Plasma Membrane Composition Phospholipid Bilayer -phospholipid molecules in a double-layered sheet -hydrophilic (water loving) head facing out -hydrophobic (water fearing) fatty acid tails facing inward -membrane not rigid but pliable (like an olive oil layer on top of water)

Plasma Membrane Composition 1. Phospholipid Bilayer -membrane not rigid but pliable fluid mosaic model – molecules of membrane flow and move about each other in constant motion sliding past one another

Plasma Membrane Composition 2. Proteins - found on surface of the membrane and in the membrane among the phospholipid molecules - identify the cell - form channels through which other molecules can be transported - act as receptors

Plasma Membrane Composition 2. Proteins Protein identifier Protein receptor Protein channel

Plasma Membrane Composition Cholesterol -plays role in stabilizing the membrane -helps keep the membrane flexible Cholesterol

Movement across a membrane. . . Plasma membranes are selectively permeable selectively permeable membrane – a membrane that allows some things to pass through it and other things not

Diffusion - the tendency of molecules to move from a higher concentration to a lower concentration until equilibrium is reached.

Movement across a membrane. . . Diffusion movement of molecules across a membrane from area of higher percent concentration to area of lower percent concentration until they are equally distributed no energy required

Passive Transport Diffusion across a membrane. Cell does not use any energy for diffusion. Selectively permeable membrane. Examples – water, O2 and CO2 gas exchange

Osmosis - passive transport of water across a semi-permeable membrane. The water is the substance that moves across membrane not the solute.

Movement across a membrane. . . Osmosis isotonic solution environment – equal concentrations of substances (solutes) and water (solvent) in cell and in environment around cell *Most bodily fluids will be isotonic to inside of cells (ex. plasma and RBCs)

Hypertonic Solution with a higher concentration of solute and a lower concentration of water. Hyper = above

Movement across a membrane. . . Osmosis hypertonic solution environment – lower concentration of water, higher concentration of solute – water leaves cell it shrinks hypertonic

Hypotonic Solution with a lower solute concentration and a higher water concentration. Hypo = below

Movement across a membrane. . . Osmosis hypotonic solution environment – higher concentration of water, lower concentration of solute – water enters the cell and it swells / bursts

Isotonic Solutions of equal solute concentration. Isos = equal

Effect on living animal cells Osmoregulation – control of water balance. Animals must use this when exposed to hypertonic and hypotonic environments for survival. Example – fresh water fish live in hypotonic environment use kidneys and gills to prevent excess water buildup in body.

Effect on living plant cells Most plants thrive in a hypotonic environment when cell wall is turgid and vacuole is full. Plants become wilted in isotonic environment. Plasmolysis – plant in hypertonic environment causes cell water loss, cell shrivels and the cell membrane pulls away from the cell wall and can kill the cell.

Other Ways to Get in. . . . Facilitated diffusion Carrier Protein Facilitated diffusion -involves protein carriers that combine w/ the molecule to move them across the membrane -the diffusion is ALWAYS from high to low concentration (down the concentration gradient) -no energy required

Other Ways to Get in. . . . Facilitated diffusion -use carrier proteins -from high to low concentration -no energy required

Other Ways to Get in. . . . active transport – uses carrier proteins to carry molecules against the concentration gradient, from low to high concentrations -requires ATP energy (backwards from diffusion - - not passive)

Other Ways to Get in. . . . Endocytosis Exocytosis process cells use to wrap membrane around a particle (usually food) and engulf it ex. leukocytes (white blood cells) use this to surround invading bacteria, viruses, and other foreign materials Exocytosis the opposite of endocytosis particles are released exocytisis endocytosis

Types of Microscopes Light Microscope -  the models found in most schools, use compound lenses to magnify objects. The lenses bend or refract light to make the object beneath them appear closer. Common magnifications: 40x, 100x, 400x *Oil Immersion lenses can improve quality of focus and magnification

Imaging technologies provide new views of life. Light microscopes (LM) Light and lenses used to magnify specimens limited magnification can be used to study living specimens shows a two-dimensional image of a specimen. Shows actual color of the specimen. stoma This light microscope shows the actual color of the specimen. Guard cells surrounding a stoma, or pore in a leaf. Use Three Way Venn Diagram LM magnification 400X 25

http://www.biologycorner.com/resources/MICRO-labeled.gif

Stereoscope- dissecting microscope This microscope allows for binocular (two eyes) viewing of larger specimens.  Usually magnifies 10x to 20x Can be used for thicker specimens Creates a 3D view of specimen

