Lecture 8 - principles of bacterial aerobic cellular respiration Flashcards
Growing cells
new biomass dominates total energy requirements
Non growing cells
repair and replacement is all that is possible
Proton motive force
gradient of both concentration and charge that is required even during non growth
3 key molecules that participate and determine the majority of catabolic and anabolic reactions
ATP, NADH and NADPH
Active vs passive transport
Active transport accumulates substrates rapidly and against concentration gradient, but has a higher energy cost than passive
3 transporters are
ABC family, MFS family, group translocation
Protein synthesis has the highest…
Protein synthesis has the highest energy requirement, making new amino acids monomers however would require more energy than protein synthesis
How do food sources get converted into NADH?
Amino acids, glucose, glycerol and fatty acid are monomers
Variety of different nutrient sources that cell can take up such as proteins, sugars and lipids. Idea behind cell metabolism in general is that we are trying to conserve backbones so that we can used conserved pathways to operate on because then you do not have to make millions of different proteins that are really hard to make so you want to make as few proteins as possible whilst still maintaining flexibility
Monomers are entered into various parts of glycolysis or the citric acid cycle//breakdown products ultimately enter the CAC and can be entered into different parts of this conserved pathway depending on the molecule or pathway used initially (see diagram)
Specialised pathways isolate the conserved carbon backbone from molecules to enter it into either glycolysis or TCA cycle
Monomers and how they are converted to NADH
Monomers are entered into various parts of glycolysis or the citric acid cycle//breakdown products ultimately enter the CAC and can be entered into different parts of this conserved pathway depending on the molecule or pathway used initially (see diagram)
Sugars/monosaccharides conversion
(6 carbon rings only)
Converted to glucose-6-phosphate or early precursors of glycolysis
Amino acids conversion
Amino (NH2) group must be removed. Variable entry into TCA
Primarily transaminate NH2 -> glutamate - key in CAC, example of how a specific amino acid can be entered into the CAC which means all the stuff that happened in glycolysis is missed and doesn’t happen and the alternative pathways need to be used
Glutamate alpha-ketoglutarate is tightly regulated by both TCA cycle and urea cycle. Deamination removes excess NH2
Fatty acids conversion
Glycerol can enter into glycolysis with only two enzyme reactions
Beta oxidation: flexibility removes acetyl-CoA or propionyl-CoA from any length fatty acids. Both enter into TCA
Two phases of glycolysis
Energy investment phase and the energy payoff phase
Glycolysis define
Glycolysis is the first of the main metabolic pathways of cellular respiration to produce energy in the form of ATP. … Overall, the process of glycolysis produces a net gain of two pyruvate molecules, two ATP molecules, and two NADH molecules for the cell to use for energy
Energy investment phase
Put in energy
ATP is used to phosphorylate sugar : unstable intermediate
6C sugar ring is broken into two 3C chains
Use ATP to further phosphorylate G6P and modify it into unstable intermediates, essentially glucose is split into two smaller things which go through the rest of the pathway twice
Energy pay off phase
Oxidations and (eventual) removal of phosphate produced ATP and NADH
Subsequent oxidation and reduction reactions to essentially create ATP or NADH, can create ATP directly or can create NADH which is involved in some catabolic steps and then will be used by respiration later
For each molecule of glucose…
2 pyruvate are produced
What happens to the 2 pyruvate produced during glycolysis?
these are then entered into the CAC and essentially the idea is that it is going around in a forward (oxidative) direction and then adding in acetyl-CoA (can come from beta oxidation but pyruvate usually gets converted into acetyl-CoA) and this gets added into some of the conserved intermediates, essentially adding carbons on to the 4C molecule and then later removing carbons to generate NADH molecules
Full cycle operates twice per glucose in glycolysis
Many reactions are reversible
Aerobically the favourable direction is oxidative (forward running cycle)
Driven by dehydrogenases - enzymes that perform oxidation reactions that can produce lots of these energy currencies
NET products produced during glycolysis
2 pyruvate, 2 ATP, 2 NADH
ATP formed and used in glycolysis
4 ATP formed, 2 ATP used, therefore net gain of 2 ATP
Products produced from pyruvate dehydrogenase (PD)
1 NADH
Products produced during 1 full cycle of TAC
3 NADH
1 GTP (can be converted into 1 ATP)
1 FADH2