Enzymes
Transcript of Enzymes
Ch 4:Ch 4: Cellular Metabolism - P Cellular Metabolism - Part 2art 2Ch 4:Ch 4: Cellular Metabolism - P Cellular Metabolism - Part 2art 2
Energy as it relates to BiologyEnergy as it relates to Biology
EnzymesEnzymes
MetabolismMetabolism Catabolism (ATP production)Catabolism (ATP production)
Glycolysis and the TCA CycleGlycolysis and the TCA Cycle Anabolism (Synthetic pathways)Anabolism (Synthetic pathways)
Protein SynthesisProtein Synthesis
MetabolismMetabolism
Definition = “All chemical reactions that take Definition = “All chemical reactions that take place within an organism.”place within an organism.”
Metabolic pathways = network of linked reactionsMetabolic pathways = network of linked reactions
Basic feature: coupling of exergonicBasic feature: coupling of exergonic rxs with endergonic rxs. rxs with endergonic rxs. (direct vs. indirect coupling)(direct vs. indirect coupling)
Review:Review: Energy = capacity to do workEnergy = capacity to do work
Usually from ATPUsually from ATP Enzymes = biological catalystEnzymes = biological catalyst
Lower activation energyLower activation energy Return to original stateReturn to original state Opportunity for controlOpportunity for control
Metabolism Metabolism p 101p 101
Anabolism Synthesis
Energy transferred commonly measured in calories: 1 cal = 1 g of H2O by 1° C
1 Kcal = temp. of 1L H2O by 1o C. = Calorie (capital C)
Energy released in catabolic reactions is trapped in Energy released in catabolic reactions is trapped in 1) Phosphate bonds1) Phosphate bonds2) Electrons2) Electrons
Catabolism Energy
Metabolic pathways: Network of Metabolic pathways: Network of interconnected chemical reactionsinterconnected chemical reactionsLinear pathway
Circular pathway
Branched pathway
Intermediates
Control of Metabolic PathwaysControl of Metabolic Pathways
1.1. Enzyme concentration Enzyme concentration (already (already covered)covered)
2.2. Enzyme modulators Enzyme modulators - Feedback- or end product - Feedback- or end product inhibitioninhibition- Hormones- Hormones- Other signaling molecules- Other signaling molecules
3.3. Different enzymes for reversible Different enzymes for reversible reactionsreactions
4.4. Enzyme isolationEnzyme isolation
5.5. Energy availability (ratio of ADP Energy availability (ratio of ADP to ATP)to ATP)
(Chapter 6)
Catabolic Pathways: Catabolic Pathways: ATP-Regeneration-Regeneration
Amount of ATP produced reflects on usefulness of metabolic pathways: Aerobic pathways Anaerobic pathways
Different biomolecules enter pathway at different points
ATP Cycle
ATP = Energy Carrier of Cell ATP = Energy Carrier of Cell (not very useful (not very useful for energy storage) for energy storage)
ATP : ADP ratio determines status of ATP synthesis reactions
GlycolysisGlycolysis
From 1 glucose (6 carbons) to 2 From 1 glucose (6 carbons) to 2 pyruvate (3 carbons) moleculespyruvate (3 carbons) molecules
Main catabolic pathway of cytoplasmMain catabolic pathway of cytoplasm
Does not require ODoes not require O2 2 common for common for (an)aerobic catabolism(an)aerobic catabolism
Starts with phosphorylation of Starts with phosphorylation of Glucose to Glucose 6-PGlucose to Glucose 6-P
(“Before doubling your money you first (“Before doubling your money you first have to invest!”)have to invest!”)
Net gain?
The Steps of The Steps of GlycolysisGlycolysis
Anaerobic catabolism: Pyruvate
Lactate
Aerobic catabolism: Pyruvate
Citric Acid Cycle
Pyruvate has 2 Possible Fates:Pyruvate has 2 Possible Fates:
Citric Acid CycleCitric Acid Cycle
Other names ?Other names ?
Takes place in ?Takes place in ?
