biol+3+faq+(nsfaq)+aos2+part1

Please write your questions on this page from now on. Link is below. ** biol 3 faq (nsfaq) aos2 part2
 * Well done on all the fantastic questions you have asked but I have now created a second page for this area of study.

 **Q. Are endocrine, paracrine and autocrine hormones all a part of the endocrine system? Or are there separate paracrine and autocrine systems to which specific hormones belong? Just wasn't really sure.**

//A. Really good question. Terminology in this section can be confusing and is debatable. For instance the definition of a horomone as a signlalling molecule has always been referred to as a substance being relased from one cell and travelling via the blood to a target cell. Yet, many hormones are known to act on nearby cells (paracrine) and on the cell itself (autocrine), thus not necessarily involving blood or distant travel. **So as far as we are concerned you can view all three types as being part of the endocrine system and that they just represent three types of signalling.** To illustrate my point and the complexity of it all, here is an intersting aside. Testosterone (a hormone produced in the testes) can act in an endocrine manner (muscle growth) as well as a paracrine manner (sperm production). But it is clear that the testes are a gland that is part of the endocrine system VM //

**Q. How specific should we be when we describe what happens when one inhibitory neuron "cancels out" the activation signal from an excitatory neuron? Should we mention the receptors, and if so how should we relate them to the signal being blocked? I know we sort of covered this in class but it's still kind of confusing.** 

//A. Hmmm... first of all the main thing to understand is how a neurotransmitter released form a pre-synaptic neuron passes into the synaptic cleft and binds to specific receptors on a post-synaptic neuron (or muscle/gland cell). As a result of binding, sodium channels are opened and an action potential can be generated. In terms of explaining the effects of inhibitory or excitory neurons, you do not need to explain their interaction in any detail, just that they would cancel each other out and therefore there would NOT be a stimulus large enough to produce an action potential in the post-synaptic neuron (if there was one of each let's say). VM //




 * Q. I was just going through the course notes questions regarding signal transduction, and I have one question. Is the reason that protein hormone responses are faster than the steroid hormone responses because of the time it takes to produce a polypeptide via transcription and translation? That seems logical...I'm not quite sure if that's the only reason though :-P **

//A. By and large the steroid hormone takes relatively longer to have an effect than non-steroid hormones for the reason you have said. Also, non-steroids tend to through the second messenger system have a more amplified effect, a number of different things can be evoked, so that the cell response may also occur quicker this way. It's not a big deal about which is quicker, more important that you are aware of the relatively slow, longer lasting effect of hormones (endocrine system) compared to the electrical impulse/neurotranmitter effects of the nervous system. VM //

**Q. What is the main difference between a G Protein, a secondary messenger, and a relay molecule?**

//A. This is a tough one and I don't think you really need to know this level of detail. I'll give it a go. Again, depending on the source of information, you will find differences between how these three terms are all related. In relation to signal transduction, relay molecules are those involved in the signal transduction pathway, ie after the hormone-receptor complex has formed up to but not including the final molecule that is produced. So, this means that G-proteins and second messengers are examples of relay molecules. Second messenger systems (there appear to be three types, one of which is cAMP) involve relay molecules that tend to have an amplified effect, ie they stimulate a number of other relay molecules as a result of the initial hormone-receptor interaction. Whether G-proteins are an actual second messenger, I am not sure but I don't think they are (some textbooks say they are). They are certainly part of signal transduction for non-steroid hormones because they are the relay molecule that converts the initial hormone-receptor interaction which then leads to the stimulus of a second messenger system. So, I think the important thing here is that you know all are part of signal transduction in the form of being relay molecules. VM //

**Q. I know we mentioned how peptide hormones are water soluble and can therefore travel in the blood to their target cell without the aid of specific plasma carrier proteins. Except I read somewhere that non-steroid hormones also bind to specific carrier proteins which prevents them from being denatured by plasma proteases in the bloodstream. Would you say it would be beneficial to know this or should we just be aware that peptide hormones can travel in the bloodstream without the aid of carrier proteins as they are water soluble?**

//A. It is probably getting into too much fine detail knowing about the transport of proteins in the blood plasma. The main thing is that you are clear on the water-soluble nature of peptide based hormones and the water-insoluble nature of steroid hormones and how this relates to the ability to pass across plasma membranes and therefore the interactions with receptors on target cells. VM //

