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UNIT 1 - CHAPTER 4: CELLULAR METABOLISMLEARNING OUTCOMES:4.1Metabolic Processes1.Compare and contrast anabolism and catabolism. 4.2Control of Metabolic Reactions2.Describe the role of enzymes in metabolic reactions.3.Explain how metabolic pathways are regulated.4.3Energy for Metabolic Reactions4.Explain how ATP stores chemical energy and makes it available to a cell. 4.4Cellular Respiration5.Explain how the reactions of cellular respiration release chemical energy. 6.Describe the general metabolic pathways of carbohydrate metabolism.4.5Nucleic Acids and Protein Synthesis7.Describe how DNA molecules store genetic information. 8.Describe how DNA molecules are replicated. 9.Explain how protein synthesis relies on genetic information. 10.Compare and contrast DNA and RNA. 11.List the steps of protein synthesis. 4.6Changes in Genetic Information12.Describe how genetic information can be altered.13.Explain how a mutation may or may not affect an organism. Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-1
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.1METABOLIC PROCESSESA.METABOLISM = the sum of an organism's chemical reactions. 1. Each reaction is catalyzed by a specific enzyme.a.Most enzymes are proteins, so protein synthesis is critical formetabolic reactions to occur.2. The reactions typically occur in pathways (i.e. in a sequence).3. Reactions are divided into two major groups, anabolism and catabolism.B.Anabolism= synthesis reactions.1.Building complex molecules from simpler ones (i.e. monomers intopolymers).2.Constructive, synthesis reactions3.Bonds are formed between monomers which now hold energy (i.e.ENDERGONIC reactions).4.Water is removed between monomers to build the bond, termedDEHYDRATION (synthesis).energy5.C + D C---Dwater6.Example is building a protein (polymer) from individual amino acids(monomers).C. Catabolism= decomposition reactions.1.Breaking complex molecules into simpler ones (i.e. polymers intomonomers).2.Degradative, destructive, digestive reactions3.Bonds are broken between monomers releasing energy (i.e.EXERGONIC reactions).4.Water is used to break the bonds, termed HYDROLYSIS.water5.A---B A + Benergy6.Example is breaking a nucleic acid (polymer) into nucleotides(monomers).*See Fig 4.1– Fig 4.3, page 124 for examples of these reversible reactions.Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-2
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.1METABOLIC PROCESSES: SUMMARY TABLE (Keyed at the end of thisoutline)ANABOLISM(SYNTHESIS REACTIONS)CATABOLISM(DECOMPOSITION REACTIONS)GENERAL DESCRIPTION (A full sentence)DESCRIPTIVE TERMSBOND FORMATION ORBREAKING?IS ENERGY REQUIREDOR RELEASED?NAME THAT TERM.HOW IS WATER INVOLVED?NAME THAT TERMEXAMPLE (in Human Metabolism)Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-3
UNIT 1 - CHAPTER 4: CELLULAR METABOLISMCopyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-4
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.2CONTROL OF METABOLIC REACTIONSA.Enzyme Action1.Definition: Enzymes are biological, proteincatalyststhatincrease the rate of a chemical (metabolic) reactionwithout beingconsumed by the reaction.2.Enzymes are globular proteins (review protein structure in chapter 2).3.Enzymes are specificfor the substance they act upon (called a substrate).a.Only a specific region of the enzyme molecule actuallybinds the substrate. This region is called the Active Site.b.The enzyme and substrate fit together like a "Lock andKey" through the active site on the enzyme. See Fig 4.4, page 126.Draw below.4.Enzymes are unchanged by the reaction they catalyze and can berecycled.5.Factors affecting the rate of chemical reactions:a.Particle size:The smaller the particle, the fasterthe reaction will occur.b.Temperature:The higher the temperature,the faster the reaction will occur (up to a point).c.Concentration: The greater number ofparticles in a given space, the faster the reaction.d.Catalysts: Enzymes in biological systems.6.Metabolic pathwaysinvolve several reactions in a row, with eachreaction requiring a specific enzyme. See Fig. 4.5, page 127.7.Enzyme names are often derived from the substrate theyact upon (providing the root of enzyme name), and the enzyme nametypically end in the suffix -ase: a.The enzyme sucrase breaks down the substrate sucrose; b.A lipase breaks down a lipid, c. The enzyme DNA polymerase allows for DNA to be synthesizedfrom DNA nucleotides.Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-5
