LECTURE 3

MICROSCOPY AND Basic Cell Structure

TODAYS MENU

• MICROSCOPY• BASIC CELL STRUCTURE• SUMMARY #1 and ASSIGNMENT 2 DUE• PAGES TO READ: 77-85

MICROSCOPY

• The microscope is used to magnify objects• Two types • A) LIGHT MICROSCOPES (LMs) – use a visible

light source and lenses to magnify image. Two kinds: a compound microscope and a dissecting microscope.

• B) ELECTRON MICROSCOPES (Ems): use an electron beam instead of a light microscope [Transmission and scanning electron microscope]

Differences between LMs and EMs

• LMs• Use light• Resolving Power ≥0.2

µm• Magnification max

1000X• Specimens can be

dead or alive

• Ems• Use electron beam• Resolving Power ≥0.1

nm• Magnification >1000X• Specimens are dead

and preparation method introduce artifacts.

Light Microscope

Electron Microscope

A comparison of microscope images

Light Microscope

• Two important parameters

• Magnification: how large to make image of specimen or ratio of an object’s image to it’s real size.

• Resolving Power: measure of clarity of image.

Parts of a compound microscope

• Eyepiece: houses ocular lens (Magnification 10X)

• Nosepiece: rotates to allow use of a particular objective lens.

• Objective lenses: Have various magnifications• Stage: holds microscope slide for viewing• Stage Manipulator rods: allow movement of slide

while viewing• Light Source: illuminates object on slide

Parts of a compound microscope

• Diaphragm: regulates amount of light transmitted through object.

• Condenser: focuses the light beam.• Coarse Adjustment Knob: for focussing changes• Fine Adjustment Knob: for very fine focussing

changes• Base and Arm: the supporting structures of the

microscope

How to Use a Compound Microscope

• Remove the cover, plug the microscope in • Always start and end with Low Power! • Place the slide on the microscope stage, with

the specimen directly over the center of the glass circle on the stage (directly over the light).

• NOTE: If you wear glasses, take them off; if you see only your eyelashes, move closer.   Be sure to close, or cover your other eye!!NOTE: If you see a dark line that goes part way across the field of view, try turning the eyepiece.  That dark line is a pointer

How to Use a Compound Microscope

• If, and ONLY if, you are on LOW POWER, lower the objective lens to the lowest point, then focus using first the coarse knob, then the fine focus knob.

• Adjust the Diaphragm as you look through the Eyepiece, and you will see that MORE detail is visible when you allow in LESS light!

• Once you have found the specimen on Low Power, unless specifically asked to draw it on low power, center the specimen in your field of view, then, without changing the focus knobs, switch it to High Power.

How to Use a Compound Microscope

• Once you have it on High Power remember that you only use the fine focus knob!

Care of the Instrument – Do’s and Don’ts

• Transport: Always carry the microscope with one hand on the Arm and one hand on the Base. Carry it close to your body.

• Clutter: Keep workstation uncluttered• Electric Cord: Place the excess cord on the

table! • The High Power Objective is very close to the

slide. Use of the coarse focus knob will scratch the lens, and crack the slide. More expensive sounds . . .Only use the fine adjustment

Care of the Instrument – Do’s and Don’ts

• The 100X objective is an oil immersion lens. Without the oil to lubricate the lens, you will destroy it! More expensive sounds . . . Also, the oil is needed to help gather enough light to actually see through the lens!

• Cleaning Tissues: Use only lint-free, optically safe tissues to clean lenses.

• Solvents: Be cautious.• Do not place microscope under running water.

Exercises

• Total Magnification: Ocular lens * Objective lens• Image Orientation: reverse of specimen• Size of object: Diameter field of view * estimate

of space taken up by image• Diameter field of view: 4X=4.3 mm; 10X =

1.7mm; 40X = 0.4mm• Working Distance and the field of view is inverse

proportional to length of Objective lens • Working distance: 4X = 25mm; 10X=8.3mm;

40X =0.5 mm

Exercises

• Total Magnification: Ocular lens 10X and Objective lens 40X = 10 * 40 = 400X

• Size of an object whose image covers half the field of view using the 10X objective length. = ½ * 8.3 mm = 4.15 mm

Basic Cell Structure

• All Living Things Are Composed of One or More Cells

• The term was coined by Robert Hooke (1665)

• All Cells Share Certain Common Features

What Are the Basic Features of Cells?

