The Cell

The structures within a cell function in providing protection and support, forming a barrier between the cell and its environment, building and repairing cell parts, transporting materials, storing and releasing energy, getting rid of waste materials, and increasing in number. These cell structures are called organelles.  

I. Cell Membrane: The doorway of the cell. A. The cell membrane provides protection and support for the cell. Animal cells do not have a cell wall, therefore, the cell membrane must provide the support and protection for the cell. The cell membrane controls the movement of materials into and out of the cells through pores. Everything from the movement of oxygen to waste particles is controlled by the cell membrane. It keeps the cell in a state of homeostasis.

II. Nucleus: The control center of the cell. A. The nucleus is a round structure in the cell that acts as the control center (brain) of the cell. It regulates or controls all activities of the cell. Chromosomes are rod-like structures, located in the nucleus that direct all activities of the cell, including growth, reproduction, and the passing of traits.

III. Mitochondria: Powerhouses of the cell. A. Mitochondria are rod-shaped structures that supply most of the energy to the cell. Inside the mitochondria, simple food substances such as sugars are broken down into water and carbon dioxide gas. Large amounts of energy is released during the breakdown of sugars. The energy is collected and stored for the cell to use.

IV. Ribosomes: Protein factories of the cell. A. Ribosomes are grain-like bodies produced in the nucleus. Many of these bodies pass out of the nucleus and attach themselves to the inner lining of the edoplasmic reticulum. (Some ribosomes float freely in the cytoplasm.). B. Ribosomes are the protein making sites of the cell. They are found inside of the endoplasmic reticulum so that they may be carried to anywhere in the cell when needed.

V. Endoplasmic Reticulum: Transportation system of the cell. A. The endoplasmic reticulum (ER) is a series of clear, tubular passageways. These passageways lead out from the nucleus to other areas of the cell or to the cell membrane. These passageways allow materials to be carried anywhere throughout the cell. B. The Rough ER is the endoplasmic reticulum with ribosomes attached to the outside and the Smooth ER is the endoplasmic reticulum without ribosomes.

VI. Lysosomes: Cleanup crews for the cell. A. Small round structures involved with the digestive activities of the cell. 1. Lysosomes contain enzymes that break down large food molecules into smaller ones. These smaller food molecules are then passed on to the mitochondria where they are “burned” to provide energy for the cell. The lysosome is covered in a membrane which keeps the enzymes in and from digesting the cell itself. 2. After cell parts outlive their usefulness, Lysosomes digest old cell parts and release substances to make new cell parts.

Lysosomes (Continued) 3. If the cell is injured or dead, the lysosomes’ enzymes can digest the whole cell such as when a tadpole becomes a frog and loses its tail. B. Lysosomes are common in animal cells, but not often seen in plant cells.

VII. Cytoplasm: Suspension system of the cell. A. Cytoplasm is the region between structures in the cell that is a clear, thick, jelly-like substance.

VIII. Flagellum and Cilia: Motion makers for the cell. A. A flagellum is a tail-like structure that stick out from the cell. The flagellum moves back and forth enabling the cell to move. B. Cilia are hair-like structures that can be found on the outside of a cell. Cilia enable a cell to move and are also used to pass water and other materials over the cell’s surface.

IX. Vacuoles: Storage tanks for the cell. A. Vacuoles store mostly water, but also store other materials as well. B. Vacuoles are found in both plant and animal cells. C. Plants cells usually have one large centrally located vacuole where animals may have several small ones. .

X. Cell Wall: Support and protection system for the cell. A. Cell wall is only found in plant cells. B. Cell wall holds the plant cell up and enables the cell to keep its shape.

XI. Chloroplasts: Solar power factories for the cell. A. Chloroplasts are small green structures that are only found in the plant cell. B. Chloroplasts take the energy from the sun and turn it into food for the plant cell.

XII. Golgi Body: Mail and package center of the cell. A. Golgi bodies store, package and deliver the proteins and lipids made in the endoplasmic reticulum.

XIII. Centrioles: Guidance counselors of the cell. A. Centrioles line up the chromosomes inside the cell and then they pull the chromosomes apart during mitosis and guide them to the right location.

____________ ________ Animal Cell _______ ___________ ____________ ________ ________ Flagellum Nucleus Centrioles Ribosomes Lysosomes Endoplasmic Reticulum Mitochondria Golgi Body Cell Membrane Cytoplasm Vacuole

Plant Cell Vacuole Chloroplasts Cell Wall