18.5 Anaerobic respiration Flashcards
(19 cards)
Define anaerobic respiration
the breakdown of complex organic molecules linked to the production of ATP in the absence of oxygen
What are the different categories of oxygen dependence
obligate anaerobes
facultative anaerobes
obligate aerobes
Benefits of being able to respire anaerobically
-fast
-failsafe for emergency situations
-allows some organisms to survive in low-oxygen environments
Define obligate anaerobe
organisms that cannot live in environments containing oxygen
almost all are prokaryotes
Define obligate aerobes
Organisms that can only respire aerobically
Define facultative anaerobes
Organisms that can respire aerobically or aerobically
Define fermentation
anaerobic respiration without the involvement of an electron transport chain.
Why does fermentation produce less ATP than aerobic respiration
-organic compounds eg glucose are not fully broken down
-the atp is synthesised by substrate-level phosphorylation
Why are mammals overall described as obligate aerobes
individual cells can be described as facultative anaerobes as they can synthesise atp anaerobically when o2 concs are low
but this is only for a short period and toxic compounds are produced that have to be broken down when o2 becomes available again
the organism as a whole is an obligate aerobe
What is fermentation in yeast (and some plants called) and what is produced in this
Alcohol fermentation that results in the production of ethanol
What’s fermentation in animals cells called and what does it produce
It’s called lactate fermentation and it produces lactate
How much of aerobic respiration is stropped due to the absence of oxygen
-when no oxygen to act as final electron acceptor at the end of the etc, flow of electrons stops
-synthesis of atp by chemiosmosis also stops
-as flow of electrons stopped, nadh and fadh2 are no longer able to be oxidised as there is no where for the electrons to go
-so nad and fad cannot be regenerated so decarboxylation + oxidation of pyruvate and krebs cycle comes to a halt as there are no coenzymes to accept Hs
-glycolysis WOULD also stop due to lack of nad but it continues due to fermentation
How does lactate fermentation take place
-pyruvate acts as hydrogen acceptor
-takes h from reduced nad
—this is catalysed by enzyme lactate dehydrogenase
-pyruvate is converted to lactate (lactic acid) and nad is regenerated
-this keeps glycolysis going, a small quantity of atp produced
What is the reason for oxygen debt in lactate fermentation
oxygen is needed to complete the conversion of lactic acid to glucose in the liver
Why can lactate fermentation not occur indefinitely
-low quantity of atp produced, not enough to maintain vital processes for long
-accumulation of lactate/lactic acid causes fall in pH, proteins denature. respiratory enzymes + muscle filaments made of protein, cease to function @ low pH
How does alcoholic fermentation take place
-pyruvate converted to ethanal, catalysed by enzyme pyruvate decarboxylase
-ethanal accepts h from reduced nad. becomes ethanol
-regenerated nad can continue to act as coenzyme, glycolysis continues
Is alcohol fermentation a long or short term process
not a short term process
can continue indefinitely in the absence of oxygen
ethanol is a toxic waste product to yeast + they die if ethanol accumulates
Investigation into anaerobic respiration
place glucose solution containing yeast in a vacuum flask (to control temperature)
insert carbon dioxide sensor
cover with paraffin (to ensure anaerobic conditions)
or
place glucose solution containing yeast in a flask, layer of paraffin
put in bung with capillary tube
measure distance moved by air bubble/stained water drop
Investigation into aerobic respiration
place maggots in test tube
add capillary tube with small volume of coloured liquid
add soda lime (absorbs CO2)
coloured liquid will move towards the maggots and show how much O2 is being taken in
this shows the rate of aerobic respiration
