Psyxwar's Biology 3/4 Question Thread

[Yacoubb]

Any other independent variables. I mean, it doesn't make sense that there will be a plateau because by increasing enzyme concentration, you wont have a point of substrate saturation, thus, no plateau. Increasing enzyme concentration increases the amount of product that is produced per unit time. Check if there are other IVs?

[psyxwar]

Any other independent variables. I mean, it doesn't make sense that there will be a plateau because by increasing enzyme concentration, you wont have a point of substrate saturation, thus, no plateau. Increasing enzyme concentration increases the amount of product that is produced per unit time. Check if there are other IVs?

The rate of reaction ends up being higher but still plateaus at the same point in time. I suppose they could cancel out, but it seems hard to believe they all plateau at the same substrate concentration

[psyxwar]

Elephantiasis is a human disease caused by the presence in the lymphatic system of a particular parasitic worm,
Wuchereria bancrofti. The adult worms block the lymphatic vessels so accumulation of lymph causes swelling
in the surrounding tissues. Adult female worms produce larvae that enter the human bloodstream.
When an infected person is bitten by a mosquito the larvae pass, with the ingested blood, into the stomach of
the mosquito. The larvae burrow their way through the mosquito stomach wall. After going through a series of
body changes the larvae move back to the mouth of the mosquito. These larvae are then passed into the blood
of a human the next time the mosquito bites a human. The larvae then move to the lymph nodes and mature
into adult worms.

What is the role of the mosquito in the life cycle of the the worm?

The answer given is that of a vector, but would intermediate host also be acceptable?

[Yacoubb]

Elephantiasis is a human disease caused by the presence in the lymphatic system of a particular parasitic worm,
Wuchereria bancrofti. The adult worms block the lymphatic vessels so accumulation of lymph causes swelling
in the surrounding tissues. Adult female worms produce larvae that enter the human bloodstream.
When an infected person is bitten by a mosquito the larvae pass, with the ingested blood, into the stomach of
the mosquito. The larvae burrow their way through the mosquito stomach wall. After going through a series of
body changes the larvae move back to the mouth of the mosquito. These larvae are then passed into the blood
of a human the next time the mosquito bites a human. The larvae then move to the lymph nodes and mature
into adult worms.

What is the role of the mosquito in the life cycle of the the worm?

The answer given is that of a vector, but would intermediate host also be acceptable?

My first answer would be vector! Could be wrong, but I don't think thats the case! The mosquito would have to show visible signs and symptoms of being infected by the endoparisitic organism to be classified as the intermediate host. However, because it merely transmits the disease from host organism to another, its just a vector.

[psyxwar]

My first answer would be vector! Could be wrong, but I don't think thats the case! The mosquito would have to show visible signs and symptoms of being infected by the endoparisitic organism to be classified as the intermediate host. However, because it merely transmits the disease from host organism to another, its just a vector.

Nah, I don't think you need to show symptoms to be an intermediate host

From wikipedia: A secondary host or intermediate host is a host that harbors the parasite only for a short transition period, during which (usually) some developmental stage is completed.

Also from wikipedia: "W. bancrofti carry out their life cycle in two hosts. Human beings serve as the definitive host and mosquitoes as their intermediate hosts. "

I'm not sure if it's acceptable to VCAA though (though secondary hosts are taught in the course afaik)

[psyxwar]

How well do we have to understand all of the phases of mitosis and meiosis?

[Yacoubb]

How well do we have to understand all of the phases of mitosis and meiosis?

* To be able to look at a microscopic image and be able to identify which phase is occuring
* To know what happens generally at each stage
* To know how many daughter cells are produced, where you're looking at sexual or asexual reproduction mode/ diploid or haploid cells
* When genetic material duplicates

[psyxwar]

Thanks. Are chromatin fibres considered chromosomes? Or is it only considered a chromosome when it actually condenses during prophase?

[Yacoubb]

Thanks. Are chromatin fibres considered chromosomes? Or is it only considered a chromosome when it actually condenses during prophase?