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.2CONTROL OF METABOLIC REACTIONSB.Enzymes and Metabolic Pathways: See Fig 4.6, page 127.In most metabolic pathways, the end-product comes back and inhibits the firstenzyme (i.e. the rate-limiting enzyme).E1E2E3E4A B C D E____________Feedback________________|C.Cofactors and Coenzymes1.The active site of an enzyme may not always be exposed (recall the 3-dimentional conformation of proteins)2.A cofactor or coenzymemay be necessary to "activate" the enzyme, so itcan react with its substrate.a.Cofactor = an ion of a metal (minerals like Fe2+, Cu2+, Zn2+). b.Coenzyme = a vitamin (primarily B vitamins).*Enzymes can become inactive or even denature in extremeconditions (review denaturation in chapter 2).a.extreme temperatures b.extreme pH valuesc.harsh chemicals4.3ENERGY FOR METABOLIC REACTIONSA.Introduction:1.Energyis the capacity to do work. 2.Common forms include heat, light, sound, electrical energy, mechanicalenergy, and chemical energy. Energy cannot be created or destroyed, butit can change forms.3.All metabolic reactions involve some form of energy.Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-6
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.3ENERGY FOR METABOLIC REACTIONSB.ATP Molecules1. Adenosine Triphosphate (ATP) is the immediate source that drivescellular work.2.Structure of ATP: See Fig 4.7, page 128. a.adenine b.ribose sugar c.three phosphate groups3.The triphosphate tail of ATP is unstable.a.The bonds between the phosphate groups can be broken byhydrolysis releasing chemical energy (EXERGONIC).b.A molecule of inorganic phosphate (Pi) and ADP are the productsof this reaction.ATP Adenosine Diphosphate (ADP) + Pi4.The inorganic phosphate from ATP can be transferred to some othermolecule which is now said to be "phosphorylated".5.ADP can be regenerated to ATP by the addition of a phosphate in anendergonic reaction; Adenosine Diphosphate (ADP) + Pi ATP6.See Fig 4.8, page 128, which illustrates how ATP and ADPshuttle back and forth between the energy-releasing reactions of CR andthe energy-utilizing reactions of the cell.7.If ATP is synthesized by direct phosphate transfer theprocess is called substrate-level phosphorylation.C.Release of Chemical Energy1.Most metabolic reactions depend on chemical energy.a.This form of energy is held within the chemical bonds that linkatoms into molecules.b.When the bond breaks, chemical energy is released.c.This release of chemical energy is termed oxidation.d.The released chemical energy can then be used by the cell foranabolism.2.In cells, enzymes initiate oxidation by:a.decreasing activation energy of a reaction orb.transferring energy to special energy-carrying molecules calledcoenzymes.Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-7
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.4CELLULAR RESPIRATION (CR)A.Introduction: 1.CR is the process by which animal cells use oxygen to release chemicalenergy from nutrients to generate cellular energy (ATP). 2.The chemical reactions in CR must occur in a particular sequence, witheach reaction being catalyzed by a different (specific) enzyme. There arethree major series of reactions:a.glycolysisb.citric acid cyclec.electron transport chain3.Some enzymes are present in the cell’s cytoplasm, so those reactions occur in the cytosol, while other enzymes are present in the mitochondria of thecell, so those reactions occur in the mitochondria. 4.Glycolysis and Electron Transport Chain are similar to those depicted inFig 4.5 and 4.6, page 127, however the Citric Acid Cycle is a metaboliccycle. See Fig 4.9, page 129. 5.All organic molecules (carbohydrates, fats, and proteins) can be processedto release energy, but we will focus on the steps of CR for the breakdownof glucose (C6H12O6). 6.Oxygen is requiredto receive the maximum energy possible permolecule of glucose, and products of the reactions include water, CO2,and cellular energy (ATP).a.Much of this energy is lost as heat.b.Almost half of the energy is stored in a form the cell can use, asATP.oFor every glucose molecule that enters CR, typically 36ATP are produced. However up to 38 ATP can begenerated. 7.Oxidation:Reduction(of CR)a.Many of the reactions in the breakdown ofglucose involve the transfer of electrons (e-). oThese reactions are called oxidation - reduction (or redox) reactions.oGlucose is oxidized (loses e- and H); Oxygen is reduced (gains e- and H).Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-8
