Neap question

[Charmz]

So I am a bit confused. I would have thought it would be D. but apparently it is wrong. I don't see how it can be B. though.

Ethanol can't be toxin for plants because they can't convert the ethanol like humans can convert lactic acid and go back along the aerobic pathway, so if a plant went along an anaerobic pathway, it would have to die, but that doesn't seem correct. As for lactic acid being an energy-rich compound, this doesn't make sense because lactic acid accumulates in the body and causes cells to shut down because of there sensitivity to pH. Therefore lactic acid is not an energy-rich compound.

I know it can't be A. because the question is about plants and  anaerobic respiration so production of lactic acid has nothing to do with this question. And C is definitely wrong because anaerobic respiration can happen at anytime. I don't see why animals don't produce CO2 (referring to the answer.

This question is from the Neap Unit 3 Biology studysmart book BTW.

Anaerobic respiration in plants.
A. Is also called fermentation and produces lactic acid
B. Produces a toxic substance for plants but an energy-rich compound for humans.
C. Occurs only at night in the absence of oxygen
D. Produces Carbon dioxide, as in animals

Answer:
B. Anaerobic respiration produces alcohol and CO2, usually occurs in the absence of oxygen and is independent of light. Anaerobic respiration in animals does not produce CO2

[HERculina]

well by using process of elimination i would say: defs not A (same reason as you), defs not C (as anaerobic respiration can occur at daytime), not D (because anaerobic respiration in animals does not produce CO2 - only lactic acid)
so the only option is B

B. Produces a toxic substance for plants but an energy-rich compound for humans.

hmm isnt ethanol and lactic acid both toxic and energy-rich?
but i would circle B because its the one that could be possible out of the rest

EDIT: O i forgot to add that lactic acid is energy rich, because little amount of usable ATP energy was released during anaerobic respiration (2 ATP); the rest would have to be stored or locked up in the lactic acid molecule itself!

[shinny]

Ethanol can't be toxin for plants because they can't convert the ethanol like humans can convert lactic acid and go back along the aerobic pathway, so if a plant went along an anaerobic pathway, it would have to die, but that doesn't seem correct.

Why are you assuming that plants can't break down ethanol? My knowledge of botany isn't the best but I'd assume they'd have to have a way. I don't see why you're assuming it can't be toxic either. Lactic acid itself is toxic to humans as well. In cases where someone doesn't get enough oxygen and they rely largely on anaerobic respiration, the body cannot get rid of all the lactic acid fast enough and their blood turns acidic leading to widespread metabolic problems. One fundamental idea of toxicology is that everything is toxic - things just vary at the dose at which they are. Even drinking excess water can kill you. I think you also assumed that aerobic respiration doesn't occur in plants, but it actually does. So the majority of the time they're running off this. However, under certain circumstances, plants will switch to anaerobic respiration, which is how I assume certain wines and such are produced).

[Charmz]

well by using process of elimination i would say: defs not A (same reason as you), defs not C (as anaerobic respiration can occur at daytime), not D (because anaerobic respiration in animals does not produce CO2 - only lactic acid)
so the only option is B

B. Produces a toxic substance for plants but an energy-rich compound for humans.

hmm isnt ethanol and lactic acid both toxic and energy-rich?
but i would circle B because its the one that could be possible out of the rest

EDIT: O i forgot to add that lactic acid is energy rich, because little amount of usable ATP energy was released during anaerobic respiration (2 ATP); the rest would have to be stored or locked up in the lactic acid molecule itself!

Thanks that helped.

Why are you assuming that plants can't break down ethanol? My knowledge of botany isn't the best but I'd assume they'd have to have a way. I don't see why you're assuming it can't be toxic either. Lactic acid itself is toxic to humans as well. In cases where someone doesn't get enough oxygen and they rely largely on anaerobic respiration, the body cannot get rid of all the lactic acid fast enough and their blood turns acidic leading to widespread metabolic problems. One fundamental idea of toxicology is that everything is toxic - things just vary at the dose at which they are. Even drinking excess water can kill you.

I was told by my biology teacher. So is it certain that plants can break down ethanol?

[shinny]

I was told by my biology teacher. So is it certain that plants can break down ethanol?

As I said, I'm not 100% but it seems illogical that they can't break down their own metabolite.

[HERculina]

Well my notes from few months ago says that when concentration of ethanol goes above 12-15% many plants such as germinating seeds, roots in waterlogged soil, yeast revert from anaerobic to aerobic respiration (convert products back to respiratory intermediates then respire aerobically... something like that) to reduce ethanol levels as ethanol again, is greatly toxic   

[Charmz]

oh thanks.