Structure of the Nucleus: Nucleolus, Nuclear Membrane, and Nuclear Pores

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  • 0:52 Nucleus Function
  • 2:19 Nuclear Structure and…
  • 4:40 Lesson Summary
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Lesson Transcript
Instructor: Kristin Klucevsek

Kristin has taught college Biology courses and has her doctorate in Biology.

In this lesson, we'll discuss the organization and importance of the nucleus in your cells. This is the membrane-bound structure responsible for containing all the genetic material essential to making you who you are.

The Nucleus

DNA is turned into RNA through transcription
DNA Changes to RNA

Your cells are fine-tuned and well-oiled machines. For the most part, they run smoothly, like a brand-new car on a freshly-paved surface. Many cells have an extremely important structure that holds all the essential information vital to their ability to perform. Each of these cells comes with an owner's manual - instructions on how to run day to day operations and specialized functions. These instructions are your DNA, which is stored in its very own cellular glove compartment - the nucleus. The nucleus is a membrane-bound structure that contains the genetic material of a cell. The plural of nucleus is nuclei. Not all cells have nuclei, but many cells, such as those in plants, fungi, animals, and protists, contain these structures.

The nucleus is not just a storage compartment for DNA. It's the site of some essential cellular processes. First, DNA can be duplicated in the nucleus. This process is called replication and creates an identical copy of DNA. Creating two identical copies of the owner's manual is the first step in cell division, where each new cell will get its own set of instructions.

Second, the nucleus is the site of transcription. The central dogma of biology states that DNA is copied into RNA, which is then turned into protein.

Transcription is the process of creating different types of RNA from DNA. Transcription would be like making copies of individual pages of the owner's manual that can then be passed out and read by the rest of the cell.

There are three types of RNA that are formed in the nucleus. mRNA, or messenger RNA, is a code that can be read by the cytoplasmic structure called the ribosome during translation. Translation is a process that creates proteins from mRNA. A ribosome, which we will discuss in future lessons, is made up of proteins and a second type of RNA, rRNA or ribosomal RNA. tRNA, or transfer RNA, is also used during the process of translation. All three of these RNA types - mRNA, rRNA, and tRNA - are created by the process of transcription within the nucleus.

Nuclear Structure and Organization

Import proteins help NLS proteins pass through the nuclear pores
Nuclear Pores Process

The nucleus is the structure responsible for containing DNA and providing a place for replication and transcription. These processes make sure that the instructions on how to make you who you are carried out. This is obviously a very important job, so to keep the cell functioning at top speeds, the nucleus is a well-organized structure.

The nucleus is surrounded by a nuclear envelope, which is a double membrane comprised of an outer membrane and an inner membrane. This double membrane shields the nucleus and its contents from unwanted guests. Some proteins need to be in the nucleus to assist in processes such as replication and transcription. Many proteins, however, have no business being there. Your DNA, your very own patented genetic owner's manual, is a unique and prized possession. It needs to be protected.

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