Smooth Endoplasmic Reticulum: Definition, Functions & Structure

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  • 0:02 Smooth ER Defined
  • 1:44 Smooth ER Function
  • 3:21 Structure
  • 4:16 Lesson Summary
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Lesson Transcript
Instructor: Julie Zundel

Julie has taught high school Zoology, Biology, Physical Science and Chem Tech. She has a Bachelor of Science in Biology and a Master of Education.

Without them you couldn't survive, but you probably know nothing about them. We're referring to an organelle called smooth endoplasmic reticulum. This lesson will explain why this organelle is important as well as look at its structure and function.

Smooth Endoplasmic Reticulum Defined

Inside of your cells there are tiny cities. These cities function in some ways just like regular cities: they have bosses or mayors, postal services, power plants, and even walls to keep invaders out. We are going to focus on one part of this tiny city - the factories.

Of course there aren't actual cities in your cells, but the organelles, or tiny parts of the cell that have a specific function, are like the parts that make up a city. You can also think of an organelle as a type of cell organ. Just like your heart, liver, and lungs have certain jobs in your body, your organelles have certain jobs to carry out in your cells. Bacteria and archaebacteria (a group of microorganisms) have prokaryotic cells and, therefore ,do not have organelles. Eukaryotic cells do have organelles and are found in animals, plants, fungi, and protista (like an amoeba).

Back to the tiny factories, which are called smooth endoplasmic reticulum or smooth ER for short. Now endoplasmic reticulum sounds pretty scary, but its name actually translates into 'within cytoplasm network,' which makes sense because it is found within the cytoplasm, or the jelly-like material found inside of a cell, and it is made up of a network of membranes.

There are actually two types of ER, rough ER and smooth ER. Rough ER has ribosomes on its surface that give it a rough appearance and name, whereas smooth ER is ribosome-free. The lack of ribosomes also gives smooth ER a different function than rough ER. Smooth ER is the one that operates just like a factory.

Smooth Endoplasmic Reticulum Function

Smooth ER is like a factory inside of your cells, so its primary function is making stuff and breaking it down. Depending on the location of the cell, the smooth ER may have different functions. A list of some of the things smooth ER does includes:

  • Makes fats (lipids)
  • Metabolizes (breaks down and builds up) carbohydrates (things like sugars or starches)
  • Makes steroids (steroids can include hormones and vitamins)
  • Detoxifies (breaks down harmful substances and turns them into safe substances)

Let's examine that list a little closer. Fats made by smooth ER are used in the manufacturing of phospholipids, which are important ingredients in cellular membranes (a cell's skin). Some of the steroids produced by smooth ER include sex hormones like testosterone (an important hormone for men and women). In fact, the cells that make these hormones, like those in testes, have more smooth ER than cells elsewhere in the body. Smooth ER found in the liver metabolizes carbohydrates, which helps regulate the amount of sugar in your blood.

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