– The Plasma Membrane Encloses the Cell and Mediates Interactions Between the Cell and Its Environment

– All Cells Use DNA as a Hereditary Blueprint and Contain Cytoplasm

– All Cells Obtain Energy and Nutrients from Their Environment

– Cell Function Limits Cell Size

frog embryo

most eukaryotic cells

mitochondrion

most bacteria

virus

proteins

diameter of DNA double helix

chicken egg

adult human

tallest trees

atoms

1 centimeter (cm) = 1/100 m1 millimeter (mm) = 1/1000 m

Units of measurement: 1 meter (m) = 39.37 inches

Diameter

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1 micrometer (µm) = 1/1,000,000 m1 nanometer (nm) = 1/1,000,000,000 m

100 µm

10 µm

1 µm

100 nm

10 nm

1 nm

0.1 nm

1 mm

1 cm

10 cm

100 m

10 m

1 m

most eukaryotic cells

mitochondrion

most bacteria

virus

proteins

diameter of DNA double helix

atoms

1 centimeter (cm) = 1/100 m1 millimeter (mm) = 1/1000 m

Units of measurement: 1 meter (m) = 39.37 inches

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1 micrometer (µm) = 1/1,000,000 m1 nanometer (nm) = 1/1,000,000,000 m

100 µm

10 µm

1 µm

100 nm

10 nm

1 nm

0.1 nm

What Are the Basic Features of Cells?

• There Are Two Basic Types of Cells: Prokaryotic and Eukaryotic

• Prokaryotic cells – represented by the Domains Archaea (archaebacteria) and Bacteria

• Eukaryotic cells – represented by the Domain Eukarya (algae, protozoans, fungi, plants and animals)

chromosome(nucleoid region)

pili

ribosomes

food granule

prokaryoticflagellum

capsule orslime layer

cell wall

plasma membranecytoplasm

plasmid (DNA)

A generalized prokaryotic cell

mitochondrion vesicle

cytoplasm

flagellum

lysosome

centriole

Golgi complex

vesicle

nuclear pore

nuclear envelope

chromatin (DNA)nucleolus

nucleus

ribosome

free ribosome

microtubules

rough endoplasmicreticulum

Smooth endoplasmicreticulum

plasmamembrane

intermediatefilaments

A generalized animal cell

central vacuole

plastid mitochondrion

vesicleplasmodesma

cell wall

plasmamembrane

intermediatefilaments

free ribosomeribosomes

nucleusnucleolus

nuclear porechromatin

nuclear envelope

Golgi complex

chloroplast

Microtubules (part of cytoskeleton)

smoothendoplasmicreticulum

roughendoplasmicreticulum

A generalized plant cell

What Are the Major Features of Prokaryotic Cells?

• Prokaryotic Cells Are Small

• Prokaryotic Cells Have Fewer Specialized Structures Within Their Cytoplasm

• Have no membrane-enclosed organelles within their cytoplasm

DNA is located in the “nucleoid”

What Are the Major Features of Eukaryotic Cells?

• Eukaryotic Cells Contain Organelles

• The Nucleus Is the Control Center of the Eukaryotic Cell (Have the DNA)

• Have membrane-enclosed organelles within the cytoplasm

Functions of Cell Structures

• Eukaryotic Cells Contain a Complex System of Membranes– The Plasma Membrane Both Isolates the Cell and

Allows Selective Interactions Between the Cell and Its Environment

– The Endoplasmic Reticulum Forms Membrane-Enclosed Channels Within the Cytoplasm

– The Golgi Complex Sorts, Chemically Alters, and Packages Important Molecules

Functions of Cell Structures

Lysosomes Serve as the Cell’s Digestive System

– Plant Cells Have Central Vacuoles

smoothendoplasmicreticulum

nuclear envelope

Golgi complex

exocytosisplasma membrane

phagocytosis

lysosomefused withfood vacuole

food vacuole

roughendoplasmicreticulum

The flow of membrane within the cell

cytoplasm centralvacuole

cell wall plasma membrane

The central vacuole and turgor pressure in plant cells

Functions of Cell Structures

• Mitochondria Extract Energy from Food Molecules, and Chloroplasts Capture Solar Energy– Mitochondria Use Energy Stored in Food

Molecules to Produce ATP– Chloroplasts Are the Sites of

Photosynthesis

Differences between plant and animal cells

• Plant cells are surrounded by a rigid cell wall• Plant cells have chloroplast• Plant cells have a large central vacuole• Plant cells contain plasmodesmata-openings in

the cell wall of adjacent cells• Animal cells have lysosomes• Animal cells have Centrioles

KEY WORDS

• Main features of Prokaryotic and Eukaryotic cells

• Functions of cell structures

• Differences between Plant and animal cells

• Types of cells

• Types of Microscopes• Magnification• Resolving Power• Calculations-

Magnification, Size of Object

• Do’s and Don’t’s of microscopes

LAB EXERCISES

• EX 1 – page 78. Fill out the labels• EX 2- page 80. The Letter E. Place the slide with

the letter E on the stage of the microscope, secure with the clips. Focus using low magnification before moving on to higher magnification. Answer the question on pg 80/81.

• EX 3 – Crossed threads, use to determine the depth of view.

• EX – 4 – Dissecting Microscope• EX – 5, pg 82 Plant Cells and Ex 6 pg 85-

Animal Cells• Assignment 3: EX 2 – Qu 1-8 and EX 5 – Qu 1-3

Next Class Menu

• Mitosis & Meiosis (Watch video)• Read pages 193