IB›IB Biology HL›Mind mapsB1.2 ProteinsIB Biology HL: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsAmino acidsAlpha carbon with amine, carboxyl, H and R-groupCondensation forms a peptide bondn amino acids make n − 1 peptide bondsEssential amino acids must come from food20ⁿ possible sequences of length nR-groupsHydrophobic (non-polar) or hydrophilicHydrophilic ones are polar or chargedPrimary structure: amino acid sequenceSequence sets the 3D conformationFoldingSecondary: backbone hydrogen bondsGives α-helices and β-pleated sheetsTertiary: bonds between R-groupsIonic bonds explain pH effectsDisulfide bonds link cysteinesHydrophobic R-groups cluster in the coreProteinsfrom chain to shapeQuaternaryTwo or more polypeptides joinedInsulin: two chains, non-conjugatedCollagen: three chains, non-conjugatedHaemoglobin: four chains plus haem, conjugatedGlobular vs fibrousGlobular: compact, soluble, precise shapeInsulin's shape binds specific receptorsFibrous: long, insoluble, strongCollagen's triple helix gives tensile strengthIntegral proteins have hydrophobic regions in the membraneExam tipsSecondary bonds are between backbone groupsDenaturation: heat or pH breaks bonds, loses functionVegan diets must combine plant proteins