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.4CELLULAR RESPIRATION (CR)A.Introduction: 7.Oxidation:Reduction(of CR)b.In redox reactions: othe loss of electrons from a substance is called oxidation.othe addition of electrons to a substance is calledreduction.oExample:|---------------Oxidation------------|Na + Cl Na++ Cl-|---------------Reduction------------|oIn organic substances it is easy to follow redox reactions.You only have to watch H movement, because where oneH goes, one electron goes.c.An electron transfer can also involve thetransfer of a pair of hydrogen atoms(which possess twoelectrons), from one substance to another. oThe H atoms (and electrons) are eventually transferred tooxygen.oThe transfer occurs in the final step of CR. oIn the meantime, the H atoms (with their electrons) arepassed onto a coenzyme molecule[i.e.NAD+(nicotinamide adenine dinucleotide) or FADH (flavinadenine dinucleotide)]H:H + NAD+ →NADH + H+H:H + FADH → FADH2+ H+This is coenzyme reduction.d.In the final step of CR:othe electron transport chainooxygen is the final electron acceptor (forming water.)oNADH or FADH2are oxidized back to their original form.oThe energy released is used to synthesize ATP.oThe process of producing ATP indirectly through redoxreactions is called oxidative phosphorylation.Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-9
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.4CELLULAR RESPIRATION (CR)B.Glycolysis:1.means "splitting of sugar”.2.A 6-carbon sugaris split into two 3-C pyruvatemolecules. 3.occurs in the cytoplasmof the cell.4.Oxygen is notrequired (i.e. anaerobic). 5.Energy yield is:a.2 Net ATPper glucose molecule, substrate-level phosphorylationb.2 NADH(stored electrons for ETS). 6.Many steps are required, and each is catalyzed by adifferent, specific enzyme.7.See Fig 4.10(1), page 130 and Fig 4.11 (Phase 1), page 131.8.See Appendix E, pages 933-934.C.Anaerobic ReactionsRecall that glycolysis results in pyruvate. If oxygen is not present (i.e. underanaerobic conditions), pyruvate can ferment in one of two ways:1.Lactic Acid Fermentation:a.Pyruvate is converted to lactic acid, a wasteproduct. b.occurs in many animal muscle cellsc.serves as an alternate method of generating ATP when oxygen isscarced.accumulation causes muscle soreness and fatigue.2.Alcohol Fermentation:a.Pyruvate is converted to ethanol.b.occurs in yeasts (brewing) and many bacteria.D.Aerobic Reactions (of Cellular Respiration)1.Conversion of Pyruvate to Acetyl Coenzyme A (Acetyl CoA):Under aerobicconditions (when O2is present):a.Pyruvate enters the mitochondrion. oUsually requires 1 ATP per pyruvateb.Pyruvate (3-C) is converted to acetyl CoA (2-C).oThe carbon is released as CO2. c.Energy yield is 1 NADH per pyruvate in this step (i.e. 2 NADHper glucose) .d.See top of Fig 4.12, page 132.Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-10
UNIT 1 - CHAPTER 4: CELLULAR METABOLISMCopyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-11
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.4CELLULAR RESPIRATION (CR)D.Aerobic Reactions (of Cellular Respiration)2.Citric Acid Cycle (Krebs Cycle): See Fig 4.12, page 132. a.occurs in mitochondrial matrixb.Acetyl CoA adds its 2 carbons to oxaloacetate (4C)forming citrate (6C).c.2-CO2are released during the series of steps where citrate(6C) is converted back to oxaloacetate (4C).dEnergy yield is: o6 NADHper glucose,o2 FADH2per glucose o2 ATPper glucose (Substrate-level phosphorylation).e.involves many steps, each catalyzed by a different enzymef.See Appendix E, pages 933, 935.3.Electron Transport Chain (ETC) See Fig 4.13, page 133.a.is located in the inner mitochondrial membrane(recall"cristae") b.During electron transport, these molecules alternatebetween reduced and oxidized states as they accept and donateelectrons. c.The molecules cause an increase in H+concentration in theintermembrane space.d.ATP synthase generates ATP when the H+ re-enter theinner