1. Specialized Cells Cells can vary in the shape, size, and content. Each type of cell is specialized to perform a different function. Structure determines function.

2. Nerve Cells or Neurons Neurons are cells of the nervous system and are specialized to carry "messages" through an electrochemical process.

3. Neurons are similar to other cells in the body because: Neurons are surrounded by a cell membrane. Neurons have a nucleus that contains genes. Neurons contain cytoplasm, mitochondria and other organelles. Neurons carry out basic cellular processes such as protein synthesis and energy production.

4. Neurons differ from other cells in the body because: Neurons have specialize cell parts called dendrites and axons. Dendrites bring electrical signals to the cell body and axons take information away from the cell body. Neurons communicate with each other through an electrochemical process.

5. Nerve Cell

7. Sperm Cell A sperm cell is the male reproductive cell that carries the male portion of chromosomes, DNA or hereditary information to be fused with the female egg, or ovum. The sperm cell is composed of three main parts: the head, middle piece and tail.

8. Parts The head contains enzymes near the tip, used to penetrate the egg; contains the nucleus and all hereditary information needed to successfully reproduce once the sperm cell has fertilized an egg. The middle piece contains mitochondria which provides energy to move the cell. The flagellating tail propels the sperm cell.

9. Sperm Cell

10. Guard Cell Guard cells are cells surrounding each stoma in plants. They help to regulate the rate of transpiration by opening and closing the stomata.

11. Guard Cell

12. Xylem and Phloem Vascular tissue in plants; contain several types of specialized cells. Xylem – made up of tracheid and vessel elements, carry water from the roots to the rest of the plant Phloem – made up of sieve tube elements and companion cells; transports food

13. Xylem and Phloem

14. Multicellular organisms begin as undifferentiated masses of cells Variations in DNA expression and gene activity determine cell specialization During differentiation, only specific parts of DNA are activated which determine the function and specialized structure of a cell

15. All cells contain the same DNA; all cells have the potential to become any type of cell Depends on the genetic instructions Stem cells – unspecialized cells which can differentiate into other types of cells (can be manipulated in laboratories under the right conditions) Stem cells→DNA→cell differentiation→specialized cells