SEM Scanning Electron microscope http://media-2.web.britannica.com/eb-media/88/113688-004-B14FDB14.gif http://www.nanosmo.com/wp-content/uploads/2012/01/26cecidomyiidae200.jpg

Scanning electron microscopes (SEM) Deflection of electrons used to magnify specimens; provides high magnification and a three-dimensional black-and-white image that can be colored by computer cannot be used to study living specimen stoma A SEM shows a three dimensional image of a specimen’s surface. A SEM is colorized by computer. The bottom part of the image shows the original black and white image. SEM magnification 1500X 29

http://upload. wikimedia. org/wikipedia/commons/thumb/a/a4/Misc_pollen http://upload.wikimedia.org/wikipedia/commons/thumb/a/a4/Misc_pollen.jpg/788px-Misc_pollen.jpg These pollen grains taken on an SEM show the characteristic depth of field of SEM micrographs. 30

Transmission Electron Microscope (TEM) http://www.jeol.com/Portals/0/prodshots/EO/jem-2100f.jpg http://www.ccber.ucsb.edu/research/esau/topics-of-study/microscopes/electron_microscope.jpg Transmission electron microscopes (TEM) are microscopes that use a particle beam of electrons to visualize specimens and generate a highly-magnified image. TEMs can magnify objects up to 2 million times. In order to get a better idea of just how small that is, think of how small a cell is. It is no wonder TEMs have become so valuable within the biological and medical fields. How Do TEMs Work? TEMs employ a high voltage electron beam in order to create an image. An electron gun at the top of a TEM emits electrons that travel through the microscope's vacuum tube. Rather than having a glass lens focusing the light (as in the case of light microscopes), the TEM employs an electromagnetic lens which focuses the electrons into a very fine beam. This beam then passes through the specimen, which is very thin, and the electrons either scatter or hit a fluorescent screen at the bottom of the microscope. An image of the specimen with its assorted parts shown in different shades according to its density appears on the screen. This image can be then studied directly within the TEM or photographed.  31

Transmission electron microscopes (TEM) Electrons passing through a specimen used to magnify specimen; provides high magnification two-dimensional black-and-white image that can be colored by computer cannot be used to study living specimens stoma A TEM shows a two –dimensional image of a thin slice of a specimen. A TEM is colorized by computer. The bottom part shows the original black-and-white image. TEM magnification 5000X Electrons passing through a specimen used to magnify specimen; provides high magnification and a two-dimensional black-and-white image that can be colored by computer; cannot be used to study living specimens 32

TEM of a cell, notice you see the inside of the cell and not the surface.

Always carry with 2 hands Only use lens paper for cleaning The Light Microscope Guidelines for Use Always carry with 2 hands Only use lens paper for cleaning Do not force knobs Always store covered Keep objects clear of desk and cords Teacher demonstrates how to hold the microscope, where the lens paper is located and how to use it. Students will be invited to turn the knobs and observe the stage as it moves up and down. Teacher will demonstrate how to store the microscope. 35

Magnification Your microscope has 3 magnifications: Scanning, Low and High. Each objective will have written the magnification. In addition to this, the ocular lens (eyepiece) has a magnification. The total magnification is the ocular x objective

2. Plug your microscope in to the extension cords. General Procedures Make sure all backpacks and junk are out of the aisles and off the tops of desks.  2. Plug your microscope in to the extension cords. 3. Store with cord wrapped around microscope and the scanning objective clicked into place.  4. Carry by the base and arm with both hands. Give students a slide from the “common things” set, each student will practice focusing and changing objectives. 37

1. Always start with the scanning objective. Focusing Specimens 1. Always start with the scanning objective.  Odds are, you will be able to see something on this setting. Use the Coarse Knob to focus, image may be small at this magnification, but you won't be able to find it on the higher powers without this first step.  Do not use stage clips, try moving the slide around until you find something. Give students a slide from the “common things” set, each student will practice focusing and changing objectives. 38

1. Scanning --> use coarse knob 2. Low power --> use fine knob 2. Once you've focused on Scanning, switch to Low Power. Use the FINE Knob ONLY to refocus. Again, if you haven't focused on this level, you will not be able to move to the next level. 3. Now switch to High Power. (If you have a thick slide, or a slide without a cover, do NOT use the high power objective). Again, ONLY use the Fine Adjustment Knob to focus specimens. Recap 1.  Scanning --> use coarse knob 2.  Low power --> use fine knob 3.  High power --> use fine knob DO NOT SKIP STEPS!!!!

