VCE Biology Question Thread

[darkz]

in my textbook certain words are used interchangeably:

- "lactate" and "lactic Acid"
- "Pyruvate" and "Pyruvic Acid"

my teacher says that lactate and lactic acid is the same thing, as with pyruvate and pyruvic acid.

is this true?

I'm asking this because during anaerobic respiration in mammals, the textbook says the output is lactate

cheers

There is a minor technical difference between the two, however for VCE, you can just assume they’re the same thing

[darkz]

So in the 2013-2016 study design's teachers handout on cell signalling, they defined transduction as "the second messenger is formed in or released into the cytosol (the second messenger amplifies the stimulus and initiates the cell’s response)." does this imply that hydrophobic ligands do not undergo the transduction stage within the 3 step signal transduction model (reception, transduction, induction) as they directly regulate gene expression - no secondary messenger?

And would the following definition for signal transduction suffice?
"Signal transduction involves the conversion by a cell of an external stimulus into a response within the cell"

[PhoenixxFire]

So in the 2013-2016 study design's teachers handout on cell signalling, they defined transduction as "the second messenger is formed in or released into the cytosol (the second messenger amplifies the stimulus and initiates the cell’s response)." does this imply that hydrophobic ligands do not undergo the transduction stage within signal transduction as they directly regulate gene expression - no secondary messenger?

And would the following definition for signal transduction suffice?
"Signal transduction involves the conversion by a cell of an external stimulus into a response within the cell"

I’ve always thought of hydrophobic signaling as not being signal transduction so I’m pretty sure that’s correct.

Yep your definition is correct.

[vox nihili]

I’ve always thought of hydrophobic signaling as not being signal transduction so I’m pretty sure that’s correct.

Yep your definition is correct.

So in the 2013-2016 study design's teachers handout on cell signalling, they defined transduction as "the second messenger is formed in or released into the cytosol (the second messenger amplifies the stimulus and initiates the cell’s response)." does this imply that hydrophobic ligands do not undergo the transduction stage within the 3 step signal transduction model (reception, transduction, induction) as they directly regulate gene expression - no secondary messenger?

And would the following definition for signal transduction suffice?
"Signal transduction involves the conversion by a cell of an external stimulus into a response within the cell"

I initially disagreed with PF on this one, but after a bit of reading about how they actually define transduction, absolutely right. It’s the conversion of one signal to another, which as you’ve rightly pointed out, doesn’t happen for hydrophobic molecules (at least not in VCE Biology!)

[Mr West]

hey guys, odd question but can insects undergo anaerobic respiration

cheers

[vox nihili]

hey guys, odd question but can insects undergo anaerobic respiration

cheers

Yes

[Scribe]

Hey guys,

Does the rate of photosynthesis affect the rate of aerobic respiration?
Also, would the rate of photosynthesis be higher under blue light or all wavelengths of light (sunlight)?

Thanks!

[PhoenixxFire]

I suppose it could affect it if there was very little glucose (produced by photosynthesis) present to act as an input for aerobic respiration. It wouldn't happen naturally but I suppose you could set up the conditions so that a slow rate of photosynthesis meant few inputs available for aerobic respiration (e.g. closed system with all oxygen coming from photosynthesis).

Assuming the same light intensity (brightness) it would be faster under sunlight - It still photosynthesises under other colours, just slower. So if you combine the rate of photosynthesis under all colours vs just under blue it will be faster under all.

[peachxmh]

If I had to give three reasons about why the same signalling molecule can cause different responses in different cells, with two of the reasons pertaining to cells and the other reason regarding a signalling molecule, what would they be? For cells, one of the reasons I've figured out is because there are different cascade pathways in each cell, correct me if I'm wrong!

Also, why are neurotransmitters degraded or recycled? Like in what scenario would they be degraded as opposed to recycled and vice versa?

Thanks, you're all absolute legends for taking the time to help!

[darkz]

If I had to give three reasons about why the same signalling molecule can cause different responses in different cells, with two of the reasons pertaining to cells and the other reason regarding a signalling molecule, what would they be? For cells, one of the reasons I've figured out is because there are different cascade pathways in each cell, correct me if I'm wrong!

Also, why are neurotransmitters degraded or recycled? Like in what scenario would they be degraded as opposed to recycled and vice versa?

Thanks, you're all absolute legends for taking the time to help!

Well there are two main reasons for why there can be different responses produced by cells and they are
- The signalling molecule uses a different receptor and secondary messenger
- The signalling molecule has a different target protein
Edit: Not really sure about a third, as for the neurotransmitters, I suppose that one scenario could be an auto-immune disease which attacks the bodies own neurotransmitters or toxins etc

[PhoenixxFire]

The only reason I can think of that the signalling molecule would change the effect would be how much was released, which should only change the scale not the result, and where it is released (e.g. the same neurotransmitter interacting with a gland or muscle would produce different results).

You don't need to know that level of details about neurotransmitters for VCE but I googled it a bit. From what I read some neurotransmitters degrade because they are involved in causing muscular contraction and if they stayed around the muscle would always be contracted. Some (e.g. serotonin) are recycled but I don't know why.

[Sine]

If I had to give three reasons about why the same signalling molecule can cause different responses in different cells, with two of the reasons pertaining to cells and the other reason regarding a signalling molecule, what would they be? For cells, one of the reasons I've figured out is because there are different cascade pathways in each cell, correct me if I'm wrong!

Also, why are neurotransmitters degraded or recycled? Like in what scenario would they be degraded as opposed to recycled and vice versa?

Thanks, you're all absolute legends for taking the time to help!

If neurotransmitteres weren't degraded and recycle they won't continue to act for example
Cocaine blocks the transporter for the uptake of noradrenaline hence longer activation of the receptor occurs and hence increases the power of the system e.g. increases HR/force of contraction and blood pressure amongst others.

[Mr West]

why is the krebs cycle termed a cycle?

is it something to do with recycled coenzymes?

[vox nihili]

why is the krebs cycle termed a cycle?

is it something to do with recycled coenzymes?

If you look at the reactions, the final product of the group of reactions (oxaloacetate) is also the starting product (along with Acetyl-CoA, which is the input from glycolysis).

In the scheme of things, it's not important to understand this.

[Mr West]

how is it that 6O₂ molecules can enter the electron transport chain, and 6H₂O molecules be produced

it seems that 12 oxygen atoms go in, and only 6 come out.