Hey Guys!
I was wondering what is Lac Operon Model used to demonstrated?
what does it require?
And what does it produce?

    yr12student22
    My memory has faded - so I can’t remember the specifics (I can look up my old textbook if u want) - but I was under the impression they replaced it with a different operon… so this may he irrelevant as well as wrong… lol

    Anyway - basically it’s a segment of DNA found in bacteria (which has three iirc gene coding regions). The gist of it was, they produce lactase (the enzyme) which broke down lactose.

    However, when lactose is in a cell, some of it is converted into allolactose - the inducer. This molecule bound to the inhibitor (which was bound to the operator region located downstream of the promoter). This caused the inhibitor to no-longer fit the operator, and the coding regions could be transcribed / the enzyme produced.

    Hence using a feedback loop. If the concentration of lactose got too high, more galactose would bind to the inhibitor - releasing it from the operator - and more enzyme would be made.

    If the concentration was too low, less enzyme would be produced. (As more inducers bound to operators).hence less energy is wasted.

      yr12student22
      Just to add to this, the lac operon is no longer in the bio study design, as it has been replaced with the trp operon. However, they both do share similar principles.

      What does the trp operon demonstrate?
      It demonstrates the importance of gene expression regulation to aid in the conservation of energy and biochemical resources.

      What does it require?
      Not sure what you mean, but it involves the amino acid tryptophan. It also involves RNA polymerase, repressor proteins, ribosomes, and tRNA.

      What does it produce?
      When the structural genes are transcribed and translated, they form enzymes that convert different chemicals into tryptophan. This is what is specifically produced (don't need to know, but it can be helpful when understanding how it all works):
      • TrpE and TrpD -> Form enzyme Anthranilate synthase, which converts chorismate (found in the cell) into anthranilate.
      • TrpC -> Forms enzyme Indole-3-glycerol-photosphate synthase, which converts anthranilate into indole-3-glycerol-photosphate.
      • TrpB and TrpA -> Forms enzyme Tryptophan synthase, which converts indole-3-glycerol-photosphate into tryptophan.
      (Requires lots of energy, meaning the process needs to be tightly regulated)

      Here is the trp operon order as well to make the above answer make more sense haha.
      3' end - Promoter - Operator - Leader (TrpL) - Attenuator - TrpE - TrpD - TrpC - TrpB - TrpA - Trailer - 5' end

      You do need to know about the two methods of gene expression regulation, which are repression and attenuation (I think the lac operon only involved a repression mechanism, but the trp operon involves the process of attenuation as well, which is more complex).

        Hi there. I was wondering if anyone would be able to explain how CRISPR CAS 9 defence system works in bacteria.

          does substrate bind to enzyme or enzyme binds to substrate?

          how do we explain anaerobic respiration? and also why is producing atp important in respiration

          6 days later

          Does the tracrRNA bind to the palindromic sequence on the CRISPR sequence or on the crRNA?

          BIOQ
          In bacteria CRISPR acts as a defence system by recognising foreign viral DNA sequences and incorporating it into the bacteria’s CRISPR sequence/genome as a “spacer” upstream of the PAM. This occurs as cas9 is able to cut the viral DNA at a specific sequence of nucleotides (restriction site) complementary to the nucletides of the short guide RNA
          This allows the bacteria to have a memory of past viral infections such that in future if the same virus invades, a faster, stronger, greater response is triggered as the cas9 rapidly cuts the viral DNA inducing a mutation in it and preventing it from replicating, hence preventing viral infection/spread in the bacterium. The PAM a sequence of nucletides downstream of the gene of interest in the virus which helps cas9 differentiate between the virus as a “non self” molecule and the bacterias own CRISPR genome as being “self”

              Yes I think sme bacteriophages can insert RNA-not entirely sure though. It’s interesting actually cos Ive only heard of bacteriophages inserting viral DNA that forms a “spacer” as part of the CRISPR sequence/genome but you might wanna double check with your teacher 🙂

              5 days later

              Hi all, can someone please explain to me in things like hayfever, does histamine cause watery eyes so that lysozymes in those "tears" can remove pollen (or other allergens)?

                chemistry1111 It is functional at both, but it must at least be at a tertiary structural level to be functional. All proteins must at least be a tertiary protein to function, but some will also have a quaternary structure and are a still functional (but not all functional proteins will have a quaternary structure).

                  Hello there,
                  Can someone please explain the process of attenuation in the regulatory mechanism of tryptophan?
                  Also, what are the key ideas that I should know about mtDNA in relation to the topic of evolution?

                  Kind regards 🙂

                    Hello MinahilMehr!

                    In short, no, allergic responses are "overreactions" and do not have any real meaning or purpose.

                      Privet NG900!

                      Attenuation inhibits expression of the structural genes of the TrpOperon in conditions of mild-to-high concentration of loaded tryptophan tRNA.
                      There is a sequence of DNA located downstream of the promoter, and upstream of the structural genes, of the TrpOperon called the TrpLeader sequence. It contains two triplets, that when transcribed, become two codons (so mRNA) for tryptophan.
                      (Recall that transcription and translation occurs concurrently in prokaryotes)
                      When the ribosome reaches these two codons, it will stall in conditions of low loaded tryptophan tRNA -- and attenuation will not occur --, it will continue normally otherwise -- and attenuation will occur --.
                      Why you ask? This you don't really need to know in detail, but basically the time taken for the ribosome to translate those two codons will determine how the mRNA section ahead is folded. Different folding patterns will result in attenuation or not, depending [again, on the time the ribosome takes to reach it].

                      Apologies if I confused you haha 😅

                          hi, can someone help me with questions 2e, 3c and all of question 9 from the 2022 vcaa sample exam? And is it just me or is this exam a lot harder than previous years vcaa exams? The question style seems skewed towards more "subjective" application questions instead of technical theory questions...

                            bioho4

                            Hmmmm... I haven't done the 2022 sample yet, so I cannot assist you with that.

                            However on the latter point, I have heard that the chief VCAA assessor for VCE Biology is also a Psychology teacher. Which would explain your observation (VCE Psychology is a borderline English subject, where you have 10 mark questions with explicit mark allocations for paragraph and sentence structuring). It is just a rumour though, do not take it as fact.

                            If it is really true, I think it would be a shame.
                            VCE Biology's content is very enjoyable, possibly the best science in the VCE in terms of theory. However I think this "subjective application", style as you call it, is the incorrect approach taken by the assessors, the proper assessment approach for Biology, would be to test "technical application" where the same theory is mapped onto unfamiliar contexts (e.g. Enzyme theory for ribozymes... etc)...