Biological Molecules Flashcards
Food Test- Proteins
Biuret Test:
-Add NaOH to sample
-Add few drops of dilute CuSO4 solution
Positive result: Solution turns mauve
Food Test- Starch
Iodine Test:
-Add a few drops of iodine solution to sample
Positive result: Turns blue-black
Food Test- Lipids
Emulsion Test:
-Dissolve sample by shaking with ethanol
-Pour solution into water in test tube
Positive result: White emulsion forms
Food Test- Reducing Sugars
Benedict’s Test:
-Heat sample with Benedict’s reagent
Positive Result: Orange-red precipitate forms
Food Test- Non-Reducing Sugars
Benedict’s Test:
-Check for reducing sugars first
-Hydrolise sample by heating with dilute HCl
-Neutralise by adding sodium hydrogen carbonate
-Test again with Benedict’s reagen
Positive result: Orange-red precipitate formed
Define macromolecules
Very large organic molecules
Define monomers
Small building blocks in molecules
Define polymers
Several monomers joined together
What is a condensation reaction?
The process by which 1 monomer joins to another (formation of bonds) and a water molecule is removed
What is a hydrolysis reaction?
Water molecules are added in the process of breaking bonds between molecules
What is a monosaccharide?
Single sugar, e.g. glucose
What is a disaccharide?
Two monosaccharides joined together, e.g. sucrose
What is a polysaccharide?
Many monosaccharides joined together to form a very large molecule, e.g. starch
What bond forms between two monosaccharides in a condensation reaction?
Glycosidic bond, e.g. maltose from alpha glucose forms 1,4-glysodic bonds.
Describe the structure of amylose
- Joined together by alpha glucose monosaccharides
- Coils up in helix
- Bonded by 1,4-glycosidic bonds
Describe the structure of amylopectin
- Branched chains of alpha glucose residues
- This is because joined by 1,6 and 1,4-glycosidic bonds`
Difference between the structure of starch molecules and cellulose molecules
- Starch is formed from alpha-glucose whereas cellulose if formed from beta-glucose
- The position of H and OH groups on Carbon-1 is inverted
- Starch doesn’t contain fibrils
- Starch doesn’t have H bonds between molecules
Name 3 adaptations of starch and explain why they are beneficial
1) Insoluble, so it won’t affect water potential
2) Helical, so it’s compact
3) It’s a large molecule, so it cant leave the cell
Describe the structure of glycogen
- Alpha glucose polymer
- Many branches on molecules, so high SA, faster hydrolysis for glucose production
What is the purpose of glycogen?
It is a polysaccharide made of excess glucose that is stored in muscles for respiration but mostly in the liver and is continuously broken down to maintain blood sugar levels.
Explain how cellulose is adapted to its function
- Long and straight chains;
- Become linked together by many hydrogen bonds to form fibrils;
- Provide strength (to cell wall).
Describe the structure of cellulose
- Made of beta glucose
- Every other glucose is upside down
- 1,4-glycosidic bonds
- Chains linked by H bonds
- Formed into strong microfibrils
- Abundant polysaccharide, enzymes can’t hydrolyse
Describe the structure of amino acids
- Central C
- Carboxyl group (OH–C=O)
- H atom
- R group
- Amine group (H–N–H)
What is the name given for a long chain of amino acids?
Polypeptides
