CH. 13 Energetics & Catabolism Flashcards
What is the basic scheme of metabolism in a cell?
The division of reactions of couple energy-requiring processes (anabolism) with energy-releasing processes (catabolism) to fulfill biological functions
What are the roles of catabolism & anabolism? How does ATP formation/ATP hydrolysis correlate to this?
Catabolism releases energy that is used for ATP formation
Anabolism requires energy for the processes/reactions and that energy is derived from ATP hydrolysis
What is Gibbs free energy? How does this value relate to whether a metabolic reaction will proceed?
Gibbs free energy (delta G) is the measurement of usable energy in the system.
A negative delta G means the reaction is exergonic (releasing energy) and is correlated with catabolism
A positive delta G means the reaction is endergonic (requires energy) and is correlated with anabolism
What are redox reactions and how do you use these to obtain energy from a molecule?
Redox reactions are the summation of oxidation and reduction reactions:
-Oxidation = the addition of oxygen or removal of hydrogen from a molecule
-Reduction = the removal of oxygen or addition of hydrogen to a molecule
It provides energy because the flow of electrons between molecules produces energy
How do organotrophs differ from lithotrophs?
Organotrophs obtain their energy from organic compounds
Lithotrophs obtains their energy from inorganic compounds
What are the prime energy carriers in a cell and how do they function as energy carriers?
- ATP: via hydrolysis and/or phosphorylation
- NAD+/NADH: electron carrier
- Others: NADP+/NADPH; FAD/FADH2; GTP
They occupy intermediate steps in the energy-supply chain between primary sources and end-use applications
What are the functions of an Electron Transport System (ETS)? What role do NADH, FADH2, & NADPH have in an ETS?
The ETS functions to maintain electron flow which maintains the proton gradient which maintains ATP production
NADH, FADH2, & NADPH deposit their electrons at the ETS
Describe the different classes of catabolism. What are different substrates bacteria might utilize for catabolism?
- Fermentation (anaerobic): incomplete oxidation of organic nutrients
- Respiration (aerobic/anaerobic): couple oxidation of organic source with electron transfer to a terminal electron acceptor
- Photoheterotrophy: use light energy to facilitate the catabolism
Some substrates bacteria might utilize for catabolism are carbohydrates, lipids, proteins, & aromatic compounds
Describe the basic differences between the Embden‐Meyerhof‐Parnas pathway, the Entner‐Doudoroff pathway, and
Pentose Phosphate shunt? What does each start and end with, and what is formed in each in terms of energy?
- Embden‐Meyerhof‐Parnas pathway (glycolysis): the oxidation of glucose to pyruvic acid; has a net gain of 2 ATP and 2 NADH
- Entner-Doudoroff pathway: conversion of sugar acids to 2 pyruvates, ATP, NADH, and NADPH
- Pentose-Phosphate shunt: conversion of glucose to 2 NADPH, ATP, and pentose sugars used for biosynthesis of aromatic amino acids, nucleotides, and formation of pyruvates
What is substrate-level phosphorylation?
The formation of ATP by the enzymatic transfer of phosphate from a substrate molecule onto ADP
What are fermentation reactions? Under what conditions do these reactions function?
Fermentation begins with glycolysis which breaks down glucose into two pyruvate molecules and produces two ATP (net) and two NADH
Fermentation allows glucose to be continuously broken down to make ATP due to the recycling of NADH to NAD+.
*known as incomplete oxidation
How does ATP generation occur in fermentation?
Fermentation uses substrate-level phosphorylation (ex. glycolysis), the transfer of a phosphate from a donor molecule to ADP to generate ATP
*makes relatively a low amount of ATP
What are mixed acid fermentations?
A six-carbon sugar (glucose) can be converted into various complex acids such as lactic acid, acetic acid, ethanol, etc.
What is the TCA cycle? What are the energy carriers formed here? How many are formed per turn of the cycle? What enters the cycle?
An aerobic metabolic pathway (also known as the Krebs cycle) where pyruvate is catabolized to carbon dioxide and water for biosynthetic processes
After the oxidation of 2 pyruvates, 2 acetyl-CoA are produced. The acetyl-CoA combines with oxaloacetate (a four-carbon molecule) to produce citric acid. The citric acid goes through a series of reaction that releases the energy molecules of NADH, ATP, and FADH2. CO2 is also produced as a waste product. Since there are 2 acetyl-CoA molecules, the cycle is completed twice
Byproducts for ONE cycle: 1 ATP, 3 NADH, and 1 FADH2
What is oxidative phosphorylation?
The process by which ATP synthesis relies on the maintenance of proton gradient and chemiosmosis through the electron transport system
