Anaerobic Respiration 18.5 Flashcards
How do we know that anaerobic respiration is far less efficient than aerobic?
Anaerobic respiration (fermentation) produces 2 molecules of ATP, aerobic produces 38 molecules of ATP.
Why is anaerobic respiration used?
If there is very little supply of oxygen, eukaryotic cells will switch to anaerobic respiration to keep vital processes running, but it is very temporary as it produces so little ATP
Obligate anaerobes
These organisms cannot survive in the presence of oxygen, they are all prokaryotes
Facultative anaerobes
They synthesis a lot of ATP with aerobic respiration, but can switch to anaerobic in the absence of oxygen. An example is yeast.
Obligate aerobes
These are organisms like mammals that can only synthesise ATP using aerobic respiration because their energy demand is so high. Individual cells in obligate aerobes can be described as facultative aerobes as they can respire anaerobically if they are not receiving enough oxygen to keep up with their demand. The compounds produced by this have to be broken down so it is an obligate aerobe
What is fermentation?
This is the breakdown of large organic compounds into smaller inorganic compounds without the use of oxygen or the etc. The organic compounds aren’t fully broken down so fermentation doesn’t; produce as much ATP.
How is the ATP made?
Substrate level phosphorylation, which is the transfer of inorganic phosphate from one molecule to another to form ATP with no etc.
What happens in aerobic respiration if there is no oxygen present?
The oxygen won’t be present to act as the final electron acceptor for the electrons at the end of the transport chain which means the flow of electrons will stop and chemiosmosis will no longer continue as there are no protons being pumped across the inner membrane to cause a proton concentration gradient. This means no more ATP is synthesized during oxidative phosphorylation. The reduced NAD and FAD also have nowhere to become oxidised because they are unable to put their electrons into the electron transport chain. Because there are no NAD+ or FAD+ there can be no more dehydrogenation in the Krebs cycle or oxidation of pyruvate in the link reaction.
What is lactate fermentation?
It is anaerobic respiration carried out in mammals that results in the production of lactate. It is also reversible
How does lactate fermentation work?
At the end of glycolysis, the pyruvate formed acts as the hydrogen acceptor for the reduced NADH to form lactate. This has to be in the presence of lactate dehydrogenase and NAD will be regenerated so glycolysis can continue to produce ATP in very small quantities.
Why do people get cramps and pant when they work out?
When you exercise, your muscles need to produce a lot of ATP and all the blood will flow there to allow them to contract. This increases the oxygen demand in the whole body, sometimes muscles will have to respire anaerobically. The lactate fermentation is supplied by ATP produced from aerobic respiration which is still happening but not in the right quantity to supply oxygen demand. Lactic acid will then be formed which causes cramps and oxygen is needed to convert the lactic acid back into glucose which is called oxygen debt and is why you pant.
Why can people become fitter and pant less if they work out a lot?
When you improve fitness, you improve blood supply to your muscles which means the lactic acid formed can be carried to the liver in order for it to be broken down into glucose. This means the rate of lactic acid removal is faster, so you don’t have to pant as hard
Why can’t lactic acid be produced indefinitely?
- It only produces a very small amount of ATP which cannot be used to sustain all of the vital processes for a long period of time.
What is alcoholic fermentation?
It occurs in yeast cells and some plant root cells. It produces ethanol and CO2. It is irreversible
How does alcoholic fermentation work?
When pyruvate is made during glycolysis, it is decarboxylated by pyruvate decarboxylase to make ethanal. The ethanal then accepts hydrogen from the reduced NAD to form ethanol and a regenerated NAD+ coenzyme. This can continue indefinitely in the absence of oxygen
