good morning everyone i hope you're all doing well today we're going to dive into one of the most important concepts in biology cell theory now I know when you hear cell theory you might be thinking what's so special about cells they sound like this tiny invisible things that don't really matter to us but I promise you understanding cells will completely change how we look at life everything in life from the tallest tree to the smallest bacterium is made up of cells cells are the basic building blocks of life imagine them as a bricks in a house or the gears in a machine without them nothing works so why is understanding how cells function and how they fit into life so crucial well that's exactly what we're going to explore today with cell theory let's take a step back in time way back to the 1600s robert Hook an English scientist was one of the first to look at cells under a microscope in 1665 he was examining a thin slice of cork and under the microscope he saw small box-like structures these tiny compartments reminded him of the small rooms where monks live which were called cells so he named them cells interestingly the hook thought the cells were dead because he was looking at pork which comes from trees he didn't realize that cells could be living however this was still an important discovery it was the first time anyone had identified this little units that formed the structure of plants and animals around the same time another scientist Antonyin van Luen Hook from the Netherlands was doing something similar but instead of cork Luen Hook was examining pond water and saw tiny moving organisms he called them animal cues which means little animals he was the first person to observe living cells in action can you imagine being the first to see living creatures under a microscope that was a huge deal back then it wasn't until the 1800s that the concept of cell theory really began to take shape two scientists Matias Schladen a botonist and Theodore Schwan a physiologist expanded on the earlier work of Hook and Luen Hook schladen concluded that all plants are made of cells while Schwan stated that all animals are made of cells their work led to the idea that cells were the fundamental unit of life no matter what type of organism you're looking at but the final piece of the puzzle came from Rudolfph Fo a German physician in 1855 he famously said omnisellular is cellula which means all cells come from preexisting cells this idea challenged the old notion of spontaneous generation the belief that life could randomly appear from non-living matter verso's discovery helped to solidify the idea that life is continuous passed on from one cell to another now that we know a little bit about the history of cell theory let's break it down into three main principles or tenets that make up the theory the first tenant all living organisms are made of cells this is the foundation of the entire theory it means that every living thing is made up of cells every animal plant fungi and even the simplest bacteria are composed of cells it's like how a building is made up of bricks no matter how big or complex the building is it's always made from the same basic unit bricks so all living organisms are essentially cellular at their core but here's an interesting point some organisms like bacteria and amiebas are unisellular this means they are made up of just one cell and that one cell does all the work needed for the organism to survive it takes in nutrients gets rid of waste and even reproduces on the other hand there are multisellular organisms like us humans animals and plants we are made up of trillions of cells working together to keep us alive and functioning isn't that amazing we start out as just one single fertilized cell and from there our body develops into a complex organism with different types of cells each having its own role the second tenant the cell is a basic unit of structure and function in living organisms now this part of cell theory is super important cells are not just little blobs of matter they have specific structures that allow them to function properly let's take a look at the structure of a cell the cell membrane is like the outer wall of the cell kind of like the walls of a house it keeps everything inside and protects the cell from the outside environment it also controls what enters and exits the cell kind of like a security guard the nucleus is the control center of the cell it contains the DNA which has all the instructions for the cell's activities think of it like the brain of the cell it tells the cell what to do and when to do it the cytoplasm is the gel-like substance that feels the cell this is where all the actions happens it's like the space inside a city where all the workers and machines function the cytoplasm holds everything in place providing structure and a medium for the chemical reactions that occur in the cell each of these parts is essential for the cell to do its job without them the cell wouldn't be able to carry out life processes like energy production growth reproduction or responding to the environment the third tenant all cells come from preexisting cells this concept is one of the most crucial ideas in biology it tells us that cells don't just appear out of nowhere every cell that exists today has come from a preexisting cell how does this happen through cell division when a cell divides it makes a copy of itself creating two new cells there are two types of cell division mitosis and meiosis mitosis is the process by which a cell divides to form two identical cells this happens when a body needs to grow heal or replace old cells for example when you cut yourself mitosis helps new skin cells grow to heal the wound meiosis on the other hand is how we make sex cells the sperm and eggs this process is a bit more complicated because it ensures that when sperm and egg combine the new organism will have the right number of chromosomes what's so important about this well this idea helped disprove spontaneous generation which claimed that life could appear from non-living matter instead Vo's idea of cells coming from other cells show that life continues through this cycle of reproduction it also set the stage for modern research in genetics because we know or we know understand how information passes from one generation to the next now what are the applications and implications of cell theory cell theory isn't just a theory stuck in textbooks it has realw world applications that impact us every day for example think about diseases like cancer cancer happens when cell grow uncontrollably if we didn't have a clear understanding of how cell division works we wouldn't be able to study or treat cancer effectively thanks to cell theory scientists can now focus on finding treatments that target abnormal cell division another huge application of cell theory is in stem cell research stem cells are unique because they can become any type of cell in the body scientists are exploring how to use stem cells to treat diseases repair damaged tissues and even grow new organs for transplants cell theory has also been central in the development of genetic engineering by understanding how cell works scientists can modify the DNA inside cells to correct genetic diseases or even create genetically modified organisms or GMOs that are more resistant to diseases or pests as you can see cell theory is not just academic it drives many of the breakthroughs that we see in science medicine and technology to wrap things up cell theory is absolutely fundamental to our understanding of biology by recognizing that all living organisms are made of cells that cells are the basic unit of life and that all cells come from other cells we've built a foundation for modern biology without cell theory we wouldn't have a clear understanding of how life works at the most basic level it explains everything from how we grow to how we heal to how diseases spread and because of the scientists who discovered and explained these ideas we've been able to make incredible advances in medicine genetics and more next time you look at a plant or animal or even a tiny organism under a microscope remember what you're seeing is a result of countless cells working together isn't that amazing it really shows us that life at its core is a complex yet beautifully organized system made possible by the smallest building blocks the SAS thank you and once again this is your instructor Medaline see you on the next module bye-bye