Intracellular: Definition & Structures

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  • 0:05 What Is Intracellular?
  • 0:57 Connection to the…
  • 2:35 The Intracellular Structures
  • 4:34 The Inside of Plant Cells
  • 5:10 Lesson Summary
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Lesson Transcript
Instructor: Christine Morgan

Christine has taught college Biology and Anatomy, and has a Master's degree in Anatomy.

The inside of a cell is more than just a place for parts that hold plants and animals together. The life of everything on the planet depends on the chemical exchanges and the tiny structures that go about their work twenty four hours a day.

What Is Intracellular?

Have you ever thought about what makes you alive? Think for a minute about the basics: breathing and eating are probably pretty high on the list. Well, almost everything that happens inside you happens inside a cell, too. Cells breathe, eat, have waste, and make energy to stay alive. The word intracellular literally means 'within the cell,' and that's where all the action is for life in our entire world.

The cell is what's known in science as the basic unit of life. All the parts that make up a cell would not be considered alive if they were on their own, but contained within a cell membrane, which keeps all the organelles of the cell and the cytoplasm contained and allows material to move in and out of the cell, life goes on, whether it's as a single cell or joined with others in a large animal or plant.

Connection to the Cellular Membrane

The cell membrane helps the cell function, keeping the cell safe, but also makes it possible for communication with the outside world, or extracellular space. In animal cells, oxygen, proteins, hormones, and other important material for life need to get to the intracellular space. Wastes, including carbon dioxide (what you breathe out), all need to get outside. Water is a big part of how that happens.

You've probably heard that our bodies are mostly made of water and, well, it's pretty much a fluid-filled world for the cell. Ninety-nine percent of the molecules inside the cell are water. This water, and all the useful things that are dissolved or suspended in it, are called the cytoplasm. Cyto- refers to 'cell,' and plasm just means the 'stuff that forms the cell.'

All the chemical reactions that define life happen right here, from breaking down larger molecules (digestion), to building new ones, including the manufacture of our genetic material, or DNA. Fortunately, anything that can be dissolved in water can move freely through the cell membrane, because it's permeable to water; it won't block or stop its movement. The amount of water and the pressure in the intracellular region is maintained by a process called osmosis.

This works naturally, with no energy, because water tends to flow to regions where it is not. If the inside of a cell has more dissolved particles compared to the outside (like sodium ions, Na+), then water will flow into the cell from the surrounding extracellular space. You can imagine that would be bad if left uncontrolled, so cells can help regulate osmosis by pumping out sodium and other ions.

The Intracellular Structures

Just like you have special organs inside, the cell has tiny organs inside that make life possible. They are called organelles. In Latin, longer anatomy-related words usually mean smaller structures. Organelles actually means 'tiny organs.' Along with the organelles, you can see a system of fibers and tubules in the cell that give everything shape and order, just like your skeleton gives you shape and order. This system of fibers and tubules is called the cytoskeleton.

The nucleus, which is round in shape, is usually the largest structure you find in a cell. This is where the genetic material stays and functions until it's time for cell division, which is when the boundary dissolves so the DNA can be split to the two new cells. Since the material in the nucleus directs cell activities, you can think of it like a brain.

All the other intracellular structures have to do with carrying out life processes that the nucleus directs or provides energy for. Something that takes up lots of space in the cell is the endoplasmic reticulum. The endoplasmic reticulum is a large series of tubes where cell products are made.

Cross Section of Animal Cell and Organelles
Image of Animal Cell and Organelles

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