matrix. e.The final electron (and H) acceptor is oxygenwhich forms water.f.Yield of energy (ATP) from the ETC is:o3 ATP/NADHand o2 ATP/FADH2oMade by oxidative phosphorylation*See Appendix E, pages 933, 936.4.Overall ATP Yield From Glucose in CR:a.4 ATPare generated directly: o2 from glycolysiso2 from Krebsb.The remaining ATP is generated indirectly through coenzymes:10 NADHare produced:o2 from glycolysis, o2 from conversion, & o6 from Krebs - The yield from NADH is 30 ATP. o2 FADH2are produced in the Krebs Cycle - The yield from FADH2is 4 ATP. c.The maximumnet yield of ATP per glucose = 38 ATP.However, it takes 2 ATP to move the 2 NADH molecules produced during glycoloysis into the mitochondrion, so normal netCopyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-12
UNIT 1 - CHAPTER 4: CELLULAR METABOLISMATP production is 36 ATP.Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-13
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.4.SUMMARY OF CELLULAR RESPIRATION: See Fig 4.14, page 133 and keyed at the end of this outline.GLYCOLYSISCONVERSIONSTEPKREBS CYCLEELECTRONTRANSPORTCHAINLOCATIONin cellIs OxygenRequired?StartingProduct(s)End-ProductsTOTALCopyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-14
UNIT 1 - CHAPTER 4: CELLULAR METABOLISME.Carbohydrate StorageSee Fig 4.15, page 134.Carbohydrates from digested food may enter catabolic or anabolic pathways. 1.Catabolic Pathwaysa.Monosaccharides enter cells and are used in CR.b.The cell can use the ATP generated for anabolic reactions.2.Anabolic Pathwaysa.Monosaccharides (when in excess) can be: ostored as glycogenoconverted to fat or essential amino acids.F.Metabolism of Other Organic Molecules:See overviewin Fig 4.16, page 135.1Lipids and proteins can also be broken down to release energy for ATPsynthesis.2.Most common entry point is the Citric Acid Cycle.3.discussed in greater detail in later chaptersCopyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-15
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.5NUCLEIC ACIDS AND PROTEIN SYNTHESISA.Introduction: Because enzymes regulate metabolic pathways that allow cells tosurvive, cells must have the information for producing these special proteins.Recall from Chapter 2, that in addition to enzymes, proteins have severalimportant functions in cells, including structure (keratin), transport (hemoglobin),defense (antibodies), etc. B.Genetic Information1.DNA holds the genetic information which is passed from parents to theiroffspring.2.This genetic information, DNA, instructs cells in the construction ofproteins (great variety, each with a different function). 3.The portion of a DNA molecule that contains the genetic information formaking one kind of protein is called a gene.4.All of the DNA in a cell constitutes the genome.a.Over the last decade, researchers have deciphered most of thehuman genome (see chapter 24).b.See text on page 134; human genome is composed of 20,325protein-encoding genes that code for over 200,000 types ofproteins.5.In order to understand how DNA (confined to the nucleus) can direct thesynthesis of proteins (which occurs at ribosomes in the cytoplasm or onrough endoplasmic reticulum), we must take a closer look at the structureof DNA and RNA molecules. C.Deoxyribonucleic Acid: (DNA) 1.DNA is composed of nucleotides, each containing the following:See Fig 4.17, page 135.a.a pentose sugarmolecule (deoxyribose)b.a nitrogen-containing baseoa purine (double ring) adenine (A) or guanine (G)oa pyrimidine (single ring) cytosine (C) or thymine (T)c. a phosphate groupCopyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-16
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.5NUCLEIC ACIDS AND PROTEIN SYNTHESISC.Deoxyribonucleic Acid: (DNA)2.Each DNA strand is made up of a backbone of deoxyribosesugars alternating with phosphate groups. See Fig 4.18, page 136.3.Each deoxyribose sugar is linked to one of four nitrogen-containing bases: A,G,C, or T. See Appendix F, pages 937-938.4.Each DNA molecule consists of two parallel strands ofnucleotides running in opposite directions. See Fig 4.19, page 136 andAppendix F, pages 937-938.5.The bases in these nucleotide strands are joined to acomplementary base on the opposite strand by hydrogen bonds formingthe following pairs: oadenine bonds thymine(through 2 hydrogen bonds) and oguanine bonds cytosine(through 3 hydrogen bonds).6.The two strands are twisted into a double helix. See Fig 4.20, page 137.D.DNA Replication:1.Introduction: DNA holds the genetic code which is passed from parentsto offspring. During interphaseof the cell cycle, DNA is replicated(duplicated), so new daughter cells are provided with identical copies ofthis genetic material. 