1 Biological Molecules and Enzymes Flashcards
Polar Molecule
A molecule with an uneven distribution of charge
Polymerisation
The process by which monomers join to form long molecules called polymers
Monomer of a polysaccharide
monosaccharide or single sugar e.g. glucose
Monomer of a polynucleotide
mononucleotide
Monomer of polypeptides
amino acids
Condensation reaction
reaction that produces water
Hydrolysis reaction
breaking down a polymer with the addition of water
Examples of monosaccharides
Glucose, galactose, fructose
Draw isomers of glucose
Alpha = H at top, OH at the bottom
Beta OH at the top, H at the bottom
Reducing sugar
All monosaccharides and some disaccharides with the ability to donate an electron to reduce another chemical
Test for reducing sugar
-Add food sample.
-Add equal volume of Benedict’s reagent.
-Heat gently in water bath.
Blue - No sugar
yellow >orange > red - Increasing amount of sugar
Bond between monosaccharides
Condensation reactions
GLYCOSIDIC bonds
Glucose + Glucose
Maltose
Glucose + Fructose
Sucrose
Glucose + Galactose
Lactose
Test for non reducing sugar
- Benedict’s test.
- then add 2cm of dilute HCl and heat in boiling water bath (hydrolysis)
- Add sodium hydrogencarbonate (neutralisation)
- Redo Benedict’s test
Blue - No sugar
yellow >orange > red - Increasing amount of sugar
Test for starch
Iodine
Orange to Blue/Black
Starch features
- found in plants
- straight or branched
- insoluble so doesn’t affect WP
- does not diffuse out of cells
- compact
- hydrolysed to form alpha glucose
- branched to release glucose quickly
Glycogen features
- found in animals and bacteria
- insoluble so doesn’t affect WP
- does not diffuse out of cells
- compact
- hydrolysed to form alpha glucose
- highly branched to release glucose quickly
Cellulose features
- Made of Beta glucose
- straight unbranched chains
- hydrogen bonding
- microfibrils to form fibres
- plant cell wall component
- strong
Roles of lipids
- Energy source
- Waterproofing
- Insulation
- Protection
Bonding in triglycerides
3 fatty acids joined to 1 glycerol molecule
condensation reactions
ESTER bonds
Saturated
Mono-unsaturated
Polyunsaturated
No double bonds in the fatty acid
One double bond
More than one double bond
Triglyceride properties
- High ratio of C-H energy storing bonds
- low mass to energy ratio (good for storage)
- Insoluble (do not affect WP)
- good source of water when oxidised
Phospholipid structure
Hydrophilic phosphate head
Hydrophobic fatty acid tail
Phospholipid properties
- polar molecules so form a bilayer / barrier around cells
- can form glycolipids important in cell recognition
Test for lipids
- Add ethanol to food sample and shake thoroughly to dissolve lipid
- Add water and shake gently
Cloudy white precipitate - lipids present
Draw an amino acid
- C in middle
- Amine (-NH2) group
- Opposite Carboxyl (-COOH) group
- H
- Opposite R (variable group)
Bonds between amino acids
Condensation reaction
Between -NH2 of one amino acid and -COOH of another
PEPTIDE bonds
Bonding in secondary protein structure
Hydrogen bonds between polar groups
Negative C=O
Positive N-H
Alpha helix and Beta pleated sheets
Bonding in tertiary protein structure
- Disulfide bonds between cysteine R groups
- Weak Hydrogen bonds between polar molecules
- Ionic bonds between amine and carboxyl groups not involved in peptide bonds
- Van der waals, very weak bonds between non polar groups
Structure of Quarternary proteins
More than one polypeptide chain
Same bonds as in tertiary structure
Can contain prosthetic (non protein) groups
Test for proteins
Add Biurets solution (weak copper (II) sulphate and mix
Blue to purple change - presence of protein
