Chapter 5 - Microbial Metabolism Flashcards
Metabolism
-the buildup and breakdown of nutrients within a cell
-sum of all chemical reactions in a living organism
-provide energy and create substances that sustain life
-the same through microbes and humans
Enzymes
-biological catalysts
-catalyze reactions for specific molecules called substrates
-accelerate reactions by lowering activation energy
-conjugated proteins: need cofactors to work
-enzymes are specific for reactions: they find their substrate with a lock and key fit
Products
-the result of transforming substrates
Catabolic Pathways
-break down macromolecules into simple components
-release energy in the process
Anabolic Pathways
-build up macromolecules by combining simpler molecules
-use energy in the process
Hydrolytic Reaction
-use water
-chemical bonds are broken
Exergonic Reaction
-produce more energy than they consume
Activation Energy
-amount of energy required to disrupt stable electronic molecules
Catalysts
-substances that speed up a reaction without being permanently altered themselves
Simple Protein Enzyme
-one of the two types of enzymes
-consists entirely of proteins
Conjugated Protein Enzymes
-one of the two types of enzymes
-consist of both a protein portion (Apoenzyme) and nonprotein (cofactor)
Apoenzyme
-inactive by themselves
-protein portion (chapter 2)
Cofactor
-the activator of apoenzyme
-non-protein component
Inorganic Cofactor
-magnesium, iron, calcium ions
Coenzyme (Organic Cofactors)
-derived from vitamin B
-used to carry electrons and proteins to oxidative phosphorylation
-ie. NAD
Holoenzyme
-whole, active enzyme
-can carry out metabolic activity
-apoenzyme + cofactor = holoenzyme
NAD+
-Nicotinamide adenine dinucleotide
-vitamin B derivative
-electron carrier in catabolic reactions
NADP+
-nicotinamide adenine dinucleotide phosphate
-vitamin B derivative
-electron carrier in anabolic reactions
Temperature on Enzymes
-bell shaped curve
-enzyme activity declines beyond optimal temperature
-optimal temp. usually between 35-45
Denaturation
-breakage of hydrogen bonds
-protein unravels and becomes useless
pH
-bell shaped curve
-enzyme activity declined above or below optimum pH
-extreme changes can cause denaturation
-acids alter protein structure because because H+ competes with bonds
Substrate Concentration
-graph increases till it plateaus
-high substrate concentration: saturated
-plateau occurs when all active sites are occupied so if you add more substrate, nothing further will happen
Inhibitors
-compete for active site on protein
-have same chemical makeup and mimic the enzyme
Competitive Inhibitor
-fill the active site of an enzyme and compete with the normal substrate
-can be reversible or irreversible
-can overcome by increasing substrate concentration
-ie. Sulfa
Sulfanilamide (Sulfa)
-mimics/inhibits PABA (Para-amino-benzoic-acid)
-used to treat bacterial infections (usually UTIs)
-PABA produces folic acid which makes DNA and RNA nucleotides
-Sulfa stimulates no folic acid which prevents DNA and RNA and leads to cell death
Why sulfa usually works on humans?
-humans get folic acid from food and don’t use PABA like bacteria
-sulfa only affects bacterial cells
Noncompetitive Inhibitors
-don’t compete with substrate for active site
-interact with another part of the enzyme
-binds to allosteric site to alter active site shape making it nonfunctional
-can be reversible or irreversible
Feedback Inhibition
-noncompetitive inhibitors
-stops cell from making more of a substance than it needs
-shut down the assembly line by stopping the first worker
-ie. E. coli
E. coli
-feedback inhibition
-inhibits the amino acid needed for cell growth
Glycolysis
-process where glucose is broken down into pyruvic acid to produce energy
-products: pyruvate x2, ATP x2, NADH x2, H2O x2
-takes place in cytoplasm
-doesn’t require oxygen
Krebs Cycle
-series of enzyme catalyzed reactions
-2 cycles needed
-occurs in mitochondrial matrix in eukaryotes
-occurs in cytoplasm in prokaryotes
-x2 acetyl-CoA is used up and forms x4 CO2, x6 NADH, x2 FADH2, x2 ATP
Electron Transport Chain
-electrons pass through proteins in inner mitochondrial membrane (eukaryote) and in plasma membrane (prokaryote)
-release energy through a series of redox reactions
-32 ATP produced
Oxidation-Reduction Reactions
-oxidation (molecule A): removal of an electron (and a proton) from a molecule that produces energy
-reduction (molecule B): gains an electron (and a proton)
-each time one molecule is oxidized another is reduced
-the foundation of glycolysis and the krebs cycle
Role of Hydrogen (Dehydrogenation)
-since an electron and a proton are lost, that is equivalent to one H+ atom
-so: molecule A loses a H+ and molecule B gains a H+
ATP Generation
-via phosphorylation of ADP (addition of a P)
-ADP + P + energy = ATP
Substrate Level Phosphorylation
-energy from the transfer of a high energy P to ADP generates ATP
-substrate ~ (high energy bond that can be broken) P + ADP = substrate + ADPᴾ (ATP)
Oxidative Phosphorylation
-electrons are transferred (oxidation) from organic compounds to electron carriers (reduction) (ie. NAD+ or FAD)
-electrons passes through the ETC, releasing energy used to generate ATP
Photophosphorylation
-only in photosynthetic cells
-light causes chlorophyll to give up electrons
-energy is released from the electron transfer (oxidation) of chlorophyll
-generates ATP
Aerobic Respiration
-has to have oxygen as the final electron acceptor in the ETC
-ATP yield: 36 eukaryotes, 38 prokaryotes
-most bacteria are aerobic
-humans can be aerobic
Role of O2 in Anaerobic Respiration
-absorb unusable byproducts (electrons)
Anaerobic Respiration
-oxygen not required
-final electron acceptors: NO3-, SO43-, CO3-
-glycolysis occurs
-yields less energy because only part of krebs cycle operates
-ATP yield varies
-humans can do sometimes
-ie. clostridium bacteria
Fermentation
-uses organic molecule as final electron acceptor
-can be in presence of oxygen or not
-glycolysis only (ATP = 2)
-no krebs cycle or ETC
-ie. Lactobacillus: makes lactic acid, yeast: makes Co2 and ethanol
-lactic acid, CO2, ethanol would be the electron acceptors
