2.0 Biological Molecules Flashcards
test for reducing sugars
1. Add benedicts reagent 1:1 (blue due to copper (II) sulfate ions)
2. heat the solution using a water bath (90 degrees)
3. positive result: coloured brown percipitate formed, blue to brown/brick-red
- copper (II) sulfate is reduced to copper (I) oxide which is insoluble in water
- semi-quantitative, degree of colour can determine the conc.
- blue -> green -> orange -> brick red
test for non-reducing sugars
- acid or enzyme hydrolysis
- sucrose (most common non-reducing sugar)
1. dilute HCL (catalyst) added to sample solution (1:2 ratio), hydrolyses into reducing sugar
2. heat in water bath for 2 min
3. hydrogencarbonate added to neutrilise (turn alkaline)
4. use indicator (red litmus paper) to identify when solution has been neutrilised
4. carry out benedicts test
test for starch
- Iodine test (orange-brown)
- iodine in potassium iodide solution (iodine is insoluble in H2O)
- iodide ions react with centre of strach molecules
- positive: blue-black colour change
- useful in enzyme digestion (amylase)
test for lipids
- lipids are non-polar molecules
- only soluble in organic solvents (ethanol)
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emulsion test
1. add ethanol to sample solution (2cm^3)
2. shake to mix solution
3. add mixture to a test tube of water
4. milky emulsion should form - the more cloudy, the greater the lipid conc.
test for proteins
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biuret test
1. sample liquid solution treated with NaOH or KOH (to make the solution alkaline)
2. few drops of copper (II) sulfate solution (blue)
3. positive: colour change from blue to purple/lilac - at least 2 peptide bonds must be present in any protein molecules
- if sample contains amino acids or dipeptides, result will be negative
semi-quantitative reducing sugars test
- setting a standard solutions with known conc. of reducing sugars
- created using serial dilution of existing stock solution
- each conc treated the same using benedicts test, in excess
- heat in water bath (5min)
- colour change of all samples according to conc.
- procedure carried out for unknown conc. sample
- time how long it takes for first colour change to occur (higher conc. shorter time)
- compare final colour of unknown conc. to stock solutions to determine conc.
Alpha and Beta Glucose
- alpha: dudd (stud)
- beta: dudu (excrement)
- down up based on Hydroxyl group
monomer
- simple molecule which is used as a basic building block for the synthesis of a polymer
- many monomers are joined together to make the polymer, usually by condensation reactions (produces h2o every bond constructed)
- monosaccharides (carb) , amino acids (protein), nucleotide (nucleic acids)
- lipids dont really have monomers
polymer
- giant molecule made from monomers
- polysaccharides, proteins, nucleic acids
macromolecule
- large and complex molecules
- **may or may not contain monomers **
- therefore polymers can be macromolecules but macromolecules cannot always be polymers
- polysaccharides, nucleic acids, proteins
monosaccharide
- a molecule consisting a single sugar unit
- the simplest form of carbohydrate and cannot be hydrolysed further
- a general formula of (CH2O)n.
- all reducing sugars
- ribose (C5H10O5)
- glucose (C6H12O6)
disaccharide
- sugar molecule consisting of two monosaccharides joined together by a glycosidic bond through condensation
- maltose (2 alpha-glucose)
- sucrose (alpha-glucose + fructose)
- lactose (alpha-glucose + Beta-glucose)
polysaccharide
-
polymer whose subunits are
monosaccharides joined together by glycosidic bonds through condensation - cellulose (Beta-glucose)
- starch (Alpha-glucose : amylose & amylopectin)
- glycogen (Alpha-glucose)
Covalent bonds
- sharing of two or more electrons between two atoms
- shared equally : non-polar
- shared unequally : polar
- stable and high in energy
- produced when two monomers are close enough to overlap
Glycosidic bonds
- a covalent bond
- occurs between monosccharides
- forms during condensation with the removal of one water molecule
- forms polysaccharides and disaccharides
- the number of bonds formed = the number of water molecules removed
breakage of glycosidic bonds
- separated by hydrolysis which breaks the glycosidic bond between monomers
- e.g.: Acid hydrolysis of non-reducing sugars (sucrose) breaks glycosidic bond in order to
retrieve its monomers (reducing sugar)
Starch
- energy store of plants
- considered as a macromolecule
- due to many monomers, takes longer to digest than glucose
AMYLOSE:
- unbranched/linear
- helix shaped / helical : more compact harder to digest
- alpha-glucose
- 1,4 glycosidic bonds
- longer chains
AMYLOPECTIN:
- branched molecule
- alpha-glucose
- 1,4 glycosidic bonds and 1,6 glycosidic bonds forming cross-links
- shorter chains
- branches result in more terminals for easier hydrolyses for cellular respiration and storage
Glycogen
- energy store of animals and fungi
- highly branched, more than amylopectin : easier to be hydrolysed
- alpha-glucose
- 1,4 and 1,6 glycosidic bonds: more 1,6 due to it having more branches
- more compact, helps animals store more energy : easier for glucose to be condensed or hydrolysed onto molecule
- liver and muscle cells have high conc. of glycogen (present as visible granules)
Cellulose
- in cell wall of plant cells
- made from β-glucose units that form β-1,4 glycosidic bonds.
- Alternate β- glucose molecules are rotated 180 degrees
- Hydrogen bonds are also formed between parallel cellulose molecules
- cellulose molecules become tightly cross-linked to form bundles called microbrils
- Microbrils held together in bundles called fibres by hydrogen bonding
- Fibres increase tensile strength to withstand osmotic pressure
- makes plant rigid and maintains cell
shape - gaps between fibres so freely permeable
Triglycerides
STRUCTURE:
- condensation of 3 fatty acid chains and a glycerol molecule
- forming an ester bond, (3 in total)
- Fatty acid chains are long hydrocarbon with carboxylic head
- Glycerol is an alcohol containing 3 OH groups
- non-polar
- unsaturated: c=c bonds that are easier to break and melt easily, more than one is polyunsaturated
- saturated: contain c-c bonds that are solids at room temperature.
FUNCTION:
- Better energy reserves than carbohydrates as more CH bonds
- Acts as an insulator and provides buoyancy
- A metabolic source of water as gives CO2 and H20 on oxidation in respiration
Phospholipids
STRUCTURE:
- hydrophilic head: a phosphate group and glycerol
- hydrophobic tail: 2 fatty acid chains
- due to the partial negative charge on the phosphate group that gets attracted to the partial positive charge on the hydrogen atom of the water molecule
FUNCTION:
- Cell Membrane and Transport > Fluid Mosaic Membranes > phospholipids
amino acids
STRUCTURE:
- only difference in the R- groups/ variable side chains and will always contain an amine group (basic), carboxyl group (acidic) and a hydrogen atom attached to the central carbon atom.
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