BRAINCAKEBiological Molecules
Revision notes for Biological Molecules in AQA Biology (7401). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- BondingIn biological molecules, aAtoms and molecules are bonded together by strong and weak bonds.
- Polymers and MacromoleculesSome molecules can be linked together by covalent bonds into long chains to form very large molecules called macromolecules.
- Condensation and HydrolysisA condensation reaction is a reaction that joins two molecules together with a covalent bond formed by removing a small molecule such as a water…
- Organic CompoundsCarbon atoms can bond to other carbon atoms.
- CarbohydratesCarbohydrates are molecules made from carbon, hydrogen and oxygen with a general formula of Cn(H2O)n.
- MonosaccharidesMonosaccharides are simple carbohydrates called sugars.
- Test for Reducing SugarsMonosaccharides such as glucose, fructose and galactose can donate electrons to other compounds.
- DisaccharidesTwo monosaccharides joined together by a covalent bonds is called a disaccharide.
- Test for Non-reducing SugarsNon-reducing sugars must first be hydrolysed before using the Benedict's test.
- PolysaccharidesMonosaccharides can also be joined by condensation reactions to form polymers called polysaccharides.
- StarchStarch is an energy storage polysaccharide found in plants.
- Test for StarchA few drops of iodine in potassium iodide solution are added to the sample.
- GlycogenGlycogen is a storage polysaccharide found in animals and bacteria.
- CelluloseThere are two isomers of glucose: α-glucose and β-glucose.
- Roles of LipidsLipids are macromolecules that contain carbon, hydrogen and oxygen.
- TriglyceridesTriglycerides consist of three fatty acids joined to a glycerol molecule by three ester bonds in a condensation reaction.
- Properties of TriglyceridesTriglycerides have a high energy:mass ratio so are an excellent source of energy that can be stored in a small space.
- PhospholipidsPhospholipids are similar to lipids except that one of the fatty acids is replaced by a phosphate group.
- Properties of PhospholipidsPhospholipids have a hydrophilic head and a hydrophobic tail.
- Test for LipidsThe test for lipids is called the ethanol emulsion test.
- Amino-AcidsAmino-acids are monomers that combine to make polymers called polypeptides.
- Peptide Bond FormationTwo amino acids combine to form a dipeptide by a condensation reaction.
- Primary StructureThe order or sequence in which amino acids are joined together to form polypeptides is called the primary structure.
- Secondary StructureEach peptide bond is the result of a condensation reaction where a water molecule is removed from a -COOH and an NH2 group to form a covalent bond.
- Tertiary StructureThe tertiary structure of a polypeptide involves is further coiling and folding to give a specific 3D structure due to covalent bonds such as…
- Quaternary StructureLarge proteins consist of more than one polypeptide chain and possibly a non-peptide prosthetic group.
- Test for ProteinsThe Biuret test detects the presence of peptide bonds.
- Globular and Fibrous ProteinsProteins perform many different functions in the cell.
- CollagenCollagen is a fibrous protein that is found in tendons, bones, muscles, skin and blood.