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Lab Topic 3
Microscopes and Cells
Introduction
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To understand the processes of life you must
first understand the structure and function of
CELLS
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Microscopes
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The human eye is unable to actually see an
individual cell
Cells must be studied using a microscope
Microscopes make objects visible that are too
difficult or too small to see with the unaided eye
Two types of microscopes which are named
according to the source of illumination:
 Light
microscope
 Electron microscope
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Exercise 3.1-Parts of the microscope
Compound microscope
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Compound means that the microscope has at least 2
magnifying lenses-usually the ocular and the objective
lens
This is essentially a reading exercise
Go through procedures 1, 2a-d
Answer all the questions
Label the parts on page 61 (We do not have phase
contrast microscopes)
Become familiar with the terms that are in bold in lab
manual
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Parts of a compound light
microscope
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Oculars
Head
Revolving nosepiece
Lenses
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Scanning
 Intermediate
 High power
 Oil immersion
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Mechanical Stage
Light intensity lever
Iris diaphragm
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Phase-contrast turret
Stage adjustment knobs
Lamp
Arm
Coarse focus
Fine focus
Base
On/off switch
Condenser
Condenser adjustment knob
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Exercise 3.2 Basic Microscope
Techniques
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Learn to use the microscope by viewing
some prepared slides
 Slide
 Slide
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with a letter “e”
with 3 crossed threads
Key Terms:
 Interpupillary distance
 Working distance
 Magnification
 Resolution
 Field of view
 Depth of field
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Use only lens paper on microscopes lenses,
never use tissues, paper towels or Kimwipes
Slides should be placed on and removed from
the stage only when the 4x objective is in place
Most microscopes have parfocal lenses which
means you should have to do little or no
refocusing as you move to a higher objective
Never focus with the coarse adjustment knob
when you are using the high-power objective
All parts of procedures 1-6; answer all questions
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Exercise 3.3 The Stereoscopic
Microscope
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Also known as a dissecting microscope
Used for viewing and manipulating larger objects
Depth of field is much greater than with the
compound microscope
The light source can be directed down on the
object which is called reflected or incident light
The light source can also be directed up through
the object when the object is thick which is
called transmitted light
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Procedures 1-4, answer all questions
 Learn the parts of the microscope and
what they do
 Use an aquatic plant called Elodea to
prepare a wet mount slide
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Homework
Review and answer all questions from
today’s lab
 Read section 3.4 on The Electron
Microscope and answer questions 1a-c
 Read section 3.5 for next week’s lab
 Extra readingBiology Text sections 4.3 - 4.19
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The Organization
of Cells
Lab 3.5
INTRODUCTION
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Living Organism
 The
cell is the smallest and simplest biological
structure possessing all the characteristics of a living
organism
 All living organisms are composed of one or more
cells and every activity that takes place in a living
organism is ultimately related to a function in cells
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There are 2 major types of cells:
 Prokaryotic
Cells: Do not have a nucleus or other
membrane bound organelles
 Eukaryotic Cells:
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Cells with a true nucleus and membrane bound organelles
Are partitioned into functional compartments which facilitates
a variety of metabolic activities
More complex than prokaryotic
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Prokaryotic Cell
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Animal cell
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Eukaryotic Organelles
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The nucleus is the cell’s genetic control
center
 It
is usually the largest organelle
 Separated from the cytoplasm by the nuclear
envelope
 Contains DNA from which RNA is synthesized
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Smooth endoplasmic reticulum (ER) has a
variety of functions
 Synthesizes
lipids
 Processes toxins and drugs in liver cells
 Stores and releases calcium
Rough endoplasmic reticulum (ER) makes
membranes and proteins
 Ribosomes on the surface of the rough ER
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 Produces
proteins that are secreted, inserted
into membranes, or transported to other
organelles
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Golgi apparatus finishes, sorts, and ships
cell products
 Stacks
of membranous sacs receive and
modify ER products
 Ships products to other organelles or the cell
surfaces
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Lysosomes are digestive compartments
within a cell
 Digest
nutrients, bacteria, and damaged
organelles
 In animal cells and some protists
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Mitochondria harvest chemical energy
from food
 Carries
out cellular respiration
 Makes energy in form of ATP for cellular work
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Cilia and flagella are locomotor
appendages
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Microtubules bend allowing the cell to move
 Found only in animal cells
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Plant Cell
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Vacuoles functions in the general
maintenance of the cell
 Mostly
found in plant cells
 Has lysosomal and storage functions
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Chloroplasts convert solor energy to
chemical energy
 Found
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in plants and some protists
Cell wall supports plant cell
 Made
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largely of cellulose
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Types of Cellular Organization
Exercize 3.5
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Unicellular organism
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Aggregate or cluster of cells
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Random group size, permanent connections between cells
Each cell has an individual cell membrane/wall
Colony
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All functions are handled by a single cell
Single celled, free living organism
Clusters that have a consistent and predictable number of cells
Multicellular
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Composed of large numbers of cells each with specialized
structure and function
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Lab Study A: Unicellular
Organism
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Examining an Amoeba
Single celled, free living organism
Picture –Color Plate 1; prepared slides, live
organisms
Aquatic organism commonly found in ponds
Put a drop of the culture in a depression slide
Do not use cover slips
DO NOT EXCEED 10X MAGNIFICATION
See if you can identify the structures in 1e
We will not be doing part 2 (termites)
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Lab Study B: Aggregate and
Colonial Organisms
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Protococcus
 Green
algae (moss) that grows on the sides
of trees
 Loose aggregates
 Picture – Color Plate 3
 Make a wet mount
 See that the size of the cell groupings is
random
 Try to view only small a few small green cells
 You should be able to see the outer cell wall
which surrounds the cells
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 Scenedesmus
Aquatic
green alga common in polluted
water
Simple Colony which does not have
physiological connections
Picture- Color plate 4; prepared slide
Forms simple colonies of 4 cells
Prepare a wet mount
Should be able to identify the nucleus,
vacuoles, spines and cell walls
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Volvox
 Aquatic
green alga found in ponds and lakesform complex colonies
 Cytoplasmic connections between cells, some
cells specialized
 Picture- Color plate- 5; prepared slides
 Do not make a wet mount or use glass chips.
 Instead, use a depression slide and only go
up to 10X magnification
 Should be able to identify cell wall, nucleus,
vacuole, chloroplasts, maybe flagella
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Lab Study C: Multi-cellular Organisms
Multi-cellular organisms are composed of
specialized cells that form tissues
 Tissues can then be grouped into organs,
and organs grouped to create organ
systems
 We will study the cells that make up the
basic tissue types found in plants and
animals
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Plant Cells
 Prepare
a wet mount of an Elodea leaf-aquatic plant
 Picture- Color plate- 6
 Examine under the compound microscope
 Try to identify: cell wall, protoplasm, cytoplasm,
central vacuole, chloroplasts, and the nucleus
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Animal Cells
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WILL NOT BE USING CHEEK EPITHELIAL
CELLS
 Picture- Human Epithelial Cells- Color plate- 7
 Prepared slides of frog cell epithelial
 Identify the cell membrane, nucleus, and the
cytoplasm
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Homework
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Review and answer all questions from today’s
lab
Fill out the chart on page 72 in your lab manualdo not need to study size of organelles
Answer questions for review on page 78.
Review handouts and pages 61, 68, 72.
Read Lab topic 2: Enzymes
We will be performing experiments 2.3
parts A, B & C
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