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VCE Biology Question Thread
Stick:
--- Quote from: DJALogical on December 27, 2013, 05:51:26 pm ---What is the point of the DNA strands found in chloroplasts?
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The reactions that make up photosynthesis are all dependent on enzymes. As you should already know, enzymes are a type of protein. In some cases, we're going to need protein synthesis to occur rather rapidly in order to keep up normal function. If we relied on nuclear DNA, it'd be a rather inefficient pathway - the DNA would be transcribed in the nucleus, the messenger RNA would have to exit the nucleus and approach a ribosome somewhere in the cytoplasm to be translated and the new protein would then have to be transported through the endoplasmic reticulum to the chloroplast before it could be used to catalyse important photosynthetic reactions. As you can see, having the DNA (and ribosomes) where the resulting protein will be used is very handy - protein synthesis occurs in the chloroplast rather than somewhere else in the cell and it can be used as soon as translation has concluded.
DJA:
Thanks for all the answers guys. Really consolidating my learning.
And on a side note congrats on your 2500th post stick :)
alchemy:
A bit late to the party here, but I'll try ask some questions while I can.
--- Quote from: alondouek on December 25, 2013, 09:43:55 pm ---Biocatalysis is also important because organisms only have a certain amount of energy that they can devote to biological reaction systems, which means that by lowering the required energy input for vital biochemical reactions, the organism's energy input (such as food) can be reduced.
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Can you please explain this again? Lower input=lower input?
--- Quote from: Yacoubb on December 26, 2013, 04:40:05 pm ---Lysosomes are basically membrane-bound sacs that contain digestive enzymes called lysosymes. These lysozymes are secreted, the lysozymes break down the matter taken up by the cell, and the lysozyme, an enzyme, is neither used up nor consumed by this catabolic reaction. So essentially, no, the lysosomes are not destroyed in this instant.
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So when lysosomes ‘recycle’ mitochondria they aren’t destroyed in that process as well, right? What happens to these hydrolytic enzymes (lysozymes) once they’ve done their job of recycling? Also, why would an organelle, such as mitochondria, be recycled by these enzymes?
psyxwar:
--- Quote from: Sheldon Cooper on December 27, 2013, 09:00:03 pm ---A bit late to the party here, but I'll try ask some questions while I can.
Can you please explain this again? Lower input=lower input?
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needing less energy to drive metabolism = animal does not need to eat as much to survive
vox nihili:
--- Quote from: Sheldon Cooper on December 27, 2013, 09:00:03 pm ---So when lysosomes ‘recycle’ mitochondria they aren’t destroyed in that process as well, right? What happens to these hydrolytic enzymes (lysozymes) once they’ve done their job of recycling? Also, why would an organelle, such as mitochondria, be recycled by these enzymes?
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Whether or not the lysosomes are destroyed is irrelevant really. In some instances their membranes will be completely voided (so yes, destroyed), others not so much. Mitochondria are recycled because they get, for want of a better way to explain it, get tired and a bit buggered essentially. Like anything, there's wear and tear on the mitochondria, so they need to be replaced.
The enzymes themselves may very well be broken down, or go onto recycling more things. Quite often they will be broken down though, or can be degraded or deactivated by other cell processes. They're all very nitpicky questions, particular about what happens with the enzymes and I daresay there's are questions we don't really yet have definitive answers to.
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