Chapter+3+Cell+Structure+MV

Molly Vaughn August 22, 2008 Human Biology

Chapter 3. Cell Structure. 1. What does the cell theory state? - Cell theory is one of the major theories of biology; states that all organisms are made up of cells and cells come only from preexisting cells. 2. Why are cells so tiny? - Cells are so tiny because they don’t need a large surface area for things to enter and exit due to the small volume that they have. 3. What are the three main parts of a eukaryotic cell? - The three main parts of a eukaryotic cell are a nucleus, plasma membrane, and cytoplasm (which contains organelles). 4. Explain how the eukaryotic cell gained mitochondria and chloroplasts. - By engulfing prokaryotic cells, the eukaryotic cell gained mitochondria and chloroplast. A mitochondrion is an organelle that carries on cellular respiration. Chloroplast is an organelle found only in plant cells that carries on photosynthesis. 5. What are glycoproteins, and what functions do proteins, including glycoproteins, have in the plasma membrane? - Glycoproteins are short chains of sugars that are attached to the outer surface of some protein and lipid molecules. These carbohydrate chains, specific to each cell, help mark it as belonging to a particular individual. Glycoproteins have a special configuration that allows them to act as a receptor for a chemical messenger, such as a hormone. Some plasma membrane proteins form channels through which certain substances can enter cells; others are enzymes that catalyze reactions or carries involved in the passage of molecules through the membrane. 6. What is endocytosis and exocytosis, and how do they occur? - During endocytosis, a portion of the plasma membrane invaginates, or forms a pouch to envelop a substance and fluid. Then, the membrane pinches off to form an endocytic vesicle inside the cell. - During exocytosis, a vesicle fuses with the plasma membrane as secretion occurs. 7. The nucleus, ribosomes, and rough endoplasmic reticulum make what contribution to protein synthesis? - The nucleus is made of chromosomes that contain a DNA molecule and associated with proteins. Also in the nucleus, RNA is produced which are where rRNA joins with the proteins to form the subunits of ribosome. - The nucleus is separated from the cytoplasm by a double membrane known as the nuclear envelope, which is continuous with the endoplasmic reticulum (ER). The nuclear envelope has nuclear pores of sufficient size to permit the passage of ribosomal subunits out of the nucleus and proteins into the nucleus. 8. The endoplasmic reticulum and the Golgi apparatus make what contribution to the processing of proteins? - The endoplasmic reticulum has two portions. Rough ER is studded with ribosomes on the side of the membrane that faces the cytoplasm. Here, proteins are synthesized and enter the ER interior, where processing and modification begin. Some of these proteins are incorporated into membrane, and some are for export. - In the Golgi apparatus proteins and lipids received from the ER are modified. Also, the Golgi apparatus is involved in processing, packaging, and secretion. 9. What is the function of smooth endoplasmic reticulum and lysosomes? - The endoplasmic reticulum forms transport vesicles in which large molecules are transported to other parts of the cell. - Lysosomes are found in all cells of the body but are particularly numerous in white blood cells that engulf disease-causing microbes. When a lysosome fuses with such an endocytic vesicle, its contents are digested by lysosomal enzymes into simpler subunits that then enter the cytoplasm. Even parts of a cell are digested by its own lysosomes. 10. What is the function of the mitochondria? - Mitochondria are often called the powerhouses of the cell because it converts the chemical energy of glucose products into the chemical energy of ATP molecules. In the process, mitochondria use up oxygen and give off carbon dioxide. All of this creates cellular respiration