VCE Biology Question Thread

[wingdings2791]

Hi, can someone help me pleaseeee

We recently did an experiment to investigate enzyme activity. The experiment used catalase (from the liver) as the enzyme and hydrogen peroxide as the substrate. In all 4 test tubes there was hydrogen peroxide added. On test tube A there was sand ( i guess to act as control group), in test tube B there was a cube of liver, test tube c there was grounded liver and sand, and testube d had boiled liver. What I don’t understand is why did the test tube c contain both sand and live? Like I understand that live contains enzyme catalase but what is the purpose of sand?

Hello, I think sand was included in test tube C to determine whether it has any effect on the rate of reaction between H₂O₂. Test tube A, containing only sand and H₂O₂, is a control used to see if there would be any reaction with H₂O₂ not involving catalase. Tube C would probably be used to see if sand interfered with the catalase or H₂O₂ (potential effects might not necessarily be observable in tube A).

[Chocolatepistachio]

if someone could help with this question

[Sine]

if someone could help with this question

paracellular since it is between cells. Transcellular would be through a cell.

[Bluebird]

Hi AN, I just needed a bit of help with this question

Outline the steps within the nucleus that occur to produce Molecule X

I wrote:
- To produce molecule X, RNA polymerase must bind to the promoter region of the gene
- mRNA unwinds the DNA strand, separating the coding and template strands. The RNA polymerase binds to and reads the template strand.
- RNA polymerase attaches complementary bases to the DNA template stand's bases
- Once the RNA polymerase reaches the terminator region, the RNA polymerase dissociates from the DNA strand and post-transcriptional editing of the pre-mRNA strand occurs where exons are spliced together and introns are removed
- The pre-mRNA has a 5' methyl cap and 3' poly-A-tail added to it becoming mature mRNA before leaving the nucleus through a nuclear pore

Am I including too much extra information? Is my clarity okay? The answer only mentions up the the attaching of complementary bases so I'm not sure whether the post-transcriptional editing bit is relevant or not to the question

[Harrycc3000]

Hi AN, I just needed a bit of help with this question

Outline the steps within the nucleus that occur to produce Molecule X

I wrote:
- To produce molecule X, RNA polymerase must bind to the promoter region of the gene
- mRNA unwinds the DNA strand, separating the coding and template strands. The RNA polymerase binds to and reads the template strand.
- RNA polymerase attaches complementary bases to the DNA template stand's bases forming a complementary premRNA strand
- Once the RNA polymerase reaches the terminator region, the RNA polymerase dissociates from the DNA strand and post-transcriptional editing of the pre-mRNA strand occurs where exons are spliced together and introns are removed
- The pre-mRNA has a 5' methyl cap and 3' poly-A-tail added to it becoming mature mRNA before leaving the nucleus through a nuclear pore

Am I including too much extra information? Is my clarity okay? The answer only mentions up the the attaching of complementary bases so I'm not sure whether the post-transcriptional editing bit is relevant or not to the question

Everything you’ve said seems correct maybe explicitly state that the process you’re describing is transcription? Also I don’t think mRNA unwinds the DNA strand I think it’s more so RNA polymerase binding to the promoter region DNA strand and then breaking hydrogen bonds in between complementary bases. In terms of amount of information, imo I like being overly specific so that teachers or marking schemes don’t have any excuse to take marks off. If you’re under time pressure though of course try and take that into account and adjust accordingly. Also I think on VCAA transcription questions usually a mark is allocated to mentioning post transcriptional mod/RNA processing along with the things you have mentioned so I think it’s good I leave it there.

[Bluebird]

Everything you’ve said seems correct maybe explicitly state that the process you’re describing is transcription? Also I don’t think mRNA unwinds the DNA strand I think it’s more so RNA polymerase binding to the promoter region DNA strand and then breaking hydrogen bonds in between complementary bases. In terms of amount of information, imo I like being overly specific so that teachers or marking schemes don’t have any excuse to take marks off. If you’re under time pressure though of course try and take that into account and adjust accordingly. Also I think on VCAA transcription questions usually a mark is allocated to mentioning post transcriptional mod/RNA processing along with the things you have mentioned so I think it’s good I leave it there.

Thank you!
Also thank you for saying that RNA polymerase breaks the hydrogen bonds between the complementary bases, I actually forgot about that so that was really helpful

[Corey King]

Hey guys
I'm curious why protein chains form into helix and pleated structures, as opposed to any other structure that is possible. I haven't been able to find an explanation for this. I know that the secondary structures coil, thought I don't know why that is helpful yet either. We haven't covered how proteins work yet.
Many thanks
Corey

[Bhrugu]

Hi
I have a test coming up on a practical experiment.
The experiment was the dialysis-tubing experiment, the one where diffusion and movement across a semi-permeable membrane is modelled.
What should I prepare for the best marks?
How should I prepare for the best marks?
What is the best study technique?

