What makes cells different

Cells have many parts, each with a different function. Some of these parts, called organelles, are specialized structures that perform certain tasks within the cell. Human cells contain the following major parts, listed in alphabetical order:. Within cells, the cytoplasm is made up of a jelly-like fluid called the cytosol and other structures that surround the nucleus.

The cytoskeleton has several critical functions, including determining cell shape, participating in cell division, and allowing cells to move.

It also provides a track-like system that directs the movement of organelles and other substances within cells. This organelle helps process molecules created by the cell. The endoplasmic reticulum also transports these molecules to their specific destinations either inside or outside the cell. The Golgi apparatus packages molecules processed by the endoplasmic reticulum to be transported out of the cell. These organelles are the recycling center of the cell. They digest foreign bacteria that invade the cell, rid the cell of toxic substances, and recycle worn-out cell components.

Mitochondria are complex organelles that convert energy from food into a form that the cell can use. For a cell to work, 's of these proteins must be made, each doing its particular job.

Eyes and lungs are so different because different sets of proteins are made in the various eye and lung cells. In other words, in the eye, genes are turned on for seeing and the "breathing" genes are off. In lung cells, the situation is reversed. A useful analogy is that of a recipe book.

Even though all of the information is in the book to make lots of different dishes, a cook will only use the souffle recipe to make a souffle. In a similar way, even though DNA contains lots of recipes, only those needed to make and run an eye are used in an eye. By Dr. Barry Starr, Stanford University. A related topic is stem cells. Stem cells are cells that have not "decided" yet which kind of cell to become. A good college level discussion of the topic.

These organized collections of actin filaments also extend into the microvilli , which are the tiny fingerlike projections that protrude from the apical membrane into the gut lumen and increase the surface area available for nutrient absorption. Additional mechanical support comes from desmosomes , which appear as plaque-like structures under the cell membrane, attached to intermediate filaments. In fact, desmosome-intermediate filament networks extend across multiple cells, giving the endothelium sheetlike properties.

In addition, within the gut there are stem cells that guarantee a steady supply of new cells that contribute to the multiple cell types necessary for this complex structure to function properly Figure 2.

The extracellular matrix ECM is also critical to tissue structure, because it provides attachment sites for cells and relays information about the spatial position of a cell. The ECM consists of a mixture of proteins and polysaccharides produced by the endoplasmic reticula and Golgi apparatuses of nearby cells. Once synthesized, these molecules move to the appropriate side of the cell — such as the basal or apical face — where they are secreted.

Final organization of the ECM then takes place outside the cell. To understand how the ECM works, consider the two very different sides of the gut endothelium. One side of this tissue faces the lumen, where it comes in contact with digested food. The other side attaches to a specialized ECM support structure called the basal lamina. The basal lamina is composed of collagen and laminin proteins, as well as various other macromolecules.

On this side of the endothelium, adhesive junctions attach cells to the ECM. Transmembrane integrin proteins in the junctions bind components of the ECM and recruit signaling proteins to their cytoplasmic sides.

From there, the signals travel to the nucleus of each cell. This page appears in the following eBook. Aa Aa Aa. Cell Differentiation and Tissue.

The gut contains a mixture of differentiated cells and stem cells. Figure Detail. Tissues are communities of cells that have functions beyond what any single cell type could accomplish. Healthy tissues require the proper mix of cells, and the cells within them must be oriented correctly and dividing at an appropriate rate.

In order to coordinate their function, organization, and rates of death and division, the cells in a tissue are constantly processing and responding to signals from one another and from the ECM around them. Cell Biology for Seminars, Unit 5. Topic rooms within Cell Biology Close. No topic rooms are there. Or Browse Visually. Student Voices. Creature Cast. Simply Science.

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