Lecture 8 Metabolism and Catabolism Flashcards
Metabolism requires enzymes describe what enzymes do and name the examples from lectures.
- Acts on substrates, convert to products
- Enzymes increase reaction rates by lowering activation energy.
Ex.) - Phosphatase, Kinase, Cellulase - Dehydrogenases - oxidation and reductions reactions
What are dehydrogenases used in?
oxidation and reduction reactions (LEO says GER)
How do enzymes lower the energy of activation?
- Increase local concentrations
- Orient substrates properly for reactions to proceed
Describe Oxidation- Reduction reactions.
- Oxidation - removal of electrons
- Reduction - addition of electrons
- Substance oxidized donor, substance reduced is acceptor (pair = redox couple)
- Redox often involve not just the transfer of electrons but both an electron + proton (H atom, example: NAD+/NADH)
What is the Psychrophilic, Obligate Anaerobe that Oxidizes Acetate with the Reduction of Iron.
Rhodoferax metabolins
Describe what Reduction Potential is (E0)
- Equilibrium constant for redox reactions
- Measures tendency of donor to lose electrons
- More negative E0 better donor
- More positive E0 better acceptor.
Describe what the electron tower is.
Greater the difference –> the more negative the Gibbs free energy is.
What are the two classes of electron Carriers in Redox Reactions?
- Freely diffusible (in cytoplasm)
ex. ) NAD+ and NADH+ - Reduced forms (NADH, NADPH) are the “reducing power” in the cell
Membrane- bound
Ex.) flavoproteins, cytochromes, quinones
What are Heterotrophs
A metabolic group
- reduced, preformed organic compounds as C source (animals, many microbes)
- Convert large amount of C to CO2
What are Autotrophs
A metabolic group
- CO2 as C source (plants, many microbes)
- synthesize organic compounds used by heterotrophs
- Also called primary producers.
Where to phototrophs get there energy from?
light
Where do Chemotrophs get there energy from?
oxidize chemical compounds (often same as their C source)
Where do lithotrophs get there electrons from?
Inorganic molecules as electron donors
- unique to few bacteria and archaea (prokaryotes)
Where do Organotrophs get there electrons from?
Organic molecules as donors
Describe the Tricarboxylic acid cycle
- Many different energy sources are funneled into common degradative pathways
- Most pathways generate glucose or intermediates of the pathway used in glucose metabolism
ATP by 2 means:
Substrate level Phosphorylation
Oxidative Phosphorylation
What are the two functions of organic energy sources?
- Oxidized the release energy
- Provide building blocks for anabolism
What are Amphibolic pathways?
- Metabolic pathways that function both catabolically and Amphibolic pathways
Describe Aerobic Respiration
- Process that can completely catabolize an organic energy source to CO2 using
- Glycolytic pathways (glycolysis)
- Tricarboxylic Acid Cycle (TCA)
- Electron transport chain with oxygen as final electron acceptor
- Produces ATP (most indirectly, via electron transport)
Breakdown of glucose to pyruvate
- Three paths
- Emden - Meyerhof (glycolysis)
- Pentose Phosphate
- Entner-Doudoroff
Embden-Meyerhof Pathway (Glycolysis)
- Most common form of glucose breakdown
- Occurs in cytoplasm
- Functions in presence or absence of 02
- Ten reactions, in two stages.
Review this pathway
Describe in painstaking detail Glycolysis, What are the Key reactions, what is the net yield
-6C Stage: glucose phosphorylated twice (requires ATP) generating fructose 1,6-bisphosphate.
- 3 C Stage:
- Fructose 1,6-bisphosphate split into 2 glyceraldehyde 3-P then converted to pyruvate
- Key Reactions
- oxidations –> NADH
- Substrate-level phosphorylated > ATP
-Net yield - 2ATP, 2NADH , 2 Pyruvate
What Kind of pathway is Glycolysis?
Amphibolic pathway
Describe the NADH and ATP Generating Steps of Glycolysis
Reaction 1
- Glyceraldehyde-3-phosphate oxidized and phosphorylated-generates high-energy P bond
- NAD+ reduced to NADH
- Enzyme used G3P dehydrogenase
Reaction 2
- Phosphorylation of ADP by high energy metabolic substrate
- Generates ATP by substrate level phosphorylation
- Enzyme used 3PG Kinase
The last reaction is also a Substrate-Level Phosphorylation
Enzyme used pyruvate kinase
Another Method of Glucose Breakdown is Pentose Phosphate describe it! Bitch!
- Starts by converting Glucose-6-P to Ribulose-5_P (pentose)
- Generates many sugars for biosynthesis
- Yields 6 NADPH(reducing power for biosynthesis) and 1 ATP
Another Method of Glucose Breakdown is the Entner - Doudoroff pathway. Describe it Now and if you don’t get it write you will be killed by hundreds of tiny turtles.
- Combines reactions of glycolysis and pentose phosphate
- 1 ATP, 1NADH, 1NADPH
Describe the Tricarboxylic Acid Sycle (Citric Acid or Krebs’s)
- Pyruvate completely oxidized to CO2
- In mitochondria of eukaryotes, cytoplasm prokaryotes
- Generates: CO2 and Numerous NADH and FADH2
!!!THE TCA CYCLE!!!
!!!THE TCA CYCLE!!!
