Nursing Preparation Study Guide

Nursing Preparation Study Guide Most proteins are synthesized by ribosomes in the rough endoplasmic reticulum (RER). Biosynthesis, an enzyme-catalyzed process, is the production of complex molecules within living organisms, also known as protein translation, or cells. Cells use their ribosomes to bind messenger RNA and transfer RNA together to manufacture polypeptides and proteins. The proteins created can be found alone or in groups within the cytoplasm and the RER. During the synthesizing process, some proteins are transported into the rough endoplasmic reticulum (RER). Other proteins get transported to and processed by the Golgi apparatus. When a transport vesicle carries a newly synthesized protein or glycoprotein that is destined for export from the cell, it travels from the ER to an organelle that resembles a stack of plates. This organelle, the Golgi apparatus , typically consists of five or six flattened membranous discs called cisternae. The Golgi apparatus has three major functions: (1) to modify and package secretions, such as enzymes, for release through exocytosis, (2) to renew or modify the plasma membrane; and (3) to package special enzymes within vesicles for use in the cytoplasm. The ER and Golgi apparatus can be thought of as the “membrane protein synthesis compartment” and the “membrane protein processing compartment,” respectively. There is a semi-constant flux of proteins through these compartments. Some proteins that are made in the cytoplasm contain structural features, which target them for transport into mitochondria or the nucleus. Some mitochondrial proteins are made inside mitochondria and are coded by mitochondrial DNA. Extracellular and cell surface proteins destined to be degraded can move back into intracellular compartments with lysosomes, where the proteins are broken down to their individual amino acids. The degradation of some membrane proteins begins at the cell surface by secretases. Proteins that function in the cytoplasm are often degraded by proteasomes. Other cellular processes include: • Active and passive transport: The movement of molecules into and out of cells; for example, diffusion is the movement from high concentration to low concentration. • Phagocytosis: The process whereby cells “eat” other cells, internal components, or microbial invaders. • Adhesion: The holding together of cells and tissues. • Reproduction: This is achieved by the combination of sperm made in the testicle and the egg made in the ovary. A new cell embryo is formed if the sperm is able to break through the hard outer shell of the egg. If an embryo is produced, it will continue to grow. In humans, the embryo will grow to full size in 40 weeks. • Cell movement: This includes chemotaxis, contraction, cilia, and flagella. • Cell signaling: The regulation of cell behavior by signals from the outside. Includes DNA repair and cell death. • Metabolism: All chemical processes in the body, such as glycolysis, respiration, photosynthesis, and transcription. • Gene: A functional unit of heredity. • Cilia: Motile microtubule-containing structures of eukaryotes.

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