Golgi Complex

Golgi Complex General description: The Golgi complex was first discovered in 1897 by Italian physician Camillo Golgi. The Golgi complex, also termed as Golgi body is a single membrane bound organelle and part of endomembrane system. Golgi complex characteristics: It consists of five to eight flattened membrane bound sacs called the cisternae. Each stack if cisternae us termed as Golgi stack. The cisternae in Golgi stack vary in number, shape and organization in different cell types. In unicellular flagellates, however, as many as 60 cisternae many combine to make up the Golgi stack. The number of Golgi complexes in a cell varies according to its function. A mammalian cell typically contains 40-100 stacks. In mammalian cells, multiple Golgi stacks are linked together at their edges. Golgi complex structure: Each Golgi stack has two distinct faces: a cis face (or the entry face) and a Trans face (or maturing face). Both cis and trans faces are closely associated with special compartments: the cis Golgi network (CGN) and the trans Golgi network (TGN), respectively. TGN was earlier known as GERL (Golgi apparatus- ER-Lysosome). Proteins and lipids enter the cis Golgi network in vesicular tubular clusters arriving from ER and exit from the trans Golgi network. Both networks are thought to be important for protein sorting. Similarly, proteins exiting from the TGN can either move onward and be sorted according to whether they are destined for lysosomes, secretory vesicles or the cell surface, or to be returned to an earlier compartment. The Golgi apparatus is especially prominent in cells that are specialized for secretion, such as the goblet cells of intestinal epithelium, which secrete large amounts of polysaccharide-rich mucus into the gut. In such cells, usually large secretory vesicles are found on the trans side of the Golgi apparatus. Secretory vesicles form from the TGN , and they release their contents to the cell exterior by exocytosis. The membrane proteins and the lipids in these vesicles provide new components for the cells plasma membrane, while soluble protein and other compounds inside the vesicles are secreted to the extracellular space. Functions of Golgi complex: The Golgi complex is often considered the distribution and shipping department for the cells chemical products. It modifies proteins and lipids that have been built in the ER and prepares them for export outside of the cell or for transport to other location in the cell. Proteins and lipids from the smooth and rough ER bud off in tiny bubble- like vesicles that move through the cytoplasm until reach the Golgi apparatus. The vesicles fuse with the Golgi membranes and release their internally stored molecules into the organelle. Glycosylation of proteins: N-linked oligosaccharide chains on proteins are altered as the proteins pass through the Golgi cisternae en route from the ER. Further modifications of N-linked oligosaccharide in the Golgi apparatus gives two broad classes of N-liked oligosaccharides, the complex oligosaccharides and the high mannose oligosaccharides. High mannose oligosaccharides have no new sugars added to them in the Golgi body. They contain just two N-acetylglucosamines and many mannose residues. Complex oligosaccharides, by contrast, can contain more than the orginal two N-acetylglucosamines as well as a variable number of galactose and sialic acid residues and, in some cases, fucose. Lipid metabolism: In addition to its activities in processing and sorting glycoproteins, the Golgi complex functions in lipid metabolism in particular, in the synthesis of glycoproteins and sphingomyelin. Ceramide, which is synthesized in the ER, is converted either to sphingomyelin or to glycolipid in the Golgi complex. The Golgi complex also acts as a major site of carbohydrate metabolism. In plant cells, it acts as the site where complex polysaccharides of the cell wall are synthesized. Complex cell wall polysaccharides such as hemicelluloses and pectins are synthesized in the Golgi apparatus and then transported in vesicles to the cell surface. In animals, most of glycoaminoglycans of the extracellular matrix are synthesized in the Golgi apparatus.

ACT Reading Tips

ACT Reading Tips The Reading section on the ACT can certainly seem daunting there are long passages to comprehend, as well as complex questions to answer. Often, the selections will be about a subject or topic you are unfamiliar with, which can be frustrating. However, the ACT does not test your knowledge of content, but instead your skills in identifying point of view, the meaning of specific words, and the main ideas of the passage, among other things. You may want to take a few ACT practice teststo help you prepareand also check out thisgreat information on how the ACT is scored. Here are several tips for increasing your score on the Reading portion. 1. Skim first As you will surely reread the passage in order to answer the questions, skim the selection first, devoting only a few minutes to it. As you practice for the ACT, you will develop a general sense for what the questions ask - main idea, theme, tone, etc. It is generally more useful to read the passage quickly before looking at the questions, rather than the reverse.Try using a prep bookto help with your reviews. 2. Summarize Reading selections is, for many, the dullest part of sitting for the ACT. It is a significant contrast to the active work of the English, Mathematics, Science, and even the Writing sections. To remain alert, write a short summary after reading the passage. Attempt to distill each paragraph into a sentence. Do this as quickly as possible, and do not worry about grammar or sentence structure. Consider the main idea being proposed or criticized, or the particular example offered by the author. Your summary will be useful in addressing questions, particularly those that ask about the main idea or structure of the selection. Here are some great ACT reading test prep tips. 3. Mark up the text Another way to remain active is to underline, circle, and even cross out key terms, phrases, and sections as you read. While the summary is a map for the selection, these notations are guides to important portions of the text. Even if you are not able to mark up the entire passage, ensure you identify and underline the topic sentence the main idea of the selection so you understand what the author is advocating or criticizing. 4. Rephrase sentences Certain questions will require you to define a particular word within the passage or to choose an appropriate synonym. Try this technique: cross out the word, and then rely upon the context of the sentence to insert a term of your own. Then, compare the answer choices with your solution. Choose the closest match. Often, the ACT will include synonyms of the term that do not suit the context. By providing your own word, you can avoid being duped. 5. Do not frequently move from piece to piece Unlike other sections of the ACT, the Reading portiondoes not order its questions by difficulty. Instead, each passage possesses easy, medium, and hard questions. Since answering the problems requires memory of the passage, and perhaps revisiting it, try to avoid moving from one text to another without finishing all questions. Otherwise, you may waste too much time by continually and unnecessarily returning to passages. If you find yourself struggling in your ACT prep you may want to consider an ACT Reading tutor.