Photosynthesis

Organisms can be classified based on how they obtain energy. There are autotrophs, organisms that manufacture their own energy, and heterotrophs, organisms that can't make their own energy. Animals, like humans, can't obtain their energy on their own, so they eat autotrpohs or heterotrophs that eat autotrophs. Confusing? Yeah, a little. Think of it like this, we eat steak, which comes from cows. But cows don't eat other cows, they eat grass. Grass is an autotroph, thus the food chain cycle is shown. But, how does a plant like grass obtain its energy? Plants get their energy through a process called photosynthesis. Photosynthesis involves a complex series of chemical reactions, even using a by product of a previous reaction. A plant releases oxygen as a byproduct in an early reaction, but need it in a later one. Back on topic, photosynthesis uses light as its fuel. A plant absorbs sunlight through chloroplasts. The light reactions take place in the thylakoids. To clear things up, the chloroplasts have a membrane surrounding three things. These are the thylakoids, grana and stroma. Thylakoids stack to form a grana, and is surrounded by a solution called the stroma. Moving on, plants are often picky with the light they absorb. As you probably know, the visible light spectrum includes red, orange, yellow, green, blue, indigo and violet. But, why are plants green most of the time? A part of the chloroplast is the chlorophyll. There are several types , but the two important ones are chlorophyll a and chlorophyll b. These are pigments, basically a compound that absorbs light. Chlorophyll a absorbs red to yellow light in the color spectrum, while chlorophyll b absorbs blue to violet light. This is why plants typically appear green. This is only the first stage in the entire process, but I'll get to electron transfer, chemiosmosis, and the different photo systems in my next post.

The Discovery of Cells

Cells are covered in many of the textbooks given to students in middle school and high school. But, who was it that discovered cells? The first observation of cells is attributed to an English scientist named Robert Hooke. He used a microscope to examine a thin slice of cork in 1665. He noticed that the cells appeared in "little boxes". You and me know that plant cells are the "little boxes" Hooke observed, but Robert was the first person to see them. He looked at carrots, ferns, and the stems of elder trees, and all of them displayed a similar formation of cells. Pattern? He was looking only at plant cells. The first person to observe living cells was a Dutch microscope maker named Anton van Leeuwenhoek. After 150 years, scientists began to organize the observations begun by Hooke and van Leeuwenhoek. They formed the cell theory. The theory has three parts: 1. All living things are composed of one or more cells. 2. Cells are the basic units of structure and function in an organism and 3. Cells only come from the reproduction of existing cells. The evidence to support this theory was provided by a trio of German scientists. In 1838, the botanist Matthias Schleiden concluded that all plants are made of cells. A year later, zoologist Theodor Schwann made the same conclusion about animals. Finally, in 1855, a physician named Rudolf Virchow reasoned that cells only come from existing ones. Over the years, modern scientists have gathered a lot of additional information that strongly supports the cell theory.