What do we mean when we say one organelle is membrane-bound and another isn’t? And what creates this distinction anyway? Complete this lesson to learn the answers to this and more!
What Are Organelles?
In your body, you have organ systems to take care of the necessities of life, like eating, breathing, moving, and pumping blood.
Although individual cells are much, much smaller, they also have specialized structures that allow them to complete their life functions. In cells, these structures are referred to as organelles, which actually means ‘little organs’.
Non-Membrane Bound Organelles
In addition to organelles, you can find a thick fluid inside cells.
This fluid is called cytoplasm. All of the internal parts of the cell are floating in cytoplasm.Many organelles are also filled with a fluid. These fluid-filled organelles are surrounded by a plasma membrane to separate their insides from the rest of the cytoplasm. These are the so-called membrane bound organelles, such as the lysosomes, Golgi complex, and mitochondria. By the way, the similarities between the terms cytoplasm and plasma membrane can help you remember and understand their meanings: the plasma membrane serves to create boundaries between objects in the cytoplasm.
Organelles that are not fluid-filled don’t need to be separated from the rest of the cell in the same way, so they don’t have a membrane. These are the non-membrane bound organelles.
Non-membrane bound organelles have a more solid make-up than the membrane-bound ones. They each have their own unique structure, function, and location within the cell. It can be quite difficult to remember the functions of all the different cellular organelles. A common tip is to write a poem or song that will stick in your memory. Suggestions are offered for each of the following organelles, but feel free to make up your own!Ribosomes are present in every type of cell, from the simplest bacteria to the most complex animal cell.
They are bundles of genetic material and protein that are the centers for protein production in the cell. Ribosomes can be found either free-floating in the cell or attached to the endoplasmic reticulum. And now the poem:If proteins are what you needribosome is your man, indeed!The cell wall is found only in plant cells and is actually not inside the cell at all. It’s located outside the cell membrane and provides support and protection for the plant.
This rigid, cellulose structure allows plants to stand up-right. An ode to the cell wall:The cell wall protects your plantthis rigid structure helps it stand!Just as the name suggests, the cytoskeleton is the cell’s skeleton. (Cyto-, by the way, means ‘cell’.) The cytoskeleton actually consists of several different types of protein fibers that stretch across the cell. Just like your skeleton, the cell’s skeleton provides structure and helps with movement.
Here is the final verse:Without a cytoskeletoncells would be like gelatin!
Just like you have organ systems, cells also have structures that are specialized to carry out important life functions. In cells, these structures are referred to as organelles. Membrane-bound organelles are surrounded by a plasma membrane to keep their internal fluids separate from the cytoplasm of the rest of the cell. Non-membrane bound organelles are more solid structures that are not fluid-filled, so they have no need for a membrane.Examples of non-membrane bound organelles are ribosomes, the cell wall, and the cytoskeleton. Ribosomes are bundles of genetic material and protein that are the centers of protein production in the cell.
The cell wall is a rigid, cellulose structure found only in plant cells. Located outside the cell membrane, the cell wall serves to protect and support the cell. Finally, the cytoskeleton consists of several types of protein fibers that provide structure for the cell and help with movement.