The Structure and Function of Large Biological Molecules

Transcription

1 Chpter 5 The nd Function of Lrge Biologicl Molecules Concept 5.: Mcromolecules re polymers, uilt from monomers All living things re mde up of four clsses of lrge iologicl molecules: crohydrtes, lipids, proteins, nd nucleic cids Moleculr nd function re inseprle Three of the four clsses of life s orgnic molecules re polymers: PowerPoint Lecture Presenttions for Crohydrtes Biology Proteins Eighth Edition Neil Cmpell nd Jne Reece Nucleic cids Lectures y Chris Romero, updted y Erin Brley with contriutions from Jon Shrp Fig. 5- The Synthesis nd Brekdown of Polymers A condenstion rection or more specificlly dehydrtion rection occurs when two monomers ond together through the loss of wter molecule Short polymer Unlinked monomer Dehydrtion removes wter molecule, forming new ond O Enzymes re mcromolecules tht speed up the dehydrtion process Polymers re disssemled to monomers y hydrolysis, rection tht is essentilly the reverse of the dehydrtion rection 4 Longer polymer () Dehydrtion rection in the synthesis of polymer Animtion: Polymers Fig. 5-4 ydrolysis dds wter molecule, reking ond Concept 5.: Crohydrtes serve s fuel nd uilding mteril Crohydrtes include sugrs nd the polymers of sugrs Monoscchride: single sugr, multiples of CO O Glucose (C6O6) is the most common Discchride: doule sugrs, glycosidic linkge Polyscchride: storge nd structurl roles () ydrolysis of polymer Animtion: Discchrides

2 Fig. 5- numer of crons in the cron skeleton Fig. 5-4 Trioses (C 6 O ) Pentoses (C 5 0 O 5 ) exoses (C 6 O 6 ) Loction of cronyl Ketoses Aldoses Glycerldehyde Dihydroxycetone Riose Glucose Glctose Sptil rrngement round symmetric crons () Liner nd ring forms () Arevited ring Riulose Fructose Fig glycosidic linkge Energy Polyscchrides Chloroplst Strch Mitochondri Glycogen grnules Glucose Glucose () Dehydrtion rection in the synthesis of mltose Mltose glycosidic linkge µm 0.5 µm Glucose Fructose Sucrose () Dehydrtion rection in the synthesis of sucrose Amylose Amylopectin () Strch: plnt polyscchride Glycogen () Glycogen: n niml polyscchride Structurl Polyscchrides The polyscchride cellulose is mjor component of the tough wll of plnt cells Like strch, cellulose is polymer of glucose, ut the glycosidic linkges differ The difference is sed on two ring forms for glucose: lph (α) nd et (β) () nd glucose ring s Glucose () Strch: 4 linkge of glucose monomers α glucose re helicl Glucose () Cellulose: 4 linkge of glucose monomers β glucose re stright Animtion: Polyscchrides

3 Fig. 5-8 Cell wlls Structurl Polyscchrides Cellulose microfirils in plnt cell wll Microfiril Chitin, nother structurl polyscchride, is found in the exoskeleton of rthropods 0 µm Chitin lso provides structurl support for the cell wlls of mny fungi 0.5 µm Cellulose molecules Prllel cellulose molecules held together when toms on one strnd cn ond with O s on other strnds Glucose monomer Concept 5.: Lipids re diverse of hydrophoic molecules () The of the chitin monomer. () Chitin forms the exoskeleton of rthropods. (c) Chitin is used to mke strong nd flexile surgicl thred. Fts Ftty cid (plmitic cid) Lipids re the one clss of lrge iologicl molecules tht do not form polymers Glycerol ydrophoic, nonpolr covlent onds () Dehydrtion rection in the synthesis of ft Sturted ftty cids mximum numer of hydrogen toms, no doule onds Ester linkge Unsturted ftty cids hve one or more doule onds The most iologiclly importnt lipids re fts, phospholipids, nd steroids Animtion: Fts () Ft molecule (tricylglycerol) Phospholipids Fts ydrophilic hed Structurl formul of sturted ft molecule ydrophoic tils Steric cid, sturted ftty cid () Sturted ft Structurl formul of n unsturted ft molecule Oleic cid, n unsturted ftty cid () Unsturted ft cis doule ond cuses ending () Structurl formul Choline Phosphte Glycerol Ftty cids ydrophilic hed ydrophoic tils () Spce-filling model (c) Phospholipid symol

4 Phospholipid Bilyer Steroids When phospholipids re dded to wter, they self-ssemle into ilyer ydrophoic tils pointing towrd the interior ydrophilic heds pointing outwrd ydrophilic hed WATER Steroids re lipids chrcterized y cron skeleton consisting of four fused rings Anolic steroids - drugs which mimic mle sex hormones nturl nolic hormone testosterone ydrophoic til WATER cholesterol, steroid synthetic steroid methndrostenolone Concept 5.4: Proteins hve mny s, resulting in wide rnge of functions Tle 5- Protein functions include structurl support, storge, trnsport, cellulr communictions, movement, nd defense ginst foreign sustnces Polypeptides re polymers uilt from the sme set of 0 mino cids A protein consists of one or more polypeptides Amino cids re orgnic molecules with croxyl nd mino s Amino cids differ in their properties due to differing side chins, clled R s Amino Acid cron Animtion: Structurl Proteins Animtion: Storge Proteins Animtion: Trnsport Proteins Animtion: Receptor Proteins Animtion: Contrctile Proteins Animtion: Defensive Proteins Animtion: ormonl Proteins Animtion: Sensory Proteins Animtion: Gene Regultory Proteins Amino Croxyl 4