2.Process of DNA Replication:See Fig 4.21, page 139.a.DNA uncoils and unzips (hydrogen bondsare broken between A:T and G:C);oEach free nucleotide strand now serves as a template forbuilding a new complementary DNA strand.b.DNA nucleotides,present in thenucleoplasm begin to match up with their complementary bases onthe templates. oDNA polymerase(an enzyme) positions and links thesenucleotides into strands.c.This results in two identical DNAmolecules, each consisting of one old and one newly assemblednucleotide strand.oThis type of replication is called semi-conservativereplication. E.Genetic Code1.Specified by sequence of nucleotides in DNA.2.Each codon(three adjacent nucleotides) “codes” for an amino acid.3.Amino acids are bonded together through peptide bonds to form aCopyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-17
UNIT 1 - CHAPTER 4: CELLULAR METABOLISMpolypeptide chain4.RNA molecules facilitate the conversion of DNA codons to anamino acid sequence.5.See Table 4.2 page 143.Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-18
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.5.NUCLEIC ACIDS AND PROTEIN SYNTHESISF. RNA Molecules: (Ribonucleic Acid)See Fig 4.22, page 140.1.RNA (like DNA) is composed of nucleotides, each containing thefollowing:a.a pentose sugar molecule (ribose)b.a nitrogen-containing base: See Appendix F, page 936.opurine: adenine (A) or guanine (G)opyrimidine: cytosine (C) or uracil (U)c.a phosphate group2.Each RNA strand is made up of a backbone of ribosesugars alternating with phosphate groups.3.Each ribose sugar is linked to either A, G, C, or U.4.Each RNA molecule consists of a single strandofnucleotides.5.Types of RNA:There are three types of RNA molecules which assist the cell in proteinsynthesis:a.Messenger RNA (mRNA)carries the code for the proteinto be synthesized, from the nucleus to the protein synthesizingmachinery in the cytoplasm (i.e. ribosome).b.Transfer RNA (tRNA)carries the appropriate amino acidto the ribosome to be incorporated into the newly forming protein.c.Ribosomal RNA (rRNA)along with protein makes up theprotein synthesizing machinery, the ribosome. * A comparison of DNA and RNA is presented in Table 4.1,page 140.Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-19
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.5.NUCLEIC ACIDS AND PROTEIN SYNTHESISG.Protein Synthesis: Protein synthesis can be divided into two major steps, transcription and translation. See Figure 4.24, page 141 and Table 4.3, page 144.1.TRANSCRIPTION:See left side of Fig 4.24, page 141, and top of Table 4.3, page 144.a.occurs in nucleusof cell, b.is process of copying information (for a particular protein)from a DNA molecule (gene), and putting it into form ofmessenger RNA (mRNA)molecule.c.DNA strands unwind and the H-bonds between the strandsare broken. Only one of the exposed templates of the DNAmolecule (i.e. the gene) is used to build mRNA strand.RNA polymerase (an enzyme) positions and links RNAnucleotides (within the nucleus) into a mRNA strand.d.The message (mRNA): ois complementaryto the bases on DNA strand (i.e. IfDNA sequence is TACGATTGCCAA, then mRNAsequence is AUGCUAACGGUU);ois in the form of a triple base code, represented bycodons/triplets(i.e. AUG, CUA, ACG, GUU). Each codon/triplet on mRNA codes for one aminoacid in the protein to be synthesized. See Table 4.2, page 143.oleaves the nucleusand travels to the ribosome,the proteinsynthesizing machinery.2.TRANSLATION: See right side of Fig 4.24, page 141, Fig 4.25, page 142 and bottom of Table 4.3, page 144.a.is process by which mRNA is "translated" into a protein.b.occurs at ribosomesthat are either free in cytoplasmor areattached to ER (as RER).c.can only start at the start codon AUG, which codes formethionined.Transfer RNA (tRNA)molecules assist in translation bybringing the appropriate amino acid for each codon to theribosome. oThe tRNA molecule has ananticodonwhich isCopyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-20
