Lesson 3 - Cytology

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  1. Studying cells is fundamental as they represent the smallest living things on earth. Knowing how they work helps us better understand functions of the human body. What is the study of cells called?
  2. Some organisms, many bacteria for example, are uni-cellular, which means they are made up of only one single cell. We on the other hand have about 75 trillion cells that make us up. What do we call that kind of organism?
  3. Cell size is measured in microns. That is a length measurement indicating something is tiny, tiny small. This small: 1 micron is 1/1000th of a millimeter (mm). A mm is about 1/25th of an inch, making 1 micron about 1/25,000th of an inch. The smallest cell we can see is an ovum (human egg) at about 120 microns. How large is a red blood cell (RBC)?
  4. These tiny living machines come in many different shapes. Their structure dictates the function they have in the body. What does that mean?
  5. An organism is made of many different types of cells: some are muscle cells, some nerve cells, others red blood cells, etc. An organism starts out with one such cell (in humans it’s a fertilized egg) that begins the multiplying process. Daughter cells adapt their size and shape to whatever task they are thought out to accomplish. What is the process called that makes them unique?
  6. Each cell has the same basic structure: a boundary giving membrane surrounding a liquid inside (cytosol). Internally, a large dark sphere in the center (nucleus) holds all the DNA, while other, smaller solid structures with specific functions (organelles) float around. What is the cytoplasm?
  7. A cell membrane surrounds the cell. It creates a boundary between the inside and outside. Since we are mostly water, a great medium for that is an oil film around the entire cell. That way, only oily type substances can pass through it, but \watery type substances cannot. What chemical molecule we learned from last class makes up that membrane?
  8. In order to let hydrophilic substances come into a cell, channel proteins inserted into the membrane let specific substances (such as glucose) through. Receptor proteins let communication molecules (such as hormones) attach. They then, through changing their shape tell the inside of a cell what to do. Pretty nifty! The outside of the membrane is also covered by molecules that identifies who they are; recognizing ones own from foreign is crucial for the immune system. What is that film of sugary molecules called?
  9. Attached to the nucleus arises the first organelle discussed, the endoplasmic reticulum (ER). It’s a bunch of channels and tubes that make proteins and lipids, and transports them to different parts of the cell. It comes in a rough as well as a smooth version. What makes it rough?
  10. Another organelle is kind of like the postal service, it packages substances that a cell exports. The packaging material itself is cell membrane that fuses with the cell’s own as the exportable substances are expelled. What organelle is this?
  11. If a cell takes in foreign substances, it often has to dismantle or even destroy them! What organelle contains digestive enzymes to do so?
  12. No matter of what a cell’s job is, any work it does requires energy in the form of ATP. Which organelle supplies that energy?
  13. This brings us to the nucleus, the large sphere in the center of most cells. It holds and protects the instructions on how to make all the different types of protein in the body. Most fundamentally, this cookbook is made up of 4 randomly repeating molecules (nucleotides) forming long strands. Each strand has a copy; two of them make up a double helix. The sequence of those 4 molecules determines the sequence of amino acids that make up protein. Some cells do not have a nucleus. This makes them unable to divide. Give an example of such a cell.
  14. The long strands of DNA double helix are tightly rolled up (around histone proteins) and well organized in to 46 chromosomes. All of our genes are carried within them. What is a gene?
  15. The double-stranded helix is interesting. Each strand is a specific sequence of four nucleotides called Adenine, Thymine, Guanine, and Cytosine. Three in sequence code for one specific amino acid. There are 20 different amino acids in the body that make up the large variety of our proteins. What do we call 3 nucleotides in sequence?
  16. Because DNA is very delicate and needs to be well protected, cells copy the sequence needed to make a protein before it is made. What is the DNA copy called?
  17. The DNA copy leaves the nucleus and feeds into a ribosome (protein factory). Other molecules collect different amino acids and by reading the codon sequence have the ability to attach them to one another in proper sequence. This makes a polypeptide chain, which is a protein in its fundamental make-up. What is that 2nd stage of protein synthesis called?
  18. It is important for cells to divide and make 2 out of 1. Before it can do that, the hereditary material (DNA) has to be copied. Once that is done, the 2 DNA copies need to be separated in a way that each daughter cell ends up with a full set. What are the steps called that describe this delicate process?
  19. Many different substances need to move in and out of a cell. Some of them move effortlessly, others have to be dragged across. Active transports require energy (ATP), passive ones don’t. Explain one example of a passive process.
  20. If a cell needs to bring in a larger molecule, it wraps it in cell membrane that simply pinch off. What is the term used for cellular eating?

Please email me the answers to the questions before the class meets to [email protected] Thank you!

These talks are 'on topic'. Cells are very small and difficult to visualize. Well, here is some amazing help in doing just that.

If you ever feel unhappy or want to just give up, enjoy this guy and celebrate his transformation. The human body is is awe inspiring.

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