7.4 Homeostasis & Cells

1. 7.4 Homeostasis & Cells

2. The cell as an organism • A single-celled organism must do everything any living organism does to maintain its’ life • HOMEOSTASIS – maintaining a relatively constant internal environment • It must grow, reproduce, respond to the environment, etc.

3. 7.4 Homeostasis & Cells

4. Multicellular life • Specialized cells – different cells for different jobs • Organization: cellstissuesorgansorgan systems • Communicate - chemical signals passed form one cell to another

5. Cells as Organisms • Organisms must maintain homeostasis to be considered alive. • So, therefore cells must maintain homeostasis. • Cells must… • Grow • Transform Energy • Respond to their Environment • Reproduce …to maintain homeostasis

6. Multicellular Organization • To be a multicellular organism the cells of the organism must be specialized to specific functions to allow the organism to perform complex tasks.

7. Multicellular Life • How do the cells of multicellular organisms work together to maintain homeostasis? • The cells of multicellular organisms become specialized for particular tasks and communicate with one another to maintain homeostasis. • The cells of multicellular organisms are interdependent, and like the members of a successful baseball team, they work together. • In baseball, players take on a particular role, such as pitcher, catcher, infielder, or outfielder. Messages and signals are sent and understood by teammates and coaches to play the game effectively. • Cells in a multicellular organism work the same way. The cells of multicellular organisms become specialized for particular tasks and communicate with one another in order to maintain homeostasis

8. Cell Specialization • The cells of multicellular organisms are specialized, with different cell types playing different roles. • Some cells are specialized to move, others to react to the environment, and still others to produce substances that the organism needs. • No matter what the role, each specialized cell contributes to the overall homeostasis of the organism.

9. Specialized Animal Cells • Particles of dust, smoke, and bacteria are part of even the cleanest air. • Specialized animal cells act like street sweepers to keep the particles out of the lungs. • These cells are full of mitochondria, which provide a steady supply of the ATP that powers the cilia on their upper surfaces.

10. Specialized Plant Cells • Pollen grains are highly specialized cells that are tiny and light, with thick cell walls to protect the cell’s contents. • Pine pollen grains have two tiny wings that enable the slightest breeze to carry them great distances.

11. Levels of Organization • The specialized cells of multicellular organisms are organized into tissues, then into organs, and finally into organ systems.

12. Levels of Organization • A tissue is a group of similar cells that performs a particular function.

13. Levels of Organization • To perform complicated tasks, many groups of tissues work together as an organ. • Each type of tissue performs an essential task to help the organ function. • In most cases, an organ completes a series of specialized tasks.

14. Levels of Organization • A group of organs that work together to perform a specific function is called an organ system. • For example, the stomach, pancreas, and intestines work together as the digestive system.

15. Levels of Organization • The organization of the body’s cells into tissues, organs, and organ systems creates a division of labor among those cells that allows the organism to maintain homeostasis.

16. Cellular Communication • Cells in a large organism communicate by means of chemical signals that are passed from one cell to another. • These cellular signals can speed up or slow down the activities of the cells that receive them, and can cause a cell to change what it is doing. • Some cells form connections, or cellular junctions, to neighboring cells. • Some junctions hold cells firmly together.

17. Cellular Communication • Other junctions allow small molecules carrying chemical messages to pass directly from one cell to the next. • To respond to one of these chemical signals, a cell must have a receptor to which the signaling molecule can bind. Sometimes these receptors are on the cell membrane, although the receptors for certain types of signals are inside the cytoplasm. • The chemical signals sent by various types of cells can cause important changes in cellular activity. For example, such junctions enable the cells of the heart muscle to contract in a coordinated fashion.

18. Levels of Organization • Define the following and give an example of each. • Tissue • Organ • Organ System • Read the analyzing data section of p216 and answer the 3 questions.

19. Cellular Communicaiton • These specialized cells in multicellular organisms must be able to communicate to synch their actions. • Cells create molecules and secrete these molecules to signal surrounding cells. • All cells have receptors which are regions of the cell membrane that are shaped to fit specific molecules or receive specific signals.