A microscope is an instrument that magnifies objects otherwise too small to
be seen, producing an image in which the object appears larger. Most
photographs of cells are taken using a microscope, and these pictures can also
be called micrographs.
There are many types of microscope (simple microscope, compound or light
microscope, and electron microscope).
In this lab we use only compound microscope also called student microscope.
These microscope consist of multiple lenses. Because of the way these lenses
are arranged, they can bend light to produce a much more magnified image
than that of a magnifying glass.
Parts of a microscope:-
1- The OCULAR (eyepiece) contains the upper most lenses of the
microscope. If your microscope has one ocular it is a monocular microscope,
if it has two, it is binocular.
2- The BODY TUBE connects the ocular to the nosepiece. This is a tube
through which light rays pass between the upper and lower lenses.
3- The NOSEPIECE is a rotating disc on which the objectives are mounted.
4- There may be three or four OBJECTIVES of different lengths and
magnifying powers attached to the nosepiece of your microscope.
Scanning lens 4X magnification
Low power lens 10X magnification
High power lens 40-45X magnification
Oil immersion lens 100X magnification
5- The ARM supports the above parts. This is one of two structures that should
be held when carrying the microscope.
6- The STAGE is the platform with a mechanical stage for holding the slides
Note the circular opening in the center of the stage, which allows light to pass
through. The object, which is to be viewed, should be centered over this
7- The DIAPHRAGM may be an iris or rotating disc, depending on the kind
of microscope. It is located below the stage.
8- Condenser lens system, located immediately under the stage, contains a
system of lenses that focuses light on your specimen. The condenser may be
raised or lowered using the condenser knob. An older microscope may have a
concave mirror instead.
10- The COARSE ADJUSTMENT is the large milled wheel on the
is used in focusing the lenses.
11- The FINE ADJUSTMENT is the smaller milled wheel on the microscope.
The wheel may be separate from the coarse adjustment wheel on some
12- The LIGHT SOURCE has an (ON/Off) switch & may have adjustable
lamp intensities & color filters.
During this lab exercise, you will:-
Prepare a temporary wet mount of sections of onion membrane and wet mount
cell of buccal cavity, view the specimen through a microscope, identify
common structures, and make a three-dimensional drawing of a typical onion
1- Obtain a clean slide and cover slip.
2- Place a single layer of onionskin (skin between the onion layers) on the
center of the slide, and then add 1 or 2 drops of iodine stain. Be sure to spread
it out evenly so there is no overlap or double layering.
3- Touch the cover slip to one edge of the drop, and gently lower it. (If you
drop the cover slip too quickly, air bubbles will be trapped. You cannot see
through an air bubble).
4- Observe these cells first at 4X, then 10X, 40X and make a sketch of a few
cells in the space provided on the data sheet. Be careful when working with
the stain You should be able to see the following structures that are typical of
plant cells: (1) cell wall, (2) nucleus, (3) one or more nucleoli in the nucleus,
and (4) cytoplasm.
How to prepare the buccal sample?
Prepare a wet-mount slide of buccal cells (lining the inner surface of the cheek
Collect the cells of the inner lining of the cheek gently by a tooth stick.
Put the sample which contains cells on a slide.
Add one drop of methylene blue stain and a cover slip.
Examine it under the microscope,
record your observations in a fully labeled drawing.
on your science book
Turn off the power, rotate the 4X objective into position, remove the slide
from the stage
and clean the stage and wash wet mount slides and throw away cover slips.
- Draw an onion cells from your specimen (4X, 10X and 40X).
- Draw buccal cells from your specimen (by 40X).
The cell concept is basic for understanding the activities and characteristics of
structure and function of an organism. As functional units, they reflect the
abilities of the organism as a whole. Some simple kinds of organisms consist
of individual cells, but many of the organisms with which we are most familiar
are multicellular. Multicellular organisms usually are composed of several
different kinds of cells, each having specific characteristics that relate to its
function. The various kinds of living things have been subdivided into three
domains: Bacteria, Archaea, and Eukaryote. The cells of the Bacteria and
Archaea are small and simple, and they lack a nucleus. These cells are called
prokaryotic cells. The cells of the Eukaryote all have a nucleus and other
kinds of structures called organelles within the cell. This type of cell is called
a eukaryotic cell.
