Information on Plant Cells

Plant cells are eukaryotic cells. As living organisms go, a eukaryote versus a prokaryote has cells with a more sophisticated internal anatomy. In a eukaryotic cell, there is an array of structures termed organelles. These are subcellular features, including a nucleus and various other components that make the cell functional. In comparison, bacterial cells are classified as prokaryotic. The prokaryotic cell lacks most of the internal structure, including the well-defined nucleus present in eukaryotic cells. Plant and animal cells share many characteristics, but at least two features distinguish plant cells. They are the cell wall and the chloroplast.

Cell Wall

Plant cells---in contrast to animal cells---have what's called a cell wall. There are frequent mistaken references to animal cells having cell walls. Both animal and plant cells do have cell membranes, but these are not the same structures as the cell wall. The cell membrane is composed of lipids and proteins in a complex arrangement. The cell wall of a plant, on the other hand, is generally a more rigid structure composed of cellulose, a polymer of the sugar glucose. To the inward side of the plant cell wall is the cell membrane. And contained within the plant's cell membrane are a number of so-called organelles.

Chloroplasts

Chloroplasts are plant cell organelles that are specialized for carrying out photosynthesis. They have an internal structure of their own, including the ability to reproduce themselves within the cell. Chloroplasts owe their green color to the pigment chlorophyll. Chlorophyll is a complex molecule that shares some traits with the hemoglobin molecule in animals. Whereas the key functional metallic element in hemoglobin is iron, that in chlorophyll is magnesium.

Nucleus and Endoplasmic Reticulum

In a sense, the nucleus is the brains of the plant cell operation. In the plant cell (and in animal cells) the nucleus coordinates the cell's various functions, including protein synthesis, metabolism and reproduction. Although considered a separate plant cell organelle, the endoplasmic reticulum (ER) is a membranous system of convoluted folds that extends out from the cell's nucleus. The ER is actually contiguous with the outer envelope of the nucleus. And the ER---in concert with the nucleus---mediates a wide range of chemical processes vital to the cell.

Ribosomes

Ribosomes are especially small and numerous plant cell organelles. Their primary function is protein synthesis. The ribosomes are, for the most part, associated with the endoplasmic reticulum. Their numbers and their close association with the ER have led to the term "rough endoplasmic reticulum" because the ribosomes make the ER surface appear rough when viewed through the microscope. (ER that lacks ribosomes is termed smooth ER.)

Golgi Apparatus

The Golgi apparatus (GA for short) is another organelle with a folded- or pleated-looking structure reminiscent of that of the endoplasmic reticulum. The folds are really more like flattened sacs stacked on top of one another. The GA serves to send, receive and refine chemical components processed in other organelles like the endoplasmic reticulum.

Specialized Plant Cells

Depending upon the type of plant, plant cells can become specialized for different functions. Just as higher animals have organs, plants feature organs of three major types---roots, stems and leaves. Within these are various tissue types, including what are termed xylem and phloem, for example. In vascular plants, some cells develop into water-conducting cells. Collectively they form a tissue called the xylem. Other cells differentiate into cells that conduct food that the plant manufactures in the form of glucose. These cells are called phloem cells, and the tissue they form is called phloem.

References

• Florida State University, Plant Cell Structure