BRAINCAKEBiological Molecules
Revision notes for Biological Molecules in Edexcel Biology (8BI0). 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.
- Organic CompoundsOrganic compounds are molecules built around a skeleton of carbon atoms, nearly always bonded to hydrogen.
- CarbohydratesCarbohydrates are organic compounds containing only carbon, hydrogen and oxygen.
- MonosaccharidesMonosaccharides are the simplest carbohydrates: single sugar units that cannot be hydrolysed into smaller sugars.
- DisaccharidesA disaccharide is formed when two monosaccharides join in a condensation reaction.
- Test for SugarsReducing sugars can donate electrons, reducing another chemical.
- PolysaccharidesA polysaccharide is a polymer made of many monosaccharide units, often thousands, joined by glycosidic bonds formed in condensation reactions.
- StarchStarch is the energy-storage polysaccharide of plants.
- Test for StarchStarch is detected with iodine solution, which is iodine dissolved in potassium iodide solution.
- GlycogenGlycogen is the energy-storage polysaccharide of animals and fungi.
- CelluloseCellulose is a structural polysaccharide and the main component of plant cell walls.
- The Nature of LipidsLipids are a varied group of organic compounds that contain carbon, hydrogen and oxygen.
- Fatty Acids and GlycerolTriglycerides and phospholipids are built from two kinds of smaller molecule: glycerol and fatty acids.
- TriglyceridesA triglyceride is made of one glycerol molecule joined to three fatty acids.
- PhospholipidsA phospholipid is similar to a triglyceride, except that one of the three fatty acids is replaced by a phosphate group.
- Unit MembraneEvery cell is surrounded by a cell surface membrane, and eukaryotic cells also have membranes around organelles.
- Test for LipidsLipids are detected with the emulsion test.
- Amino-acidsAmino acids are the monomers of proteins.
- Hydrogen BondingA hydrogen bond is a weak attraction between a slightly positive (δ+) hydrogen atom that is covalently bonded to an electronegative atom (O or N)…
- Disulfide BridgesA disulfide bridge is a covalent bond between two sulfur atoms (S–S) in a protein.
- Ionic BondsSome amino acids have R groups that carry an electric charge in the conditions inside cells.
- Protein StructureProteins are described at four levels of structure.
- Globular ProteinsGlobular proteins are proteins whose polypeptide chains are folded into compact, roughly spherical shapes.
- Fibrous ProteinsFibrous proteins are long, thin proteins made of polypeptide chains arranged in parallel to form fibres or sheets.
- CollagenCollagen is the most abundant protein in mammals.
- Conjugated ProteinsA conjugated protein is a protein that is permanently joined to a non-protein component.