Warm up 1.Are there some cells in your body that look different? 2.Do you think your brain cells do the same job as your stomach cells? 3.How do you think they get to be “different”?

Bio.1.1.3: Cell differentiation and cell speciation

Objectives: 1.Students can explain what cell differentiation is. 2.Students can explain how instructions in DNA lead to cell differentiation

Word Definition Picture 1. Cell differentiation (difference) The process by which cells change in structure and become capable of carrying out specialized functions. This occurs in multicellular organisms. Red blood cell White blood cell

As the result, cells become different from each other. The design and shape of a cell is very much dictated by its function and the conditions under which it works Red blood cell Nerve cell White blood cell muscle cells Stomach cell

NERVE CELLS are responsible for the rapid conduction of messages throughout the body. Consequently, they are very long and have branches that enable them to connect to other nerve cells and deliver messages quickly. Nerve cell

WHITE BLOOD CELLS are primarily responsible for fighting foreign organisms that enter the body. They have the ability to change shape to squeeze through cell membranes to get to damaged cells. White blood cells have different shapes, depending on their function. White blood cells

Because cells in tissues perform specific functions, they often contain organelles that are different from the ones found in a "typical" cell.

MUSCLE CELLS are responsible for producing movement and to maintain posture. Muscle tissues have the ability to shorten or contract. Muscle cellshave huge mitochondria and many microfibers. Because a muscle cell's length is much greater than its width, they are frequently referred to as muscle fibers. Muscle cells

RED BLOOD CELLS have disk-like flattened membranes. This shape gives them a maximum amount of surface area while still remaining smooth enough to slide through the smallest capillaries. Because red blood cells are manufactured for limited-time use, they have lost nearly all of their internal organelles, including nuclei. Red blood cell

Why? And How? 1. The cell differentiation is coded in DNA in the nucleus. 2. Most of our cells cannot differentiate, but our body produce “stem cellS” which can differentiate, depends on its specialized needs.

How? With few exceptions, all of the cells in a multicellular organism contain the same DNA. This is not surprising, given that organisms develop from mitotic divisions of one original cell, called a zygote. However, it is clear that there are many different cell types in the bodies of multicellular organisms. How do these cells ‘mature’ to take on specific roles for an organism?

How? Basically, organisms begin life as a cell whose only developmental restrictions are based on the genome it carries. For instance, an early embryonic animal cell does not have the proper genes to develop into a leaf, but it can develop into any cell type found in the mature animal. Cells with such unlimited developmental potential, like cell of very early embryos, are often referred to as totipotent. As an organism develops, the processes of cell signaling, cell determination and cellular differentiation lead to the maturation of cells and tissues that perform specific functions for an organism

How? The way in which these cells become specialized starts out with a chemical signal. In response to a given signal or signals, cells can change the way they function and develop, most often by controlling what genes are expressed at what time. This process of cellular determination and differentiation happens most commonly in developing embryos, where the cells don’t yet have a specific function, but can occur in certain cells of adult organisms.