BISC 101 Lecture Notes - Lecture 2: Collagen, Triple Bond, Guanine
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19 Jun 2015
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BISC 101 – Lecture 2 - Biological Molecules
The Molecules of Life
•Living things are made up of four classes of large biological molecules:
oProteins
oNucleic Acids
oCarbohydrates
oLipids
Macromolecules Are Polymers, Built from Monomers
•Polymer: A long molecule consisting of many similar building blocks
oThe building block molecules are called monomers
oPolymer is like a chain while the links within the chain are the monomers
•Three of the four classes of life’s organic molecules are polymers
oCarbohydrates, proteins, and nucleic acids are all polymers
oLipids are NOT polymers
Synthesis and Breakdown of Polymers
•Condensation or Dehydration Reactions: A process where monomers form
polymers by removing a water molecule to form a new bond
•Hydrolysis: A process where polymers form monomers by adding a water
molecule to break a bond
Carbohydrates Serve as Fuel and Building Material
•Carbohydrate: Any of a class of molecules that contain a carbonyl (C=O) group,
several hydroxyl groups (-OH), and several carbon – hydrogen bonds (C-H)
•Carbohydrates include both sugars and their polymers
•Monosaccharide: Simplest carbohydrates, sugar or monomer
•Glucose: C6H12O6 is the most common monosaccharide
•Monosacharrides are classified by:
oThe location of the carbonyl group: Aldehyde Sugar (Aldose) or Ketose
Sugar (Ketose)
oAldose sugar is found at the end of a chain
oKetose sugar is found within the carbon chain
•Monosaccharides are also classified by the number of carbons in their carbon
skeleton
oTrioses: Three carbon sugars
oPentose: Five carbon sugars (Ribose)
oHexose: Six carbon sugars (Glucose)
•Monosaccharides are also classified in their spatial arrangement of their atoms
oMonosaccharides may be linear or can form ring structures
oIn aqueous solution, sugars tend to form ring structures
Carbon 1 bonds to the oxygen attached to carbon 5
oGlucose can form into a linear form or ring form
oDifferent configurations produce alpha – glucose and beta – glucose
Alpha – Glucose: The C – OH bond is forming downwards
Beta – Glucose: The C – OH bond is forming upwards
•Dissacharides: Contains two sugars/monosaccharides joined by a glycosidic
linkage
•The two monomers can be identical
oEx: Glucose + glucose = Maltose
•The two monomers can be different
oFructose + Glucose = Sucrose
•Polysaccharides: Polymers that form when two or more monosaccharides are
linked together
oAKA. Complex carbohydrates
•Glycosidic Linkage: Simple sugars polymerize when a condensation reaction
occurs between tow hydroxyl groups resulting in a covalent bond
•Location of glycosidic bonds vary as every monosaccharide contains at least 2
hydroxyl groups
Storage Polysaccharides
•Starch: Storage Polysaccharide in Plants
oConsists of entirely alpha – glucose monomers joined by glycosidic
linkages
oStarch is a mixture of amylose and amylopectin
oAmylose: Unbranched molecule, soluble, linear
oAmylopectin: Branched, insoluble
•Glycogen: Storage Polysaccharide in Animals
oGlycogen is stored in the liver and in muscles for humans
oWhen you exercise, enzymes break gown glycogen into glucose
monomers for energy
oGlycogen is a branched polymer of alpha – glucose
Structural Polysaccharides
•Cellulose: A Structural Polysaccharide in Plants
oCellulose is the major component of the tough cell wall for plants
oPolymer of glucose but has different glycosidic linkages than starch
oCellulose is a polymer of beta – glucose monomers joined by glycosidic
linkages
oHas flipped orientation in the glycosidic bonds
oThe flipped orientation allows
A linear molecule rather than a helix formation
Permits multiple hydrogen bonds to form between adjacent parallel
strands of cellulose = allows strong structural support
•Chitin: Structural Polysaccharide in Fungi and Animals
oMost important component of the external skeletons of insects,
crustaceans, anthropoids, and cephalopod beaks
oProvides structural support for the cell walls of fungi
oCan be used for surgical thread
oSimilar to cellulose
oNot made of glucose but instead made of N – acetylglucosamine
oAlso have a flipped orientation between hydrogen bonds
oThe subunits form hydrogen bonds between adjacent strands
oProvide a stiff and protected sheet
Lipids: A Diverse Group of Hydrophobic Molecules
•Lipids: Carbon – containing compounds in organisms that are largely nonpolar
and hydrophobic
oDoes not dissolve
oLipids do dissolve in liquids consisting of nonpolar organic compounds
•Lipids cannot dissolve in water because they have many hydrocarbons which
form non – polar covalent bonds
•Lipids have little or no affinity for water
•Lipids are the one class of large biological molecules that do NOT form polymers
•Fatty Acid: Consists of a hydrocarbon chain bonded to a carboxyl functional
group
oFatty acids are key building blocks of the lipids found in organisms
Fats
•Subcategory of lipids; Fat is a type of lipid
•Fats are constructed from two types of smaller molecules; Glycerol and fatty
acids
•Glycerol: Three – carbon alcohol with a hydroxyl group attached to each carbon
•Fatty Acid: Consists of a carboxyl group (COOH) attached to a long carbon
skeleton
•Fats: Composed of three fatty acids linked to 1 glycerol
oC – C bonds and C – H bonds hold a lot of energy
oCondensation occurs between a hydroxyl group of glycerol and carboxyl
group of a fatty acid
oEster linkage: Bond between the glycerol and fatty – acid molecules
•Fats are also called triglycerides
•Fats are not polymers* Fatty acids are not monomers*
•Fatty acids are not linked to form macromolecules like amino acids
•Fats separate from water because water forms hydrogen bonds with each other
and excludes fats
•Fatty acids vary in length, number and locations of their double bonds
•Saturated Fats
oMaximum number of hydrogen atoms possible
oNo double bonds