5.5 Multicellular Life TEKS 5B, 5C, 10C The student is expected to: 5B examine specialized cells, including roots, stems, and leaves of plants; and animal cells such as blood, muscle, and epithelium; 5C describe the roles of DNA, ribonucleic acid (RNA), and environmental factors in cell differentiation;

5.5 Multicellular Life TEKS 5B, 5C, 10C (continued) 10C analyze the levels of organization in biological systems and relate the levels to each other and to the whole system

5.5 Multicellular Life TEKS 5B, 5C, 10C KEY CONCEPT Cells work together to carry out complex functions.

5.5 Multicellular Life TEKS 5B, 5C, 10C 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 TEKS 5B, 5C, 10C Homeostasis: Is maintained by the interaction of different organ systems that coordinate the body’s functions

5.5 Multicellular Life TEKS 5B, 5C, 10C 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 TEKS 5B, 5C, 10C Defining Characteristics: Stem cells can develop into different cell types. Stem cells have the ability to –divide and renew themselves for long periods of time –remain undifferentiated in form –develop into a variety of specialized cell types

5.5 Multicellular Life TEKS 5B, 5C, 10C Potential: 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 TEKS 5B, 5C, 10C Possible uses: The use of stem cells offers many current 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 TEKS 5B, 5C, 10C 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 TEKS 5B, 5C, 10C 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.