Your slide MUST be focused on low power before attempting this step Click the nosepiece to the longest objective Do NOT use the Coarse Focusing Knob, this could crack the slide or the lens Use the Fine Focus Knob to bring the slide Have students exchange slides so they can look at different things, walk them through using the high power objective to focus slides. Emphasize not using the coarse objective during this process, as it will crack the slides. 40

Drawing Specimens 1. Use pencil - you can erase and shade areas 2. All drawings should include clear and proper labels (and be large enough to view details). Drawings should be labeled with the specimen name and magnification. 3. Labels should be written on the outside of the circle. The circle indicates the viewing field as seen through the eyepiece, specimens should be drawn to scale - ie..if your specimen takes up the whole viewing field, make sure your drawing reflects that.

Making a Wet Mount 1. Gather a thin slice/piece of whatever your specimen is. If your specimen is too thick, then the coverslip will wobble on top of the sample like a see-saw, and you will not be able to view it under High Power. 2. Place ONE drop of water directly over the specimen. If you put too much water, then the coverslip will float on top of the water, making it hard to draw the specimen, because they might actually float away. (Plus too much water is messy) 3. Place the cover slip at a 45 degree angle (approximately) with one edge touching the water drop and then gently let go. Performed correctly the coverslip will perfectly fall over the specimen. Do not drop vertically, set one edge down and let the other side drop.

How to Stain a Slide 1. Place one drop of stain (iodine, methylene blue..there are many kinds) on the edge of the coverslip. 2. Place the flat edge of a piece of paper towel on the opposite side of the coverslip. The paper towel will draw the water out from under the coverslip, and the cohesion of water will draw the stain under the slide. 3. As soon as the stain has covered the area containing the specimen, you are finished. The stain does not need to be under the entire coverslip. If the stain does not cover as needed, get a new piece of paper towel and add more stain until it does. 4. Be sure to wipe off the excess stain with a paper towel.

Cleanup Store microscopes with the scanning objective in place. 2. Wrap cords and cover microscopes.                       *Double check to make sure you didn't leave a slide 3. Wash slides in the sinks and dry them, placing them back in the slide boxes to be used later.  4. Throw coverslips away. (these are not reusable)        *Be careful not to drop these in the sink, they can clog drain. 5. Place microscopes in their designated location (probably a cabinet)

Troubleshooting Occasionally you may have trouble with working your microscope. Here are some common problems and solutions. 1. Image is too dark! Adjust the diaphragm, make sure your light is on. 2. There's a spot in my viewing field, even when I move the slide the spot stays in the same place! Your lens is dirty. Use lens paper, and only lens paper to carefully clean the objective and ocular lens. The ocular lens can be removed to clean the inside.  The spot is probably a spec of dust. 3. I can't see anything under high power! Remember the steps, if you can't focus under scanning and then low power, you won't be able to focus anything under high power.  Start at scanning and walk through the steps again.  4. Only half of my viewing field is lit, it looks like there's a half-moon in there! You probably don't have your objective fully clicked into place..

Practice Labeling the Parts

Quiz Over the Microscope 1.  When focusing a specimen, you should always start with the ___________________ objective. 2.  When using the high power objective, only the ________   ___________ knob should be used. 3.  The type of microscope used in most science classes is the _________________ microscope 4.  Stains can be drawn under the slide (and over a specimen) by using a _____________________ 5.  What part of the microscope can adjust the amount of light that hits the slide? ______________________________

6.  You should carry the microscope by the ________ and the __________. 7.  The objectives are attached to what part of the microscope (it can be rotated to click the lenses into place):      _______________    ________________   8.  You should always store you microscope with the  ________________ objective in place.  9.  A microscope has an ocular objective of 10x and a high power objective of 50x.  What is this microscope's total magnification?  ____________ 10. SEM is an abbreviation for ____________  ____________   ________________