Welcome back to What a Plant Knows. This week we're going to talk about what a plant smells. Now, plants smell. That's not too surprising to you because plants obviously give off odors that we smell and we're attracted to. But what's surprising is that plants smell, in that they sense their own odors and even the odors of their neighbors. Plants know when their fruit is ripe, because they can smell it. They know when their neighbor is being eaten by hungry bugs, because they can smell it. There are even plants that can differentiate between the smell of a tomato and the smell of wheat. Now unlike the large spectrum of visual input that we learned about last week that a plant experiences, if you remember we learned that plants can see or respond to light that we're blind to, such as UV light or far red light. And that they have a larger number of photo receptors than people have. When it comes to smell, a plant's range is rather limited and it is much less than what humans have. But a plant's sense of smell is still highly sensitive. And it communicates a great deal of information about both the environment and the plant's physiology. But before we continue with understanding what plants smell, I want to go over some basic cell biology that may help us further understand the concepts that we'll be talking about both in this lecture and in future lectures. Now if you have a good biology background, especially a good cell biology background, you're welcome to skip ahead a few slides or you could just stay with us as we go over this review of plant cell biology. So, cells are the smallest basic unit of life. It's the smallest part of life that is independent, that can divide and transfer genetic material to further generations. With, independent of any other cells touching them necessarily. While all cells have similar characteristics. Each cell type is also unique, which then gives each type of tissue its own characteristics. For example, liver cells make a liver. Insulin-making cells make the pancreas. Skin cells protect our bodies. Just like a leaf cell in a plant is different than a root cell. now to see most cells, though, we have to use microscopes, and that's how we study them. There are very few cells that we can see with the naked eye, one of them being, for example a frog egg. But again, for most cells we need to use microscopes, and for eukaryotic cells, for plants cells and human and animal cells, it's enough to use a light microscope. With these we can see both the cells and the parts within the cell. Oh, historically, the first microscope built was in the 17th century. And the first cells detected were in cork, a plant. Robert Hook built the first microscope. It could magnify tissues about 15 times. And he, this is actually similar to what he was seeing, and he noticed that there were, what he called, chamber cells in the cork. He didn't understand or comprehend that all the big organisms were made of cells. He thought it was specific for cork. Today we now know though that all living organisms are made of cells. Now I want to go into a little bit more detail about cell structure. All cells, whether plant cells or animal cells, are basically like a bag of liquid where you have an outer membrane which encloses a soluble interior. You could imagine it as a balloon. Within the inside of the cell, we can find the nucleus which has the DNA, the hereditary material. Other small parts of the cell, which are called organelles, such as the mitochondria, which makes energy. different types of membrane structures within the cell, which aren't so important for this class. so a cell is the outer membrane, which is called the plasma membrane and the inner parts, which are called the cytoplasm. This is to both for a animal cell and for a plant cell. But a plant cell has a few other organelles. For example all plant cells have outside of the plasma membrane, a structure which we call the cell wall. The cell wall is what gives a plant its structure in lieu of a bony skeleton. And all cells are, all plant cells are first a cell wall, which bounds the cell membrane, which holds the cytoplasm. Now, the membrane and the cytoplasm together, we call a protoplast. So a plant cell is actually a cell wall, plus the balloon, the protoplast within it. Plant cells also contain the few other organelles. One being the plastids, of which the best example, is the chloroplast. This is the organelle which makes energy through photosynthesis. Turning sunlight into energy. And there's another organelle, which we're going to talk about a bit later in the, in this lecture series, called the central vacuole. This is a balloon, within a balloon. That is basically a type of warehouse, for the plant. we are not going to go into too many details about the central vacuole now, just know that it exists. I just want to talk a few minutes about, what a membrane is. A membrane is basically a phospholipid. It's a type of fat which has a polar side, a part that has a charge, which is next to the soluble part either outside or inside the cell, and a lipid which is apolar, which is hydrophobic, which doesn't allow water to pass, which is on the inside of the membrane. Or these phospholipids associate together, and they form a protective covering which encases the entire cell. We see things that are similar to membranes formed, for example, by fat on chicken soup, or when a soap bubble is made, these are, again, hydrophobic molecules which associate into small circles, into small balloons. Within the membranes, there can be different types of proteins. Now the ty-, different types of proteins often characterize what type of cell there are. But among the types of proteins, we'll find that there are proteins which go from one side of the cell, from the inside, to the outside through the membrane. These are proteins that are often involved in signaling information from inside to the out. We'll see an example of this in a few more minutes. There are proteins which can be bound only on the inside. And there are proteins which could be bound only on the outside. There are also other examples of molecules which could be found within the membranes, for example, such as cholesterol in animals. but all membranes basically have this same structure. So, what I want you to do though before we go on, is to look at this animal cell. You can actually see some, learn a bit more about the different organelles online. And fill in the blanks, of what are the different organelles that we would also find, in a plant cell.
