Chapter 5 - Microbial Metabolism PDF

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Chapter 5 - Microbial Metabolism
Professor: B. Samuel
Includes textbook and in-class notes ...

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Chapter 5 – Microbial Metabolism Metabolism - Sum of all chemical reactions that happen within the cell.  Synthesis, store and utilize that energy

Pathways of Metabolism Catabolism  The breakdown of molecules (Hydrolytic reactions in which produces ATP  Degradative  Hydrolysis  Exergonic Reactions  Produces energy  ATP production Anabolism  The Synthesis of larger molecules from smaller ones. (Dehydration reactions that use ATP)  Biosynthetic  Dehydration  Lose H2O  Endergonic Reactions  use energy  By releasing the last phosphate in ATP  3 PO4- turns into 2 PO2-  ADP *LEGEND: ~ = Unstable bond

Two Key Players in Metabolism 1) ATP  Considered the cells currency because you can save it, use it, or even exchange it.  Principle form of energy in all organisms  Immediately available 2) Enzyme  Acts as a biological catalyst for speeding up chemical reactions  By lowering the activation energy  Increase the likelihood of the reaction  Remain unchanged after a reaction  Influenced by various factors in our genetic makeup

Enzyme Components 1) Apoenzyme  Protein portion  Inactive 2) Cofactor  Nonprotein component o Inorganic Molecules  Ca+, Fe+, Mg, Mn+

o Organic (Carbon is present) Molecules  Also called Coenzymes  The activator 3) Holoenzyme: Apoenzyme plus Cofactor 4) Active Site: Where the substrate combines with the enzyme to activation the reaction and form the enzyme-substrate complex

Examples of Coenzymes 

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NAD+ o Nicotinamide Adenine Dinucleotide o Derived from Vitamin B  Mostly taken in through diet NADP+ o Nicotinamide Adenine Dinucleotide Phosphate o Derived from Vitamin B FAD o Flavin Adenine Dinucleotide FMN o Flavin Mononucleotide Coenzyme A Coenzyme Q  Ubiquinone

** These are used for oxidation reduction

Simple Vs Conjugated Enzymes 1) Simple  Are proteins 2) Conjugated  Apoenzyme + Cofactor = Holoenzyme (Whole enzyme)  Holoenzyme  Active enzyme  ** Apoenzyme + Cofactor are inactive when separate

Factors Influencing Enzyme Activity a. Temperature  As reaction rate increases, temperature increases until a maximal point is reached

 

The best reaction rate happens at 37 degrees  Optimum temperature Why Does Enzyme Reaction Cease Beyond at 37 Degrees? Denaturation of proteins  The active site has been unraveled and lost ** Will be a question in the exam

b. pH  Most active at a pH of 5.0 c. Substrate Concentration  When the concentration of substrate increases, so does the reaction until all the active sites have been occupied and the complex is completely saturated d. Inhibitors  Two Types  Competitive 1. Behinds to the active site and stops the substrate from occupying the site 2. Ie. #1  Sulfanilamide  Sulfa Drug  Inhibits Folic Acid in bacteria  Leads to bacterial cell death  ** Do not use during pregnancy 3. Ie. # 2  Para Amino Benzoic Acid (PABA)  Creates folic acid  Important in creating new DNA 

Non-Competitive 1. Allosteric Binding

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When excess end product is produced, it travels to the allosteric binding site of the first enzyme and shuts down production  Feedback inhibition

Oxidation Reduction 

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Oxidation I. Removal of electrons and proton II. Removal of hydrogen atom  Dehydrogenation III. NADH or FADH = Glucose + NAD/FAD Reduction I. Gain of electrons and proton II. Gain of hydrogen atom  Hydrogenation III. Glucose + NAD or FAD = NADH or FADH

Redox Reaction - The removal of hydrogen through the process of oxidation. When hydrogen atoms are added it’s called reduction. Phosphorylation = ADP + Inorganic Phosphate  Basic Mechanism by which ATP is generated Dehydrogenations – Electrons are often associated with hydrogen atoms Types 1) Substrate Level o Energy from the transfer of a high energy PO4 to ADP generates 2) Oxidative Level o Redox reaction  Reduce coenzymes  Enter electron transport chain  Leaves the H atom  Chemiosmosis of H  Creates ATP o Energy released from the transfer of electrons (oxidation) compound to another (reduction) is used to generate ATP in the electron transport chain 3) Photophosphorylation o Light causes chlorophyll to give up electrons. Energy released from transfer of electrons (oxidation) of chlorophyll through a system of carrier molecules is used to generate ATP

Carbohydrate Catabolism Glycolysis

o

The breakdown of glucose to pyruvic acid produces 2 ATP and 2 NADH

Kreb’s Cycle  Happens twice as it needs to process each pyruvic acid individually o 2 x Pyruvic acid molecules enter and goes through oxidation reaction o Creates NADH x 2, changes pyruvic acid  Acetyl-CoA o Acetyl-CoA enters the cycle and goes through 8 steps

Aerobic

Respiration o Requires all 3 cycles o Produces 38 ATP in bacteria, 36 in Humans o Requires Oxygen to be present o Common in most bacteria

Anaerobic o Happens during glycolysis and part of Kreb’s o # variable amount of ATP is produced o Oxygen is not present as an electron acceptor o

o

Uses Nitrates, sulfates, bicarbonates are used as electron acceptors Rare in bacteria

Fermentation o Only glycolysis o Creates 2 ATP o The electron acceptor is an organic molecule o Lactobacillus species o Creates Lactic acid

Pathway

Eukaryote

Proka

Glycolysis

Cytoplasm

Cytop

Intermediate step

Cytoplasm

Cytop

Krebs cycle

Mitochondrial matrix

Cytop

ETC

Mitochondrial inner membrane

Plasm

Types of Respiration in Prokaryote 1) Aerobic Respiration – The final electron acceptor in the electron transport chain is molecular oxygen 2) Anaerobic Respiration – The final electron acceptor in the electron transport chain is not O2. Yields less energy than aerobic respiration because only part of the krebs cycle operates under anaerobic conditions 3) Fermentation – Uses an organic molecule as the final electron acceptor. It does not use the Krebs cycle or ETC...