VCE Biology Question Thread

[sweetcheeks]

whats the best way to remember the graphs for high conc of enzymes vs low substrate conc etc. and all their variations
i seem to have to rote learn it because i always forget it/ get mixed up with it ah!

also- are we meant to know the term intermediate inheritance..? coming up in company papers haha

The best way to remember the graphs is to draw the various ones and write notes around them.

Intermdiate inheritance is another way of saying incomplete dominance, something that is no longer on the study design. I find that some questions have been recycled from old papers, keeping in some questions that are not relevant to our study design.

[Springyboy]

Hey everyone,

Has anyone been able to work out the answer for vcaa 2003 exam 2 question 6b?

The question is this:

The differences between the mitochondrial DNA recorded are the result of base substitutions. There are 77 nucleotide differences between Human 1 and Chimpanzee 1.
Explain why 77 nucleotide differences is a minimum number of base substitutions.

Only 1% of people doing the exam got it right and my teacher was unable to work it out as well

Thanks,

James

[sweetcheeks]

@Springyboy
Quite a difficult question. What it is asking is why the difference of 77 nucleotides would be the minimum amount of mutations that have occurred. Over time, the mtDNA will undergo mutations. e.g going from ACACTG to ACATTG, but another mutation may occur reversing the initial mutation, ACATTG back to ACACTG, so the mtDNA may have had more mutations than the 77 different nucleotides, therefore 77 differences, which have been observed can be said to be the minimum (as more mutations may have occurred but they can't be detected).

Whilst we can observe that 77 is the number of base differences, many more substitutions may have occurred but subsequent changes may have reserved the changes, which we cannot determine.

[alastair.98]

Hi Everyone,
Are proteins produced by free ribosomes exported out of the cell and those produced by the RER for use in the cell?
Thanks

[arshi.a]

i just wanted to know if i should still attempt those questions regarding homeostasis in past papers of the old study design or is that completely out of the new study design and also could someone please explain rational drug design and how it relates to enzymes.

[thuynh]

Guys I am super confused

Glycolysis--> THE BREAKING DOWN OF GLUCOSE! like its in the bloody name
Yet VCAA 2007 Exam 1 Multi Choice Q8 says lipids would be broken down before starch is if all glycogen was depeleted. I pressumed the starch was externally consumed from plants.  And I ruled lipids out since they can't be broken down in glycolysis.... yet the answer was friggin lipids.

It's because humans don't have starch as storage. We store energy in the form of glycogen and fat. So once the glycogen is gone we turn to fat. 

Hope that makes sense

[thuynh]

Hi Everyone,
Are proteins produced by free ribosomes exported out of the cell and those produced by the RER for use in the cell?
Thanks

Other way around rough endoplasmic reticulum produce the proteins to be exported.

Also make sure you don't abbreviate it to RER in the exam

[The Usual Student]

Other way around rough endoplasmic reticulum produce the proteins to be exported.

Also make sure you don't abbreviate it to RER in the exam

Just to be specific, make sure to mention the RIBOSOMES on the rough ER produce proteins to be exported not the rough ER istelf which functions to package.

In regards to the Glycolysis question
I understand that but I don't understand how Lipids could be used as an energy source via GLYCOLYSIS if glycolysis is about breaking down glucose. I figured you could consume starch and break it down with the assistance of amylase. But to be frank I kinda think its a grey area on the course.

[hodang]

Can anyone provide me a more clearer answer to the one listed below to this question that would give me for example full marks?

Question: Compare the speed at which responses to protein hormones occur to the speed at which responses to steroid hormones occur?

Answer: Responses to protein hormones occur faster than those to steroid hormones
Although steroid hormones enter target cells rapidly the hormone/receptor complex has to move to the nucleus bind to DNA and trigger protein synthesis. As proteins will be produced, response would be slow as activation of proteins are already present inside the cell.

[hodang]

When antigens are recognized as foreign are they engulfed by phagocytes or macrophages? Are we allowed to say either?

[sweetcheeks]

When antigens are recognized as foreign are they engulfed by phagocytes or macrophages? Are we allowed to say either?

Macrophages are a special type of phagocyte, phagocytes is a collective term for cells that engulf foreign material. I would say macrophages when talking abut antigens, as they are capable of presenting antigens to T helper cells through the use of MHC class 2 markers (which will subsequently result in antibody production).

[hodang]

Thankyou sweetcheeks

[hodang]

For allopatric speciation, can we say mutations accumulate over time when populations become isolated etcc.? Can we write mutations accumulate over time? Btw can we also say that when these species are brought back together "they were unable to interbreed to produce a fertile offspring" Can we use the word interbreed in this case? Thanks x

BTW what is the difference between allopatric speciation and speciation? How can we differentiate the two? Is it just when theres a geographical barrier its allopatric?

[The Usual Student]

can someone explain to me why steroid hormones and long lasting but peptide and protein hormones are temporary?

[sweetcheeks]

For allopatric speciation, can we say mutations accumulate over time when populations become isolated etcc.? Can we write mutations accumulate over time? Btw can we also say that when these species are brought back together "they were unable to interbreed to produce a fertile offspring" Can we use the word interbreed in this case? Thanks x

BTW what is the difference between allopatric speciation and speciation? How can we differentiate the two? Is it just when theres a geographical barrier its allopatric?

You can say that mutations occur. Make sure that you pair it up with favouring of these changes. It is preffered to state that the produce viable, fertile offspring rather than just fertile offspring (at least thats what my teacher said). Interbreed is a fine term to use.

Speciation in terms of VCE biology refers to allopatric speciation, as that is the only type covered. This is where there is a physical separation of two populations occur. Another form not part of VCE is sympatric, which is where they exist in the same environment