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Stofwisseling les 3 samenvatting
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Werkcollege stofwisseling les 3The most important large molecules found in al livings can be sorted into just four main classes:
- Carbohydrates
- Lipids
- Proteins
- Nucleic acids
Macromolecules: in molecular scale; these molecules are huge:
- Carbohydrates
- Proteins
- Nucleic acids
Macromolecules are polymers built from monomers
Large carbohydrates, proteins and nucleic acids are chain-like molecules called polymers.
A polymer is a long molecule consistng of many similar or identcal building blocks linked by covalent
bonds. The repeatng units that serve as the building blocks of a polymer are smaller molecules
called monomers.
The syntheses and breakdown of polymers
Although each class of polymer is made up of a diferent type of monomer, the chemical mechanisms
by which cells make and break down polymers are basically the same in all cases.
In cells, these processes are facilitated by enzyme, specialized macromolecules that speed up
chemical reactons.
The reacton connectng monomers is a good example of a dehydraton reacton, a reacton in which
two molecules are covalently bonded to each other with the loss of a water molecule.
Dehydrated reacton; synthesizing a polymer: Uit een polymer verdwijnt de H2O (komt vrij) en zo
ontstaat een lange polymer.
Hydrolysis breaking down a polymer: Hierbij wordt H2O toegevoegd en wordt een lange polymer
afgebroken.
De OH sluit aan bij de monomer, en de H sluit aan bij de polymer. Dus OH komt bij de molecuul die al
een H heef en de H komt bij de molecuul die al een OH heef.
Dehydraton reactons and hydrolysis can also be involved in the formaton or breakdown of
molecules that are not polymers, such as some lipids.
The diversity of polymers
The macromolecules are constructed from only 40 to 50 common monomers and some others that
occur rarely. Building a huge variety of polymers from such a limited number of monomers is
analogous to constructng hundreds of thousands of words from only the 26 leters from the
alphabet.
The key is arrangement, the partcular linear sequence that the units follow.
The molecular logic of life is simple but elegant; small molecules common to all organism’s act as
building blocks that are ordered into unique macromolecules.
, Carbohydrates serve as fuel and building material
Carbohydrates include sugars and polymers of sugars.
The simplest carbohydrates are the monosaccharides; these are the monomers from which the more
complex carbohydrates are built.
Disaccharides are double sugars, consistng of two monosaccharides joined by a covalent bond.
Carbohydrate macromolecules are polymers called polysaccharides, composed of many sugar
building blocks.
Sugars
Monosaccharides generally have molecular formulas that are some multple of the unit CH 2O.
Glucose has an structure with C=O and –OH. Depending on the locaton of the carboxyl group, a
sugar is either an aldose (aldehyde sugar) or an ketose (ketone sugar).
A criterion for classifying sugars is the size of the carbon skeleton, which ranges from three to seven
carbons long (hexoses, pentoses, trioses are the most common).
Monosaccharides, partcularly glucose, are major nutriton’s for cells. In the process known as
respiraton, cells extract energy from glucose molecules by breaking them down in a series of
reactons.
Disaccharide consists of two monosaccharides joined by a glycosidic linkage, a covalent bond formed
between two monosaccharides by a dehydraton reacton.
Dehydraton reacton: Hierbij komt H2O vrij wanneer er 2 monosaccharides samenbinden.
Disaccharides must be broken down into monosaccharides to be used for energy by organisms.
Polysaccharides
Polysaccharides are macromolecules, polymers with a few hundred to a few thousand
monosaccharides joined by glycosidic linkages.
Some polysaccharides serve as storage material, hydrolyzed as needed to provide sugars for cells.
Other polysaccharides sere as building material for structure that protect the cell or the whole
organism.
The architecture and functon of polysaccharide are determined by its sugar monomers and by the
positons of its glycosidic linkages.
Storage polysaccharides
Plants store starch, a polymer of glucose monomers, in amylose (unbranched) and amylopectn
(somewhat branched).
Glucogen is stored in muscle tssue and is extensively branched.
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