BIOL1020 Lecture Notes - Lecture 3: Dehydration Reaction, Covalent Bond, Polymerization

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20 May 2018
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L3 - Components of a cell!
Macromolecules
Cell are made up of macromolecules !
carbohydrates !
Lipids !
Proteins !
Nucleic acids !
Why do I need to know this:!
-knowledge about macromolecules good for dietary choices because macromolecules are in our
food !
Polymers
Polymerisation: the process through which monomers form repeated chains of molecules
through. This happens through a dehydration reaction. !
Dehydration reaction (synthesising polymer):
Two molecules covalently bond through loss of water molecule !
Short polymer provides the +H ion!
Unliked monomer provides the -OH ion !
Hydrolysis (breaking down polymer):
polymers are shortened by removing monomers from each end using hydrolysis !
In cells, enzymes facilitate this process by attacking a polymer bond!
A water molecule is added to the polymer to break up a covalent bond. One side will hold the
OH and the other side will take the +H !
In the body !
we eat complex polymers that are broken down through hydrolysis !
The monomers are then absorbed into blood stream and distributed to body cells !
Cells then use dehydration to assemble monomers into new polymers for cell function!
These two reactions are not just for polymers but other bonds too like lipids.!
Carbohydrates
Carbohydrates are fuel and building material !
the monomeric units of carbohydrates are sugars (saccharides) !
There are three types of carbohydrates!
Monosaccharides !
simplest sugars !
During cellular respiration, glucose is broken down for energy; it is a fuel. Sugar is more simple
to break down than fat and so is a fast fuel !
Their carbon skeletons are materials for small organic molecules like amino acids !
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They are the monomers from which larger carbohydrates are built !
They can be linear or form rings in water (usually forms rings because its most stable as rings). !
Readily moved through blood stream!
!
(know the ring structure and the
position of the carbons)!
Monosac. Has a carbonyl group
(pink) and many OH groups. !
Know the bottom 1-4 glucosidic
linkage!
Disaccharides!
two monosac. Linked by glycosidic linkage (this is the name for the covalent bond between two
monosac. Via dehydration reaction. !
Example: glucose + glucose = maltose !
Example: glucose + fructose = sucrose !
Example: glucose + galactose = lactose !
Even disaccharides need to be broken back down intro monosac. To be used !
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Polysaccharides!
they are polymers of thousands of monosac. Joined via glycosidic linkage !
Some examples are starch and glycogen !
Starch
is a polymer of glucose monomers !
Form of glucose storage in plants inside plastids !
Plants then use this starch later via hydrolysis !
Most glucose monomers are joined by 1-4 linkage and has few (1-6 linkage)!
1-6 linkage causes branching because joining those carbon make very irregular shapes !
Humans and animals have enzymes to hydrolyse plant starch !
This is because glucose monomers are in alpha configuration!
Gylcogen
animals and humans store sugar as glycogen because it is very branded and easier to break
down !
1-6 glycosidic linkage. The 1st carbon is connected to the 6th carbon at an angel. !
has alpha configuration !
We store glycogen in muscles and liver ready to
be burned up !
Cellulose
Only in plants and not for energy but for shape !
It cannot be broken down due to no branches
and linking hydrogen bonds in between !
It is a beta configuration!
Branched polymer is easier to use because there
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