VCE Biology Question Thread

[HasibA]

describe the consequence of the degeneracy of the genetic code to the likely effect of a change to one base in a triplet
- what is this question asking me to do? i have a hunch thinking i was going to talk about the fact that multiple different codons code for the same amino acids, but does this question want me to mention mutations and such? thanks
edit: few more questions
can someone explain the difference between positive control and negative control in regards to repressor proteins and gene regulation? do i have to know this- thanks

[grannysmith]

describe the consequence of the degeneracy of the genetic code to the likely effect of a change to one base in a triplet
- what is this question asking me to do? i have a hunch thinking i was going to talk about the fact that multiple different codons code for the same amino acids, but does this question want me to mention mutations and such? thanks
edit: few more questions
can someone explain the difference between positive control and negative control in regards to repressor proteins and gene regulation? do i have to know this- thanks

Yeah, so since the genetic code is degenerate, a base change in one triplet doesn't necessarily mean a different amino acid. This is called a silent mutation.

Positive control involves transcription stimulation whereas negative control involves transcription inhibition, both of which usually involve a protein (an activator and repressor protein, respectively) binding to DNA. In this way gene regulation is achieved.

[HasibA]

legend- thanks

[HasibA]

do i have to know any names of restriction enzymes?
how much do i have to know about 'taq polymerase'? function/role enough?
which company of prac exams are generally the hardest/easiest?
annealing: joining together single strands of dna/rna to create a polynucleotide- is this correct/good definition ?

[grannysmith]

do i have to know any names of restriction enzymes?
nah definitely not
how much do i have to know about 'taq polymerase'? function/role enough?
yep, function/role and also why it's used
which company of prac exams are generally the hardest/easiest?
STAV/Neap are well-known to be the gold standard (a good level of difficulty and similarity to the actual VCAA ones). Don't worry about the easy ones - just aim to complete STAV/Neap/VCAA and then maybe Lisachem/TSSM if you have time? I'm probably forgetting several other companies but it's been some time :p
However IIRC some of the company exams include essentially rephrased questions from the previous year's VCAA exam, so bear that in mind and maybe do VCAA exams first (it certainly isn't a 'waste' to do this).
annealing: joining together single strands of dna/rna to create a polynucleotide- is this correct/good definition ?
Yeah you might wanna say joining of complementary single strands to form a double-stranded polynucleotide (or a part thereof, as in the case of DNA probes/primers)

[HasibA]

always coming through with the info- thanks mate

[Butterflygirl]

I lost a mark on the following question but I don't understand why...

There was a table (don't know how to insert table on here), and one of the column's said "Cellular or non-cellular" and I had to fill it in for the following pathogens. The second column said "susceptible to antibiotics" and I had to say yes or no. I lost a mark for saying that the parasite (worm) was not susceptible to antibiotics because apparently, it is susceptible. Can someone explain??? I've been taught that ONLY bacteria are susceptible to antibiotics??

Pathogens:
Bacteria. Cellular. Yes.
Virus. Non-cellular. No
Parasite (worm). Cellular. No.
Prion. Non-cellular. No.

[vox nihili]

I lost a mark on the following question but I don't understand why...

There was a table (don't know how to insert table on here), and one of the column's said "Cellular or non-cellular" and I had to fill it in for the following pathogens. The second column said "susceptible to antibiotics" and I had to say yes or no. I lost a mark for saying that the parasite (worm) was not susceptible to antibiotics because apparently, it is susceptible. Can someone explain??? I've been taught that ONLY bacteria are susceptible to antibiotics??

Pathogens:
Bacteria. Cellular. Yes.
Virus. Non-cellular. No
Parasite (worm). Cellular. No.
Prion. Non-cellular. No.

I think your teacher has misconstrued the meaning of antibiotic, taking it to mean that they work against any "living" thing (as viruses and prions are technically not living). This is wrong; your answer is correct. Bacteria are the only things susceptible to antibiotics. Those drugs that kill worms are called antihelmintics

[The Usual Student]

quick questions

Getting mixed information
Textbook says glycogen is water soluble whilst other commercial notes say complex carbohydrates and polysaccharides are insoluble due to their size

Also, why would glycogen need to be soluble? Like the textbook rationalizes that it need to be able to move through the bloodstream but glycogen doesn't move through the blood stream.... I thought it was just the monosaccharide/glucose that does? hence only the monosaccharide needs to be water soluble ( which glucose is)

[doher109]

Hey!