Energy Produced:Energy Produced:1 ATP1 ATP3 NADH 3 NADH 1 FADH1 FADH22
Waste – 2 COWaste – 2 CO22
Electron transport System
NADH
NADHNADH
FADH2
Energy Yield of Krebs Cycle
See Fig. 4-24
Final step:Final step: Electron Transport System Electron Transport System
Chemiosmotic theory / oxidative phosphorylation
Transfers energy from NADH and FADHTransfers energy from NADH and FADH22 to ATP to ATP (via e(via e- - donation and Hdonation and H++ transport) transport)
Mechanism:Mechanism: Energy released by Energy released by movement of emovement of e-- through transport system through transport system is stored temporarily in His stored temporarily in H++ gradient gradient
NADH produces a maximum of 2.5 ATP NADH produces a maximum of 2.5 ATP FADHFADH22 produces a maximum of 1.5 ATP produces a maximum of 1.5 ATP
1 ATP formed per 3H+ shuttled through ATP Synthase
Fig 4-25
Cellular Cellular RespirationRespiration
Maximum potential yield for aerobic glucose metabolism: 30-32 ATP synthesized from ADP
H2O is a byproduct
Summary of CHO catabolism
Protein Catabolism??Protein Catabolism?? ProteasesProteases PeptidasesPeptidases Deamination (removal Deamination (removal
of the NHof the NH33)) NHNH3 3 becomes ureabecomes urea
Pyruvate, Acetyl CoA, Pyruvate, Acetyl CoA, TCA intermediates are TCA intermediates are left.left.
Lipid Catabolism??Lipid Catabolism??
LipolysisLipolysis Lipases break lipids Lipases break lipids
into glycerol (3-C)into glycerol (3-C)
Glycerol enters the Glycerol enters the glycolytic pathwayglycolytic pathway Called Called ββ-oxidation-oxidation
Synthetic PathwaysSynthetic Pathways
Unit molecules Macromolecules
PolysaccharidesLipidsDNA
Protein
nutrients & energy required
Anabolic reactions synthesize large Anabolic reactions synthesize large biomoleculesbiomolecules
GlucoseAmino Acids
Glycogen SynthesisGlycogen SynthesisMade from glucoseMade from glucose
Stored in all cells but especially inStored in all cells but especially in Liver Liver (keeps 4h glycogen reserve for between meals)(keeps 4h glycogen reserve for between meals)
Skeletal Muscle Skeletal Muscle muscle contraction muscle contraction
GluconeogenesisGluconeogenesisGlycolysis in reverse Glycolysis in reverse
From glycerol, aa and lactateFrom glycerol, aa and lactate
All cells can make G-6-P, only liver and All cells can make G-6-P, only liver and Kidney can make glucoseKidney can make glucose
Proteins are necessary for cell functionsProteins are necessary for cell functions
Protein synthesis is under nuclear direction Protein synthesis is under nuclear direction DNA specifies ProteinsDNA specifies Proteins
Protein SynthesisProtein Synthesis
DNA DNA mRNA mRNA Protein Protein? ?
1 start codon1 start codon
3 stop codon3 stop codon
60 other codons for 60 other codons for 19 aa19 aa
Redundancy of Genetic Code (p 115)
A combination of three bases forms a codon
TranscriptionTranscription
DNADNA is transcribed into is transcribed into complementary complementary mRNAmRNA
byRNA PolymeraseRNA Polymerase
+ nucleotides+ Mg2+
+ ATP
Gene = elementary unit of inheritance
Compare to Fig. 4-33
Protein synthesis Protein synthesis fig 4-27fig 4-27
TranslationTranslationmRNA is translated into string of aa mRNA is translated into string of aa (= polypeptide)(= polypeptide)
mRNA + ribosomes + tRNA meet in cytoplasm
Anticodon pairs with mRNA codon aa determined
Amino acids are linked via peptide bond.
2 important components ??
Fig 4-34
Primary Structure
Protein SortingProtein Sorting No signal sequence No signal sequence protein stays in cellprotein stays in cell
Signal sequence Signal sequence protein destined for translocation protein destined for translocation into organelles or into organelles or for for exportexport
Post – Translational protein modifications: Folding, cleavage, additions glyco- , lipo- proteins
Modifications in ERModifications in ER
Transition vesicles toTransition vesicles to
Golgi apparatus for further Golgi apparatus for further modificationsmodifications
Transport vesicles to cell Transport vesicles to cell membranemembrane
For “export proteins”: Signal sequence For “export proteins”: Signal sequence leads growing polypeptide chain across ER leads growing polypeptide chain across ER membrane into ER lumenmembrane into ER lumen
DNA Replication DNA Replication
Semi- Semi- conservativeconservative
DNA DNA polymerasepolymerase