CARBOHYDRATES
,• Carbohydrates make up most of the organic matter on Earth
because of their extensive roles in all forms of life.
• First, carbohydrates serve as energy stores, fuels, and
metabolic intermediates.
• Second, ribose and deoxyribose sugars form part of the
structural framework of RNA and DNA.
• Third, polysaccharides are structural elements in the cell
walls of bacteria and plants. In fact, cellulose, the main
constituent of plant cell walls, is one of the most abundant
organic compounds in the biosphere.
• Fourth, carbohydrates are linked to many proteins and lipids,
where they play key roles in mediating interactions among
cells and interactions between cells and other elements in
the cellular environment.
, Intro. to Carbohydrates
• Carbohydrates are the most abundant biomolecules on Earth. Each year, photosynthesis
converts more than 100 billion metric tons of CO2 and H20 into cellulose and other plant
products.
• Carbohydrates are polyhydroxy aldehydes and ketones, or substances that yield such
compounds on hydrolysis.
• Many, but not all have the empirical formula (CH2O)n, but some also contain nitrogen,
phosphorus, or sulfur.
• Carbohydrates occur in four main size classes: monosaccharides, disaccharides,
oligosaccharides, and polysaccharides.
• The most abundant monosaccharide in nature is D-glucose, which is also known as
dextrose.
• A common disaccharide, sucrose, consists of the six-carbon sugars D-glucose and D-
fructose.
• Common polysaccharides include cellulose and starches. Both of these are
homopolymers of D-glucose units, but with different linkages between residues.
• More complex carbohydrate polymers attached to a protein or lipid moiety
(glycoconjugates) are also prevalent in nature.
, Carbohydrates
hydrates of carbon: general formula Cn(H2O)n
Plants: photosynthesis
6 CO2 + 6 H2O C6H12O6 + 6 O2
hn
Polymers: large molecules made up of repeating smaller units
(monomer)
Biopolymers: Monomer units:
carbohydrates (Chapter 23) monosaccharides
peptides and proteins (Chapter 25) amino acids
nucleic acids (Chapter 26) nucleotides
4
,• Carbohydrates make up most of the organic matter on Earth
because of their extensive roles in all forms of life.
• First, carbohydrates serve as energy stores, fuels, and
metabolic intermediates.
• Second, ribose and deoxyribose sugars form part of the
structural framework of RNA and DNA.
• Third, polysaccharides are structural elements in the cell
walls of bacteria and plants. In fact, cellulose, the main
constituent of plant cell walls, is one of the most abundant
organic compounds in the biosphere.
• Fourth, carbohydrates are linked to many proteins and lipids,
where they play key roles in mediating interactions among
cells and interactions between cells and other elements in
the cellular environment.
, Intro. to Carbohydrates
• Carbohydrates are the most abundant biomolecules on Earth. Each year, photosynthesis
converts more than 100 billion metric tons of CO2 and H20 into cellulose and other plant
products.
• Carbohydrates are polyhydroxy aldehydes and ketones, or substances that yield such
compounds on hydrolysis.
• Many, but not all have the empirical formula (CH2O)n, but some also contain nitrogen,
phosphorus, or sulfur.
• Carbohydrates occur in four main size classes: monosaccharides, disaccharides,
oligosaccharides, and polysaccharides.
• The most abundant monosaccharide in nature is D-glucose, which is also known as
dextrose.
• A common disaccharide, sucrose, consists of the six-carbon sugars D-glucose and D-
fructose.
• Common polysaccharides include cellulose and starches. Both of these are
homopolymers of D-glucose units, but with different linkages between residues.
• More complex carbohydrate polymers attached to a protein or lipid moiety
(glycoconjugates) are also prevalent in nature.
, Carbohydrates
hydrates of carbon: general formula Cn(H2O)n
Plants: photosynthesis
6 CO2 + 6 H2O C6H12O6 + 6 O2
hn
Polymers: large molecules made up of repeating smaller units
(monomer)
Biopolymers: Monomer units:
carbohydrates (Chapter 23) monosaccharides
peptides and proteins (Chapter 25) amino acids
nucleic acids (Chapter 26) nucleotides
4
