Anatomy & Physiology I and II

Anatomy & Physiology Study Guide

©2018 Achieve Test Prep Page 28 of 367 is a general term for the material located between the plasma membrane and the membrane surrounding the nucleus. Cytoplasm, a jelly-like material, contains more proteins than extracellular fluid. The cytoplasm contains cytosol and organelles. Cytosol is the intracellular fluid that contains dissolved nutrients, ions, soluble and insoluble proteins, and waste products. Organelles are “little organs” or structures within the cytosol that perform specific functions within the cell. Organelles perform most of the tasks that keep a cell alive and functional. These tasks are related to cell structure, growth, maintenance, and metabolism. Cytoskeleton The cytoskeleton provides an internal protein framework that functions as a skeleton for the cell and gives the cytoplasm strength and flexibility. Microfilaments The smallest of the cytoskeletal elements are the microfilaments (diameter less than 6 nm). They have three major functions: (1) anchor the cytoskeleton to integral proteins of the plasma membrane, (2) contribute to the consistency of the cytoplasm, and (3) produce active cell movement of a portion or to change the shape of the entire cell. Vesicular Transport In vesicular transport, materials move in or out of the cell in vesicles. Vesicles are small membranous sacs that form at, or fuse with, the plasma membrane. Because tiny droplets of fluid and solutes are transported rather than single molecules, this process is also known as bulk transport. The two major categories of vesicular transport are endocytosis and exocytosis. Endocytosis Extracellular materials can be packaged in vesicles at the cell surface and imported into the cell. This process, called endocytosis, involves relatively large volumes of extracellular material and requires energy in the form of ATP. The two types of endocytosis are pinocytosis and phagocytosis. Both are active processes that require energy in the form of ATP. • Pinocytosis, or “cell drinking,” is the formation of endosomes filled with extracellular fluid. The target is the fluid contents in general. • Phagocytosis, or “cell eating,” produces phagosomes containing solid objects that may be as large as the cell itself. In this process, cytoplasmic extensions called pseudopodia surround the object, and their membranes fuse to form a phagosome. This vesicle then fuses with many lysosomes, and its contents are digested by lysosomal enzymes. Exocytosis Exocytosis is the reverse of endocytosis. In exocytosis, a vesicle created inside the cell fuses with the plasma membrane and discharges its contents into the extracellular environment. The ejected material may be mucins, hormones, or waste products. Cytoplasm