Anaerobic Respiration Flashcards
What are obligate anaerobe organisms? Give examples
-only survive in the absence of oxygen
-e.g some prokaryotes and fungi
What are facultative anaerobes? Give an example
-usually make ATP by aerobic respiration, but can switch to anaerobic if oxygen runs out
-e.g yeast
What are obligate aerobes? Give an example and explain it
-can only make ATP in the presence of oxygen
-e.g mammals = some of our cells can supplement ATP production by using anaerobic respiration, but as an organism we can’t switch to anaerobic respiration
Why will oxidative phosphorylation, Krebs cycle, and the link reaction all stop in the presence of oxygen?
-OPP= needs oxygen as the final electron acceptor. Without oxygen the electrons have nowhere to pass to, so the whole chain stops
-Krebs and link= both release hydrogen atoms which pass to either NAD/FAD reducing it, before releasing electrons to the ETC. if the ETC stops the reduced NAD/FAD have nowhere to pass their hydrogen atoms onto so they remain “reduced” and so can’t accept any more hydrogen atoms
Explain why glycolysis is sometimes called the ‘common pathway’
-it occurs in both aerobic and anaerobic respiration conditions
-in order to keep glycolysis going the reduced NAD has to pass its hydrogen atoms somewhere to become NAD again
How does anaerobic respiration occur in muscle cells (animals)
-lactate/ lactic acid fermentation
How does anaerobic respiration occur in fungi/ plants/ yeast cells?
-ethanol fermentation
In all eukaryotes how many ATP will be made per glucose respired in glycolysis?
2ATP = anaerobic respiration generates just a little ATP to keep cells alive until o2 becomes available again
Describe how anaerobic respiration takes place in mammalian muscle cells
-Glycolysis is the only stage to occur
-the reduced NAD made is reoxidised to NAD, so that it can be reused to keep glycolysis going and continue accepting more H atoms
-Pyruvate acts as the hydrogen acceptor, picking up the hydrogen atoms from reduced NAD (which are usually released at the cristae in aerobic conditions) so that NAD is regenerated
-lactate is produced as the product therefore, requiring the enzyme lactate dehydrogenase
What happens to the lactate produced in the mammalian muscle cells? Why is it important it’s removed quickly?
-it is carried from the muscle to the liver, so when oxygen is available it is turned back into glucose, which can either enter glycolysis or be stored as glycogen
-or it can be converted to Pyruvate and enter the link reaction of respiration
-ATP energy is needed to deal with the lactate
-if lactate builds up this will reduce the pH of the muscle cells, inhibiting enzymes, and therefore inhibiting muscle contraction
Describe how anaerobic respiration takes place in plants/fungi/yeast
-glycolysis is the only stage to occur
-each Pyruvate molecule loses a carbon dioxide (is decarboxylated) to form ethanal
-this is catalysed by the enzyme Pyruvate decarboxylase (enzyme not found in mammals)
-the ethanal then acts as the hydrogen acceptor, accepting the H atoms from the reduced NAD (which is reoxidised) and the ethanal is reduced to ethanol, using the enzyme ethanol dehydrogenase
Why does the build up of lactic acid eventually stop muscle contraction?
-lactic acid reduces pH, muscle contraction depends upon proteins (enzymes and contractile proteins), reduced pH causes enzymes to denature so they can no longer function
Why is glycolysis the only source of ATP production in red blood cells?
-red blood cells don’t have mitochondria so can’t do link, Krebs or oxidative phosphorylation reactions
-this is good as there is more room for haemoglobin to be stored so more oxygen can be carried around the body
Why is it useful that cardiac muscle is adapted to reduce the chances of anaerobic respiration being needed?
-wouldn’t want anaerobic respiration in cardiac muscle because lactic acid would stop the muscle contracting properly by denaturing the enzymes involved, causing fatigue and reduction in blood pumped around the body, which is potentially very dangerous
Why will plants die if they’re left in water logged soil for too long?
There are no air pockets in the water logged soil so the root cells don’t have access to oxygen, therefore switch to anaerobic respiration. This can’t be sustained for long as it doesn’t make enough ATP for the active processes in cells, and it produces ethanol which is toxic to the root cells in accumulation
