Plant Cells

1. Describe the structure of a generalized eukaryotic plant cell. Indicate the ways in which a nonphotosynthetic prokaryotic cell would differ in structure from this generalized eukaryotic plant cell.

Plants are unique among the eukaryotes. The interiors of plant cells, like all eukaryotic cells, contain numerous organelles, which are membrane bounded structures that close off compartments within which multiple biochemical processes can proceed simultaneously and independently. The cell membrane of the plant cell has a phospholipid bilayer. Plant cells often have a central vacuole, which is a large membrane-bounded sac that stores proteins, pigments, and waste materials. The central vacuole, in most mature plants, occupies a major portion of the internal volume of the cell and has a phospholipid bilayer. Inside the nucleus, an organelle with a phospholipid bilayer that regulates cell activity, the DNA is wrapped tightly around proteins and packaged into compacts units called chromosomes. The DNA is double stranded. Also inside the nucleus is the nucleolus that is made of protein and ribosomal DNA (rDNA) sequences of chromosomes. Plant cells also have a cytoskeleton, an internal protein scaffold that supports the cell. The cytoskeleton is composed of microtubules and microfilaments. Microfilaments are solid rods made of globular proteins called actin. Microtubules are straight, hollow cylinders are found throughout the cytoplasm of all eukaryotic cells and carry out a variety of functions, ranging from transport to structural support. This type of eukaryotic cell also contains a strong cell wall composed of cellulose or chitin fibers embedded in a matrix of other polysaccharides and proteins. Furthermore, a generalized eukaryotic plant cells also contains cytoplasm, which is a fluid with dissolved substances, and mitochondria, which produce cellular energy (ATP) and has folding convolutions called cristaes. In the plant cell, there are also ribosomes which have two subunits and are made up of 60% RNA and 40% protein. The most important characteristic of plants is their ability to photosynthesize, in effect, to make their own food by converting light energy into chemical energy. This process is carried out in specialized organelles called chloroplasts which contain stroma, a cytoplasm-like fluid that contains DNA and ribosomes, and granas, which are stacks of thylakoids. The endoplasmic reticulum (E.R.) is a network of sacs that manufactures, processes, and transports chemical compounds for use inside and outside of the cell. In plants, the endoplasmic reticulum also connects

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