MICR221 Lecture 8 - Principles Of Bacterial Aerobic Cellular Respiration Flashcards
what is converted to form NADH?
food sources
what is cell metabolism?
taking everything down to a conserved backbone that allows conserved pathways to be operated on meaning that it will not have to produce lots of different proteins
what is the function of specialised pathways?
to isolate the conserved carbon backbone from molecules so it can either enter into glycolysis or the CAC
how many carbon rings do sugars/monosaccharides contain?
6 carbon rings only
what are sugars/monosaccharides converted to?
converted to glucose-6-phosphate or early precursors of glycolysis
what is the relationship between entry into the CAC and an amino acid with a removed amino (NH2) group
the amino (NH2) group must be removed to have variable entry into the CAC
what can NH2 be converted to?
converted into glutamate
what can glutamate be converted to?
can be converted to alpha-ketoglutarate
what is the relationship between alpha-ketoglutarate and the CAC?
alpha-ketoglutarate is key in the CAC as it determines the overall rate of the CAC
what is the conversion of glutamate to alpha-ketoglutarate regulated by?
the process is tightly regulated by both the CAC and the urea cycle
what is the purpose of deamination?
removes excess amino groups (NH2)
can the process of glutamate conversion to alpha-ketoglutarate be reversed?
yes it can be reversed
what are fatty acids?
glycerol
when does glycerol enter glycolysis?
glycerol enters the later stages of glycolysis with only 2 enzyme reactions
what is the relationship between when a molecule enters a pathway and energy investment?
if a molecule enters later in a pathway then they can only get the benefits/products from when they entered the pathway but this means the molecule requires a lower energy investment to enter
what is beta-oxidation?
the flexible removal of acetyl-CoA or jpropionyl-CoA from any length fatty acid depending on if the chain is odd or even numbered. Both of these molecules can enter the CAC
what are the 2 phases of glycolysis?
energy investment phase
energy payoff phase
what is the energy investment phase of glycolysis?
ATP is used to further phosphorylate sugar so it forms an unstable intermediate. The 6C sugar ring is then broken down in 2 3C chains that go through the glycolysis cycle twice more
what is energy payoff phase of glycolysis?
the production of ATP and NADH from oxidations and the eventual removal of phosphate
how many molecules of pyruvate are produced for each molecule of glucose?
2 pyruvate for each molecule of glucose
what is the catabolic process to produce NADH?
1) the 2 pyruvate are entered into the CAC and the cycle moves in the forward direction
2) acetyl-CoA is added in and bound to the conserved intermediates (carbons are added on these 4C molecules and they are later removed to generate NADH at the same time)
what are many of the catabolic reactions to produce NADH driven by?
driven by dehydrogenase
what is the favourable reaction direction aerobically?
aerobically the favourable direction is oxidative –> forward cycle
what is the function of dehydrogenase?
performs oxidation reactions that can produce a lot of energy currencies
what are the 2 major routes of ATP production?
substrate level phosphorylation
oxidative phosphorylation
what is substrate level phosphorylation?
makes ATP as a consequence of cytoplasmic reactions such as glycolysis and the CAC. It is low efficiency but is simple and not limited by electron acceptor although it is eventually limited without regenerating NAD+ (e.g fermentation). Low amounts of ATP are produced but smaller amounts of proteins are made
what are fermenters?
bacteria that have evolved to make ATP purely from cytoplasmic substrate level phosphorylation
what do cytoplasmic reactions require?
require NAD+ to drive redox reactions and oxidise glucose
what is oxidative phosphorylation?
uses reducing powers to generate ATP and the ETC + ATP synthase also. It is high efficiency but complex and limited by the electron acceptor but regenerates NAD+. It is linked by PMF also known as cellular respiration
what are the reducing powers of oxidative phosphorylation?
FADH2 and NADH
what establishes the concentration gradient for oxidative phosphorylation?
electrons that are put onto oxygen
what is oxidative phosphorylation good for in terms in types of organisms?
good for organisms that need to produce lots of ATP (fast growth rates or need to use their carbon sources more efficiently for persisters and slow growing cells)
how does oxidative phosphorylation compare with substrate level phosphorylation in terms of the amount of ATP produced?
oxidative phosphorylation produces up to 10 times more ATP than substrate level phosphorylation because the presence of oxygen hugely impacts ATP yields
what processes is ATP required for?
anabolic processes like polymer synthesis
what does the growth of bacteria depend on in terms of ATP?
growth of bacteria depends on ATP yields
what is redox (reduction) potentials?
electrons in redox active molecules have an inherent energy which is measured in voltage. These molecules have electrons within them that exist in different energy levels and this is the molecules reduction potential
what is the relationship between low energy electrons and stability?
molecules with low energy electrons such as oxygen are more stable as they are more positive
what is reduction potential?
the tendency of a molecule to accept or release electrons
what does it mean if the reduction potential is more negative?
a more negative reduction potential means they are more likely to release electrons so the electron is in a higher energy orbital/state. Energy release form transferring electrons can be used to do work by being coupled to proton pumps
what is the lowest energy electron acceptor in biological systems?
oxygen
what is aerobic respiration?
respiration where oxygen is used as the terminal electron acceptor
what is anaerobic respiration?
respiration where no oxygen is available so bacteria use an alternative electron acceptor
what are oxidation reactions?
reactions that release electrons from the donor and protons are pumped by enzymes then electrons are passed to certain carrier molecules which then pass them onto other enzymes which can do further perform proton pumping actions and will ultimately give electrons to terminal electron acceptor proteins
what does the ETC involve?
involves a series of membrane bound proteins and cofactors
what does catalysation of the redox reactions in the ETC produce?
usually produces a proton motive force (PMF)
what makes bacteria flexible?
their mitochondrial configuration
what are the 4 key features of the electron transport chain (ETC)?
membrane
oxidative protein complexes
cofactors
reductive protein complexes
what is a membrane?
a physical barrier that is needed to create a concentration gradient
what are oxidative protein complexes?
complexes that liberate electrons from reducing powers and may pump H+
what is the function of cofactors?
to transfer electrons between enzymes
what is the function of reductive protein complexes?
to finally transfer electrons to a terminal electron acceptor and may pump H+
what is complex I?
NADH dehydrogenase (large multisubunit enzyme) that oxidises NADH and reduced coenzyme Q (ubiquinone) by inducing structural changes that pump protons
what is reduced coenzyme Q?
ubiquinone
what is complex II?
succinate dehydrogenase which is the same enzyme from the CAC that generally does not pump protons
what occurs at complex II?
- FAD is a covalently bound intermediate here
- succinate is oxidised
- quinone is directly reduced
what is quinone?
a small lipophilic chemical with an aromatic head group that accepts electrons with many different types with redox potentials
what is a quinol?
a reduced quinone that is a small molecule that can freely diffuse through the membrane to the terminal enzyme
what is cytochrome c?
a small protein that contains a heme group that accepts electrons that is generally only associated with oxidase enzymes that perform oxygen reduction
what is cytochrome P4SO?
a heme containing enzyme that performs reactions
what is complex III?
cytochrome bci transfers between quinol and cytochrome c by indirectly transferring protons using electron carrier acid/base chemistry. They are linked to complex IV and in many bacteria they are a super complex
what is the function of complex IV?
takes electrons from cytochrome c and is used to terminally reduce oxygen by cytochrome c oxidase. Protons are taken up during catalytic intermediates and pumped
