bio molecules Flashcards
Carbohydrates
- Polysaccharides of monosaccharides
- contain C, H, O
- monosaccharides joined by condensation reactions
= disaccharides, then poly - form glycosidic bonds
- broken by hydrolysis
Disaccharides
Glucose + fructose = sucrose
Glucose + glucose = maltose
Glucose + galactose = lactose
Reducing sugars test
Monosaccharides and some disaccharides
- add Benedict’s reagent to sample (in excess)
- heat in water bath
+ coloured precipitate
(Blue to brick red)
- blue
Non-reducing sugars test
Eg sucrose
If reducing sugars test negative
Break into monosaccharides:
- add dilute HCl
- heat in water bath
- neutralise with sodium hydrogencarbonate
Do reducing sugars test
+ coloured precipitate
(Blue to brick red)
- blue
Starch
Plants store excess glucose as starch
2 polysaccharides of alpha glucose
Amylose
- long, unbranded chain of alpha glucose
- angle of glycosidic bonds = coiled
- compact for storage
- 1,4 glycosidic bonds
Amylopectin
- long, branched chain of alpha glucose
- branches allow enzymes to hydrolyse glycosidic bonds easier, released quick
- 1,4 and 1,6 glycosidic bonds
Insoluble in water
- doesn’t affect water potential or osmotic activity
- good for storage
How to test for starch
- Add iodine dissolved in potassium iodide solution
+ blue-black - brown/orange
Glycogen
Animals store glucose as glycogen
Polysaccharides of alpha glucose
Long, branched chain
Enzymes can hydrolyse glycosidic bonds easier, broken down and released quick
Compact for storage
(Angle of glycosidic = coiled)
- 1,4 and 1,6 bonds
Cellulose
In plant cell walls
Long, unbranched chains of beta glucose
= straight cellulose chains
1,4 glycosidic bonds
Linked by hydrogen bonds = microfibrils
Strong fibres to provide structural support
Due to positive of OH and H in beta, to form glycosidic bonds:
- every other molecule of b inverts
- allows hydrogen bonds between chains
Triglycerides
Glycerol + 3 fatty acids
- lipid
- joined by condensation reactions
- hydrophobic tails - insoluble in water
Fatty acid tails - contain chemical energy
- lots of energy released when hydrolysed
Insoluble - don’t affect water potential
- no osmotic activity
- arrange in droplets with hydrophobic tails facing in
function of triglycerides
energy storage
- long hydrocarbon tails store lots of energy in bonds, released when broken down
insoluble as hydrophobic - doesn’t affect water potential
act as insulator eg myelin sheath
Saturated fatty acids
Saturated
- no double binds between carbon
Unsaturated
- at least one double bind between carbons
Phospholipids
Glycerol + 2 fatty acids + phosphate
- phosphate group hydrophilic
- fatty acids hydrophobic
= arrange in belayer
Centre hydrophobic
- water soluble substances can’t pass through, barrier
Test for lipids
Emulsion test
- shake substance with ethanol (until dissolves)
- poor solution in water
+ milky solution
Proteins
Polymers of amino acids
- formed by condensation reactions = dipeptides, then poly
- form peptide bonds
Have same general structure
- carboxylate group, amine group
And variable group
- 4 structural levels
Quaternary, tertiary, secondary and primary
Structural levels of proteins
Primary
- sequence of amino acids in a polypeptide
Secondary
- folding of primary using hydrogen bonds
- alpha helix or beta pleated sheet
Tertiary
- folded and coiled further
- hydrogen, ionic and disulphide bridges
- for 1 chain = final 3D structure
Quaternary
- multiple polypeptide chains joined by bonds
- final 3D structure
4 functions of proteins
Enzymes
Antibodies
Transport proteins
Structural proteins
Test for proteins
Biuret test
- add sodium hydroxide (=alkaline)
- add copper II sulphate solution
+ purple
- blue
What are enzymes?
Catalyse metabolic reactions
- lower activation energy for a reaction
- less energy (heat) needed for reaction to start, speeds up rate
Can hold molecules together to join them
- bonds form more easily
Or binds to active site and puts pressure on bonds (bends them)
- substrate breaks up more easily
Proteins with specific tertiary structure = specific shape active site
If denatured, tertiary structure (shape) changes
= doesn’t fit so can’t catalyse