Chapter 10: Types of Cells
Come visit the Sensational Cell Circus, and then find out how form and function determine the shape of cells.
Part 1: The Sensational Cell Circus
By the help of a microscopes, there is nothing so small as to escape our inquiry; hence there is a new visible world discovered to the understanding.
-Robert Hooke – discoverer of plant cells
Step right up ladies and gentlemen, boys and girls to the Sensational Cell Circus! You might have met all the creatures in the Kingdoms of Creation, but you have never seen them like this. Unless you’ve been walking around with a microscope, you haven’t been seeing the cells – they’re just too small! ‘Why would I want to see something so small, so miniscule, so insignificant,’ I hear you scoff. Why, cells are the very building blocks of life. So step right up, folks, and you can see some of the best cells in all of creation.
First up, we have our tiny town tenants – some of the finest specimens known to man from the Kingdoms of Archaea and Bacteria. We’ve got long, skinny pills and short strings of pearls. We’ve got ones that look like lumpy pillows and ones that look like they’re covered with hair. But the greatest of them all is Tetanus – don’t get too close now. It looks like a worm with one giant eye, and that’s not just for show; this microscopic creature is extremely dangerous!
Next, we have our three Protist sisters – Plant-like, Animal-like, and Fungus-like. These lovely cells are all from the same “family,” but they look nothing alike. Well, of course they are all different: the Kingdom of Protists is home to all the misfit creatures, perfect for our circus! Plant-like is almond shaped and can’t move at all. Animal-like has “pseudo-arms” that reach out and then get sucked back in as she creeps forward. Fungus-like, on the other hand, is enormous with creeping fingers that help her go about the work of decomposition.
Next on our stage we have our Plants and Fungi. You’ve seen them on the hills, you’ve seen them in the valleys, and now you can see them up close and personal. Really up close – we’re talking about cells after all. Like conjoined twins, these creatures cells are stuck together, making bigger, more complex creatures. Plant’s cells are like a quilt filled with rectangles or hexagons but with rigid walls. Fungus, though, is a much more laid back creature, more round and blobby but still with stiff walls.
And now, for the main event – the parade of Animal cells. Animals are so complex that they have a whole menagerie of different types of cells. There’s the wall of rectangular skin cells; the red blood cells that look like a thumb-print cookie; the long, skinny muscle cells; and the squishy, pillowy fat cells.
Last but not least, we have one final cell for you to see on this very stage. We have scoured the Earth, looking for the longest cell, and we are pleased to have brought it here for you to see for yourself: the giraffe’s neck nerve cell. This magnificent creation is 12 m (40 ft) long, a true giant among nerve cells that might be only nanometers long (that’s 12 billion times smaller). Whether large or small, nerve cells have arms that reach out to connect them together into a great web that covers a creature’s entire body, letting it go out and explore all of creation.
Check out Chapter 10A Podcast Episode!
Part 2: What’s Shape Got to Do with It? – Cell Form and Function
Cut your morning devotions into your personal grooming. You would not go out to work with a dirty face. Why start the day with the face of your soul unwashed?
-Robert Hooke – discoverer of plant cells
You might be thinking to yourself, after hearing about all of those different types of cells: why would there be so many? Why wouldn’t every type of creature have the same cells? After all you can build a house or a church or a bank out of bricks. But would you want to drive a brick car or wear a brick dress? Do you think a brick water pitcher would even hold water? While you could make a chair out of bricks, perhaps foam cushions would be more comfortable. We use other materials, such as wood, clay, fabric, or glass simply because they work better for the job. In the same way, different types of cells help the creature do different things.
Many bacteria, archaea and some protists look like they have fur or a tail; those are cillia (the hair-like things) or flagella (looks kind of like a tail) to help them swim around. What if the little creature needs to move to find food? Then pseudopods (bits of the cell extending out and retracting) or creeping tendrils work well for searching for and capturing food. What if instead the creature is more plant-like? Since they make their own food, they often do not move at all on their own but instead float along as the ocean takes them.
Plants and fungi both need cells that can give them structure but don’t need to be able to move around, so their cells are both rather stiff. However, I’m sure you’ve noticed that mushrooms are much spongier than say your wooden chair – why? Towering trees need much more rigid cells in order to give them the strength to stand, whereas mushrooms are quite low to the ground and can get by with softer cells. These different types of cells are a gift from the Creator for not only the creatures but for us as well – wood makes much better tables than mushrooms.1
Animals have many different types of cells, each with their own jobs. The rectangular skin cells act like bricks in the wall of a castle, protecting us from the outside world. Red blood cells look like thumb-print cookies – this shape allows them to absorb more oxygen to deliver to our muscles. Those muscle cells are long and thin, and just like the rubber bands they resemble, they stretch and contract as needed to move your arms and legs. Your fat cells, on the other hand, are blobby and round since this shape can store the most stuff. Nerve cells, though, are the coolest; their long tendrils allow them to reach out to one another, to make connections from one cell to the next all throughout your body, so that your brain can tell your feet what to do.
All of these various types of cells illustrates an important concept in science: the relationship between form and function. That is, the way something looks or how it is shaped affects what it does. A paper clip, for example, is made of a rigid material and has a curvy, twisted shape which allows it to hold together papers (or make lovely chain necklaces). What if it were made of jelly? Would it still be able to do its job? What about if it weren’t twisted – could it still hold the papers? In order for the paper clip to do its job, it must have the form that it usually has. Similarly, a red blood cell has been carefully crafted by the Creator into an admittedly unusual shape in order to do its job. Watch for form and function all around you – you will find it throughout all of creation (and the man-made world, too).
1Some people are actually trying to make furniture and other household goods out of fungus mycellium grown inside a frame. Because mycellium can grow very tightly packed together, they actually do make a rather admirable building material...I’m just not sure that I really want that in my house.
I enjoy seeing the creative ways you make science fun!