Topic 2 Biological molecules Flashcards
Test for reducing sugar
Benedict’s test
Test for starch
Iodine test
Test for lipid
Emulsion test
Test for protein
Biuret test
Test for non-reducing sugar
- Add dilute hydrochloric acid
- Boil for at least 3 min
- Cool test tube
- Add dilute sodium hydroxide solution
- when nuetralised, test with Benedict’s solution
Define monomer
made of elements (carbon, hydrogen, oxygen, nitrogen)
eg. glucose, amino acid, nucleotides
Define polymer
repeating monomers
eg. starch, protein, DNA
State examples of:
1. monosaccharide
2. disaccharide
3. Polysaccharide
- monosaccharide
- glucose
- fructose
- galactose - disaccharide
-sucrose - Polysaccharide
- starch
Define macromolecule
Large polymers
Role of covalent bond in joining smaller molecules
condensation- two molecules combine by removal of water; forming a covalent bond
Hydrolysis- molecules break down by addition of water
Reducing sugar and non-reducing sugar
reducing sugar
- glucose
- fructose
- maltose
non-reducing sugar
- sucrose
State Polysaccharides
Starch, glycogen, cellulose, amylose, amylopectin
Role of Starch
- storage molecule in plants
- food reserve
- amylose+amylopectin
Structure of Amylose
- made of a-glucose
- linked by 1-4 glycosidic bond
- long, helical
- unbranched, linear chain
Structure of Amylopectin
- made of a-glucose
- linked by 1-4 and 1-6 glycosidic bond
- branched, shorter chains
Structure of Glycogen
- (similar to amylopectin)
- more branched than amylopectin
- made of a-glucose
- linked by 1-4 and 1-6 glycosidic bond
- storage of carbohydrated in animals
- clumped together
- abundent in liver and muscle cells
Structure of cellulose
- structural role in plants (prevent cell bursting, withstand pressure, fully permeable)
- made of B-glucose
- linked by 1-4 glycosidic bond
- unbranched, straight chain, linear
- form fibres
- provide tensile strength
What proteins are made of
carbon, hydrogen, oxygen, nitrogen (or sulphur)
2 types of amino acids
- Glycine (R groups is H)
- Cysteine (R groups contains sulphur)
Properties of a peptide bond
- very strong covalent bond
- between -COOH and -NH2
Protein Bonds
- Hydrogen bond
- individually weak but cumulatively strong
- between NH- and CO- - Disulphide bond
- very strong covalent bond
- between sulphur atoms of cysteine - Ionic bond
- between ionised amine and carboxlyic group
- easily broken by pH and temperature changes - Hydrophobic interactions
- between non-polar R groups
- weakest type of bond
Hydrophobic < Hydrogen < Ionic < Disulphade, peptide
Protein structure (primary, secondary, tertiary, queternary)
Primary
- linear sequence of amino acids
- peptide bond
- condensation reaction
Secondary
- alpha helix, Beta pleated sheet
- Hydrogen bond
- between O or carboxyl group and H or amino acid group
Tertiary
- Hydrogen, Disulphide, Ionic, Hydrophobic
- coil and folding of secondary structure (into 3D shape)
- One polypepetide chain only
Queternary
- Hydrogen, Disulphide, Ionic, Hydrophobic
- 2 or more polypeptide chains
(eg. Haemoglobin, Collagen)
Globular and Fibrous protein structure
Globular protein
- Spherical/ ball shape
- mostly tertiary (sometimes queternary)
- soluble
- more functional roles
- (eg. enzymes, antibodies, hormones, haemoglobin)
Fibrous protein
- long, parallel strands
- mostly secondary structure
- insoluble
- more structural roles
- (eg. collagen, keratin)
Collagen Structure
- Long, thin structure
- Insoluble
- structural function
- provide tensile strength
- 3 polypeptide chain
- triple helix held by covalent bonds (covalent bonds are strong)
- triple helices are staggered (no weak areas)
- every 3rd amino acid is glycine
- quaternary structure
- less sensitive to changes in pH and temperature
- polypeptide -> Triple helical collagen molecule -> fibrils -> fibres
