VCE Biology Question Thread

[Butterflygirl]

Quick question...

How can an enzyme with several polypeptides (quaternary), catalyse many steps in a process? I don't understand how its related to catalysing different steps apart from maybe more polpeptides=more active sites for different substrates?

Thanks >.<

[doher109]

Quick question...

How can an enzyme with several polypeptides (quaternary), catalyse many steps in a process? I don't understand how its related to catalysing different steps apart from maybe more polpeptides=more active sites for different substrates?

Thanks >.<

Hey that's basically it!

An enzyme can have 1 or more sites that a substrate can bind to. So if it has 2 active sites it can catalyse 2 reactions at once (these can be the same or different reactions).

[Butterflygirl]

Thanks! and for the question:

Androstenone is a steroid found in high concentrations in the saliva of male pigs and was the first mammalian pheromone to be identified. When sniffed by a female pig that is in heat, it results in the female assuming the mating stance. Using your understanding of signal transduction, discuss the action of androstenone.

I wrote:
Androstenone would have been released into the external environment of the male pig to then bind with receptors found in the cytosol or nucleus of the female pig and results in it assuming the mating stance.
Feedback?

The actual answer was: Androstenone would move through cell membranes to bind to a receptor in the cytosol. This will lead
to the expression of a gene.

Am I supposed to know that the mating stance is triggered through the expression of a gene?

Also, do I need to know what a monoclonal antibody is? I saw it in a practice exam and I have no idea what it is...

Thankyouu >.<

[plsbegentle]

Thanks! and for the question:

Androstenone is a steroid found in high concentrations in the saliva of male pigs and was the first mammalian pheromone to be identified. When sniffed by a female pig that is in heat, it results in the female assuming the mating stance. Using your understanding of signal transduction, discuss the action of androstenone.

I wrote:
Androstenone would have been released into the external environment of the male pig to then bind with receptors found in the cytosol or nucleus of the female pig and results in it assuming the mating stance.
Feedback?

The actual answer was: Androstenone would move through cell membranes to bind to a receptor in the cytosol. This will lead
to the expression of a gene.

Am I supposed to know that the mating stance is triggered through the expression of a gene?

Also, do I need to know what a monoclonal antibody is? I saw it in a practice exam and I have no idea what it is...

Thankyouu >.<

1. the expression of a gene is how signalling transduction works since androstenone is a steroid hormone, it will bind to a receptor either in the nucleus or cytosol which then binds to a specific regulator site for a targeted gene. This stimulates the gene to produce mRNA which produces a specific protein so a response is made.
2. im not sure about this one, but i havent come across a "monoclonal antibody".

[Butterflygirl]

1. the expression of a gene is how signalling transduction works since androstenone is a steroid hormone, it will bind to a receptor either in the nucleus or cytosol which then binds to a specific regulator site for a targeted gene. This stimulates the gene to produce mRNA which produces a specific protein so a response is made.
2. im not sure about this one, but i havent come across a "monoclonal antibody".

Lol I didn't know that genes are expressed like that. I haven't learnt that at school yet. Is that to do with translation and transcription or something? I don't even know what "gene expression" is. We're up to non-disjunction of chromosomes in school.
Thankyou 

[mtse]

Also, do I need to know what a monoclonal antibody is? I saw it in a practice exam and I have no idea what it is...

2. im not sure about this one, but i havent come across a "monoclonal antibody".

you do NOT need to know about monoclonal antibodies in VCE biology
but if you're interested they are basically specific antibodies that have been identified, selected and produced by a single clone of B cells in the lab setting so that they can be used in the treatment of autoimmune diseases and as anticancer therapy

[plsbegentle]

Lol I didn't know that genes are expressed like that. I haven't learnt that at school yet. Is that to do with translation and transcription or something? I don't even know what "gene expression" is. We're up to non-disjunction of chromosomes in school.
Thankyou 

Yes, its transcription (gene expression, where dna is copied into mRNA) and translation ( the mRNA is read by ribosome to code for a protein). On that note, typically only steroid hormones act by stimulating gene expression, say if it was a water-souble hormone, they usually act by causing biological process in the cytoplasm.

[mtDNA]

A quick question - is post-transcription modification part of the transcription process? Or is it identified as a separate process?
So, if there were to be an exam or SAC question asking to explain the process of transcription, is it necessary to include post-transcription modification?
Thanks 

[vox nihili]

A quick question - is post-transcription modification part of the transcription process? Or is it identified as a separate process?
So, if there were to be an exam or SAC question asking to explain the process of transcription, is it necessary to include post-transcription modification?
Thanks 

They're separate processes.

