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26

The answer to this, I reckon, is that they don't. They use molecular oxygen (O2) dissolved in the water for respiration, where it acts as a terminal electron acceptor, just as we use molecular oxygen in the air for respiration. We can speak of the water as being oxygenated. Water is split in photosynthesis, where reducing equivalents from water are used ...


18

The phosphate group in NADPH doesn't affect the redox abilities of the molecule, it is too far away from the part of the molecule involved in the electron transfer. What the phosphate group does is to allow enzymes to discriminate between NADH and NADPH, which allows the cell to regulate both independently. The ratio of NAD+ to NADH inside the cell is high, ...


16

No, hydrogen could not replace oxygen because it has entirely different characteristics. The most important one is probably its electronegativity - oxygen 'pulls' electrons much 'stronger' than hydrogen. Basics: Reduction potential Oxygen is the so-called terminal electron acceptor of the electron transport chain in eukaryotes. You can see "reduction ...


16

Oxygen is actually highly toxic to cells and organisms – reactive oxygen species cause oxidative stress, essentially cell damage and contributing to cell ageing. A lot of anaerobic organisms have never learned to cope with this and die almost immediately when exposed to oxygen. One classical example of this is C. botulinum. Oxygen is incorporated in several ...


16

Nice question! Oxygen is actually not needed in the Krebs cycle - it is needed in the electron transport chain that is upstream of the Krebs cycle to regenerate NAD+ from NADH. NAD+ is a co-enzyme and acts as an electron carrier in oxidizing reactions at various positions in the Crebs cycle. However, note that without O2, NADH accumulates and the cycle ...


15

Superoxide, O2− is created by the immune system in phagocytes (including neutrophils, monocytes, macrophages, dendritic cells, and mast cells) which use NADPH oxidase to produce it from O2 for use against invading microorganisms. However, under normal conditions, the mitochondrial electron transport chain is a major source of O2−, converting up to perhaps 5% ...


15

According to "Resolution of distinct rotational substeps by submillisecond kinetic analysis of F1-ATPase" (Yasuda et al., Nature, 2001), ATPase rotates at 130 revolutions per second when saturated with ATP.


14

CO2 is a product of Cellular Respiration, which generally takes Glucose and molecular Oxygen to produce Carbon Dioxide, water, heat, and allows ADP to be regenerated into ATP (or other various oxidation reactions). The Carbon comes from wherever the acetyl-CoA used in the Citric Acid Cycle came from - either carboyhydrates or fatty-acids (saturated carbon ...


11

You probably know by now that cytochrome c oxidase, the last complex of the electron transport chain, belongs to a class of enzymes called oxidoreductases, that use oxygen atoms as electron acceptors. One type of oxidoreductases are oxidases, enzymes that (at least in theory [1]) use molecular oxygen--O2, like in air--as their electron acceptor. From what I ...


11

Mitochondria are very similar to bacteria and are thought to have originated from bacteria. This points you to the answer: bacteria produce ATPs the same way mitochondria do, with the oxidation machinery place in their plasma membrane (analogous to the mitochondrial membrane).


10

There is a good review in the Journal of Experimental Biology (Bickler and Donohoe 2002, JEB 205, 3579–3585) I will just summarize for those that do not have access to the review. Neurons use lot of energy to maintain their polarized state, this is not required to other cells. When O2 or blood flow is reduced, the neuronal ATP levels breaks down very fast, ...


10

Anaerobic respiration is a respiration where the final electron acceptor is different than oxygen. The final acceptor can be a less oxidizing than oxygen, like sulfate (SO42-), nitrate (NO3-), or sulfur (S). For example bacteria that use sulfate are obligate anaerobs. The Krebs cycle cannot take place in the absence of oxygen, although oxygen is not ...


10

Mitochondria are comprised of ~3000 proteins. However, the mitochondrial genome has only 13-14 protein-encoding genes. The remaining 99.6% of mitochondrial proteins are encoded by genes in the nuclear genome. (Wikipedia) Chloroplast genomes are only slightly larger (~100 genes). Gene regulation and signaling between the nucleus and mitochondria (and between ...


9

Here's an illustrated example in neurons: ATP, of course, is generated by aerobic respiration. The critical biochemical reaction in the brain that is halted due to lack of ATP (and therefore O2) is the glutmaine synthetase reaction, which is very important for the metabolism and excretion of nitrogenous wastes: The body uses this reaction to dump excess ...


9

Just to expand slightly on the answer by Jack Aidley: Have a look at this section from Stryer's Biochemistry text book, particularly Fig 10.17, where you can see that haemoglobin has evolved to have a high affinity for oxygen at the O2 concentrations present in the lungs, but a low affinity at the O2 concentrations present in the peripheral tissues. This is ...