Could be wrong but I think chromosomes are made up of chromatin fibres. For eukaryotes, chromosomes are condensed forms of the genetic material in the nucleus. But I'd be curious to know if we could say that about prokaryotes, because their DNA is always coiled into one large chromosome (circular) with other smaller rings of DNA (plasmids), that only duplicate during binary fission in the case of prokaryotes. Dunno...could someone clarify this?

[psyxwar]

^yeah I dunno either.

Another question: are introns always introns? That is, for different proteins coded for by the same gene, is it possible for an "intron" in one type of mRNA coding process to be an exon in another? Or are your different mRNA sequences simply composed of different exons?

[psyxwar]

Also: what do we need to mention in hypotheses?

The STAV papers seem to have things like "that sucrose concentration affects the amount of mass gained or lost by the potato cube" or something. I was under the impression hypotheses need to specify direction (ie. increasing solute concentration increases mass loss). Am I allowed to just write something so general in the exam?

Also:

The answer they gave to the 2 mark question "Is there a control in this experiment? Explain:"

"There is no control as such but the various factors that need to be controlled are the amount of solution, the size and shape of potato cubes and the time left in solution."

How does that even work? Control =/= whether or not the experiment was valid.

Third edit: why do animals use both polysaccharide and lipids as an energy source whereas plants use only polysaccharide?

Would an answer about animals being mobile and therefore needing a more compact energy store (lipids, due to their higher energy/gram ratio) so they use lipids for long term storage and carbs for short, whereas plants do not need a compact store and therefore can just use the readily accessible polysaccharides?

The answer given by STAVs is that "plants have less energy needs, therefore can use complex carbs, whereas fats give more energy per gram and therefore animals use it for long term and carbs for short term". I'm not sure how that actually explains why animals don't just use carbohydrates exclusively though? There's no explanation for why compactness is preferred over more ready access.

[vox nihili]

^yeah I dunno either.

Another question: are introns always introns? That is, for different proteins coded for by the same gene, is it possible for an "intron" in one type of mRNA coding process to be an exon in another? Or are your different mRNA sequences simply composed of different exons?

Typically introns are long repeated sequences of the same base or of the same two bases. No doubt it is probably possible in a very small number of cases, though it's probably safe to assume that this is not the case. Often with genetics there are special cases where there are exceptions to the rules, however, at a VCE level, you hardly need to worry about these things. It's certainly not something they will examine. The most they'll ask about introns and exons is to identify which is left in and which is taken out in post transcriptional modification.

[vox nihili]

Could be wrong but I think chromosomes are made up of chromatin fibres. For eukaryotes, chromosomes are condensed forms of the genetic material in the nucleus. But I'd be curious to know if we could say that about prokaryotes, because their DNA is always coiled into one large chromosome (circular) with other smaller rings of DNA (plasmids), that only duplicate during binary fission in the case of prokaryotes. Dunno...could someone clarify this?

The statement about chromatin is certainly true and them being condensed. Chromatin is essentially the genetic material, coiled around proteins called histones. Then there are further histones that actually help to clamp them down. This is the structure of chromatin.
In prokaryotes, the DNA isn't truly condensed as it doesn't interact with any histones. The histones are the key point to make here.

I should also note in relation to the original question, the chromosomes do exist in every phase of the cell cycle. A chromosome describes the collection of all of those genes. If they didn't exist in the nucleus, how would they ever be used? How would the cell cycle receive the instructions it needs to progress to the next stages? Part of division is that the chromosomes themselves condense, so they can be seen. They just haven't supercoiled in the other stages of the cell cycle.

[stonecold]

Another question: are introns always introns? That is, for different proteins coded for by the same gene, is it possible for an "intron" in one type of mRNA coding process to be an exon in another? Or are your different mRNA sequences simply composed of different exons?

AFIAK, yes, introns are always introns and are never included in the mature mRNA.
Alternative splicing to produce different isoforms of the same protein is achieved by using different combinations of exons, NOT introns.

[vox nihili]

Go with that answer instead of mine, knows what he's talking about! ^