1st. Glycogen is definitely water soluble. This is due to it's size and the fact it is polar.

2nd. Glycogen doesn't 'need' to be water soluble. It's just it's inherent chemistry that allows it to be. Correct, it enters the mouth as glycogen and is broken down in the GIT by enzymes to become a Monosaccharide.

[Butterflygirl]

Just a few questions... 

When the solution surrounding a plant cell is isotonic, it's referred to as "flaccid"? What does that actually mean in this context?
Can animal cells be referred to as flaccid when in an isotonic solution?

Also is this definition okay for plasmolysis?
Plasmolysis is when water leaves a plant cell causing the cell to lose turgor but the shape is maintained by the cell wall.

What's the difference between cytosol, cytoplasm, protoplasm and nucleoplasm? I don't understand which ones overlap..

Last questions...Are both carrier mediated and channel mediated diffusion specific in their action or is only carrier mediated? Are my definitions of the process detailed and accurate enough:

Channel: Channel mediated diffusion is a form of facilitated diffusion in which specific large polar molecules passively diffuse through a protein channel.

Carrier: Carrier mediated diffusion is a form of facilitated diffusion in which specific large polar molecules bind to a specific carrier protein which then goes through a conformational change allowing it to carry the molecule though the channel without the expenditure of energy (passive).


Thankyou so much >.<

[doher109]

Just a few questions... 

When the solution surrounding a plant cell is isotonic, it's referred to as "flaccid"? What does that actually mean in this context?
Can animal cells be referred to as flaccid when in an isotonic solution?

Also is this definition okay for plasmolysis?
Plasmolysis is when water leaves a plant cell causing the cell to lose turgor but the shape is maintained by the cell wall.

What's the difference between cytosol, cytoplasm, protoplasm and nucleoplasm? I don't understand which ones overlap..

Last questions...Are both carrier mediated and channel mediated diffusion specific in their action or is only carrier mediated? Are my definitions of the process detailed and accurate enough:

Channel: Channel mediated diffusion is a form of facilitated diffusion in which specific large polar molecules passively diffuse through a protein channel.

Carrier: Carrier mediated diffusion is a form of facilitated diffusion in which specific large polar molecules bind to a specific carrier protein which then goes through a conformational change allowing it to carry the molecule though the channel without the expenditure of energy (passive).


Thankyou so much >.<

1. I've never seen the term 'flaccid' used to describe animal cells. Essentially it means there is not pressure exerted on the cell wall by the plasma membrane (it is flaccid).

2. I wouldn't worry about the last 2. Cytoplasm is everything inside of the membrane (all of the cell) but excluding the nucleus. The cytosol is the fluid component of the cell. A key difference in cytoplasm includes organelles, cytosol doesn't.

3. Your definitions are great! Both are specific in what they let though.

Hope that helps!

[Butterflygirl]

1. I've never seen the term 'flaccid' used to describe animal cells. Essentially it means there is not pressure exerted on the cell wall by the plasma membrane (it is flaccid).

2. I wouldn't worry about the last 2. Cytoplasm is everything inside of the membrane (all of the cell) but excluding the nucleus. The cytosol is the fluid component of the cell. A key difference in cytoplasm includes organelles, cytosol doesn't.

3. Your definitions are great! Both are specific in what they let though.

Hope that helps!

Very helpful, thankyou

[codebreaker1_91]

What is the difference between:

• haploid
• diploid
• monoploid
• polyploidy

Thanks !

[doher109]

What is the difference between:

• haploid
• diploid
• monoploid
• polyploidy

Thanks !

Ploidy -> refers to how many sets of a chromosomes a cell has.
Monoploid -> 1 set of chromosomes
Polyploidy -> more than 2 sets of chromosomes

Haploid v. Diploid = When fertilisation occurs a sperm meets an egg. Essentially the sperm/egg contains 1 set of chromosomes (they are haploid). Then the sperm fertilises the egg it becomes a zygote with 2 sets of chromosomes (it is a diploid)

Ploidy -> refers to how many