All help appreciated!

[Chocolatepistachio]

Centrioles are formed by modified microtubules and other proteins.

How exactly are they formed

During facilitated diffusion using carrier proteins can they bind more than one specific solute at a time

[Owlbird83]

Hey guys
I'm curious why protein chains form into helix and pleated structures, as opposed to any other structure that is possible. I haven't been able to find an explanation for this. I know that the secondary structures coil, thought I don't know why that is helpful yet either. We haven't covered how proteins work yet.
Many thanks
Corey

Hi Corey,
I'm pretty sure these alpha helices and beta pleated sheets form because of the attractions between hydrogens in the amino acids in the polypeptide chains, as these shapes are held by hydrogen bonding.

Hi
I have a test coming up on a practical experiment.
The experiment was the dialysis-tubing experiment, the one where diffusion and movement across a semi-permeable membrane is modelled.
What should I prepare for the best marks?
How should I prepare for the best marks?
What is the best study technique?

All help appreciated!

Hi Bhrugu,
As well feeling comfortable with diffusion/semipermanent membrane content, it would be good to have an understanding of experimental design stuff such as differences between systematic and random errors and examples specific to this prac, and also differences between the terms validity, accuracy, reliability and precision and how they relate to your results. Maybe practice writing a conclusion to your prac using your results to make sure you understand why you've gotten those results and brainstorm possible causes of error if your results aren't as expected.

Centrioles are formed by modified microtubules and other proteins.

How exactly are they formed

During facilitated diffusion using carrier proteins can they bind more than one specific solute at a time

Hi Chocolatepistacio,
I'm not super sure about how centrioles are formed, but since they are made from proteins, all the individual polypeptide chains in the centriole would follow the normal protein synthesis pathway of transcription of a gene in the DNA into mRNA and then translation of the mRNA by the ribosome creating the polypeptide.

It depends on the specific type of carrier protein. Some can only do one at a time, others have binding spots for more than one.
For example the Na+/K+ ion pump has binding spots for 3Na+ and 2K+molecules each time. However there are other carrier proteins that can only transport one molecule at a time. ((wait now I'm over-thinking whether ion pumps are carrier proteins, they are aren't they??))

[Sine]

Hey guys
I'm curious why protein chains form into helix and pleated structures, as opposed to any other structure that is possible. I haven't been able to find an explanation for this. I know that the secondary structures coil, thought I don't know why that is helpful yet either. We haven't covered how proteins work yet.
Many thanks
Corey

Typically those structures allow the proteins to form the most energetically favourable structures possible.

[Chocolatepistachio]

How is ethanol fat soluble? It has H bonding

[beep boop]

Hey Guys,

Can someone please explain to me what translation, transcription, mRNA, tRNA is? I'm kinda confused atm lol.

[vox nihili]

How is ethanol fat soluble? It has H bonding

You're right, the alcohol group doesn't like fat very much but the carbon backbone does. It's the big carbon backbone that plonks nicely into lipids.

[Owlbird83]

Hey Guys,

Can someone please explain to me what translation, transcription, mRNA, tRNA is? I'm kinda confused atm lol.

Transcription and translation are steps in protein synthesis.
Transcription is when the DNA unwinds and a complementary strand of mRNA is created to carry the info out of the nucleus. Using an analogy I've heard, DNA is like a large instruction manual that sits in the library(nucleus). You don't want to take a large book(DNA) out of the library, and you also only need the info from one page of the book (the gene for making the specific protein), so you take a photocopy of that page, and the photocopy is what you take from the library. The photocopy (mRNA) has the instructions you need.
Then the mRNA undergoes some modifications so it's ready to be read by the ribosome (i forgot what this was in the analogy, let's say head engineer?). Translation then occurs. The ribosome travels along the mRNA and reads the instructions while assembling a polypeptide chain. Each codon on the mRNA corresponds with a specific amino acid (building blocks of the polypeptide) that needs to be added to the polypeptide chain. The tRNA molecules are like workers bringing the parts for the ribosome to assemble the polypeptide chain. Each tRNA molecule has 3 bases (anticodon) that is complementary to the 3 base codon on the mRNA, they also each carry a specific amino acid. There are tRNA molecules with different anticodons in the cytoplasm carrying each of the 20 amino acids. The correct amino acid will be brought to the ribosome by the correct tRNA because only the tRNA with the complementary codon can bind to the mRNA. The tRNA drops off its amino acid, then leaves. Eventually you get a long polypeptide chain /protein that the ribosome has synthesised.
I hope this helps a bit! I recommend watching a few different YouTube videos on it, because i think the repetitive exposure to the process it helps it click faster.