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You may know that your body is made up of cells (trillions and trillions of them). You may also know that the reason you need to eat food such as veggies is so that you have the energy to do things like play sports, study, walk, and even breathe. But what exactly happens in your body to turn the food energy stored in broccoli into a form that your body can use? And how does energy end up stored in the broccoli to begin with, anyway? The answers to these questions have a lot to do with two important organelles: mitochondria and chloroplasts. Chloroplasts are organelles found in the broccoli's cells, along with those of other plants and algae. They capture light energy and store it as fuel molecules in the plant's tissues. Mitochondria are found inside of your cells, along with the cells of plants. They convert the energy stored in molecules from the broccoli (or other fuel molecules) into a form the cell can use. Let's take a closer look at these two very important organelles. Chloroplasts Chloroplasts are found only in plants and photosynthetic algae. (Humans and other animals do not have chloroplasts.) The chloroplast's job is to carry out a process called photosynthesis. In photosynthesis, light energy is collected and used to build sugars from carbon dioxide. The sugars produced in photosynthesis may be used by the plant cell, or may be consumed by animals that eat the plant, such as humans. The energy contained in these sugars is harvested through a process called cellular respiration, which happens in the mitochondria of both plant and animal cells. Chloroplasts are disc-shaped organelles found in the cytosol of a cell. They have outer and inner membranes with an intermembrane space between them. If you passed through the two layers of membrane and reached the space in the center, you’d find that it contained membrane discs known as thylakoids, arranged in interconnected stacks called grana (singular, granum). The membrane of a thylakoid disc contains light-harvesting complexes that include chlorophyll, a pigment that gives plants their green color. Thylakoid discs are hollow, and the space inside a disc is called the thylakoid space or lumen, while the fluid surrounding the thylakoids is called the stroma. You can learn more about chloroplasts, chlorophyll, and photosynthesis in the photosynthesis topic section. Mitochondria Mitochondria (singular, mitochondrion) are often called the powerhouses or energy factories of the cell. Their job is to make a steady supply of adenosine triphosphate (ATP), the cell’s main energy-carrying molecule. The process of making ATP using chemical energy from fuels such as sugars is called cellular respiration, and many of its steps happen inside the mitochondria. The mitochondria are suspended in the jelly-like cytosol of the cell. They are oval-shaped and have two membranes: an outer one, surrounding the whole organelle, and an inner one, with many inward protrusions called cristae that increase surface area. #Mitochondria #Chloroplast #biology #CircularChromosome