The complexity in the cell:
• The Eukaryote cell are more complex than Prokaryote.
• Eukaryote have nuclei and compartments organelles
• Prokaryotic cells lack nuclei and other organelles , and tend to be less
Organelles of the cell:
• Commonly found in plant & bacteria.
Bacterial cell walls are composed of peptidoglycan, but in plant made of
• The Plasma membrane also called cell membrane is the outer lining of the
• They made of a double layer of phospholipid molecules.
leave the cell
• Within cells, the Cytoplasm is made up of a jelly-like fluid (called the
cytosol) and other structures that surround the nucleus.
• The cytoplasm contains the chemical wealth of the cell: the sugars, amino
acids, and proteins the cell uses to carry out its everyday activities.
• The cytoskeleton is an intricate network of proteins filaments that crisscross
the cytoplasm of cells
• Structural support and cell movement.
• It include:
1. Microtubules (tubulin).
2. Microfilaments (Actin).
3. Intermediate filaments (Keratin).
• The nucleus (plural-nuclei) is roughly spherical and is surrounded
by two membranes.
• In animal cells, they are typically located in the central region of the cell.
• Our genetic material (DNA), in the form of chromosomes, is stored in this
• The ER is composed of a lipid bilayer embedded with proteins (the source of
• It weaves in sheets through the interior of the cell, creating a series of channels
• This organelle helps process molecules created by the cell.
• consists of two types:
1. Rough ER synthesizes proteins,
2. while smooth ER organizes the synthesis of lipids and other biosynthetic
Golgi apparatus (Delivery System of the Cell):
• Golgi bodies: Flattened stacks of membranes, often occur interconnected
with one another
• Collectively the Golgi bodies are referred to as the Golgi apparatus
• The Golgi apparatus functions in the collection, packaging, and distribution
of molecules synthesized at one place in the cell and utilized at another
location in the cell.
Lysosomes and Micro-bodies:
• Lysosomes membrane-bounded digestive vesicles.
• Throughout the lives of eukaryotic cells, lysosomal enzymes break down old
organelles, recycling their component molecules and making room for newly
• Microbodies are found in the cells of plants, animals, fungi, and protists. Plant
cells have a special type of microbody called a glyoxysome that contains
enzymes that convert fats into carbohydrates
• peroxisome, contains enzymes that catalyze the removal of electrons and as
associated hydrogen atoms
• Ribosomes are made up of several molecules of a special form of RNA called
ribosomal RNA, or rRNA, bound within a complex of several dozen different
• Each ribosome is composed of two subunits.
• Bacterial ribosomes are smaller than eukaryotic ribosomes.
• Can float freely in the cytoplasm or be connected to the endoplasmic
• Mitochondria (singular, mitochondrion) are typically tubular or sausage-
shaped organelles about the size of bacteria and found in all types of
contiguous layers called cristae.
• Contain enzymes that carry out cellular respiration and generate ATP using
• Mitochondria have their own DNA
• Plants and other eukaryotic organisms that carry out photosynthesis typically
contain from one to several hundred chloroplasts. Chloroplasts contain the
• Photosynthetic pigment chlorophyll that gives most plants their green color.
• In addition to the outer and inner membranes, have a closed compartment of
stacked membranes called grana (singular, granum), which lie internal to the
• Each granum may contain from a few to several dozen disk-shaped structures
• Surrounding the thylakoid is a fluid matrix called the stroma.
• Chloroplasts have their own DNA
• The main role of chloroplasts is to conduct photosynthesis, where the
photosynthetic pigment chlorophyll captures the energy from sunlight and
converts it and stores it in the energy-storage molecules ATP and NADPH
while freeing oxygen from water.
• It’s a membrane bound organelle which is present in all plant and fungal cells
and some protist, animal and bacterial cells.
