VCE Biology Question Thread

[TheAspiringDoc]

By no means do I know for sure, but I'd assume so for the same reason you gave - lack of surface area.

How would cellular respiration occur in the cytoplasm and cell membrane? Especially the cytoplasm. Is there a different process to how it occurs in mitochondria in eukaryotic cells? Just having a hard time imagining how cellular respiration could occur in a fluid substance.

And also, in regards to transcription and translation, is it true that the mRNA part occurs in the nucleus, and then the mRNA leaves the nucleolus and enters the nucleus where the rRNA read it and also where the tRNA are found?
Or does the mRNA part occur simply in the nucleus but not in the nucleolus, and the translation part occurs outside the nucleus completely and instead somewhere in the cell?
Thanks.

mRNA is transribed in the nucleus. From there, it travels through pores in the nuclear membrane through to the ER (remember that the ER is continuous with the surface of the nucleus). The ER has 'tunnels' through which the mRNA can travel to the ribosomes studded on its surface. Once the mRNA is at the ribosome, it is read by the small ribosomal subunit and the large ribosomal subunit attaches amino acids (which are brought in on tRNA) together to form a polypeptide chain (which will undergo further modifications (in the ER and Golgi apparatus I think). So the transcription bit (mRNA synthesis) occurs in the nucleus, while the translation occurs in the ribosomes in the cytoplasm (although I believe the ribosomes are often bound by little vesicles from the ER). The nucleolus, on the other hand, is where ribosomal RNA resides (it forms part of the structure of the ribosomes).

You know so much about bio, have u done vce bio already?

Haha nah I'm starting 1/2 in a few weeks

[TheAspiringDoc]

An Amoeba is a unicellular organism found in ponds. It is capable of extending out parts of its body to move and feed. An Amoeba has a large surface area to volume ratio. Why is a large surface area to volume ratio necessary for the survival of an Amoeba?

b) So that an Amoeba does not need any organelles

or

d) To allow an Amoeba to exchange gases with its environment via diffusion


Can someone please explain to me why the answer is (b) not (d)? Is it because of the fact that it can still have diffusion even with less SA:vol, just that it would be negligible?

While we're on the topic, am I right in thinking that people with a lower SA:vol will 'cop the heat' more?

cheers

[TheAspiringDoc]

This is an excerpt from my school's biology website under the heading of "The functions of lipids"

AMPHIPHATIC FATS
These are partially soluble in water e.g. phospholipids have a polar hydrophilic head made of glycerol and a hydrophobic tail made up of 3 molecules of fatty acids.

Is it meant to say:
Amphipathic phospholipids are partially soluble in water as they have a hydrophilic head made of glycerol (and organic molceules such as choline) and phosphate, and a hydrophobic tail made up of 2 fatty acids
?

[Butterflygirl]

mRNA is transribed in the nucleus. From there, it travels through pores in the nuclear membrane through to the ER (remember that the ER is continuous with the surface of the nucleus). The ER has 'tunnels' through which the mRNA can travel to the ribosomes studded on its surface. Once the mRNA is at the ribosome, it is read by the small ribosomal subunit and the large ribosomal subunit attaches amino acids (which are brought in on tRNA) together to form a polypeptide chain (which will undergo further modifications (in the ER and Golgi apparatus I think). So the transcription bit (mRNA synthesis) occurs in the nucleus, while the translation occurs in the ribosomes in the cytoplasm (although I believe the ribosomes are often bound by little vesicles from the ER). The nucleolus, on the other hand, is where ribosomal RNA resides (it forms part of the structure of the ribosomes).
Haha nah I'm starting 1/2 in a few weeks

Whaa, so u just read the whole course for fun??

[TheAspiringDoc]

Whaa, so u just read the whole course for fun??

I've read 3/4 of the 3/4 course so far

[@#035;3]

Damn. You should do 3/4 Bio this year!
I've only done 3 chapters lol.

[geminii]

I know that a condensation reaction doesn't occur when any two molecules are made to react with each other - so are there specific reactants that, when combined, create a condensation reaction? Is it two amino acids that react to form a condensation reaction?
Thanks

[sunshine98]

An Amoeba is a unicellular organism found in ponds. It is capable of extending out parts of its body to move and feed. An Amoeba has a large surface area to volume ratio. Why is a large surface area to volume ratio necessary for the survival of an Amoeba?

b) So that an Amoeba does not need any organelles

or

d) To allow an Amoeba to exchange gases with its environment via diffusion


Can someone please explain to me why the answer is (b) not (d)? Is it because of the fact that it can still have diffusion even with less SA:vol, just that it would be negligible?

