Biological Molecules Flashcards
What is covalent bonding?
Atoms share a pair of electrons in their outer shells. As a result the outer shell of both atoms is filled and a more stable compound called a molecule is formed
What is Ionic bonding?
Ions with the opposite charges attract one another. This electrostatic attraction is known as an ionic bind. They are weaker than covalent bonds
What is hydrogen bonding ?
The electrons within a molecule are not evenly distributed but tend to spend more time at one position. This region is more negatively charged than the rest of the molecule. A molecule with an uneven distribution of charge is said to be polarise so is a polar molecule. The negative region of one polarise molecule and the positively charged region of another attract each other. A weak electrostatic bond is formed between the two. Although each bind is individually weak they can collectively form important forces that alter the physical properties of molecules. This is true for water.
What is hydrolysis
Water molecules are used to break down bonds that link the sub-units of a polymer into monomers
What is a condensation reaction?
The formation of polymers from bonding monomers with water molecules
What is a monosaccharide
A sweet-tasting soluble single sugar monomer
Have the formula (CH2O)n
n can be 3-7
Examples of monosaccharides
Glucose- hexose sugar- C6H12O6
Test for Reducing Sugars
Benedict’s Test
Benedict’s reagent is an alkaline solution of copper(II) sulfate
Ensure sample is already in liquid form
Add 2cm3 of food sample to be tested to a test tube
Add an equal volume of Benedict’s reagent
Heat the mixture in a water bath for 5 minutes
Should turn Blue to Orange
What are disaccharides
Pairs of monosaccharides
Examples of disaccharides
Glucose+glucose= maltose
Glucose+ fructose= sucrose
Glucose+ galactose= lactose
What type of reaction occurs when monosaccharides join
Condensation reaction
The bond formed is a glycosidic bond
Test for non- reducing sugars
Sample is in liquid form
Add 2cm3 of the food test to Benedict’s reagent and filter
Gently boil the test tube for 5 mins
Colour change should not occur
Add another 2cm3 of the food sample to 2cm3 of HCL in a water bath for 5 mins
The dilute HCL will hydrolyse any disaccharides present
Slowly add Sodium Hydrocarbonate
Retest with Benedict’s reagent
Should turn orange-brown
What are polysaccharides
Polymers that formed by combining together many monosaccharide molecules formed by condensation reactions
They are insoluble
Examples of polysaccharides
Starch that is found in plants
Test for Starch
Place 2cm3 of the Samoa’s being tested into a test tube
Add 2 drops of iodine solution and shake
Should turn yellow to blue-black
