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Topic 1-A. Biolgical Molecules (Carbohydrates (Starch (Starch is made up…
Topic 1-A. Biolgical Molecules
Sugars
There are 3 main monosaccharides that need to be known. They are;
Glucose (The structure needs to be also known)
Fructose
Galactose
Monosaccharides form with each other to produce disaccharides (2 monomers) more than this and it becomes a polysaccharide.
The -OH groups on each monosaccharide join to form water with and oxygen left over. This produces a glycosidic bond -O- between the molecules. This is known as a condensation reaction.
The combinations for disaccharides are;
Glucose + Glucose ---> Maltose
Glucose + Galactose ---> Lactose
Glucose + Fructose ---> Sucrose
Benedicts Test for sugars
Heat sample with benedicts reagent and 90 degrees
Sample stays blue
No reducing sugar present
Heat solution with HCl then neutralise with NaCOOH. Heat with benedicts reagent
Sample stays blue
No non-reducing or reducing sugar present
Sample forms green, yellow, orange, brick red precipitate
Non-reducing sugar present
Sample forms green, yellow, orange, brick red precipitate
Reducing Sugar present
Lipids
There are 2 main types of lipids;
Triglycerides
Phospholipids
Triglycerides
These contain a glycerol backbone bonded to three fatty acid tails. The two -OH groups on the glycerol and fatty acid join together to form an -O- bond and water.
The structure is very good for storing energy. The fatty acid hydrocarbon tails contain very large amounts of energy that can be released when the structure is broken down. For this reason triglycerides are used as a storage molecule.
Phospolipids
Phospholipids differ in that they only contain two fatty acid tails. Instead of the third they have a phosphate head. The fatty acid tails have no charge and are non-polar. The phosphate head has a slight negative charge and therefore is polar. This is very important for their function.
Phospholipids play an important role in the structure of our cell membrane. Because the phosphate head is polar, this makes it hydrophilic, because the fatty acid tails are non-polar, they are hydrophobic. This results in phospholipids pairing up with the heads facing outwards and the tails facing inwards. The cell membrane is mainly made up of these phospholipids arranged in a spherical shape
The bonds between glycerols and fatty acids is called an ester bond.
Proteins
Enzymes
Models of Enzymes
Induced Fit Theory
The substrate enters the active site
The binding of the substrates induces the change in the shape of the active site of the enzyme
When the substrate leaves the active site it then returns to its original shape
Lock and Key
The substrate enters the active site
The substrate fits exactly into the active site, they're complementary.
This forms an enzyme substrate complex
Products are formed and no longer fit into the active site
The enzyme is free to take part in another reaction
Definitions/Theory
Definitions
Enzymes are proteins, they have an active site which is the area of the enzyme in which the substrate binds to. Enzymes are
highly specific
due to their tertiary structure
Enzymes are
biological catalysts
. They speed up reactions
without being used up
.
How do they work-
For a reaction to take place, there needs to be energy supplied to the reactants called the activation energy, enzymes lower the activation energy required for a reaction to take place. This lowers the temperature required for such reactions
If two substrate's are
joining together
, the enzyme holds them together overcoming repulsive forces making bonding easier
If the substrate is
breaking down
, fitting into the active site places strain on the bonds making breaking it easier
Carbohydrates
Starch
Starch is made up of two different polysaccharides of alpha glucose, amylose and amylopectin.
Amylose is a long unbranched chain of glucose forming a helix. This makes it compact and good for storage.
Amylopectin is a long branched chain of glucose. The side branches mean the surface area is increased and the enzymes can break it down rapidly back into glucose.
Glycogen
Glycogen is similar in structure to amylopectin. It's a long branched chain of glucose. The only difference is that it contains more branches than amylopectin.
Cellulose
Cellulose is made of B-glucose rather than A-glucose. It is made of long straight chains of glucose in which each glucose is reversed orientation by 180. The chains run parallel and pack close together where the hydrogens form crosslinks between the chains called microfibrils.
The bonds in all carbohydrates is called a glycosidic bond.