Expert: John Locke - 9/18/2010

Question
What kind of cells would need a lot of mitonchondria to carry out a lot of cellular respiration? Cells like muscle cells??
What part of the plant are there more chloroplasts? roots or leaves? why?

Answer
Thanks for using AllExperts. Mitochondria are subcellular structures--known as organelles--that are responsible for conversion of simple molecules of sugar, protein, and fat into a common energy currency of the cell. In the case of animals, a molecule called adenosine triphosphate (ATP) is the common energy carrier for the entire organism: every cell and every cellular process is capable of using ATP as a source of energy. Since mitochondria produce ATP, and since cells generally make most of the ATP that they need, mitochondria can serve as a basic indicator of the cell's energy production: the more mitochondria in a cell, the higher the energy production of that cell.

That provides an answer for your first question. In fact, you answered your own question. Cells that carry out a lot of cellular respiration are the cells that require lots of mitochondria. Of course, this ultimately means that cells that have a high energy turnover must have lots of mitochondria. Specifically, skeletal muscle cells, cardiac muscle cells, and neurons in the brain have high concentrations of mitochondria because they all have high energy turnover.

Since chloroplasts are the organelles responsible for photosynthesis, and since photosynthesis requires sunlight for completion, chloroplasts logically would be found in the parts of the plants with the most exposure to sunlight. Leaves have the most exposure to sunlight, and greatest concentration of chloroplasts. In fact, leaves are specialized organs specifically for photosynthesis. Part of this adaptation is a high concentration of chloroplasts.