Cell Structure

Most human cells contain small structures known as Organelles, each of which performs a specialized task, such as manufacturing protein. Organelles, most likely surrounded by a membrane, float in a jellylike substance called cytoplasm. Most of the cytoplasm is actually water; it also contains enzymes, amino acids, and other molecules needed for cell functions (Human Body, pg. 46).

Nucleus

- Found in most Eukaryotic Cells

- Most of the cell's Genetic Material is housed here (DNA Molecules)

- Its function is to maintain the integrity of the Genes and control cell activities by regulating Gene Expression

- Membrane Enclosed

Centrioles

- Found in most Eukaryotic Cells

- Often called Basal Bodies

- Absent in higher Plants and Fungi

- May be used in the formation of Flagella or Cilia

- Plays a role in Cell Division

- Help to organize the assembly of Microtubules during cell division

Mitochondrion

- Found in most Eukaryotic Cells

- Generate most of the cell's ATP supply (Adenosine Triphosphate) which is used as a source of Chemical Energy

- Involved in the control of the Cell Cycle and Cell Growth

- Thought to be descended from Prokaryotes

- Stores Calcium

Endoplasmic Reticulum (ER)

- Responsible for the production of protein and lipid components of most cell organelles

- Two types of ER; Rough, which is coated with Ribosomes; Smooth, which isn't covered in Ribosomes

- The Rough ER is the site of Protein Synthesis

- The Smooth ER is where vesicles carrying synthesized proteins are budded off

Golgi Complex

- Found in most Eukaryotic Cells

- Consists of a stack of about six flat disks

- Composed of smooth Cisternae coated with lipid membranes

- Contains Vesicles used to send molecules to the cellular membrane

- Receives proteins made in the ER

- It changes and packages proteins ready for export from the cell

Lysosome

- Found in all Eukaryotic Cells

- Digest Macromolecules and Organelles when needed

- Contain Hydrolytic Enzymes that break down what is digested

- Materials to be digested reach the enzymes through Endocytosis

Vacuole

- Plays a role in Intracellular Digestion and the release of cellular waste products

- Tend to be large in plant cells

- Perform functions such as storage, ingestion, digestion, excretion, and expulsion of excess water

- Especially in Protozoa, vacuoles are Cytoplasmic Organs