UNIT 1 - CHAPTER 4: CELLULAR METABOLISMcomplementary to the codon on the mRNA strand.oIf the codon for Glycine is GGG, then the anticodon on thetRNA molecule that carries Glycine to the ribosome isCCC. Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-21
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.5.NUCLEIC ACIDS AND PROTEIN SYNTHESISG.Protein Synthesis2.TRANSLATIONe.Two codons of mRNA are read in ribosome at same time. otRNA molecules deliver amino acids to ribosome, andpeptide bondis formed between adjacent amino acids. oThe mRNA molecule is read codon by codon, with eachcorresponding amino acid being added to the chain ofamino acids.oA protein is synthesized. f.The mRNA molecule is read until a stop codon (UAA,UAG, UGA) on the mRNA is reached.oThe protein is released into the cytoplasm or RER.oThe mRNA molecule can be read again and again.H.PROTEIN SYNTHESIS SUMMARY TABLE (Keyed at the end of this outline)Also see Table 4.3, page 144 for a comparison of Transcription and Translation.MAJOR STEPGENERAL DESCRIPTIONLOCATION IN CELLMOLECULES INVOLVED AND HOW?OVERALL RESULTCopyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-22
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.5.I. PROTEIN SYNTHESIS SUMMARY FLOWCHARTCopyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-23
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.5 NUCLEIC ACIDS AND PROTEIN SYNTHESIS J. PROTEIN SYNTHESIS WORK SHEET (This worksheet is keyed at the end ofthis outline).DNA Base Sequence(GENE)Messenger RNA BaseSequence (mRNA)Amino Acid Sequence(PROTEIN)Transfer RNA (tRNA)anticodon sequenceTACTTGCAATCGATT* Use Table 4.2 on page 143: Codons (mRNA Three-Base Sequences) to determine appropriateamino acid sequence. Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-24
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.6.CHANGES IN GENETIC INFORMATIONA.Introduction1.We are more alike than different: Human genome sequences are 99.9%the same among individuals (i.e. 99.9% of us make the proteins, keratin,hemoglobin, etc, and necessary enzymes that regulate metabolicreactions).2.The tenth of a percent that can vary from person to person include rareDNA sequences that affect health or appearance, as well as common DNAbase variations that do not exert any noticeable effects.3.A DNA molecule contains a great deal of information (i.e. genes).a.A mutation changes the genetic information.B.Nature of Mutations1.Mutations arerare distinctions in DNA sequences (genes) that alter healthor appearance.2.More common genetic variants with no detectable effects are calledsinglenucleotide polymorphisms (SNP’s, pronounced “snips”).a.Polymorphism means many forms.3.Mutations to genes are caused by a variety of sources, calledmutagens.a.Mutagens include UV rays, and are also found in hair dyes,smoked meats, food additives, et cetera.4.Mutations may be spontaneous or induced.5.DNA changes are transmitted when the cell divides.6.A protein synthesized from an altered DNA sequence mayor may not function normally.a.If a mutation occurs in a gene, the end-product, the protein may bealtered or absent: See Fig 4.26, page 145.7.Mutations and Diseasea.An enzymemay not be made at all;E1E2E3E4(not made)ABCDE(reaction stops)oWhen an enzyme is lacking from a metabolic pathway,childhood storage diseases (accumulation of a substrate) result.This occurs in porphyria-related disorders, PKU, and Tay-Sachs.b.A proteinmay have altered function.oIn cystic fibrosis (altered chloride pump) & sickle-cell anemia(altered hemoglobin structure).c.A protein may be produced in excess.oIn epilepsy where excess GABA leads to excess norepinephrineand dopamine.C.Protection Against Mutation1. Usually repair enzymesprevent mutations by correcting DNA sequence.2.The genetic code protects against some mutations.D.Inborn Errors of Metabolism: See Mutations and Disease (B.7)above.Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-25