5 Fig. 5-7 Nonpolr Fig. 5-8 Peptide ond Glycine (Gly or G) Alnine (Al or A) Vline (Vl or V) Leucine (Leu or L) Isoleucine (Ile or Ι ) Methionine (Met or M) Phenyllnine (Phe or F) Polr Trypotphn (Trp or W) Proline (Pro or P) () Serine (Ser or S) Threonine (Thr or T) Cysteine (Cys or C) Electriclly chrged Tyrosine (Tyr or Y) Asprgine (Asn or N) Glutmine (Gln or Q) Peptide ond Side chins Acidic Bsic Bckone Asprtic cid Glutmic cid (Asp or D) (Glu or E) Lysine (Lys or K) Arginine (Arg or R) istidine (is or ) () Amino end (N-terminus) Croxyl end (C-terminus) Four Levels of Protein Sickle-Cell Disese: A Chnge in Primry Norml hemogloin Primry Primry Vl is Leu Thr Pro Glu Glu Sickle-cell hemogloin Vl is Leu Thr Pro Vl Glu Primry Secondry Tertiry Quternry Secondry nd tertiry s suunit Secondry nd tertiry s Exposed hydrophoic region suunit pleted sheet + N Amino end Exmples of mino cid suunits helix Quternry Norml hemogloin (top view) Quternry Sickle-cell hemogloin Animtion: Protein Introduction Animtion: Primry Protein Function Molecules do not ssocite with one nother; ech crries oxygen. Function Molecules interct with one nother nd crystllize into fier; cpcity to crry oxygen is gretly reduced. Animtion: Secondry Protein Animtion: Tertiry Protein Red lood cell shpe Norml red lood cells re full of individul hemogloin moledules, ech crrying oxygen. 0 µm Red lood cell shpe Fiers of norml hemogloin deform red lood cell into sickle shpe. 0 µm Animtion: Quternry Protein Protein Folding in the Cell Chperonins re protein molecules tht ssist the proper folding of other proteins ollow cylinder Cp Chperonin (fully ssemled) Polypeptide Steps of Chperonin Action: An unfolded polypeptide enters the cylinder from one end. The cp ttches, cusing the cylinder to chnge shpe in such wy tht it cretes hydrophilic environment for the folding of the polypeptide. Correctly folded protein The cp comes off, nd the properly folded protein is relesed. Concept 5.5: Nucleic cids store nd trnsmit hereditry informtion The mino cid sequence of polypeptide is progrmmed y unit of inheritnce clled gene Genes re mde of DNA, nucleic cid There re two types of nucleic cids: Deoxyrionucleic cid (DNA) Rionucleic cid (RNA) DNA provides directions for its own repliction DNA directs synthesis of messenger RNA () nd, through, controls protein synthesis Protein synthesis occurs in riosomes 5

6 Fig Fig DNA DNA Synthesis of in the nucleus Synthesis of in the nucleus NUCLEUS CYTOPLASM NUCLEUS CYTOPLASM Movement of into cytoplsm vi nucler pore Fig DNA The of Nucleic Acids 5 end Nitrogenous ses Synthesis of in the nucleus 5 C C Nucleoside Pyrimidines Nitrogenous se Cytosine (C) Thymine (T, in DNA) Urcil (U, in RNA) NUCLEUS CYTOPLASM Purines Movement of into cytoplsm vi nucler pore Riosome Phosphte 5 C C () Nucleotide end () Polynucleotide, or nucleic cid Sugr (pentose) Adenine (A) Gunine (G) Sugrs Synthesis of protein Deoxyriose (in DNA) Riose (in RNA) Polypeptide Amino cids (c) Nucleoside components: sugrs Fig. 5-8 ' end Evolution Connection Sugr-phosphte ckones Bse pir (joined y hydrogen onding) Old strnds 0. Comprisons of mino cid sequences cn shed light on the evolutionry divergence of relted species. Would you expect ll the proteins of given set of living species to show the sme degree of divergence? Why or why not? ' end New strnds ' end Nucleotide out to e dded to new strnd Some function re more essentil thn others. Proteins perform most cellulr functions, so some proteins re more essentil thn others. One should therefore, expect the mino cid sequences of essentil proteins to e more highly conserved (retined without chnge or with little chnge) reltive to the mino cid sequences of less-essentil proteins. Moreover, different species often live in different hitts nd experience different selection pressures. Even if the selection pressures re similr, their intensities proly re not. So, one should expect different degrees of divergence mong the proteins shred y given set of species. ' end 6

7 You should now e le to: You should now e le to:. List nd descrie the four mjor clsses of molecules. Descrie the formtion of glycosidic linkge nd distinguish etween monoscchrides, discchrides, nd polyscchrides 5. Distinguish etween the following pirs: pyrimidine nd purine, nucleotide nd nucleoside, riose nd deoxyriose, the 5 end nd end of nucleotide. Distinguish etween sturted nd unsturted fts nd etween cis nd trns ft molecules 4. Descrie the four levels of protein 7