VCE Biology Question Thread

[Gogo14]

My class skipped human intervention in evolution. What kind of stuff will we be tested on, are we expected to know the stages of cloning?

[The Usual Student]

My class skipped human intervention in evolution. What kind of stuff will we be tested on, are we expected to know the stages of cloning?

thestudy design will list everything you need to know about that topic,
its really important since one of the bio lecturers I heard from said that since human intervention was being expanded upon in the new study design so it is likely they will throw in a few harder questions on the topic to see how students react.

ALSO:
Anyone know why it is important for glycogen/cellulose/starch to be water insoluble?
Is it so they can function without being dissolved in the cytoplasm which would interfere with their bonding?

And, lets say I put a hypotonic cells ( in regards to glucose being the solute ) into a hypertonic solution. Why wouldn't the glucose just diffuse into the cell instead of the water leaving the cell? Why is it that osmosis occurs but not simple diffusion?

[sweetcheeks]

thestudy design will list everything you need to know about that topic,
its really important since one of the bio lecturers I heard from said that since human intervention was being expanded upon in the new study design so it is likely they will throw in a few harder questions on the topic to see how students react.

ALSO:
Anyone know why it is important for glycogen/cellulose/starch to be water insoluble?
Is it so they can function without being dissolved in the cytoplasm which would interfere with their bonding?

And, lets say I put a hypotonic cells ( in regards to glucose being the solute ) into a hypertonic solution. Why wouldn't the glucose just diffuse into the cell instead of the water leaving the cell? Why is it that osmosis occurs but not simple diffusion?

I'd say you are correct. If these compounds were soluble, they wouldn't be able to perform the function required e.g. cellulose wouldn't be able to act as an appropriate cell wall.

Glucose doesn't undergo simple diffusion, it undergoes facilitated diffusion, having to rely on protein channels (it can also be actively transported). Glucose will still diffuse, but at a much slower rate, due to it being of larger size and the protein channels becoming saturated. Water, being able to move directly across the phospholipid bilayer, allows it to move at a faster rate/faster volume.

[The Usual Student]

I'd say you are correct. If these compounds were soluble, they wouldn't be able to perform the function required e.g. cellulose wouldn't be able to act as an appropriate cell wall.

Glucose doesn't undergo simple diffusion, it undergoes facilitated diffusion, having to rely on protein channels (it can also be actively transported). Glucose will still diffuse, but at a much slower rate, due to it being of larger size and the protein channels becoming saturated. Water, being able to move directly across the phospholipid bilayer, allows it to move at a faster rate/faster volume.

cheers that makes so much sense!
bwt why does the charge of an ion influence how fast it can diffuse?

[Gogo14]

cheers that makes so much sense!
bwt why does the charge of an ion influence how fast it can diffuse?

No, At least from my knowledge

1. Also what is the significance and applications of stem cell differentiation in human intervention
2. How does selective breeding limit/affect the gene pool?
Edit:
3. are we expected to know that thyroxine is hydrophobic? There was a q on it and one paper said that it binded to membrane receptors, while another paper asked a similar question and said that it binds to cytoplasm receptors

[FatimaEl]

No, At least from my knowledge

1. Also what is the significance and applications of stem cell differentiation in human intervention
2. How does selective breeding limit/affect the gene pool?

Hi, charge does influence the movement of substance between the phospholipid molecules, uncharged molecules move more easily than charged. However 'The Usual Student' was asking why the charge influences the diffusion rate, the answer to which i do not know :/

As for your questions

• Im not sure what you mean by 'significance' the study design does say 'application' however. Application of stem cell differentiation in human intervention refers to how stem cells can be used to replace damaged or diseased cells by healthy, functioning cells by differentiating. This is a type of human intervention because cells that are yet to be specialised (stem cells) are extracted from embryos or the placenta and differentiated into the desired cell type by the use of a biochemical solution, they are then surgically implanted into a patients tissues, the host immune system is suppressed to prevent rejection of these cells, and then the cells of the patient are monitored to ensure that they do not become cancerous. Hope that made sense.
• Selective breeding reduces variation in the gene pool, this is because desired traits are selected for, manipulating the natural gene pool, and decreasing variety in allele frequencies

[Gogo14]