8

Image from wikipedia page on ATP synthase In brief, the addition and release of protons to the structure cause a conformational change that leads to another conformational change. This series of conformational changes occurs in such a way that it induces a rotational motion. The rotation of the central axel that extends through both hemispheres of ...


7

There are metabolic processes in which ATP is synthesised without the involvement of ATP synthase. The best examples are, in fact, two steps in the glycolytic pathway, catalysed by phosphoglycerate kinase and pyruvate kinase. This is why, in the absence of any aerobic metabolism, many organisms (like yeast for example) can grow quite happily, producing two ...


7

Your question is based on a bit of confusion about electron acceptors that is very common and that drives microbiologists crazy. Energy (as ATP) is generated when electrons are moved from an electron donor to an electron acceptor. In respiration, the electron acceptor is inorganic -- oxygen for aerobic respiration or an inorganic molecule such as sulfate or ...


7

They do generate heat. They just do not SPEND energy specifically on heating their bodies by raising their metabolisms. This is a form of energy conservation. The metabolic rate they need to live is not nearly enough to heat their bodies. An example of spending energy to heat the body is seen in humans shivering. Here muscle is activated not for its usual ...


6

The overwhelming use of oxygen is to provide us (in combination with food) with energy. We have a great need for energy in our cells, which is why we have these lungs, diaphragms, red blood cells, etc.; they assure we get the oxygen to obtain the energy (via the electron transport chain). The overall metabolism of glucose (C6H12O6) is a representative ...


6

The textbook version for the regulation of ATP involves a feedback loop with phosphofructokinase (PFK). The relative concentrations of ADP and ATP are characteristic of the energy state of the cell. If the cell is using energy, then there will be an excess of ADP. If not, then ATP. ATP is an inhibitor of PFK, which in turn slows glycolysis (thus reducing ...


6

Adenosine triphosphate (ATP) is often thought of as the energy currency of cells. It is not "used up" per se, but energy is released from the conversion of ATP to ADP (adenosine diphosphate), and yet more can be obtained by removing another phosphate to make AMP (adenosine monophosphate). Here's a chemical schematic of ATP, you can see the three phosphates ...


6

Aren't there any other alternatives for this acceptor? Yes, there are multiple other acceptors used by anaerobic bacteria. Iron is probably the most common other acceptor used by a range of organisms in a range of environments but others are used as well, such as sulphur. Aren't there any other alternatives for this acceptor? Oxygen is already ...


5

I might be taking a bit of a simplistic view on this, but I'm not sure what the confusion is. The ring of 10 c subunits constitute a motor which uses a proton gradient to drive the rotation of the FoFc synthase. (image reference is a nice lecture on ATP synthase). The motor of c subunits has a 10 fold symmetry. Each subunit releases a proton as it ...


5

Just wanted to supplement to the other two answers... I was trying to use comments but ran out of space. @AlanBoyd s figure tells you a lot - you can see that myoglobin (Mb) has a much higher affinity for oxygen, so it will sit in the muscle and take the oxygen the tissue needs from the hemoglobin (Hb) as the blood flows through the tissue. But what ...


5

The passage of protons through the FO (membrane) portion of the molecule (driven by the electrochemical gradient of protons across the respiratory membrane) generates torque at the interface between the a and c subunits. This mean that the ring of 10 c subunits rotates relative to the a subunit. The γ subunit in the stalk rotates along with the ring ...


5

You haven't directed us to any evidence for your assertion, so it is difficult to evaluate. I'm not a plant physiologist, so I will argue from first principles: photosynthesis consumes CO2 and produces O2: 6CO2 +6H2O -> C6H12O6 + 6O2 respiration consumes O2 and produces CO2: C6H12O6 + 6O2 -> 6CO2 +6H2O Plants do both of these things at the same ...


5

Aren't there any other alternatives for this acceptor? Not that we're aware of. Every other alternative requires an anaerobic environment - which means small, and often less efficient. Oxygen is already recognized to have several harmful effects to cells - wouldn't another molecule be a better choice? When we're talking about a molecule's fit ...


5

There are some recipes available on the web, my answer is based on this webpage and this information: The process itself is rather easy and you can either use ready bought apple juice, homemade juice or apple cider (basically unfiltered apple juice). You will need some specially cultivated yeast, baker's yeast is generally not recommended since it might ...


4

For starters, see this thread. My understanding is that the ancient predecessors of mitochondria were free-living unicellular organisms. Supposedly at one point, these mitochondria-like cells developed an endosymbiotic relationship with a larger cell. This relationship was advantageous for both cells: the smaller cell could focus on energy production, ...



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