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Structure and Function of the Nucleus in Animal Cells

Lia Kim, Amanda Robb
  • Author
    Lia Kim

    Lia Kim has a B.S. in Earth Systems from Stanford University. She also has certifications in Phytobiotechnology and Ethnopharmacognosy from University of Hawai'i of Manoa.

  • Instructor
    Amanda Robb

    Amanda has taught high school science for over 10 years. She has a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. She is also certified in secondary special education, biology, and physics in Massachusetts.

Do animal cells have a nucleus? Yes! Learn the structure of the nucleus and understand its functions within the cell. Updated: 12/01/2021

The Nucleus

A nucleus is an organelle within a cell that encloses DNA. DNA stands for deoxyribonucleic acid, a molecule that contains genetic information. The nucleus not only stores DNA but directs the synthesis of ribosomes, acting like the boss of a cell.

Do animal cells have a nucleus? Yes! All animals are eukaryotes, meaning they are made up of many cells with a true nucleus. The animal nucleus is membrane-bound, which is one of the many structural components that differentiates them from prokaryotic organisms like bacteria.

The dark brown circle is the nucleus of a living onion skin cell. All eukaryotic cells have a membrane-bound nucleus.

The dark brown circle is the nucleus of a living onion skin cell. All eukaryotic cells have a membrane-bound nucleus.

Animal Cells vs. Plant Cells

Both animals and plants are eukaryotes, meaning they both have a nucleus, plasma membrane, ribosomes, mitochondria, peroxisomes, and cytoplasm. However, animal cells and plant cells have important structural differences.

  • Animal cells have centrosomes and lysosomes, while plant cells do not.

The centrosome is a cellular structure, or an organelle, involved in animal cell division that is found near the nucleus. It is also where all microtubules originate. Microtubules are major components involved in cell division and maintenance of cell shape. The microtubules help separate the chromosomes into the daughter cells. It is important to note that while plant cells do not have centrosomes, they are still capable of cell division.

The lysosome is an organelle that contains digestive enzymes. Plant cells do not have lysosomes, but instead, have vacuoles. Both lysosomes and vacuoles break down waste products, excess or worn-out cell parts, or destroy viruses and bacteria.

Animal cells have both lysosomes and vacuoles, while plant cells only have vacuoles. Plant cells also have a large central vacuole, which stores water to maintain pressure in the cell.

  • Plant cells have a rigid cell wall, plasmodesmata, chloroplasts, and plastids, which are all lacking in animal cells.

The cell wall in plant cells helps maintain the shape of the cell and protects it. The main component within the plant cell wall is cellulose, a polysaccharide. The crunchiness in raw vegetables is due to cell walls breaking! Plant cells also contain plasmodesmata, which are membrane-lined channels that connect different plant cells together and enable cell-to-cell communication. Animal cells have gap junctions, which have a similar function to plasmodesmata but are structurally different.

Another unique organelle within a plant cell is a chloroplast. Chloroplasts allow plant cells to conduct photosynthesis, an important series of reactions that convert carbon dioxide, water, and energy from light into sugar and oxygen. The greenness of plants is due to the pigment called chlorophyll that is found in chloroplasts. Plant cells also have plastids, which stores pigments, unlike animal cells.

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.

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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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The Animal Nucleus Structure

In a eukaryotic cell, the nucleus is one of the largest organelles. It is not just a rigid, solid ball-like structure; it has pores, a nuclear membrane, nucleoli, and is filled with nucleoplasm.

  • The double-layered membrane that encloses the nucleus (which differs eukaryotic cells from prokaryotic cells) is called the nuclear membrane, or nuclear envelope. The inner membrane is called the nuclear lamina.
  • The nuclear membrane has pores to allow certain molecules to pass in and out of the nucleus with the help of certain proteins.
  • The nucleolus (plural: nucleoli) is a small, dense structure within the nucleus that contains ribosomal DNA, RNA, and ribosomal proteins to form ribosomes. The ribosomes, after they are transported out of the nucleus to the endoplasmic reticulum, become sites of protein synthesis. The nucleus can contain up to four nucleoli.
  • The nucleoplasm is a semifluid, gel-like matrix where the nuclear components like chromatin (a complex of DNA and protein) are suspended.

Nucleus Function in an Animal Cell

What does the nucleus do in an animal cell? It does many important things that allow for animals to live. The function of the nucleus in an animal cell include organizing, protecting, storing, and copying DNA, as well as making ribosomes. The following sections will elucidate each of the functions of the nucleus.

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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Video Transcript

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.

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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Frequently Asked Questions

What are the main functions of nucleus?

The function of the nucleus in an animal cell include organizing, protecting, storing, and copying DNA. The nucleus also contains nucleoli, a site that makes ribosomes, an important organelle for protein synthesis.

Do all animal cells have a nucleus?

All animals are eukaryotes. They belong to the Domain Eukarya. All eukaryotes have a membrane-bound nucleus. Thus, animal cells have a nucleus!

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