Download Biological Macromolecules

Biological Macromolecules
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Large molecules that perform many important
biological functions
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Carbohydrates
Lipids
Proteins
Nucleic Acids
Many are polymers
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Large molecule that is made of repeating units
of identical or similar subunits
Each subunit=monomer
Biological Polymerization
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Accomplished through covalent
bonding
Often takes place via
dehydration reactions which
result in the release of a water
molecule/bond formed
Process can be reversed by
hydrolysis which breaks bonds
by the addition of water
Fig. 5-2
HO
1
2
3
H
Short polymer
HO
Unlinked monomer
Dehydration removes a water
molecule, forming a new bond
HO
2
1
H
3
H2O
4
H
Longer polymer
(a) Dehydration reaction in the synthesis of a polymer
HO
1
2
3
4
Hydrolysis adds a water
molecule, breaking a bond
HO
1
2
3
(b) Hydrolysis of a polymer
H
H
H2O
HO
H
Carbohydrates
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Comprises sugars and polymers of sugars
Used for variety of functions
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Energy-simple sugars
Storage of energy-starches
Structural components-cellulose and chitin
Monosaccharides
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Simple sugars=monomers
Usually have chemical composition of CxH2xOx
Can exist as chains or rings (usually rings in solution)
Monosaccharides combine to form disaccharides
Sugar Classification
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Sugars may be classified by:
Number of carbons in chain
 Location of carbonyl group
 Position of side groups from asymmetrical carbon
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Fig. 5-3
Trioses (C3H6O3)
Pentoses (C5H10O5)
Hexoses (C6H12O6)
Glyceraldehyde
Ribose
Glucose
Galactose
Dihydroxyacetone
Ribulose
Fructose
Disaccharide Formation
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Disaccharides are formed by the dehydration reaction
between two monosaccharides
Bond between monosaccharides is called the glycosidic
linkage
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Linkage may occur between different different carbons
Fig. 5-5
1–4
glycosidic
linkage
Glucose
Glucose
Maltose
(a) Dehydration reaction in the synthesis of maltose
1–2
glycosidic
linkage
Glucose
Fructose
(b) Dehydration reaction in the synthesis of sucrose
Sucrose
Storage Carbohydrates
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Polysaccharides=many monomers in one polymer
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Starches =plants use for energy storage
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Glucose is most common monomer used
Amylose is unbranched chain of glucose monomers
Glycogen=animals use glycogen as medium-term
energy storage
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Glycogen is highly-branched polymer of glucose
monomers
Cells contain enough glycogen for approximately one
day’s activity
Structural Carbohydrates
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Cellulose
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Most abundant organic compound on earth
Plants use cellulose as structural component of cell
walls
Most animals cannot digest
Certain bacteria can degrade cellulose
 Cows and termites have symbiotic relationship w/ bacteria
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Fiber in your diet usually means cellulose
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Not digested so acts as a mechanical cleansing
mechanism as it passes through the intestines
Comprises polymerized units of glucose
Starch vs Cellulose
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Both use 1-4 glycosidic
linkage of glucose
Starch uses a
configuration of glucose
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Results in helical
molecule
Cellulose uses B
configuration of glucose
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Forms linear strands
that interact to form
fiber bundles
Structural Carbohydrates 2
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Chitin
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Comprises polymer of N-acetylglucosamine (NAG)
Similar to glucose but possesses a nitrogen-containing
side chain
 Major component of insect and crustacean exoskeleton
 Major component of fungal cell walls
 Can be flexible or made rigid by interacting with calcium
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Cross-links the structure
Carbohydrate Summary
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Can be used for energy, storage and structural
uses
Designated by length of carbon chain, location of
carbonyl group, and position of side groups
around asymmetric carbons
Glucose and modified glucose is used in all three
major functions of carbohydrates