[mtDNA]

Also:
Are there tRNA molecules with a STOP anti-codon and with no amino acid, or are they non-existent - The reason I ask is that if there are tRNA molecules with a STOP anti-codon, then there is a possibility of obtaining 64 permutations of anti-codon sequences. However, if there are no tRNA molecules with a STOP anti-codon, then there are only 61 possible permutations of anti-codon sequences.

In addition, how does the ribosome know when to stop synthesising the polypeptide and to remove it? The mRNA has STOP codons, but what do they actually do when they encounter the ribosome during translation? How does the ribosome perceive and respond to the STOP codon?

Thanks - appreciate the assistance 

[vox nihili]

Also:
Are there tRNA molecules with a STOP anti-codon and with no amino acid, or are they non-existent - The reason I ask is that if there are tRNA molecules with a STOP anti-codon, then there is a possibility of obtaining 64 permutations of anti-codon sequences. However, if there are no tRNA molecules with a STOP anti-codon, then there are only 61 possible permutations of anti-codon sequences.

In addition, how does the ribosome know when to stop synthesising the polypeptide and to remove it? The mRNA has STOP codons, but what do they actually do when they encounter the ribosome during translation? How does the ribosome perceive and respond to the STOP codon?

Thanks - appreciate the assistance 

Interesting questions, but neither one is particularly relevant to VCE

To answer it though: there are no tRNA molecules that recognise stop codons, so I guess in some ways there are only 61 different tRNAs (although this is a lot more complicated than you might initially believe; for instance, some species lack certain tRNAs altogether). Termination of translation occurs as the result of proteins called release factors binding to the mRNA and signalling to the ribosome that time's up and that translation is over.

Obviously, don't commit to learning that, but you seem curious so I didn't want to leave you without an answer.

[mtDNA]

Sorry for asking so many questions, but...

What happens to the mRNA and tRNA molecules after translation? I have read mixed responses online, some stating that the tRNA is reused, while other responses stating that they are degraded alongside with the mRNA strand...
Which is correct?

THANK YOU SO MUCH 

[vox nihili]

Sorry for asking so many questions, but...

What happens to the mRNA and tRNA molecules after translation? I have read mixed responses online, some stating that the tRNA is reused, while other responses stating that they are degraded alongside with the mRNA strand...
Which is correct?

THANK YOU SO MUCH

Not really sure to be honest. I suspect probably a combo of both, but it's not something that really matters a whole lot to be perfectly honest with you.

you do NOT need to know about monoclonal antibodies in VCE biology
but if you're interested they are basically specific antibodies that have been identified, selected and produced by a single clone of B cells in the lab setting so that they can be used in the treatment of autoimmune diseases and as anticancer therapy

Just btw, they're adding monoclonals to the course next year. Thought that was pretty cool that they're doing that

[anotherworld2b]

Hi
I was wondering if I could have help in answering some questions

Q1. Find out how the ancient Greeks and Romans tried to stop the spread of malaria
The Ancient Greeks and Romans tried to stop the spread of malaria by .... (i don't know )

I was wondering would these answers I have for this question be right? I am still a bit confused for how to write a hypothesis and outline an investigation?
Q2. American Dr William Bean studied the growth of his fingernails for 35 years. He filed a horizontal line on his thumbnail just above the cuticle (the strip of skin at the base of the nail). By recording recording how long it took the mark to reach the tip of the thumbnail he was able to calculate the growth rate. He was eventually able to conclude:

‘A 35-year observation of the growth of my nails indicates the slowing of growth with increasing age. The average daily growth of the left thumbnail, for instance, has varied from 1.123mm a day during the first part of the study when I was 32 years of age to 1.1.95mm a day at the age of 67.’
Suggest a hypothesis that Dr Bean was testing
An increase in age will decrease the rate of the growth of nails

Which was the independent variable and which was the dependant variable in this investigation?
Independent variable: growth of nails
Dependent variable: age

List some of the variables that should have been controlled in Dr Bean’s study
Diet?

Describe one source of random error in the investigation
An error in the accuracy of the measurement of the growth of the nail

Measure the length of your thumbnail. Assume that your thumbnail grows at the same rate as that of the 32-year-old Dr Bean. How long did it take the tip of your thumbnail to grow from the cuticle to its present position?
My nail: 12 mm. Dr Bean’s nail’s growth : 1.123m.
12/ 1.123 = 10.68 so approximately 11 days?

