Cell specialization

What TWO different things can the stem cell do? Self-renewal Differentiation

Why self-renew AND differentiate? 1 stem cell Why self-renew AND differentiate? 1 stem cell 4 specialized cells Self renewal – makes sure stem cells don’t run out Differentiation - replaces dead or damaged cells throughout your life The stem cell is dividing along the way. At the end of the process, you still have 1 stem cell but 4 new specialized cells. The key take-home messages are: 1) Self renewal is needed because if the stem cells didn’t copy themselves, you would quickly run out. It is important for the body to maintain a pool of stem cells to use throughout your life. 2) Differentiation is important because specialized cells are used up, damaged or die all the time during your life. Specialized cells cannot make copies of themselves, but they need to be replaced for your body to carry on working. Stem cells solve this problem. 4

What happens when you run out of stem cells What happens when you run out of stem cells? What do you think would happen if your body ran out of blood stem cells? You stop replenishing the damaged and dead cells in your body.

Where can I find Stem cells? Adult Stem Cells Embryonic Stem Cells We all have stem cells located throughout our bodies which we call Multi-potent stem cells or Adult Stem Cells .They develop into the different cell types within the tissue they are found in. They are essential for keeping us fit and healthy. They replace cells that are damaged or that have died. Pluri-potent Stem cells also known as Embryonic stem cells are found in the initial stages of the embryo and are capable of forming an entire organism because they can specialize into any cell they want.

blastocyst - a very early embryo Embryonic Stem Cells Tissue stem cells embryonic stem cells blastocyst - a very early embryo around 100-150 cells fetus, baby and all your life This is a very early embryo – an extremely early stage of development of a baby, about 5 days after the sperm fertilizes the egg. It is a ball of 100 to 150 cells. They are found inside the blastocyst and they can make all the cells in the body. 7

Blood stem cells: A type of tissue stem cell white blood cells differentiation differentiation red blood cells found in bone marrow Blood stem cells are found in your bone marrow. They are a type of tissue stem cell and they can make the different kinds of cells in your blood. We saw that earlier with the stem cell decision maker. The answer is about 3 months (120 days). And white blood cells live for an even shorter time (different types have different life spans). That’s why your body needs to make new blood cells all the time. How long do you think a red blood cell lives ? 8

Nearly 4 times around the earth’s equator How hard are they working? If you lined up all the red blood cells from your body, how far would they stretch? Nearly 4 times around the earth’s equator Set the class a challenge: “So these blood stem cells are busy in your body making white and red blood cells all the time. It’s a pretty big job because you’ve got a lot of red blood cells. Now we’re going to see if we can take on a class challenge together: to figure out just how hard these cells have to work.” “You’ve got a lot of red blood cells. Each one is really tiny – smaller than the head of pin. If you lined them all up end to end, how far do you think they would stretch?” Take guesses. 9

Making red blood cells 1 second! To count to 2 million it would take… We counted to 20 in… 2 seconds 2 days 3 seconds 3 days 4 seconds 5 days 5 seconds 6 days 6 seconds 7 days To make 2 million red blood cells it takes your body… 1 second! It generally takes students 3 or 4 seconds to count to 20 if they are really focussed on doing it quickly. This will reveal how long it would take to count to 2 million if you carried on counting at that speed, without any breaks for breathing, eating, sleeping, going to the toilet etc. ‘To make 2 million red blood cells it takes your body…’ This helps illustrate how amazing it is that your body makes so many blood cells every second. Students sometimes ask how many cells there are in your whole body. Your body has about 25,000,000,000,000 red blood cells.

Stem cells in plants Meristematic cells: Undifferentiated plant tissue from which new cells are formed. They are found at the tip of a stem or roots. The undifferentiated plant tissue from which new cells are formed, as that at the tip of a stem or roots.

Specialized Cells Shape of the cell contributes to its function Cell of epidermis (skin cells): flat for good protection Neurons (nerve cells): elongated for conducting messages throughout your body Red blood cells: are suspended in your plasma to form a liquid tissue that transports oxygen throughout your body

Cell specialization lab looking at how the shape of the cell contributes to its function you will look at these specialized cells under the microscope you will need to draw 4 different ones name the cell name the function where is it located in your body Review Activities Workbook: page 20-23