A&P 1 Cellular Anatomy, Division & Mitosis - Pre-Lab Exercises

Transcription

1 A&P 1 Cellular Anatomy, Division & Mitosis - Pre-Lab Exercises Have someone in your group read the following out loud, while the others read along: In this "Pre-lab Guide", we will be going over some of the content seen in the videos. However, this content is for lecture & lab, and you are responsible for it in both places. NOTE: This guide contains a lot of conceptual content which will NOT be on the lab practical. Stick to your word list! The lab itself will mostly be anatomy, pointing at the structures seen here. Introductory paragraph: Putting things in perspective Cells have specific roles in the body. These jobs are performed (mostly) through the production of proteins. Almost everything we talk about in lecture that does something within your body is a protein (insulin, antibodies, neurotransmitters, hormones, digestive enzymes, collagen, etc.). Proteins are strings of amino acids. We ll talk more about that in lecture. But, the amino acids must be strung together correctly for the protein to be able to do its job. The genes found on the genetic material within the nucleus are those instructions. Cells make their proteins using cellular machinery called organelles. One special organelle, called a ribosome, can read the instructions or genetic code found in the genetic material and string the amino acids correctly. Other organelles are providing energy, structure, waste management, and other supportive roles.

2 Step 1. Cell Parts #1 Basic Cell Parts All cells have 3 main regions (see image below): Nucleus Plasma Membrane Cytoplasm (includes organelles) We can talk about the inside & outside of the cell (see image below): Intracellular Matrix= fluid inside cell, (by convention, "down" on the images - see below image). Extracellular Matrix = fluid outside of cell, (by convention, "up" on the images - see below image).

3 #2 Details of the Plasma Membrane SEE IMAGE NEXT PAGE Read Me On the image on the next page, notice that we are "zooming in" to a close-up of the plasma membrane, in order to get a better look. It then looks at the phospholipid bilayer, and a phospholipid molecule. The following notes are lecture notes, but they are pertinent to the image. PM = 2 parallel sheets of phospholipid molecules, with other molecules embedded Embedded Molecules - Most of the PM's metabolic roles arise from 2 MAIN CHARATERISTICS (we will discuss in more detail later): - In order to perform these 2 tasks, there are molecules embedded in the PM. Closer look: PM is a fluid matrix - A CHANGING FLUID MOSAIC PATTERN. Embedded Molecules include: a. Proteins - 1/2 of the membrane by weight; 2 types embedded proteins: 1) INTEGRAL ("A part of") - inserted w/in the bilayer. Some face the environment (inside or outside of cell) on one side. If it goes all the way across the membrane it is a "transmembrane protein". Many are channels in or out of cell. 2) PERIPHERAL - "to the side" - not embedded at all. * Many on extracellular side = enzymes or attachment areas for signal molecules. Also see discussion on carbohydrates below. * Many on the intracellular side attach membrane to CYTOSKELETON = A cell s skeleton (see later discussion during "organelle" section of module). b. Carbohydrates - I m including other molecules with a sugar attached, including some proteins: * The prefix or suffix 'glyco' = sugar, lipo = fat, proteo = protein * Glycolipid = fats with sugars attached. * Proteoglycans - mostly protein, with a carbohydrate attached. * Glycoproteins - mostly carbohydrate, with a protein attached. - All of these face EXTERNALLY (outside) of cell. Help form GLYCOCALYX = "sugar coating" - uses of glycocalyx: (i) Immune system: as identification markers. Immune cells use them to ID "self" from "non-self" cells. (ii) Anchor cell (iii) Lubricate & protect cell (iv) Other uses: too numerous to name all of them!

4 c. Cholesterol - Recall from your biochemistry module: Cholesterol is a steroid = a lipid-based molecule, and lipids are soluble in other lipids. - Cholesterol floats inside the fluid-y matrix, act to stabilize inside the membrane. * Phospholipid molecules are attracted to the cholesterol molecule, so they don't disperse as easily. Make sure you can ID these structures on an image for the lab practical.

