5.5 Multicellular Life KEY CONCEPT Cells work together to carry out complex functions. Peace, man!

5.5 Multicellular Life How many cells in your hand did you think of? Hopefully, NOT your Cell phone! Skin Hair Fingernails Muscle Bone Blood Nerves Oh, and by the way, guess how many types of cells humans have??????

5.5 Multicellular Life Remember when you were a kid playing in the sand at the beach or riding your Big Wheel or playing with your Hot Wheels? You are getting older. What are you going to be when you grow up???? Will you be a professional sand castle builder? A home builder? A doctor? A lawyer? A teacher, perhaps? What will your SPECIALTY be????? What will you be specialized to do or perform in your life ahead? We can think of CELLS as specialized, too! They are all specialized to carry out very specific jobs or functions.

5.5 Multicellular Life Specialized cells perform specific functions. Cells are the smallest, most basic structural unit of life. Cells typically become specialized to carry out 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 As organ systems work together, they help an organism maintain homeostasis. Homeostasis is the maintenance of a stable environment. Let’s use plants as our example: Plants must have a supply of water in order to maintain homeostasis, or they will wilt and die. They absorb water through their root system and release it as water vapor through stomata, which are holes in their leaves. Guard cells within the stomata control the stomata and close or open it. When plants are at a water loss, the stomata close so that they plant can reserve it’s supply of water. We’ll look at plants closer in a later chapter.

5.5 Multicellular Life Multicellular organisms depend on interactions among different cell types. Tissues are groups of cells that work together to perform a similar function. Organs are groups of tissues that work together to 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 How did you get here? Your body began as a single fertilized egg. If the egg just divided to make lots of identical cells, you would not be here. The structures that make you YOU were from cells specializing to create all of the similar AND unique features that God had in mind for you! Cell differentiation is the process when unspecialized cells become specialized into their more mature forms to carry out their specific functions. A cells location within the embryo helps determine how it will differentiate.

5.5 Multicellular Life Stem cells are unique body cells. Defining Characteristics of Stem Cells: 1.the ability to divide and renew themselves 2.remain undifferentiated in form 3.can 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 cell Origins: Adult and Embryonic –Adult stem cells are partially undifferentiated cells located among the specialized cells of many organs and tissues. (located throughout the body: brain, liver, bone marrow, organs, tissues, in kids in umbillical cord blood and even fat) –They have been studied for decades, but the ability to grow them was developed in –Few in number; can be hard to isolate and grow. –The use of adult stem cells may prevent transplant rejection. –Embryonic cells are cells taken from clusters of undifferentiated cells in a 3-5 day old embryo. –Most come from donated embryos from clinics. –The use of embryonic stem cells raises ethical issues –Embryonic stem cells are pluripotent (can grow into any of the 200 types of cells) –They can be grown indefinitely in culture.

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