//A. An interesting question. The colours you see during autumn are the result of pigments that are present in the leaves already. Normally, the chlorophyll would be masking these pigments but as autumn arrives the daylight hours decreases. This results in a reduction in photosynthesis but primarily a reduction in the production of chlorophyll. So, yes the light intensity and duration of light is influencing this process. The plants are preparing for winter, colder temperatures and rely on the stored sugars for energy during this period of minimal photosynthesis. This is my superifical attempt, there is probably more to this though. VM//
 * Q. So i was just a little curious, as it is Autumn now and all the leaves are turning red and orange. I was just wondering if you could explain the reason behind this in Biological terms, does this relate to the amount of light the plants recieve? Or the pigments that are absorbing the light which are becoming dominant or something-or-other? **

<span style="COLOR: rgb(241,14,89)"><span style="COLOR: rgb(225,5,86)">**Q. As this is a frequently asked question… can we sing you our fabulous song in class tomorrow <span style="COLOR: rgb(225,5,86)">!? ** <span style="COLOR: rgb(225,5,86)">**? (if yes.. voy..start practicing your guitar-ing skills!)**

//<span style="COLOR: rgb(23,6,106)">A. I would luv us to be able to share in the joyous singing of your song on respiration but you must ensure that the time I set aside for it is not compromised as tomorrow's lesson unfolds. VM // <span style="COLOR: rgb(69,134,227)">

<span style="COLOR: rgb(236,14,207)">**Great Question Tam! one of the best i have seen in ages..** those dates as lessons or just Tuesday 15th? My second question is, while i was doing my daily biology research, i came across peptide hormones and neurotransmitters. When these two signalling molecules bind to receptors, why does the receptor for peptide hormones have an enzyme attached to it in the inside of the cell and the receptor in which neurotransmitters bind to doesn't? ** <span style="COLOR: rgb(19,22,241)">The biol lesson will be on Sunday 13th April from 10.00am to ~1.00pm. There will be no Tuesday 15th April lesson. VM
 * <span style="COLOR: rgb(113,187,244)">Q. Just so i can fit our holiday biol lesson in to my VERY busy schedule, we originally said the lesson would be on Sunday 13th April, but then changed it to Tuesday the 15th April. My point is, are we having both

<span style="COLOR: rgb(166,5,245); FONT-FAMILY: Georgia,serif">This isn't really a question but i didn't know where else to put it.. On the 18th of May, there is a fabulous 4 hour lecturer at Monash that goes over the Biology course and is a great way to revise. It costs $45.50 each (there is a group discount, for 5+ students it is $39.50 each) I went last year for psych, and its great. They have lots of guest speakers, and you also get a pack of notes too. Let me know if you want to come, and bring the money by next friday so i can book.:) Lozz <span style="COLOR: rgb(19,22,241)">I encourage all of you to attend these revision lectures. It is important that you hear explanations from someone else other than me. VM VM you can come too, we can make this a good, fun, educational field trip. and teachers can come for FREE <span style="COLOR: rgb(19,22,241)">It is not important that I come along. But I will (as long as I am available) if you really want me too. Thank you for the invite.VM

<span style="COLOR: rgb(117,10,86)">**Q. I'm a bit confused regarding the different types of ions involved in neuron communication - what is the distinction between the roles played by potassium ions and calcium ions?**

//A. This is a question that has a lot to it. I would be very surprised if you need to know any sort of detail between the role of these two ions. Potassium ions "work" with sodium ions to maintain membrane potential in cells and are the primary ions involved in propogation of an action potential. Calcium ions are more involved with what happens at the axon terminals and release of neurotransmitters, as well as the generation of muscle contraction ( in muscle cells) after stimulation by a motor neuron. VM//


 * Q. I have finished all my 'compare and contrast' sheets. Can you place a link somewhere, so i can print off some more. Thankya.

**// A. No worries. I have placed a link in the "activties" section or you can click on the links here. VM [|compare and contrast template.doc] [|terminology analysis template.doc] //

**Q. Im not quite sure what the second messenger system is or a relay messneger, do you think you could explain them plz thanx :) sar** // A. I have sort of addressed these terms in an earlier question above. The key thing to understand is that a second messenger is a type of relay molecule which and these are part of the signal transduction pathway. Signal transduction is the ordered set of events that occur within the cell from the time a signalling molecule binds to a receptor (on or within the target cell) to the production of a cellular response. cAMP is an example of a second messenger.  These relay molecules are how the stimulus is converted into a response. VM //