Lab Topic 3 Microscopes and Cells. 2 Introduction To understand the processes of life you must first understand the structure and function of CELLS

Lab Topic 3

Microscopes and Cells

Microscopes and Cells 2

Introduction To understand the processes of life you must

first understand the structure and function of CELLS


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


Exercise 3.1-Parts of the microscopeCompound 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


Parts of a compound light microscope

Oculars Head Revolving nosepiece Lenses

Scanning Intermediate High power Oil immersion

Mechanical Stage Light intensity lever Iris diaphragm

Phase-contrast turret Stage adjustment knobs Lamp Arm Coarse focus Fine focus Base On/off switch Condenser Condenser adjustment knob


Exercise 3.2 Basic Microscope Techniques

Learn to use the microscope by viewing some prepared slidesSlide with a letter “e”Slide with 3 crossed threads

Key Terms: Interpupillary distanceWorking distanceMagnificationResolutionField of viewDepth of field


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


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


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


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 reading- Biology Text sections 4.3 - 4.19

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


Prokaryotic Cell


Animal cell


Eukaryotic Organelles

The nucleus is the cell’s genetic control center It is usually the largest organelle Separated from the cytoplasm by the nuclear

envelopeContains DNA from which RNA is synthesized


Smooth endoplasmic reticulum (ER) has a variety of functionsSynthesizes lipidsProcesses toxins and drugs in liver cellsStores and releases calcium

Rough endoplasmic reticulum (ER) makes membranes and proteins

Ribosomes on the surface of the rough ERProduces proteins that are secreted, inserted

into membranes, or transported to other organelles


Golgi apparatus finishes, sorts, and ships cell productsStacks of membranous sacs receive and

modify ER productsShips products to other organelles or the cell

surfaces Lysosomes are digestive compartments

within a cellDigest nutrients, bacteria, and damaged

organelles In animal cells and some protists


Mitochondria harvest chemical energy from foodCarries out cellular respiration Makes energy in form of ATP for cellular work

Cilia and flagella are locomotor appendages Microtubules bend allowing the cell to moveFound only in animal cells


Plant Cell


Vacuoles functions in the general maintenance of the cellMostly found in plant cellsHas lysosomal and storage functions

Chloroplasts convert solor energy to chemical energyFound in plants and some protists

Cell wall supports plant cell Made largely of cellulose


Types of Cellular OrganizationExercize 3.5

Unicellular organism All functions are handled by a single cell Single celled, free living organism

Aggregate or cluster of cells Random group size, permanent connections between cells Each cell has an individual cell membrane/wall

Colony Clusters that have a consistent and predictable number of cells

Multicellular Composed of large numbers of cells each with specialized

structure and function


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)


Lab Study B: Aggregate and Colonial Organisms

ProtococcusGreen algae (moss) that grows on the sides of treesLoose aggregatesPicture – Color Plate 3Make a wet mountSee that the size of the cell groupings is randomTry to view only small a few small green cellsYou should be able to see the outer cell wall which

surrounds the cells


ScenedesmusAquatic green alga common in polluted

waterSimple Colony which does not have

physiological connectionsPicture- Color plate 4; prepared slideForms simple colonies of 4 cellsPrepare a wet mountShould be able to identify the nucleus,

vacuoles, spines and cell walls


VolvoxAquatic green alga found in ponds and lakes-

form complex coloniesCytoplasmic connections between cells, some

cells specializedPicture- Color plate- 5; prepared slidesDo not make a wet mount or use glass chips. Instead, use a depression slide and only go

up to 10X magnificationShould be able to identify cell wall, nucleus,

vacuole, chloroplasts, maybe flagella


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


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


Homework Review and answer all questions from today’s

lab Fill out the chart on page 72 in your lab manual-

do 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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Lab Topic 3 Microscopes and Cells. 2 Introduction To understand the processes of life you must first understand the structure and function of CELLS