Do you think your fingernails and toenails grow at the same rate? Propose a hypothesis and outline an investigation that you could do to test your hypothesis
I do not think that fingernails and toenails grow at the same rate. I believe that fingernails grow at a faster rate than toenails.

Hypothesis: Over time fingernails will grow at a faster rate than toenails.
Outline an investigation (write up a whole investigation?)
File a horizontal line on each thumbnail as well as toenail? (singular/plural?)
Measure the growth of each thumbnail and toenail every day and record measurement.

Q3. Patients who have suffered severe blood loss or dehydration have to be given large volumes of fluid. A fluid that is often given is a 0.9% solution of sodium chloride, known as normal saline. Why is saline solution given rather than just plain water?

The fact that normal saline has 0.9% of sodium chloride means that its composition is comparatively similar to the amount of ‘salt’ in the blood stream. Whereas, if plain water is given to the patient the normal concentration of ‘salt’ in the blood will decrease causing the blood to become dilute. If this happens the body’s natural response would be to extract the excess water and expel it from the body through the anti diuretic hormone. Therefore, saline solution is given to prevent dehydration. (would this be right?) How would saline solution stop blood loss?

[plsbegentle]

Hi
I was wondering if I could have help in answering some questions

Q1. Find out how the ancient Greeks and Romans tried to stop the spread of malaria
The Ancient Greeks and Romans tried to stop the spread of malaria by .... (i don't know )

I was wondering would these answers I have for this question be right? I am still a bit confused for how to write a hypothesis and outline an investigation?
Q2. American Dr William Bean studied the growth of his fingernails for 35 years. He filed a horizontal line on his thumbnail just above the cuticle (the strip of skin at the base of the nail). By recording recording how long it took the mark to reach the tip of the thumbnail he was able to calculate the growth rate. He was eventually able to conclude:

‘A 35-year observation of the growth of my nails indicates the slowing of growth with increasing age. The average daily growth of the left thumbnail, for instance, has varied from 1.123mm a day during the first part of the study when I was 32 years of age to 1.1.95mm a day at the age of 67.’
Suggest a hypothesis that Dr Bean was testing
An increase in age will decrease the rate of the growth of nails

Which was the independent variable and which was the dependant variable in this investigation?
Independent variable: growth of nails
Dependent variable: age

List some of the variables that should have been controlled in Dr Bean’s study
Diet?

Describe one source of random error in the investigation
An error in the accuracy of the measurement of the growth of the nail

Measure the length of your thumbnail. Assume that your thumbnail grows at the same rate as that of the 32-year-old Dr Bean. How long did it take the tip of your thumbnail to grow from the cuticle to its present position?
My nail: 12 mm. Dr Bean’s nail’s growth : 1.123m.
12/ 1.123 = 10.68 so approximately 11 days?

Do you think your fingernails and toenails grow at the same rate? Propose a hypothesis and outline an investigation that you could do to test your hypothesis
I do not think that fingernails and toenails grow at the same rate. I believe that fingernails grow at a faster rate than toenails.

Hypothesis: Over time fingernails will grow at a faster rate than toenails.
Outline an investigation (write up a whole investigation?)
File a horizontal line on each thumbnail as well as toenail? (singular/plural?)
Measure the growth of each thumbnail and toenail every day and record measurement.

Q3. Patients who have suffered severe blood loss or dehydration have to be given large volumes of fluid. A fluid that is often given is a 0.9% solution of sodium chloride, known as normal saline. Why is saline solution given rather than just plain water?

The fact that normal saline has 0.9% of sodium chloride means that its composition is comparatively similar to the amount of ‘salt’ in the blood stream. Whereas, if plain water is given to the patient the normal concentration of ‘salt’ in the blood will decrease causing the blood to become dilute. If this happens the body’s natural response would be to extract the excess water and expel it from the body through the anti diuretic hormone. Therefore, saline solution is given to prevent dehydration. (would this be right?) How would saline solution stop blood loss?

Q1.The romans and the greeks tried to stop the malria by draining the marshlands on a consistent basis because they  thought it was caused by bad air coming from areas of standing water and swamps.☺

Q2.For a hyptothesis, it should just be a short statement about the experiement, it must include the dependent variable ( what u are measuring) and the indepdent variable ( what changes).😊i would say the indepdent variable is the age haha😀, while the growth of nails is the depedent variable. As i mentioned before the depedent variable is what u are finding/measuring!☺

Your hyptothesis is fine but i would of made mine a tad longer.😆

Q3.
-the size of the horizontal line each day he puts it on his thumbnail
-when he places the horizontal line
-where he places the horizontal line