Nucleus Function in Animal Cells

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  • 0:00 The Nucleus
  • 1:17 Structure
  • 2:27 Storing DNA
  • 3:39 Making Ribosomes
  • 3:58 Copying DNA
  • 5:20 Lesson Summary
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Lesson Transcript
Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson, we'll go over what a nucleus is and some of its important structures. We'll also learn what the nucleus does in animal cells and why those functions are important.

The Nucleus

In a factory, the boss is the top dog, calling the shots and deciding what type of products are made when. He or she tells the workers how much of each product to make, and even hires and fires employees. Sometimes, he/she might need more assembly line workers, and other times, a bigger janitorial staff. A similar process takes place inside cells when we view them under the microscope.

In the microscopic world, cells are bossed around by DNA, which is short for deoxyribonucleic acid. In cells like ours, the DNA has a special office, just like a boss does; it's called the nucleus. Animal cells, plant cells, and fungi have a nucleus. However, bacteria and viruses do not. Their bosses just have a desk in the factory not an office.

In this lesson, we're going to look specifically at animal cells. Animal cells are eukaryotic, meaning they have a nucleus. They don't have a cell wall and are part of bigger multicellular organisms, like people. To understand what the nucleus does in the cell, let's first examine its structure.


The nucleus has an outer barrier called the nuclear envelope or nuclear membrane surrounding it. Just like an envelope surrounding a letter, the nuclear envelope contains all the important information in the nucleus. The nucleoplasm is a thick gel that fills the inside of the nucleus. Inside the nucleoplasm are large structures called nucleoli. Nucleoli are like tiny factories that make important parts of the cell called ribosomes. We'll look more at this process later.

Since the nucleus makes things, the nucleus must ship materials in and products out. The doors of the nucleus are called nuclear pores. Nuclear pores serve as gateways, selectively allowing things in and out of the nucleus. Since the nucleus contains so many important things, substances in the cell must possess special tags in order for them to enter the nucleus. Think of these special tags as key cards necessary to gain entrance into a very important building. Now that we know how the nucleus looks, let's look at what it does for the cell.

Storing DNA

The nucleus has one main job. It keeps the DNA safe from the rest of the cell. Why must DNA be kept safe? DNA is the basis of the genetic code that directs all of a cell's operations. The nuclear envelope and the nuclear pores protect the DNA in the nucleus. They keep things that should not be in the nucleus out and let things that are needed in.

Since DNA is so important, it's not just inside the nucleus floating around. There's a specific way the nucleus stores DNA, just like you would store special photographs in a nice picture album, instead of tossing them inside a box. DNA is stored inside chromatin in a cell that isn't dividing. Although chromatin looks like a thick mess when viewed through a microscope, the DNA is carefully wound like a string around tiny proteins that resemble beads. The resulting structures called nucleosomes fold up to form loops, which are then compressed into tight chromatin coils. This method of storing the DNA enables the nucleus to organize the DNA and fit so much of it into a tiny space.

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