7.4 Homeostasis & Cells

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.

7.4 Homeostasis & Cells

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

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

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.

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

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.

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.

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.

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

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

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.

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.

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.

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.

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.

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.

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.