Schuams pg 294

[Mstoothlady2012]

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Okay so on that page it explains about how there are two types of hormones, one that works through second messenger (eg insulin) and another that can go directly to the nucleus and induce transcription of specific gene (eg steroid hormones).

The paragraph under the pic says "The second messenger often activates enzymes that are part of a system whose final step produces the actual end action of the hormone. Generally, this mechanism for hormone action is faster than the mechanism involving modulation of the genome". I read this over and over but doesn't make sense to me. I learned in my biochem class that second messenger system is slow b/c it has to go through so many steps but long lasting. Whereas the direct transcriptional step is pretty fast but doesn't last too long. I am guessing that when they say "modulation of genome" they are talking about those other types of hormones that can directly enter the nucleus and start the transcription.

What am I missing? Thanks!

 

[Thundercatz]

I think initially the 2nd messenger system may be slower, but once it is started it can induce a chain of reactions. I hope that helps. hehehe

 

[Mstoothlady2012]

I think initially the 2nd messenger system may be slower, but once it is started it can induce a chain of reactions. I hope that helps. hehehe

hmm... that doesn't make sense to me. I thought the chain of reactions itself is what slows down the whole system.

 

[Thundercatz]

hmm... that doesn't make sense to me. I thought the chain of reactions itself is what slows down the whole system.

Well, think about it this way. It takes one steroid to a single job, but an insulin can induce many workers via the 2nd messenger system to do the job. Which is faster? One member to finish a job or mulitple workers?

 

[Mstoothlady2012]

Well, think about it this way. It takes one steroid to a single job, but an insulin can induce many workers via the 2nd messenger system to do the job. Which is faster? One member to finish a job or mulitple workers?

This is how I think about it. 2 people have to go to work. 1 owns a car so can drive straight to the work place. The second person doesn't own a car and have to take 3 different buses in order to get there. Yes more transportation vehicles involved for the second person but it still takes him longer to get there.

 

[Thundercatz]

This is how I think about it. 2 people have to go to work. 1 owns a car so can drive straight to the work place. The second person doesn't own a car and have to take 3 different buses in order to get there. Yes more transportation vehicles involved for the second person but it still takes him longer to get there.

Hehe... But your analogy is flawed because that isnt how a 2nd messenger system works. Insulin is a peptide hormone therefore it is able to move freely through the blood but not the cell membrane, so it cant reach the target cell (effector). Insulin will then bind to a receptor on the membrane and activate the 2nd messenger system.

The 2nd messenger system can then activate/deactivate the ions channels and allow certain ions into the membrane and create a chain reaction that amplifies the effect of the insulin hormone.

The insulin hormone isnt taking different routes/methods per say as in your analogy. Its sending many workers to get the job done.

 

[jojo12]

From what I understand, peptide hormones active the 2nd messenger pathway, which then affects the activity of enzymes, proteins right away. On the other hand, steroid hormone must first affect the DNA transcription and consequently synthesis of proteins, which will then affect their activity.

 

[DRHOYA]

Mstooth. Think of it this way. In the case of insulin, it will bind to a receptor on the cell surface and initate a second messenger system. Well, one may say that this is slower due to the number of interactions going on. However, think of it in terms of end result/product. The insulin sets of a CASCADE of effects within the cytoplasm that result in its function to lower blood glucose. Also, these cascades resulting from the second messenger can be turned off, or stopped, inhibited etc..... On the other hand a steroid hormone that flies right into the nucleus, effects gene transcription. When that happens, the effect is long lasting compared to the short burst of action of the second messenger cascade. Hope that helps.

 

[Mstoothlady2012]

From what I understand, peptide hormones active the 2nd messenger pathway, which then affects the activity of enzymes, proteins right away. On the other hand, steroid hormone must first affect the DNA transcription and consequently synthesis of proteins, which will then affect their activity.

Ahh!! there is my answer thank you so much!!! 🙂

 

[Mstoothlady2012]

Mstooth. Think of it this way. In the case of insulin, it will bind to a receptor on the cell surface and initate a second messenger system. Well, one may say that this is slower due to the number of interactions going on. However, think of it in terms of end result/product. The insulin sets of a CASCADE of effects within the cytoplasm that result in its function to lower blood glucose. Also, these cascades resulting from the second messenger can be turned off, or stopped, inhibited etc..... On the other hand a steroid hormone that flies right into the nucleus, effects gene transcription. When that happens, the effect is long lasting compared to the short burst of action of the second messenger cascade. Hope that helps.

Drhoya, I understand both pathways and I also know that steroid goes into the nucleus and initiates transcription and its effect is longer than the peptide. What I didn't understand is why it takes longer for steroid than peptide. All this time I kept on thinking about the pathway. But what we have to think about is the end result. Steroid hormones have to initiate transcription, go through translation and then you get the protein. Wheres for peptide hormones second messenger can phosphorylate the proteins right away, so its faster.