VCE Biology Question Thread

[grannysmith]

in nerve impulses do the sodium and potassium ions move by facilitated diffusion or active transport? or both?

Both

[Yacoubb]

Hey guys

Just thought I'd let you know that a lot of things about action potentials that you once needed to know, have been taken off the study design. Now, you really just need to know that action potentials are an all-or-nothing process involved in firing nerve impulses through neurons.

You don't need to know an awful lot of detail about it all (e.g. Na+ and K+ ions)

[jessica666]

Hey guys

Just thought I'd let you know that a lot of things about action potentials that you once needed to know, have been taken off the study design. Now, you really just need to know that action potentials are an all-or-nothing process involved in firing nerve impulses through neurons.

You don't need to know an awful lot of detail about it all (e.g. Na+ and K+ ions)

Thanks! there is heaps of info in the textbook that i was not sure if it was necessary, like the charge and voltage, Na+ and K+ ions, threshold etc. Do we need to know any of that?

[vox nihili]

Thanks! there is heaps of info in the textbook that i was not sure if it was necessary, like the charge and voltage, Na+ and K+ ions, threshold etc. Do we need to know any of that?

No and you never did

[Jason12]

I don't get the signal transduction pathway for hydrophillic and hydrophobic hormones

[vox nihili]

I don't get the signal transduction pathway for hydrophillic and hydrophobic hormones

Then don't worry about it.


Just know:

lipophillic can go through the membrane (that should be obvious) and thus, their receptor is on the inside of the cell.
Hydrophillic can't go through, so their receptor is on the outside.

[alchemy]

I don't get the signal transduction pathway for hydrophillic and hydrophobic hormones

In a nutshell: signal transduction is the amplification of a stimulus so that the cell can produce a response. Hydrophilic hormones (such as protein hormones) are transported freely in the blood, whereas hydrophobic hormones (such as steroid hormones) require a carrier protein to be transported in blood, as blood has a water base. Now think about how different substances enter cells; hydrophilic substances cannot simply diffuse into the cell, while only hydrophobic ones can. Therefore, the hydrophilic substances bind to a receptor ('G-protein linked receptor) on the membrane. A 'second messenger' called a G-protein transmits the message into he cell, causing a cascade of events, involving relay molecules and proteins, that ultimately amplifies the signal for the cell to respond. Hydrophobic substances bind to a receptor in the cytosol inside the cell, as they can simply diffuse across the membrane. Similarly, a cascade of events occurs to amplify the signal.

So that's the general picture, but you may wonder about how does the cell actually produces this response once it has received the signal. The activated proteins in signal transduction can stimulate the production of transcription factors that enter the nucleus and activate specific genes. The activated genes then produce a protein product in response to the stimulus. An example is insulin (protein product) produced in response to elevated glucose levels.

[Jason12]

Excess energy-rich compounds produced during photosynthesis are transported to different parts of the plant and are sometimes stored.

a) which of the following would be transported; starch, glucose or sucrose? Explain your choice

b) which of the 3 options above would be stored? Explain

I'm thinking glucose for a and starch for b but I'm not exactly sure why/how to explain it

[nhmn0301]

Excess energy-rich compounds produced during photosynthesis are transported to different parts of the plant and are sometimes stored.

a) which of the following would be transported; starch, glucose or sucrose? Explain your choice

b) which of the 3 options above would be stored? Explain

I'm thinking glucose for a and starch for b but I'm not exactly sure why/how to explain it

a) Sucrose is transported in plants. Because if we transport glucose, (which is water-soluble), it will be very hard to for them to travel through the phloem, xylem system. Hence, by putting it in a form of sucrose, transport will be much easier since a disaccharide is always less soluble than a monosaccharide.
b) Yes. Starch is stored in plants because if you look at their structure, it has a spiral shaped, which obviously insoluble and won't create any effect on osmotic action in cell, so it's safe to be store. When energy is needed, plants can easily broken down starch to obtain energy.
Hope this helps!

[Rishi97]

Excess energy-rich compounds produced during photosynthesis are transported to different parts of the plant and are sometimes stored.

a) which of the following would be transported; starch, glucose or sucrose? Explain your choice

b) which of the 3 options above would be stored? Explain

I'm thinking glucose for a and starch for b but I'm not exactly sure why/how to explain it

I remember doing this question, it was on a neap yeah?
For b, I wrote that starch would be stored because it is insoluble in water
Pls check my answer someone

[Rishi97]

a) Sucrose is transported in plants. Because if we transport glucose, (which is water-soluble), it will be very hard to for them to travel through the phloem, xylem system. Hence, by putting it in a form of sucrose, transport will be much easier since a disaccharide is always less soluble than a monosaccharide.
b) Yes. Starch is stored in plants because if you look at their structure, it has a spiral shaped, which obviously insoluble and won't create any effect on osmotic action in cell, so it's safe to be store. When energy is needed, plants can easily broken down starch to obtain energy.
Hope this helps!

Thanks for that... I just got part a wrong on my neap test then.  Ah well, you learn something new everyday.

[Jason12]

the vcaa study design says 'nature of the stimulus response model' so far i am up to ch5 of nature of biology book and it only has the negative feedback model so how is the stimulus response model different? examples?

[howlingwisdom]

Excess energy-rich compounds produced during photosynthesis are transported to different parts of the plant and are sometimes stored.

a) which of the following would be transported; starch, glucose or sucrose? Explain your choice

b) which of the 3 options above would be stored? Explain

I'm thinking glucose for a and starch for b but I'm not exactly sure why/how to explain it

Another possible answer for a) is that the plant will likely use up the glucose for cellular respiration if it is transported in that form instead of sucrose.

[Jason12]

I remember doing this question, it was on a neap yeah?
For b, I wrote that starch would be stored because it is insoluble in water
Pls check my answer someone

yeah it was from neap

[howlingwisdom]

the vcaa study design says 'nature of the stimulus response model' so far i am up to ch5 of nature of biology book and it only has the negative feedback model so how is the stimulus response model different? examples?

I think our study design is  mostly focused on the stimulus response at a cellular level (involving signal transduction) but we do not need to know negative/positive feedback (According to the Biology FAQ on the VCAA page) because that was covered in Unit 2.