BIOLOGICAL MOLECULES
1.1-1.9
1.2. Carbohydrates - monosaccharides
Biological molecules
1. Carbohydrates
2. Proteins
3. Lipids (fats and oils)
4. Nucleic acids (DNA and RNA)
★ Most of these molecules are polymers made up of monomers.
Polymers and monomers:
● Certain molecules, known as monomers, can be linked together to form
long chains.
● Many organic molecules, including carbohydrates are made up of a chain
of individual molecules (monomers)
● These long chains of monomer subunits are called polymers and the
process by which they are formed is therefore called polymerisation.
Monomers Polymers
Monosaccharide (simple sugars) Polysaccharides (carbohydrates)
Amino acids Polypeptide (proteins)
Nucleotide Polynucleotide
★ These polymers are based on just a small number of elements: carbon,
hydrogen, oxygen and nitrogen.
, ★ Lipids are NOT polymers! They are not long-chained molecules (no long
chains of monomers).
Carbohydrate structure
● Contains 3 elements: carbon, hydrogen and oxygen
● In carbohydrates, the basic monomer is a sugar (also known as a
saccharide).
● A single monomer is therefore called a monosaccharide, a pair is
disaccharide. Many monosaccharides can be combined in much larger
numbers to form a polysaccharide.
● They can therefore be grouped into 3 categories:
1. Monosaccharides (‘single’ sugars)
2. Disaccharides (‘double’ sugars)
3. Polysaccharides (sugar ‘chains’)
Monosaccharides
● Monosaccharides are sweet-tasting, soluble substances.
● Their general formula is (CH2O)n where n can be any number from three
to seven.
● Contains only 3-9 carbon atoms
● C=3 (triose) important in respiration and photosynthesis.
● C=5 (pentose) important in DNA and RNA
● C=6 (hexose) important energy source (digestion, respiration)
Examples of monosaccharides:
- Glucose (hexose) sugar. Its formula is C6H12O6
- Galactose
- Fructose
,Structure of monosaccharides
● All but one C-atom, have an -OH (alcohol or hydroxyl) group attached.
● It can have a chain form or ring form (which is a more stable form).
● Examples: glucose, fructose
1. GLUCOSE
➢ Carbon atoms 2-6 have a hydroxyl (OH) group
attached. 5 hydroxyl groups attached to carbon
atoms.
➢ The first carbon atom (at the top) has an
oxygen atom attached by a double bond
➢ 7 hydrogen bonds
Glucose ring form:
★ The carbon, hydrogen and oxygen atoms can be arranged in different
ways, including a ring structure.
★ Carbon atom 1 connects to Carbon atom 5!
★ The sixth carbon atom then protrudes as a straight line off of carbon 5.
★ It is easier for the glucose molecule to stay intact if it is in a ring
structure.
★ In a ring structure, glucose has 2 isomers: alpha glucose and beta
glucose.
, Alpha glucose
➔ Look at carbon atom number 1
➔ The OH- group is BELOW the plane of the ring.
➔ When the OH- group is below the plane of the ring, it is ALPHA glucose
(α-glucose).
Beta glucose
1.1-1.9
1.2. Carbohydrates - monosaccharides
Biological molecules
1. Carbohydrates
2. Proteins
3. Lipids (fats and oils)
4. Nucleic acids (DNA and RNA)
★ Most of these molecules are polymers made up of monomers.
Polymers and monomers:
● Certain molecules, known as monomers, can be linked together to form
long chains.
● Many organic molecules, including carbohydrates are made up of a chain
of individual molecules (monomers)
● These long chains of monomer subunits are called polymers and the
process by which they are formed is therefore called polymerisation.
Monomers Polymers
Monosaccharide (simple sugars) Polysaccharides (carbohydrates)
Amino acids Polypeptide (proteins)
Nucleotide Polynucleotide
★ These polymers are based on just a small number of elements: carbon,
hydrogen, oxygen and nitrogen.
, ★ Lipids are NOT polymers! They are not long-chained molecules (no long
chains of monomers).
Carbohydrate structure
● Contains 3 elements: carbon, hydrogen and oxygen
● In carbohydrates, the basic monomer is a sugar (also known as a
saccharide).
● A single monomer is therefore called a monosaccharide, a pair is
disaccharide. Many monosaccharides can be combined in much larger
numbers to form a polysaccharide.
● They can therefore be grouped into 3 categories:
1. Monosaccharides (‘single’ sugars)
2. Disaccharides (‘double’ sugars)
3. Polysaccharides (sugar ‘chains’)
Monosaccharides
● Monosaccharides are sweet-tasting, soluble substances.
● Their general formula is (CH2O)n where n can be any number from three
to seven.
● Contains only 3-9 carbon atoms
● C=3 (triose) important in respiration and photosynthesis.
● C=5 (pentose) important in DNA and RNA
● C=6 (hexose) important energy source (digestion, respiration)
Examples of monosaccharides:
- Glucose (hexose) sugar. Its formula is C6H12O6
- Galactose
- Fructose
,Structure of monosaccharides
● All but one C-atom, have an -OH (alcohol or hydroxyl) group attached.
● It can have a chain form or ring form (which is a more stable form).
● Examples: glucose, fructose
1. GLUCOSE
➢ Carbon atoms 2-6 have a hydroxyl (OH) group
attached. 5 hydroxyl groups attached to carbon
atoms.
➢ The first carbon atom (at the top) has an
oxygen atom attached by a double bond
➢ 7 hydrogen bonds
Glucose ring form:
★ The carbon, hydrogen and oxygen atoms can be arranged in different
ways, including a ring structure.
★ Carbon atom 1 connects to Carbon atom 5!
★ The sixth carbon atom then protrudes as a straight line off of carbon 5.
★ It is easier for the glucose molecule to stay intact if it is in a ring
structure.
★ In a ring structure, glucose has 2 isomers: alpha glucose and beta
glucose.
, Alpha glucose
➔ Look at carbon atom number 1
➔ The OH- group is BELOW the plane of the ring.
➔ When the OH- group is below the plane of the ring, it is ALPHA glucose
(α-glucose).
Beta glucose