While we're on the topic, am I right in thinking that people with a lower SA:vol will 'cop the heat' more?

cheers

The way I would've thought of it was that D cant really be the answer because that would happen regardless- that is , if the amoeba had a low SA:V ratio it would still exchange gases with its environment via diffusion , except it wouldn't be efficient enough for survival. So , what I'm trying to say is that for d to be the answer , it should've had the word 'efficiently' or the likes.
Yes, living things with a lower SA:V struggle to survive. But evolution means that most organisms develop mechanisms/feautres to increase their SA, etc etc.

This is an excerpt from my school's biology website under the heading of "The functions of lipids"
Is it meant to say:
Amphipathic phospholipids are partially soluble in water as they have a hydrophilic head made of glycerol (and organic molceules such as choline) and phosphate, and a hydrophobic tail made up of 2 fatty acids
?

Yep  you're right. That they wrote 3 fatty acids is so incorrect tho 

[sunshine98]

I know that a condensation reaction doesn't occur when any two molecules are made to react with each other - so are there specific reactants that, when combined, create a condensation reaction? Is it two amino acids that react to form a condensation reaction?
Thanks

In bio we look at condensation reactions as the reactions that occur when monomers bond together with a loss of a water molecule.  All polymers of biomacromolecules ( carb, lipids, proteins , nucleic acids) are made through the condensation of their respective monomers.
However, in chem the definition of 'condensation reactions' is not so specific. Its basically when two functional groups react and a small molecule is lost (iirc) . If you were to go in the chemistry of it (for proteins as an example)  a hydroxyl functional group( -OH) reacts with a carboxyl functional group (-COOH) with the loss of a water molecule (the water being the small molecule).

[TheAspiringDoc]

Beyond VCE

I'm a little bit confused as to how insertional inactivation (the insertion of a fragment of DNA into the middle [or thereabouts] of a coding region of DNA in a plasmid, resulting in the inactivation of that gene) works.

Does the gene actually produce a non-functional protein, or does it just not produce anything (if so, by what mechanism?)

[vox nihili]

I'm a little bit confused as to how insertional inactivation (the insertion of a fragment of DNA into the middle [or thereabouts] of a coding region of DNA in a plasmid, resulting in the inactivation of that gene) works.

Does the gene actually produce a non-functional protein, or does it just not produce anything (if so, by what mechanism?)

That sounds about right, just remember if you're going to ask something post-VCE to try to label it as beyond VCE

[TheAspiringDoc]

That sounds about right, just remember if you're going to ask something post-VCE to try to label it as beyond VCE

okay

erm, which one sounds right?

[vox nihili]

okay

erm, which one sounds right?

The former. It'd produce a truncated protein, probably. There are mechanisms to prevent RNAs that ar likely to produce truncate proteins from being translated though, so it'd probably, at the end of the day, prove nothing.

Long story short: both are right haha

[geminii]

Hey! I have two questions..

Is it correct to say that the polymer of amino acids are proteins, but amino acids are also made of proteins? So it's kind of like:
An amino acid makes a protein, which makes amino acids, which makes proteins, which makes amino acids, etc.?

Also, I was listening to Douchy's biology podcast and he said if the molecule has carbon and hydrogen then it is organic, but my teacher says it has to have all of carbon, hydrogen and oxygen? Can anyone tell me which is correct?

Thanks!

[sunshine98]

Hey! I have two questions..

Is it correct to say that the polymer of amino acids are proteins, but amino acids are also made of proteins? So it's kind of like:
An amino acid makes a protein, which makes amino acids, which makes proteins, which makes amino acids, etc.?

yeh , I guess. But I think it would be better for u to think that:
- amino acid undergo condensation reactions to form proteins
And
- proteins undergo hydrolysis to form amino acids again
Also , worth noting that as a 'polymer' proteins are often referred to as polypeptides. I remember, however ,  that there was a quite small distinction between the terms proteins and polypeptides but as far as i know in vce bio it is quite negligible
Your second question ( which for some reason I can't quote ) as far as I know both are correct. I was once told , however , that the formal definition of organic is the one Douchy mentioned and that the other one arises because all organic molecules tend to have oxygen anyways( think about the elements involved in carbs ,lipids , proteins and nucleic acids.