Let's look closer at the organelle called the nucleus.
"See? The nucleus is just a place to put the DNA. Everything that works on the DNA lives here, too. Like Polly. Polly's cousins that live inside Ishy, they just swim around anywhere inside, because Ishy's just not very organized. RNA molecules, like RayNA, whom you haven't met yet, are born inside the nucleus, but then they leave through the nuclear pores. The pores are like doorways so things that need to come and go, can. But, the DNA doesn't really need to go anywhere, so it stays put. Did you notice that there are several chromosomes? And did you notice that there are two of each one? Rudy got one chromosome from his mother and one from his father. That's just like you!
"Just one more thing to look at before we go find Leanda the leaf cell. Let's look at the endoplasmic reticulum. Those are pretty big words, so scientists usually call it the ER. The ER is just a ribbon-like membrane that is dotted with ribosomes.
"RayNA will show you more about ribosomes. Let's go on up to meet Leanda, the leaf cell. So Long Rudy!! And Thanks!
"Don't get up Leanda. We're just looking at the differences between you and Rudy. Do you mind?
"No, No, I don't mind. As long as you don't block my sunshine!"
"Maybe you noticed that there is one type of organelle inside Leanda that isn't inside Rudy. Its called the chloroplast. That's what I am. And like I mentioned before, my job is to turn sunshine into sugar. Take a look!
"Don't you wish scientists would use English? Grana are just the stacks of stuff that contains chlorophyll. Chlorophyll is what makes plants green. The chlorophyll absorbs energy from sunlight and passes that energy into the stroma. The stroma contains enzymes that can turn that energy into sugar and oxygen from water and carbon dioxide.
SUNLIGHT + CO2 + H2O = SUGAR + O2
"You know how good sugar is, but even better is the oxygen that plants give you to breath. You, in turn, exhale carbon dioxide for plants to use to make more oxygen.
"If you noticed, we chloroplasts also have our own DNA. It only codes for a couple of proteins, but is very important for us to do our jobs.
"Both Leanda and Rudy have exactly the same DNA, but they don't look alike or act alike! Do you know why? Its because they don't have the same genes turned on. Its like when your family goes to a restaurant. You all order from the same menu, but you end up with different meals. The DNA in any one cell is identical to the DNA of every other cell in an organism, but some of the genes are turned on and some are turned off. The DNA can be thought of as the menu, and each cell orders the genes it wants. That's how different cells can look and act differently.
"Why don't we go see some animal cells. They are a little different from plant cells, as you'll find.
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