can be joined together
to form disaccharides (two units) and release H2O in
the process (condensation reaction)
 Monosaccharides and disaccharides are called simple
sugars.
 Complex carbohydrates are called polysaccharides.
Simple carbohydrates
 Have one or two sugar units
 Their general formula is (CH2O)n.
 Monosaccharides
 e.g. glucose (C6H12O6) (also called grape sugar)
Monosaccharides
 Glucose is the product of photosynthesis
 Simple long chain sugars form rings
 Other monosaccharides include galactose, mannose
and fructose (C6H12O6) (see below)
Disaccharides
 Sucrose (glucose + fructose
 Sucrose (C12H22O11)
sucrose + water)
Polysaccharides
 Complex carbohydrate
 Examples
 Starch
 Cellulose
 Glycogen
Polysaccharides
 Glycogen
 form of energy storage in animals
 contains a protein as a starting point
 circular in shape
Protein
Polysaccharides
 Starch
 Main form of sucrose storage in plants
Polysaccharides
 Cellulose
 structural polysaccharide
 formula similar to starch
 every plant cell wall contains cellulose
Proteins
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very large molecules
fold and form complex shapes
four different levels of organisation
thousands of different proteins in each cell
example
 casein in milk (C708H1130N180O224S4P4)
Primary shape
 linear sequence of amino acids (monomers)
 different proteins have different sequences of amino
acids
 20 different naturally occurring amino acids
Primary shape
 two amino acids join together to form a dipeptide
 many amino acids join together to form a polypeptide
Condensation Reaction
Primary shape
Primary shape
Secondary shape
 Amino acid chain can fold in three different ways
 Hydrogen bonds (weak) form between units to
stabilize shape
 Alpha helix (α-helix)
 Beta pleated sheets (β-pleated sheets)
 Random coils
Secondary shape
 Alpha helix (α-helix)
Secondary shape
 Beta pleated sheets (β-pleated sheets)
Secondary shape
 Random coils
Tertiary structure
Quaternary structure
Proteins….
If there is a job to be
done in the molecular
world of our cells,
usually that job is done
by a protein.
CATALASE
An enzyme which removes Hydrogen
peroxide from your body so it does not
become toxic
A protein hormone which helps to regulate your
blood sugar levels
Examples of proteins include: hormones acting as
messengers; enzymes speeding up reactions; cell receptors
acting as ‘antennae’; antibodies fighting foreign invaders;
membrane channels allowing specific molecules to enter or
leave a cell; they make up the muscles for moving; let you
grow hair, ligaments and fingernails; and let you see (the lens
of your eye is pure crystallised protein).
Proteins….
 Proteins are large complex molecules
built of monomers called amino
acids. The amino acids are held
together by peptide bonds, so
proteins are known as polypeptides.
 There are usually multiple peptide
chains joined together e.g.
Haemoglobin has 4 polypeptide
chains comprising it.
 The polypeptide chains are then
folded into a particular shape unique
to that type of protein
 Proteins can be fibrous or globular;
fibrous proteins normally are
involved in body structures
(structural proteins), globular
proteins are normally biochemical.
Globular Proteins
 The globular proteins have a number of biologically
important roles. They include:
 Cell motility – proteins link together to make filaments to make
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movement possible.
Organic catalysts in biochemical reactions – enzymes that speed up
reactions.
Regulatory proteins – hormones transcription factors.
Membrane proteins – MHC markers, protein channels, gap junctions.
Defence against pathogens – poisons/toxins, antibodies.
Transport and storage – haemoglobin, myosin.
Structural Proteins
 Hair (keratin)
 Fingernails (keratin)
 Skin (collagen)
 Muscles (myosin, etc)
 Cartilage (glycoprotein: proteins attached to
carbohydrates
 Ligaments (collagen plus glycoproteins)
 Eye cornea (collagen/keratin)
Conjugated Proteins
 Some proteins have chains of amino acids conjugate
with other groups.
 e.g. nucleoproteins – they comprise a molecule
containing both protein and nucleic acid
 haemoglobin – four molecules of protein, each
conjugated with an iron molecule
Inactive to active molecules
 Insulin (a hormone) when initially produced is
inactive.
 It is produced as a single chain of amino acids with
the folds held together by three disulfide bonds.
 It is activated by the removal of a length of the
amino acid chain to leave two chains of amino acids
held together by three disulfide bonds.
Inactive to active molecules
Proteome
 The complete array of proteins produced by a single
cell or organism in a particular environment is called
the proteome of the cell or organism
 The study of the proteome is called proteomics.
 No protein acts in isolation; therefore scientists are
moving away from studying single proteins
Lipids
 Lipids (oils and fats) are another class of organic
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compounds built from oxygen, hydrogen, and carbon.
Lipids have little affinity for water.
Lipids have a structural role, for example the plasma
membrane is composed to a large part by phospholipids.
Lipids also have biochemical role, for example some
hormones are made of lipids (e.g. steroids).
Lipids are the long term energy storage molecule for all
animals.
Lipids carry more energy per molecule than either
carbohydrates or proteins.
Lipids
 Fats are composed of the subunits fatty acids and
glycerol.
 Triglycerides are a common form of fat.
 Triglycerides have a single glycerol with three fatty acid
chains attached
This diagram represents a
triglyceride, a simple and
common form of fat
Triglycerides
 The fatty acid chains have no affinity for water and are
insoluble in water
 They are called hydrophobic (hate water)
 Some common formulae for fats are:
 stearin (C57H110O6)
 palmitin (C51H98O6)
 linolein (C57H98O6)
 Lipids with straight fatty acid chains pack closely together
and are solid at room temperature.
 Lipids with bent fatty acid chains are further apart and
are liquid at room temperature.
Phospholipids
 Consists of two fatty acid chains attached to a glycerol
molecule with a a phosphate molecule also attached.
 Other small molecules may also attached to the
phosphate
 Phospholipids are a major component of cell membranes.
Hydrophilic
Hydrophobic
Nucleic acids
 Very large macromolecules concerned with the storage
and transmission of inherited information and protein
synthesis.
 Made up of repeating units called nucleotides.
 Two types:
 deoxyribonucleic acid (DNA)
 located in the nucleus of eukaryotes
 ribonucleic acid (RNA).
 formed using a DNA template (transcription) in the
nucleus and used to make, in conjunction with
ribosomes, proteins in the cytosol (translation).
Nucleic acids
 Each nucleotide unit, or monomer, is made up of
 a sugar (deoxyribose or ribose) part
 ‘deoxy’ means ‘missing an oxygen molecule’
 a phosphate part
 a Nitrogenous (N) base
Deoxyribonucleic acid
 made of two sugar – phosphate backbones
 has four different N-bases
 Adenine (A)
 Thymine (T)
 Cytosine (C)
 Guanine (G)
 A binds with T and G binds with C
 Complementary base pairs
 Forms a double helix
 DNA double helix is 2 nm wide and one complete turn
of the helix is 3.4 nm
The four DNA nucleotide
Nitrogenous bases
Ribonucleic acid
Three different types of RNA
 messenger RNA (mRNA) – carries genetic message
from nucleus in eukaryotic cells to ribosomes in the
cytosol
 ribosomal RNA (rRNA) – with particular proteins makes
up part of the ribosome
 transfer RNA (tRNA) – carry amino acids to ribosomes
where they construct proteins
 The strands of nucleotides in each of the RNAs fold
differently