Endosymbiosis question please help... Due tomarrow!?

Question

Consider the mitochondria, chloroplast, and the cytoskeleton. Which of these were acquired by endosymbiosis? Which of these three cellular structures were acquired first, and why is this crucial? What is the evidence that suggests which one was aquired second?

Answer 1

Mitochondria in the animal cell was obtained first. If you remember, these are the powerhouses of the cell, without it you would not have enough energy to drive cellular processes. Therefore, the actuall making and breaking of the cellular components of the cytoskeleton would be difficult.

This would be the same for the cholorplast but for the plant cell.

Answer 2

Okay, well this is a tricky question, mainly because no one really knows for sure what came first and second and how. I learned one theories in consideration though, so i'll use that:

All of those organelles were acquired by endosymbiosis, which is theorized because supposedly eukaryotes evolved from prokaryotes, and prokaryotes don't have any of those 3 fancy organelles. Except the cytoskeleton is really of unknown origin, so they kinda just ASSUME on that one, i think.

The cytoskeleton is actually what is thought to have been taken in first. This was really important because it created a cell that can move on its own and prey on stuff, like other cells, for instance (see how it's all coming together? yeah, neither did i when i read it. I think they just randomly decided this as well, but i'm not sure. that's what the dudes who wrote the book say

So this new predator cell that was created started eating other cells, and eventually the mitochondria was taken in, and later on the chloroplast.

The evidence that suggests which came first between the mitochondria and the chloroplast... hmm... well, one piece of logical evidence is that pretty much every cell that has a chloroplast has mitochonria, which shows that the mitochondria might have come later on as some cells that already had them took in chloroplasts. ---- In other words, with the addition of mitochondria, you've got your basic eukaryotic cell. And then since the cells with chloroplasts also have mitochondria, scientists can sorta tell that the mitochondria was already there before, otherwise every cell with mitochondria would have chloroplasts.

Hope it's easy enough to understand (by which i mean, hope you don't get TOO big of a headache reading this. I know I would..). Also, if you still don't quite trust this, you can look it up in your bio book. it should be in the chapter about protists and the "dawn of eukarya", no matter which book you're using

Answer 3

The current theory is that proteobacteria formed mitochondria. Some of the cells with mitochondria then acquired photosynthetic cyanobacteria (the chloroplasts). All eukaryotic cells require mitochondria. The mitochondria use oxygen (which would otherwise be toxic to the cell) and generate energy (in the form of ATP) which the cell can use. Chloroplasts are used to generate a food source (sugar) using sunlight - however this food source could not be used effectively by eukaryotes if mitochondria were not already present.

The cytoskeleton was not acquired by endocytosis.