Microscopy & Cell Theory

Bell ringer Electron microscope Reminder: Project for Tues, 8/28 Produce an annotated poster displaying an animal or a plant cell. Your cell must be hand – drawn! (Organelles to include as appropriate: Cell surface membrane, Nucleus, nuclear envelope, nucleolus, Endoplasmic reticulum (smooth and rough), Golgi apparatus (Golgi complex, Golgi body), Mitochondria (including small circular DNA), Ribosomes (differentiate 80S and 70S), Lysosomes, Centrioles + Microtubule, Chloroplasts (including small circular DNA), Cell wall and plasmodesmata, Large permanent vacuole and tonoplast)

Learning objectives explain and distinguish between resolution and magnifcation, with reference to light microscopy and electron microscopy calculate the linear magnifcations of drawings, photomicrographs and electron micrographs use an eyepiece graticule and stage micrometer scale to measure cells and be familiar with units (millimetre, micrometre, nanometre) used in cell studies calculate actual sizes of specimens from drawings, photomicrographs and electron micrographs describe and interpret electron micrographs and drawings of typical animal and plant cells as seen with the electron microscope

Scanning Electron Microscope (SEM) Transmission Electron Microscope (TEM) Electrons don't pass through the specimen. They bounce off the specimen. 3D view Magnification is x 100 000 Electron beam passes through a thin sample Electrons pass through the denser parts less easily – contrast Image is 2D Magnification is x 500 000

Electron microscope: advantages and disadvantages Resolution is 0.1nm Detailed images or organelles 3D images-shows contours (SEM) Disadvantages: Electron beams deflected by air molecules - vacuum needed. Expensive Skill & training needed

Coloured electron micrographs Electron micrographs are always black, white & grey when they are produced Colours can be added afterwards using computer software=false colour electron micrographs

Development of Cell Theory SCHWANN HOOKE SCHLEIDEN 1665: pore-like structures “cells” 1839 - All animal tissues are composed of cells. VIRCHOW 1858 - All cells must arise from preexisting cells. 1838 - All plants are made of cells

Cell theory All living beings are made up of cells. Cell is the most basic unit of life. All cells must come from pre-existing cells.

Investigating cell make-up Cells are very small, therefore we need to produce images that are enlarged & more detailed to study them Light microscope improvements Electron microscopes Investigating chemical reactions occurring in different parts of the cell

Magnification vs. Resolution Magnification is how much bigger a sample appears to be under the microscope than it is in real life. Resolution is the ability to distinguish between two points on an image - the amount of detail. e.g. if two objects are less than 200nm apart they are seen as one object. Total Magnification = objective magnification x eyepiece magnification

Magnification Resolution

Magnification Resolution Increasing the magnification does not increase the resolution of the image!!

Light Microscope Resolution: 200nm Magnification: x4, x10, x40 Invention of microscope Light Microscope http://sciencevideos.wordpress.com/2008/01/26/cell-theory/ Resolution: 200nm Therefore any images closer together than 200nm will be seen as 1 object Due to magnitude of the wavelength of light 2 objects can only be seen if light can pass between them Human eye resolution = 100μm Magnification: x4, x10, x40 x100 (oil immersion)

Add labels to your diagrams Arm Base Body tube Coarse adjustment screw Condenser lens Eye Eyepiece Fine adjustment screw High power objective lens Lamp Low power objective lens Mirror Objective lens Specimen Stage

Light passes from the bulb, then through the specimen Beam of light is focused through the objective lens, then through the eyepiece lens X4, X10, X40, X100 Objective lenses The eyepiece lens then magnifies image again by x10 Therefore total magnifications of x40, x100, x400, x1000 MAX light microscope magnification =x1500 (x15 eyepiece x100 objective lens)

Using a Microscope Start on the lowest magnification Don’t use the coarse adjustment knob on high magnification…you’ll break the slide!!! Place slide on stage and lock clips Adjust light source (if it’s a mirror…don’t stand in front of it!) Use fine adjustment to focus

Home Learning Preparing a slide Info and question sheet

Working out magnification Magnification = Observed size of the image actual size Remember to convert values to the same unit first!

Complete practice sheet on magnification calculations Measuring cells Complete practice sheet on magnification calculations Work through pages 8 – 9, take notes on how to measure cells, calculate magnification of a photograph or image, and calculating magnification from a scale bar.

Electron micrographs Name the structures

Nucleus with Nucleolus

Golgi apparatus wit Vesicles

Mitochondrion

Chloroplast

Endoplasmic reticulum

Lysosomes

Vacuoles

Bacterium with flagella

Task In pairs look at electron micrographs of cells and identify as many organelles as possible. Look at at least two different micrographs

Summary Quiz Complete the Quiz on calculations and organelle identifications using micrographs. (15min)

Can you guess what it is? A fly!!

Can you guess what it is? Carpet!

Can you guess what it is? A feather!!

Can you guess what it is? A flower!!

Can you guess what it is? A grape!

Can you guess what it is? Snowflakes!

Things found in your nose! Can you guess what it is? Things found in your nose!

Can you guess what it is? Seaweed!

Can you guess what it is? Skin!

Swine Flu’! (don’t worry it’s a picture!) Can you guess what it is? Swine Flu’! (don’t worry it’s a picture!)

Can you guess what it is? Velcro!

Can you guess what it is? Vitamin C!

The leg of a Water Boatman! Can you guess what it is? The leg of a Water Boatman!