Biology Unit 3 Questions Megathread

[HERculina]

correcto!
if the q. had sed yeast cells instead of muscle cells would it still be c too?

[shinny]

correcto!
if the q. had sed yeast cells instead of muscle cells would it still be c too?

Yeh, yeast can do either as well.

[HERculina]

o really? does that mean no organisms only respire anaerobically? wat about organisms which only live in areas without O2 (or is there no such thing)

[kaushik]

There are a few select organisms which can live without oxygen such as obligate
anaerobes. In fact they would die if they had oxygen lol.

[HERculina]

out of interest, would you say that obligate anaerobes respire anaerobically or is it more accurate to say they respire through fermentation? :/
 

[shinny]

out of interest, would you say that obligate anaerobes respire anaerobically or is it more accurate to say they respire through fermentation? :/
 

There's a few distinctions that need to be made here. Obligate anaerobes are organisms that can only respire anaerobically - whether that be through true anaerobic respiration (similar to aerobic respiration, but using substances other than oxygen in the electron transport chain) or anaerobic fermentation (the correct name for what is commonly stated - even in academic circles - as anaerobic respiration).  So they can do either; the bottom line is that they don't need oxygen (and as kaushik said, can die from it). So your first statement is kinda correct; that obligate anaerobes respire (only) anaerobically. If you're asking about the whole respiration vs. fermentation thing, then for a Bio 3/4 level, then it'd be fermentation which is more correct. I've never actually learnt about true anaerobic respiration formally. It's just something I've come across in Wiki, so you don't really need to know about it either. In an exam, I'm fairly sure that they'd accept either since many textbooks muddle up the terms as well.

[poojas73]

By use of a diagram/flow chart show why phototropism fits the stimulus/response model.

?? :O
help please!

[scocliffe09]

By use of a diagram/flow chart show why phototropism fits the stimulus/response model.

?? :O
help please!

Ask yourself these questions: What is the stimulus? What sort of receptors measure that change? What happens (for this example, think at a cellular level) when these sensors/receptors are triggered? what is the overall/end result of the plant's response to the change?

As an aside, you'll often be asked to consider then whether the response reduces (negative) or compounds (positive) the effect of the stimulus = what is the feedback mechanism.

[HERculina]

do enzymes denature in pH outside the optimal pH range because they act as buffers and donate Hyrdrogen ions to the pH environment, disrupting the Hydrgoen bonds in active site?

[WhoTookMyUsername]

yes, though their not really buffers as that is not their aim (although sum amino acids are buffers)

[poojas73]

By use of a diagram/flow chart show why phototropism fits the stimulus/response model.

?? :O
help please!

Ask yourself these questions: What is the stimulus? What sort of receptors measure that change? What happens (for this example, think at a cellular level) when these sensors/receptors are triggered? what is the overall/end result of the plant's response to the change?

As an aside, you'll often be asked to consider then whether the response reduces (negative) or compounds (positive) the effect of the stimulus = what is the feedback mechanism.

i'm not too sure what the receptor and control centre for this would be though?

[scocliffe09]

By use of a diagram/flow chart show why phototropism fits the stimulus/response model.

?? :O
help please!

Ask yourself these questions: What is the stimulus? What sort of receptors measure that change? What happens (for this example, think at a cellular level) when these sensors/receptors are triggered? what is the overall/end result of the plant's response to the change?

As an aside, you'll often be asked to consider then whether the response reduces (negative) or compounds (positive) the effect of the stimulus = what is the feedback mechanism.

i'm not too sure what the receptor and control centre for this would be though?

ok - photoreceptors measure light - and as plants don't have a central nervous system there is a chemical response (movement of auxins to dark side of stem) which results in cellular changes...

[WhoTookMyUsername]

exaltly how do the stimulus trigger a chemical response in plants/

[scocliffe09]

You really don't need to know more details than that of the textbook with regard to tropisms - basically just that the receptors (photo, chemo, whatever) trigger the release / production / movement of a plant hormone (auxin, ABA, gibberellins etc).
If you want to learn more -  read the third paragraph of this wiki entry http://en.wikipedia.org/wiki/Phototropism
but tbh- not really relevant.

[dooodyo]

Hey Russ,

Could you possible upload the questions soon that is if you're not too busy.
Haha thanks in advance.

Kind regards,
Dooodyo