LaboratoryExercise4BasicCellCharacteristics..docxVIP

Laboratory Exercise #4Basic Cell CharacteristicsI. IntroductionThe cell is the basic unit of life. All organisms are composed of cells. Some organisms are made up of only one cell. These are referred to as unicellular organisms, such as bacteria and some protistans. Most organisms consist of many cells and these are referred to as multicellular organisms.There are two fundamentally different kinds of cells: prokaryotic cells and eukaryotic cells. Prokaryotes have a very simple structure. The prokaryotic cell tends to be smaller than eukaryotic cells. They lack a true membrane-bound nucleus and have no discrete membrane bound organelles. Bacteria are typical prokaryotes. They come in many shapes and sizes (Fig. 4-1). The eukaryotic cell is characterized by the presence of a nucleus that is separated from the rest of the cell by a nuclear membrane. Additionally, the eukaryotic cell usually contains other membrane-bound organelles. Both plant and animal cells are eukaryotic, but they differ from one another in three specific ways. First, plant cells have a cell wall, while animal cells do not. Second, plant cells have organelles called plastids. The most well known plastid is the chloroplast. The chloroplast is the site of photosynthesis in plant cells and is the organelle where the pigment chlorophyll is stored. Finally, plant cells have large central vacuoles. All three of these plant structures are readily seen using the light microscope.One characteristic that all cells have in common is a plasma membrane. This is a very dynamic structure that not only defines the boundaries of cell, but also selectively regulates the transport of material into and out of the cell. The plasma membrane is composed of a phospholipids bi-layer with many proteins, glycoproteins, and carbohydrates embedded within it. Substances are moved across the plasma membrane by two different methods of transport. The first is passive transport, which requires no energy expendit