5 #3 Organelle Background. Organelle Function - Summary Table Classification & Name Function Special Features/Info Non-Membranous Cytoplasmic Organelles Ribosomes Cytoskeleton Centrioles Perform translation (protein synthesis in the cytoplasm). Series of proteins tubules that give cell shape, and hold organelles in place. Protein tubules that have a special role in mitosis. Ribosomes are proteins, made in the nucleus. Attach to anchor proteins embedded in the plasma membrane. Also help form cilia & flagellum. Basal body of cilia and flagellum is a modified centriole. Centrioles make the spindle fibers during mitosis.

6 Organelle Function - Summary Table (continued) Classification & Name Function Special Features/Info Membrane-bound Cytoplasmic Organelles Rough Endoplasmic Reticulum (RER) Golgi Mitochondria Smooth Endoplasmic Reticulum (SER) Lysosomes Peroxisome Plasma Membrane Special Structures Villus (Villi) Cilia Nuclear Structures Nuclear envelope, with pores Chromatin Produce proteins for export, and modify them (this modification can be several things, all of which get them ready to function!) Package proteins for export, and further modify proteins. Produce ATP. Site of "AEROBIC RESPIRATION". Break down toxins, produce lipidbased molecules Digestive vesicles. Contain hydrolytic enzymes. Digestive vesicles. Oxidative enzymes. Increase surface area of the boundary (plasma membrane) Move substances past the cell's surface, among other things. Allow controlled movement in and out of nucleus Contains the genetic information RERs have ribosomes attached, which perform synthesis of proteins for (mostly) transport out of cell. RER places them in its cisternae (inner branching chambers). Places proteins in Secretory Vesicles, for ex[port out of cell. Contain inner membrane with shelf-like structures called cristae. Studded with enzymes that perform aerobic respiration. Continuous with RER; simply has no ribosomes attached Liver, testes, small intestines: Roles vary. Fuses with Phagosome. Contain oxidative enzymes. They do not move! (see below for comparison) They Move! Double Membrane! Do not call it the "nuclear membrane"! Composed of DNA & proteins. Nucleolus (Nucleoli) Site of active protein synthesis Often more than 1 in the nucleus

7 Step 2. Mitosis #1 Overview of the cell cycle Cells make proteins. They have specific jobs in the body, which they perform, for the most part, via protein production. The genetic material within the nucleus provides the directions to the cellular machinery on how to make the proteins correctly. We ll talk about this in more detail in lecture. During this time, the cell is in INTERPHASE, producing proteins and doing what it was designed to do. After awhile, the cell gets old and worn out, and can no longer maintain homeostasis. The body signals it to divide with any one of a number of hormones; we'll be studying them later. The cell will re-generate everything and split into 2 new cells called Daughter Cells. The 2 daughters will need the genetic material so they can produce the proteins needed. It is essential that they both receive a complete set of instructions. Mitosis is the even distribution of genetic material during cellular division (which is called cytokinesis). But, the genetic material is long and fragile, so before dividing them between the 2 daughters, the chromatin is condensed into chromosomes, to make dividing it evenly easier. In the accompanying image, we can see the genetic material condensing into chromosomes, and the nucleus disappearing, as the cell gets ready for division. The cell then goes into the 2nd major stage of its life: "Cellular Division and Mitosis". From this stage, 2 new Daughter Cells will be formed, replacing the old worn out cell. They will now go into their own Interphase, although that is not being shown on the diagram. Mitosis Arrange the chromosomes correctly so they are distributed evenly! Cytokinesis

8 #2 Chromosome structure The cell only has chromosomes when it is getting ready to divide. Usually, the genetic material is unwound chromatin. It is wound into a chromosome to make dividing it easier. In the image to the right, we first notice that you have two pairs of all your chromosomes (and the genes upon them!). One from Mom, the other from Dad. These are homologous pairs. Why do you have duplicate pairs of all your genes (and the chromosomes they sit on?). That way, if one is bad because it was damaged (a mutation ), you have a spare. MORE IN THE GENETICS SECTION OF CLASS. Then we see the genetic material replicating itself while condensing, forming 2 sister chromatids. Each of the new daughter cells will get 1 chromatid. During the first part of mitosis, we want the 2 sister chromatids to stay together while they are moved around the cell. They are held together using a structure called a centromere.

9 #3 Putting it all together, and the stages of mitosis Both Interphase and Mitosis can be further broken down into individual steps. Here, we will be only looking at the steps of mitosis. When we look at the slides and/or models of mitosis, we'll be seeing the arrangement of genetic material as the cell gets ready to divide.