Monday, September 23. What is the name given to the cell membrane to describe its structure and why was it given this name?

Transcription

1 Monday, September 23 Bell Work: What is the name given to the cell membrane to describe its structure and why was it given this name? 1

2 Phospholipid Polar heads are hydrophilic because they are waterloving and attract water molecules. Nonpolar tails are hydrophobic because they are waterfearing and repel water molecules. Think of a sandwich: The polar heads are the bread, they form the outer surface of the membrane and interact with the environment. The nonpolar tails are the peanut butter and are protected from the watery environment. 2

3 The proteins are embedded in the phospholipids and help materials move across the membrane. Protein channels make passageways for molecules to move across the membrane. The carbohydrates that are attached to some of the proteins act like ID tags to identify one cell type from another. The cholesterol molecules strengthen the cell membrane. 3

4 Fluid Mosaic Model The fluid mosaic model describes the arrangement of the molecules that make up the cell membrane. 2 Characteristics Fluid because the phospholipids can move side to side and slide past one another. Mosaic the different molecules imbedded throughout the phospholipids have different textures and patterns like mosaic tile. 4

5 Selective Permeability Selective permeability allows some, but not all materials to cross the membrane. Water Proof clothing is an example of semipermeable material, meaning small air molecules can get through the clothing, but large drops of rain cannot. Selective permeability helps to maintain homeostasis because it controls the import and export of certain molecules and ions. So, even if the ion concentration outside the cell changes drastically, the cell can survive. Small Polar molecules are transported across the membrane by proteins Small Nonpolar molecules easily pass through the membrane. Large molecules are moved in by vesicles. What is a vesicle? 5

6 Microscope Compound Light 1500x living preserved 6

7 Electron 100,000x protein molecules living specimen vacuum 7

8 Scanning (SEM) electrons 3-D metal Transmission (TEM) 2D magnification colorized 8

9 microscopenotes.notebook TEM of stomata of a leaf original and colorized. Magnification 5000x 9

10 microscopenotes.notebook SEM of stomata in a leaf. Magnification 1500x 10

11 When carrying any microscope, always carry it by the BASE and the ARM. The microscope that we will be using in the lab is the COMPOUND LIGHT microscope which we will be using to see through objects (transparent). Biologists use this microscope to look into cells. 11

12 The first lens used in any microscope is the lens in the EYEPIECE. This lens usually magnifies the object 10 times its actual size. The other lenses are called OBJECTIVES. The shortest one is used to find the object we wish to magnify (SCANNING LENS). The middle lens is called the LOW power lens. The longest lens is called the HIGH power lens. There are two ways to focus on an object. The first is the _COARSE adjustment. This can be used while using the scanning lens only. The second is the _FINE adjustment. This knob ONLY must be used when using the low and high powered lens. 12

13 When there are no slides on the microscope, the microscope must be set on the scanning (shortest) lens and the objectives are to be moved as far away from the stage as possible. 13

14 Compound Light Microscope Microscope used to see transparent (see through) objects like cells and water. 14

15 Eyepiece the part of the microscope that you look through to view the object. Body Tube connects the eye piece to the objective lenses Arm Supports the tube and connects it to the base Stage The part the microscope slide lays on Coarse Adjustment Knob Large, located on the slide, used for focusing the specimen 15

16 Fine Adjustment Knob Small, located on the side, used to fine tune focus specimen Light Source allows light to reflect upward through the diaphragm, the specimen, and the lens Revolving nose piece allows you to rotate the objectives Scanning Lens lowest power lens (shortest) used to find objects 16

17 Low power objective magnifying power of 10x High power objective magnifying power of 40x Diaphragm regulates the amount of light entering the microscope Base the bottom of the microscope, used for support Stage Clips hold microscope slide in place 17

18 Magnificaon Magnificaon is the measure of how much larger the object appears through the microscope than it actually is. For example if you are looking at leaf using a stereomicroscope with 3x magnificaon, the parts of the leaf will appear 3 mes larger than they actually are. Magnificaon can be determined by mulplying the magnificaon of each lens used to see the object. 10x X 4x = 40x magnification magnification total of eyepiece of objective magnification Complete the chart below to calculate the total magnification of an object. 4x 60x 100x 800x 1. Which combinaon of lenses would allow you to see the object with greatest magnificaon? 2. Which combinaon of lenses would allow you to see the largest area of the specimen? Field of View the amount of an object you can see while looking into the microscope 18

19 MICROSCOPE RULES MICROSCOPES SHOULD BE PUSHED BACK AWAY FROM THE EDGE OF THE TABLE. ALWAYS BEGIN AND END A SLIDE WITH THE SCANNING LENS! WHEN FINISHED WITH A SLIDE, ALWAYS CLEAN THE SLIDE AND COVER SLIP WITH FRESH WATER AND WIPE DRY WITH A PAPER TOWEL. CLEAN LENSES WITH LENS PAPER ONLY! REPORT ANY BROKEN MATERIALS TO TEACHER IMMEDIATELY. 19

20 20