Cell Nucleus: Definition & Examples

Cell Nucleus: Definition & Examples
Coming up next: Cells With a Nucleus & Membrane-Bound Organelles

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  • 0:01 What Is the Nucleus?
  • 0:55 Structure of the Nucleus
  • 1:57 Cells With a Nucleus
  • 2:30 Examples of Nuclei
  • 3:17 Lesson Summary
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Lesson Transcript
Instructor: Stephanie Matalone

Stephanie taught high school science and math and has a Master's Degree in Secondary Education.

In this lesson, we will discuss the structure of the nucleus and how it is in charge of what goes on inside the cell. We will also talk about what types of cells have a nucleus including animal, plant, and fungal cells.

What Is the Nucleus?

Cells are all around us, they make up all living things, from that bacteria that made you sick last week to the tree outside your window, to the cells in your own body. Cells have something called organelles inside them that are specialized structures responsible for different tasks within the cell. For example, the cell membrane protects and surrounds the cell while the mitochondria are responsible for making energy for the cell.

If you compare a cell to the human body, the nucleus would be considered the brain of the cell. This is because the nucleus is responsible for everything that goes on in the cell. Just as the brain tells your different body parts what to do, the nucleus tells the organelles what to do! Even further, the nucleus houses the cell's genetic information called deoxyribonucleic acid (DNA).

Structure of the Nucleus

As we already know, the nucleus houses DNA. It surrounds the DNA with a protective membrane called the nuclear envelope, similar in structure to the cell membrane that protects the entire cell. The nuclear envelope provides another layer of protection for the DNA and has small holes in it called pores.

These pores allow proteins in that are needed to help wind up the long DNA strands so they can be stored more easily. DNA inside the nucleus is stored as chromatin, which is just folded up DNA. The pores also allow copies of the DNA, called RNA, to leave the nucleus when they are needed for protein production at the ribosomes, small organelles outside the nucleus that make proteins.

The nucleus has another structure inside called the nucleolus, which is a circular structure that does not have a membrane. This is where parts of the ribosomes are created which ultimately will make proteins for the cell.

Cells with a Nucleus

There are two main types of cells: prokaryotes and eukaryotes. Prokaryotes are simple cells that make up most single-celled organisms like the bacteria that make you sick. Eukaryotes are larger, more complex cells that make up multi-celled organisms like humans and plants.

The main difference between the two types of cells is that eukaryotes have a nucleus and other membrane-bound organelles. This means that all the cells that make up your body have a nucleus, apart from the bacteria that live inside you.

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