Psyxwar's Biology 3/4 Question Thread

[ealam2]

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120069/bio08.swf::Signal%20Amplification

 

Thank you!

[psyxwar]

Yes

How would this happen though? If there are no second messengers to amplify it I mean?

Another question: do nervous impulse always have to involve a stimuli? I mean, what happens if I just wanted to move my finger (to say, type?). Is that just a message from CNS -> effector?

[alondouek]

Another question: do nervous impulse always have to involve a stimuli? I mean, what happens if I just wanted to move my finger (to say, type?). Is that just a message from CNS -> effector?

It helps to differentiate between the two types of stimulus-response models that occur (i.e. homeostatic mechanisms vs. movement)

Here, the stimulus itself arises due to the message from the brain that 'requests' an action by the muscular effectors. From here, you have signal transmission from the brain to effectors in the PNS via interneurons in the spinal cord.

It's possible to draw somewhat of a parallel between this and a reflex arc, but for two major differences: 1. A reflex arc does not travel to the brain (as it is an unconscious response) and 2. It results from physical external stimuli rather than conscious need (e.g. typing, writing etc).

[psyxwar]

It helps to differentiate between the two types of stimulus-response models that occur (i.e. homeostatic mechanisms vs. movement)

Here, the stimulus itself arises due to the message from the brain that 'requests' an action by the muscular effectors. From here, you have signal transmission from the brain to effectors in the PNS via interneurons in the spinal cord.

It's possible to draw somewhat of a parallel between this and a reflex arc, but for two major differences: 1. A reflex arc does not travel to the brain (as it is an unconscious response) and 2. It results from physical external stimuli rather than conscious need (e.g. typing, writing etc).

I see, thanks. So there would be no involvement of the sensory nervous system?

[alondouek]

There definitely is, especially in regards to 'muscle memory', as well as the controlling of the final movement that results from the signal transmission. In writing, even the ability to hold the pen involves the sensory nervous system.

The whole process (like much of anatomy and physiology) is really very mindblowing when you consider how specifically everything works in a system as complex as the human body. Each process and system is tied to many, many others - just like how different areas of the nervous system are 'tethered' to each other but have markedly different specific functions.

[psyxwar]

There definitely is, especially in regards to 'muscle memory', as well as the controlling of the final movement that results from the signal transmission. In writing, even the ability to hold the pen involves the sensory nervous system.

The whole process (like much of anatomy and physiology) is really very mindblowing when you consider how specifically everything works in a system as complex as the human body. Each process and system is tied to many, many others - just like how different areas of the nervous system are 'tethered' to each other but have markedly different specific functions.

Thanks. Interesting stuff, I really should read up on it

How reliant on the light independent stage happening is the light dependent stage? I mean, if a plant was unable to go through the Calvin Cycle but had the means to go through the light dependent reactions, would it just be able to go on indefinitely? Or does the plant just cease the reactions once it has say, x amount of NADPH or ATP?

[alondouek]

How reliant on the light independent stage happening is the light dependent stage? I mean, if a plant was unable to go through the Calvin Cycle but had the means to go through the light dependent reactions, would it just be able to go on indefinitely? Or does the plant just cease the reactions once it has say, x amount of NADPH or ATP?

I think you may have gotten it a bit backwards. The light-dependent (LD) stage occurs before the light-independent (LI), as the products from the splitting of water in the LD phase are the reagents in the LI stage.

If a plant could undergo that first phase, but not the Calvin Cycle, it could never live. It can't synthesise the vital carbohydrates it requires for both energy storage (starch) and structure (cellulose) amongst many others.

[psyxwar]

I think you may have gotten it a bit backwards. The light-dependent (LD) stage occurs before the light-independent (LI), as the products from the splitting of water in the LD phase are the reagents in the LI stage.

If a plant could undergo that first phase, but not the Calvin Cycle, it could never live. It can't synthesise the vital carbohydrates it requires for both energy storage (starch) and structure (cellulose) amongst many others.

What I mean is that is the LI doesn't occur, how long would the LD keep going for?

More specifically, would noncyclic photophosphorylation just stop if there was a build up of NADPH?

[alondouek]

What I mean is that is the LI doesn't occur, how long would the LD keep going for?

More specifically, would noncyclic photophosphorylation just stop if there was a build up of NADPH?

Okay, let's take a hypothetical fully-developed plant. Then, we knock out the ability to perform the LI reactions - the plant cannot photosynthesise, and it cannot produce those vital complex carbohydrates. All of the plants functions would cease, and its structure would degrade very quickly as it cannot replace old cell walls etc.

As for the second point, you'd definitely have a case of substrate inhibition with one or more of the critical enzymes in the process. But it wouldn't even get to this stage in a non-hypothetical situation

[Yacoubb]

It helps to differentiate between the two types of stimulus-response models that occur (i.e. homeostatic mechanisms vs. movement)

Here, the stimulus itself arises due to the message from the brain that 'requests' an action by the muscular effectors. From here, you have signal transmission from the brain to effectors in the PNS via interneurons in the spinal cord.

It's possible to draw somewhat of a parallel between this and a reflex arc, but for two major differences: 1. A reflex arc does not travel to the brain (as it is an unconscious response) and 2. It results from physical external stimuli rather than conscious need (e.g. typing, writing etc).

So could we say that typing is a conscious response. Is that ultimately because if we compared that to say an involuntary reflex arc, the conscious response would not bypass the brain, just like a reflex arc would and instead travel only through the spine?

[alondouek]

Correct.

[psyxwar]

In the context of VCE Biology, does abscisic acid promote leaf abscission? I know that it doesn't in reality, but apparently it does in VCE Bio?

[friedchicken]

In the context of VCE Biology, does abscisic acid promote leaf abscission? I know that it doesn't in reality, but apparently it does in VCE Bio?

In the context of VCE Bio, nope, it doesn't. This is going by Dr. S's powerpoints from last year and I'm sure he knows what VCAA wants or not.

[Yacoubb]

In the context of VCE Bio, nope, it doesn't. This is going by Dr. S's powerpoints from last year and I'm sure he knows what VCAA wants or not.

On the 2011 Biology exam, abscisic acid was actually accepted as response to leaf abscission. Ethylene was the other

[psyxwar]

For an experiment that tests the following types of light (white, red, blue, green) on photosynthesis, what would be a suitable hypothesis?

Something like "that white light will result in the highest photosynthetic rate, followed by red, blue then green" doesn't seem like a good hypothesis, but I'm not sure what else to put.