Chapter Summary1. All life on Earth, including plant life, has a cellular organization. The plant cell shares many characteristics in common with other eukaryotic cells. The plant protoplast includes the cytoplasm with the embedded organelles and nucleus. Within the nucleus is DNA, the genetic blueprint of all cells.
2. The plasma membrane, composed of phospholipids and proteins according to the fluid mosaic model, regulates the passage of materials into and out of the cell. Numerous mitochondria can be found within the cytoplasm; they are the sites of cellular respiration. The endoplasmic reticulum, Golgi apparatus, and microbodies make up an internal membrane system that functions in the synthesizing, packaging, and transporting of materials.
3. Some features of a plant cell are unique. The primary cell wall containing cellulose surrounds a plant protoplast providing protection and support. In certain specialized plant cells, a secondary cell wall, impregnated with the toughening agent lignin, imparts extra strength. Chloroplasts are the site for photosynthesis; they are one of several types of plastids. Other plastids are the food-storing leucoplasts and the pigment-containing chromoplasts. A large central vacuole may take up approximately 90% of the mature plant cell and act as a storage site for many substances.
4. The life of a cell can be described in terms of a cycle. Most cells spend the majority of the time in interphase, a nondividing stage. But at certain times in its life, a cell may undergo division whereby one cell divides into two. Mitosis is the duplication of the nucleus into two exact copies. There are four intergrading stages in mitosis: prophase, metaphase, anaphase, and telophase. The division process is complete when, in the process of cytokinesis, the cytoplasm is split, and two identical daughter cells are formed.
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2003 McGraw-Hill Higher Education