Unit 3 Packet 1 End of Notes

​Multicellular Life

Unlike most unicellular organisms, the cells of humans and other multicellular organisms do not live on their own. They are interdependent. Like the members of a baseball team, they work together. In baseball, each player occupies a particular position: pitcher, catcher, infielder, outfielder. To play the game effectively, players and coaches communicate with one another by sending and receiving signals. Cells in a multicellular organism work the same way.



The cells of multicellular organisms become specialized for particular tasks and communicate with one another 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 even cause a cell to change what it is doing in a most dramatic way.

​Certain cells in the heart, the liver, and other organs form connections, or cellular junctions, to neighboring cells. Some of these junctions, such as those shown in Figure 8-24, hold cells together firmly. Others allow small molecules carrying chemical messages or signals 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. Some receptors are on the cell membrane. Receptors for other types of signals are inside the cytoplasm

Multiple Choice

Control ​ ​

​ ​

• nucleus
• mitochondria
• cell membrane
• ribosome

Multiple Choice

3. Making Proteins

• nucleus

• mitochondria

• cell membrane

• ribosome

Multiple Choice

4. Boundaries

• nucleus

• mitochondria

• cell membrane

• ribosome

Multiple Choice

2. Energy

• nucleus

• mitochondria

• cell membrane

• ribosome