CN Cell Differentiation #69

Transcription

1 Questions: Five study Questions EQ: What factors influence how and when cells differentiate within different organisms? Cell theory states that living things are made of cells some are unicellular (one cell) and some are multicellular (many cells) Multicellular organism have different kinds of cells Example: humans have skin cells, muscle cells, bone cells, heart cells, etc. Mitosis (cell division) makes more cells that are identical to each other How do cells in multicellular organisms become different from each other? Differentiation Cells must differentiate to develop new structures Differentiation Key Idea The process by which cells change in structure and become capable of carrying out specialized functions As cells differentiate, they become different from one another. They also form groups made of other, similarly specialized cells. These groups then form tissues and organs. Differences in Structure Multicellular organism start out as one cell This one cell uses mitosis and differentiation to become an organism with specialized structures

2 Example: plants have cells that can differentiate (become different) into leaf cells, root cells, and stem cells. They all look different and have different jobs. LEAF ROOT STEM Differences in Function Cells with different structures carry out different functions Example: Plants leaf cells have chloroplasts which capture sunlight and use photosynthesis to make food for the plant root cells are underground, don t have chloroplasts and don t do photosynthesis; instead they have fingerlike projections that reach into the soil to absorb water Tissues, Organs, and Systems When cells differentiate, they become organized Tissues cells that work together to carry out specific jobs

3 Example: Muscle cells are organized into long strands of muscle tissue that can move legs or arms Organs tissues that work together to form organs (example: the stomach of an animal or root of plants) Systems when organs work together (example: the digestive system needs the stomach, intestines, blood vessels to all work together) Increasingly Specialized Cells As development continues, more specialized differentiation occurs More specific structures=more specific functions Example: the retina in your eye has 2 types of cells sensitive to light (rods= function in dim light; cones=detect color) How Cells Differentiate DNA in cells determines what each cell will become Once a cell s future has been determined, when and how much it changes depends on its DNA, its function, and the type of organism Some cells differentiate completely during development, others don t change until later Cell Differentiation Among Animals Cells at the point of injury can differentiate, forming new muscle, bone, blood, and nerves Example: many animals like insects and reptiles can grow a limb or tail to replace a lost one (lizards!) Humans cannot grow new limbs; once human cells differentiate they lose the ability to become other types of cells EXCEPT stem cells

4 Stem Cells CN Cell Differentiation #69 Stem cells: certain cells in humans that can differentiate throughout life Stem cells in humans can provide new blood cells (red blood cells that carry oxygen, white blood cells that fight infection, platelets that help with blood clotting) Cell Differentiation in Plants Differentiated cells become roots, stems, leaves Cells can differentiate further and become more specialized Example: some cells in the stems of plants transport food from leaves to roots while others transport water from roots to leaves Plants also have the ability to grow new roots, stems, and leaves through differentiation

5 An entirely new plant can grow from one leaf in some cases!