Hi, charge does influence the movement of substance between the phospholipid molecules, uncharged molecules move more easily than charged. However 'The Usual Student' was asking why the charge influences the diffusion rate, the answer to which i do not know :/

As for your questions

• Im not sure what you mean by 'significance' the study design does say 'application' however. Application of stem cell differentiation in human intervention refers to how stem cells can be used to replace damaged or diseased cells by healthy, functioning cells by differentiating. This is a type of human intervention because cells that are yet to be specialised (stem cells) are extracted from embryos or the placenta and differentiated into the desired cell type by the use of a biochemical solution, they are then surgically implanted into a patients tissues, the host immune system is suppressed to prevent rejection of these cells, and then the cells of the patient are monitored to ensure that they do not become cancerous. Hope that made sense.
• Selective breeding reduces variation in the gene pool, this is because desired traits are selected for, manipulating the natural gene pool, and decreasing variety in allele frequencies

Oh thanks,
Does gene refer to just the segment of DNA, or does it include DNA as well as histone proteins

[FatimaEl]

Oh thanks,
Does gene refer to just the segment of DNA, or does it include DNA as well as histone proteins

All a gene is is a sequence of nucleotide that code (for protein, mRNA, rRNA or tRNA).
I think what you might be referring to when you say DNA that has histone proteins is a chromosome

[The Usual Student]

can someone explain ( preferably in exam language )
why a higher Surface area to volume ratio is more efficient?

[Gogo14]

What is the function of the rough endoplasmic reticulum?
I wrote that it synthesises proteins for secretion but the vcaa answers says "transport system"
Would my answer be accepted or is not that great?

[sweetcheeks]

can someone explain ( preferably in exam language )
why a higher Surface area to volume ratio is more efficient?

The process of diffusion is made lot more efficient. It allows cells to be able to export waste and products quickly.

When you look at the nervous system, you will notice that neurotransmitters are used as signalling molecules. The nervous system has a fast response. If you look at normal hormones, most take a while to move around the body and initiate a response. The reason that the neurotransmitters can have such a quick effect is that they only have to move a small distance, rather than moving a large distance.

[Calebark]

can someone explain ( preferably in exam language )
why a higher Surface area to volume ratio is more efficient?

To use exam language, might need to know the context of the question so it can be related to the stem. I'll use plant leaves as an example:
-Allows more area of absorption of sunlight by chlorophyll
-Allows photosynthesis to occur at a faster rate
-Allows more energy to be produced due to glucose produced

But also things such as diffusion (simple and facilitated), and with enzymes & substrates.

What is the function of the rough endoplasmic reticulum?
I wrote that it synthesises proteins for secretion but the vcaa answers says "transport system"
Would my answer be accepted or is not that great?

Hmm, I'd say no, as that's more the role of the ribosome, which the endoplasmic reticulum holds.

[FatimaEl]

What is the function of the rough endoplasmic reticulum?
I wrote that it synthesises proteins for secretion but the vcaa answers says "transport system"
Would my answer be accepted or is not that great?

Unfortunately your answer wouldnt be accepted, this is because it is not the rough ER that synthesises proteins, but rather the ribosomes on the ER that is responsible for protein synthesis. You could say that rough ER is involved in protein synthesis as the ribosomes are attached to it, but ER as a whole functions  as transport system for eukaryotic cells.
And just going to throw it in there that smooth ER is involved with lipid synthesis.

can someone explain ( preferably in exam language )
why a higher Surface area to volume ratio is more efficient?

Im guessing this is in regards to diffusion?
in "exam langauge":
A higher surface area to volume ratio means that surface area is greater in size in relation to volume, the higher the SA : VOL ratio is, the smaller the cell becomes. And vice versa, "...the surface area to the volume ratio gets smaller as the cell gets larger. Thus, if the cell grows beyond a certain limit, not enough material will be able to cross the membrane fast enough to accommodate the increased cellular volume." 
The last sentence i found online, however i think it explains the importance of a large surface area to volume ratio well.
Hope that helped

[The Usual Student]

Thanks for all the responses!
Ok so just to clarify,
A high SA:V ratio  is much more efficient as the cell can perform certain process ( diffusion, phtosynethis exocytosis to export waste) to occur more efficiently whilst without having to increase the cells volume and consequently increase its needs.

[solution]

In VCE bio land, is mitosis regarded as the division of a cell, or replication of a nucleus?