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Lab Topic 3
Microscopes and Cells
Introduction
To understand the processes of life you must
first understand the structure and function of
CELLS
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Microscopes
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
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
Oculars
Head
Revolving nosepiece
Lenses
Scanning
Intermediate
High power
Oil immersion
Mechanical Stage
Light intensity lever
Iris diaphragm
Microscopes and Cells
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
Learn to use the microscope by viewing
some prepared slides
Slide
Slide
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
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
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
There are 2 major types of cells:
Prokaryotic
Cells: Do not have a nucleus or other
membrane bound organelles
Eukaryotic Cells:
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
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
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
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
Cilia and flagella are locomotor
appendages
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
Chloroplasts convert solor energy to
chemical energy
Found
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
Unicellular organism
Aggregate or cluster of cells
Random group size, permanent connections between cells
Each cell has an individual cell membrane/wall
Colony
All functions are handled by a single cell
Single celled, free living organism
Clusters that have a consistent and predictable number of cells
Multicellular
Composed of large numbers of cells each with specialized
structure and function
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Lab Study A: Unicellular
Organism
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
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
Animal Cells
WE
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
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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