In Part 16 of this series, we briefly discussed the nuclear membrane and that its main function of compartmentalizng the nucleus off from the rest of the cell. Additionally, we mentioned that the nuclear membrane contained pores that help in the communication pathways between the nucleus and the rest of the cell. Today, we will go further into depth on the structure and function of the nuclear membrane.
When I first studied the cell in high school some 40 years ago, I was taught that the nuclear membrane like the cell membrane was nothing more than an envelope that surrounded the nucleus and divided it off from the rest of the cell. Since those days, technology has greatly improved and with those improvements so has our knowledge and understanding of the nuclear membrane and its functions.
The nuclear membrane is known by a variety of names including nuclear envelope, perinuclear envelope, nucleolemma or karyotheca. It consists of 3 main components, the external or outer membrane, the internal or inner membrane and the nuclear pores.
The outer membrane surface not only shields the rest of the nucleus from the cytoplasm, but it also is continuous with the endoplasmic reticulum. As ribosomes are synthesized inside the nucleus, a number of them pass through nuclear pores directly to the outer membrane and endoplasmic reticulum.
The inner membrane contains a number of membrane bound proteins. Some of the inner nuclear membrane proteins are associated with the chromatin and nuclear lamina inside the nucleus while others function in the formation of the nuclear membrane during the latter stages of mitosis. Other membrane bound proteins are involved with certain transcriptional processes involved with the synthesis of the complimentary RNA copies of various DNA sequences.
During the prometaphase stage of mitosis, the nuclear membrane begins to breakdown, allowing for the separation of the nucleus into two new nuclei. After the chromosomes have separated at the end of the anaphase stage of mitosis, the endoplasmic reticulum and nuclear lamina help to form the new missing sections of nuclear membrane necessary to complete the nuclear division process.
The space between the outer and inner nuclear membranes is called the perinuclear space. Just as the outer nuclear membrane is continuous with the endoplasmic reticulum, the perinuclear space is also continuous with the lumen of the endoplasmic reticulum.
Functions of the nuclear membrane include:
- Compartmentalizing. The nuclear membrane is vital in separating the nuclear material from the cellular material. Compartmentalization is vital in eukaryote cells to prevent the free mixture of cellular material with the nuclear material.
- Shape and stability of the nucleus. With the help of the lamina inside the nucleus, the double membrane helps keep the nucleus from collapsing and interfering with the functions of the nucleus.
- Regulation of substances in and out of the nucleus. Proper function of the nucleus requires the regulation of what proteins and enzymes are allowed in and out of the nucleus. The control of these passages is carried out by the thousands of nuclear pores. Each pore has its own regulatory proteins that only allow specific substances to pass in or out of the nucleus.
- Communication. The nuclear membrane and nuclear pores regulate the chemical communication between the nucleus and the rest of the cell. This communication is vital to the overall welfare and function of the cell.
Like the previous parts of the Simple Cell series, we see that nothing is left to chance or randomly happens in the cell. Every molecular detail is ordered and directed. It’s like listening to a world class symphony. To begin with some had to design and construct all of the difference instruments used in the symphony. Each instrument has its own musical score to follow. Add them all together and you have a beautiful piece of music. Take any of the parts out and while the symphony will continue on, it never sounds as good or complete as it does with the whole. More importantly, everyone knows that a number of people and intelligence created the instruments and wrote all of the music for the symphony.
If evolutionists viewed the symphony like they do the cell, they would have you believe that all of the instruments were created by random chance processes. Then more random chance processes wrote all of the different scores to the music and that by more random chance all of the pieces of music blended together so well that the result is the beautiful symphony you are listening to.
I don’t know of any evolutionists that would believe that about a symphony, but they do want you to believe it about the cell and all of its parts. They admit that a great deal of intelligence was involved in creating the instruments and symphony, but that no intelligence was involved in the formation of the cell and all of its parts.
The detail of the cell is one of the greatest compositions our great Composer God has ever created.