5.5 Multicellular Life Activate Prior Knowledge Look at one of your hands. What are some of the different ypes of cells in your hand? Those making up skin, hair, fingernails, muscle, bone, blood, nerves Are the cells in the trunk of your body any different? similar types of cells, but in addition, many more associated with internal organs Discuss differentiation as how cells are different and how they are allocated.

5.5 Multicellular Life FLT Describe the specialization in multicellular organisms. Identify different types of stem cells.

5.5 Multicellular Life KEY CONCEPT Cells work together to carry out complex functions.

5.5 Multicellular Life Multicellular organisms depend on interactions among different cell types. Tissues are groups of cells that perform a similar function. Organs are groups of tissues that perform a specific or related function. Organ systems are groups of organs that carry out similar functions. CELLTISSUEORGAN vascular tissue leaf stem lateral roots primary root SYSTEMS root system shoot system

5.5 Multicellular Life Specialized cells perform specific functions. Cells develop into their mature forms through the process of cell differentiation. Cells differ because different combinations of genes are expressed. A cell’s location in an embryo helps determine how it will differentiate. Outer: skin cells Middle: bone cells Inner: intestines

5.5 Multicellular Life Power Notes Organ systems: organs that carry out similar functions Organs: groups of tissues that work together to perform similar or related functions Tissues: groups of cells that work together to perform a similar function

5.5 Multicellular Life Power Notes Cells: smallest, most basic structural unit of life; typically become specialized homeostasis: maintained by the interaction of different organ systems that coordinate the body’s functions

5.5 Multicellular Life Stem cells are unique body cells. Stem cells have the ability to –divide and renew themselves –remain undifferentiated in form –develop into a variety of specialized cell types

5.5 Multicellular Life Stem cells are classified into three types. –totipotent, or growing into any other cell type –pluripotent, or growing into any cell type but a totipotent cell –multipotent, or growing into cells of a closely related cell family

5.5 Multicellular Life First, an egg is fertilized by a sperm cell in a petri dish. The egg divides, forming an inner cell mass. These cells are then removed and grown with nutrients. Scientists try to control how the cells specialize by adding or removing certain molecules. Stem cells come from adults and embryos. –Adult stem cells can be hard to isolate and grow. –The use of adult stem cells may prevent transplant rejection. –The use of embryonic stem cells raises ethical issues –Embryonic stem cells are pluripotent and can be grown indefinitely in culture.

5.5 Multicellular Life The use of stem cells offers many currently realized and potential benefits. –Stem cells are used to treat leukemia and lymphoma. –Stem cells may cure disease or replace damaged organs. –Stem cells may revolutionize the drug development process.

5.5 Multicellular Life Power Notes Defining characteristics: 1.Ability to divide and renew themselves for long periods of time 2.Remain undifferentiated in form 3.Can develop into a variety of specialized cell types.

5.5 Multicellular Life Power Notes Possible uses: treat patients with leukemia and lymphoma, may help cure diabetes, repair or replace damaged organs, and improve current drug testing techniques

5.5 Multicellular Life Power Notes Origin: 1. Adult stem cells; partially undifferentiated cells located among the specialized cells of many organs and tissues. 2. Embryonic stem cells: taken from clusters of undifferentiated cells in a 3–to-5–day-old embryo; pluripotent; can be grown indefinitely in culture

5.5 Multicellular Life Power Notes Potential: 1. Totipotent: can grow into any other cell type; includes only a fertilized egg and cells resulting from the first few divisions 2. Pluripotent: can grow into any cell type other than a totipotent stem cell 3. Multipotent: can only grow into cells of a closely related family of cells