Question

explain about nucleus with a diagram

Answer 1

A nucleus is like the brain of your cells. In this lesson, you will learn about its various responsibilities, and then you can test how well you grasp this material by taking a quiz.

Types of Nucleus

The word 'nucleus' can refer to the center of an atom or the control center of a cell. This lesson will discuss the nucleus of a cell.

You have over 200 different types of cells in your body. Some can be really thin and long, like a nerve cell that runs all the way from your spinal cord to your foot. Some, like a fat cell, have a more rounded shape. No matter what your cells look like, there is one important thing they all have in common: a nucleus. This is a control center that is found inside all of your cells at some point during their life. A nucleus is responsible for determining and controlling what a cell looks like and what it does.

Structure

A nuclear envelope encloses the nucleus to keep it separate from surrounding materials in the cell. Sometimes substances need to move into or out of the nucleus, and this is possible because there are little holes in the nuclear envelope called nuclear pores. Inside the nucleus is at least one dark-colored mass called a nucleolus. DNA occupies most of the rest of the space inside a nucleus. DNA is genetic material that has the instructions necessary to build proteins. Proteins are responsible for helping with most activities in a cell.

Answer 2

The nucleus is enclosed by a thin covering called the nuclear membrane. The nuclear membrane separates the nucleus from the rest of the cell. The nuclear membrane has pores through which chemical signals, nutrients, and water can pass.

The nucleus contains nearly all of the cell’s genetic (hereditary) material, in long, threadlike structures calledchromosomes (see Chromosome ). The chromosomes hold genes, the basic units of heredity. Genes control the passing on of characteristics from parents to offspring. The genes are encoded in the sequence of a molecule called DNA (deoxyribonucleic acid).

A major function of the nucleus is to make structures called ribosomes. Ribosomes manufacture proteins. They are created in the nucleoli. Nucleoli are round bodies that form in certain regions of specific chromosomes. Ribosomes pass out of the nucleus into the main body of the cell (see Ribosome ).

The nucleus uses chemical signals to control the cell’s activities. If the cell lacks certain nutrients, for example, it will send a chemical signal to the nucleus. This chemical signal will cause the nucleus to read a particular gene and make messenger RNA. RNA (ribonucleic acid) is a molecule closely related to DNA. This process of making messenger RNA is called transcription. Messenger RNA is sent out of the nucleus to the ribosomes. The ribosomes use the messenger RNA as a template (pattern) to make a protein. In this example, the protein might help the cell take up nutrients. When the cell has taken up enough nutrients, it will send a second signal to the nucleus. This signal will cause the nucleus to stop producing the messenger RNA. Without messenger RNA, the ribosome can no longer create the protein, which stops the uptake of nutrients.

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