UNIT 1 - CHAPTER 4: CELLULAR METABOLISM4.6CHANGES IN GENETIC INFORMATIONE.MUTATION/PROTEIN SYNTHESIS Problems (keyed at the end ofthis outline).The following genes code for what amino acid sequences/proteins?1. The normal gene 2. Has an A to T substitution of the 4thnucleotide. 3. Has an A to G substitution of the 6thnucleotide.1.T A C A A A C G T C C G T A A A T T2.T A C T A A C G T C C G T A A A T T3.T A C A A G C G T C C G T A A A T T* Notice that these single base substitutions may or may not alter the amino acid sequence.** Try your own problems with nucleotide additions or deletions. How is this different?OTHER INTERESTING TOPICS:A.THE WHOLEPICTURE. See page 122.B.CAREER CORNER, Personal Trainer. See page 123.C.From Science to Technology 4.1: The Human Metabolome. See page 126.D.Clinical Application 4.1: Inborn Errors of Metabolism. See page 128.E.A Glimpse Ahead: Energy Processes. See page 131.F.From Science to Technology 4.2: DNA Profiling Frees A Prisoner, page 138. CHAPTER ASSESSMENTS– see page 145-146.INTEGRATIVE ASSESSMENTS/CRITICAL THINKING – see page 146.Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-26
UNIT 1 - CHAPTER 4: CELLULAR METABOLISMCHAPTER SUMMARY– see pages 147-148.Metabolism Comparison TableANABOLISM (SYNTHESIS REACTIONS)CATABOLISM(DECOMPOSITION REACTIONS)GENERAL DESCRIPTION(A full sentence)Synthesis involves the building of a large molecule (polymer) from smaller building blocks (monomer).Degradation involves the breakdown of polymer into individual monomers.DESCRIPTIVE TERMSbuildingconstructiveanabolicbreakdowndigestivecatabolicBOND FORMATION ORBREAKING?Bonds are formed.Bonds are broken.IS ENERGY REQUIREDOR RELEASED?NAME THAT TERM.Energy is required to form the bond.EndergonicEnergy is released when the bond is broken.ExergonicHOW IS WATER INVOLVED?NAME THAT TERM.Water is released when the bond is formed.DehydrationWater is required to break the bond.HydrolysisEXAMPLE(in human metabolism)Building a protein from individual amino acids;Building a triglyceride from glycerol and 3 fatty acids, etc.Breaking a protein into individual amino acids;Breaking starch down into monosaccharides, etc.GLYCOLYSISCONVERSIONSTEPKREBS CYCLEELECTRONTRANSPORTCHAINLOCATIONcytoplasmmitochondriamitochondrial matrixmitchondrial innermembraneOxygenRequired?NoyesYesyesStartingglucose 2 pyruvatesAcetyl CoA10 NADHCopyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-27
UNIT 1 - CHAPTER 4: CELLULAR METABOLISMProduct(6-C)(2 x 3C)(2 x 2C)2 FADH2End-Products2 pyruvates(2 x 3-C)2 ATP2 NADH2 Acetyl CoA2 NADH2 CO26 NADH2 FADH22 ATP4 CO230 ATP4 ATP4 ATP38 ATPTOTALMinus 2 ATP for 2 NADH from glycolysis to entermitochondria36 ATPSUMMARY OF CELLULAR RESPIRATIONCopyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-28
UNIT 1 - CHAPTER 4: CELLULAR METABOLISMPROTEIN SYNTHESIS SUMMARY TABLEMAJOR STEPTRANSCRIPTIONTRANSLATIONGENERAL DESCRIPTIONwhen the code (gene) for a protein to be synthesized is copied from the DNA and is put in the form of a Messenger RNA strand (mRNA)when a strand of mRNA (carrying the code for the protein to be synthesized) is translated into a proteinLOCATION IN CELLNucleusat a ribosome that is either free in the cytoplasm or on rough endoplasmic reticulumMOLECULES INVOLVED AND HOW?DNA: unwinds & unzipsRNA Polymerase (an enzyme) positions the complementary RNA nucleotides along the DNA template and zips up their backbone.mRNA carries the message for the protein to be made to the ribosome.Ribosome is the protein synthesizing machinery.Transfer RNA (tRNA) bring the appropriate amino acid tothe ribosome to be incorporated into the protein.Many enzymes.OVERALL RESULTA strand of mRNAA proteinCopyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-29
UNIT 1 - CHAPTER 4: CELLULAR METABOLISMPROTEIN SYNTHESIS WORK SHEETDNA Base Sequence(GENE)Messenger RNA BaseSequence (mRNA)Amino Acid Sequence(PROTEIN)Transfer RNA (tRNA)anticodon sequenceTACTTGCAATCGATTAUGAACGUUAGCUAAMethionineAsparagineValineSerineSTOPUACUUGCAAUCGNACopyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-30
UNIT 1 - CHAPTER 4: CELLULAR METABOLISMMUTATION/PROTEIN SYNTHESIS Problems The following genes code for what amino acid sequences/proteins?1.T A C A A A C G T C C G T A A A T TMet-Phe-Ala-Gly-Ilu-Stop2.T A C T A A C G T C C G T A A A T TMet-Ilu-Ala-Gly-Ilu-Stop3.T A C A A G C G T C C G T A A A T TMet-Phe-Ala-Gly-Ilu-StopAdditions and deletions are much more severe than substitutions because theycompletely change the reading frame of the codons. Called a frameshiftmutation. This is in contrast to missensemutations, which do not substitute anamino acid of the protein.Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.4-31