• The organelle has no basic shape or size; its structure varies according to the
needs of the cell
• Plant cells often have a large membrane-bounded sac called a central
• Centrosomes are key to the division of cells and produce the spindle fibers
that are required during metaphase of mitosis.
• They are found in the cells of animals and most protists.
• Each centrosome consists of two centrioles that are orientated at right-angles
to each other.
• Each centriole is a cylindrical array of 9 microtubules
Transportation of materials through Cell Membrane
All molecules and ions in the body fluids including water molecules and
dissolved substances are in constant motion.
Transport through the cell membrane either directly through the lipid bilayer
or through proteins (integral or intrinsic proteins).
1. Active transport requiring cellular energy.
2. Passive transport requiring no energy (Diffusion, Osmosis).
Diffusion could be simple or facilitated.
Exercise No (2) part (1):-
1- You will draw the different organelles from the animal and plant cell
2- Write the different between animal and plant cell.
To demonstrate the movement of solutes (particles) from high concentration
to low concentration.
Test tube, Ink, dropper and water.
Add a drop of ink to the water in the test tube.
Record your observation.
Experiment No (2): Osmosis
To demonstrate the movement of water across a differentially permeable
NaCl crystal, potato, razor blade and a Petri dish.
Cut the anterior and the posterior ends of the potato tuber. Make a small
groove on one end
and fill it with NaCl crystals. Put the potato in a Petri dish. Leave it for one
Record your observations.
Experiment No (3): Plasmolysis
Refers to the shrinking of the cytoplasm of a cell in response to diffusion water
out of the cell. This may occur when cells are placed in a solution containing
a high concentration of solutes.
Slides, coverslip, hypertonic, isotonic and hypotonic solutions, onion and
(Isotonic: the solutions being compared have equal concentration of solutes ("
ISO" means the same). Hypertonic: The solution with the higher
with the lower concentration of solutes ("HYPO" means less).
Remove the thin onion layer from the onion slice then transfer it to a Petri dish
either hypertonic, isotonic or hypotonic solution and leave it for 2- 3 minutes.
Put it on slide
and put the cover slip. Examine under the microscope.
To demonstrate the permeability of the cell membrane.
Beetroot dilute, NaOH, dilute HCl and test tubes.
Cut a fresh beetroot to small cubes and wash under running water to remove
the red color
of the anthocyanin pigments. Transfer 3-4 cubes to three test tubes containing
a dilute NaOH and dilute HCl and distilled water solutions and leave it for 5
minutes. Observe the changed in color.
Record your observations.
2. Effect of Heat and Alcohol:
Beetroot, distilled water, alcohol, test tube and water bath.
Cut a fresh beetroot to small slices and wash under the running water. Then
transfer the beet
cubes into tubes containing the flowing:
3-4 cubes =5 ml distilled water, leave for 5 minutes.
3-4 cubes=5ml distilled water, heat for 5 minutes.
3-4 cubes =5 ml of alcohol, leave for 5 minutes
Shake the tubes well after 2 minute and record you observations in a table.
The protozoa are the simplest and most primitive animals, usually defined as
"unicellular" animals, the protozoa are classified into four classes based on
the structures them possess for locomotion:
1- Class: Sarcodina:
Protozoa with locomotion by means of pseudopodia (Rhizopoda).
Mostly free living, some are parasitic.
Reproduction: asexually by binary fission and sexually by syngamy.
Examples: Amoeba, Entamoeba.
Protozoa with locomotion by means of flagella.
Free living or parasite.
Reproduction: A sexual reproduction by longitudinal fission.
this class divided into two types depending on method of feeding:
Parasitic protozoa without locomotion structure but move by gliding.
Contractile vacuoles is absent.
Body covered with pellicle.
Reproduction: Asexual reproduction by fission and Sexual reproduction by
Protozoa with locomotion by means of cilia.
Body covered by pellicle.
Reproduction: Asexual reproduction by binary fission. Sexual reproduction
Nuclei 2 types i.e. macronucleus and micronucleus.
Examples: Paramecium, Balantidium
Bacteria are the sole members of the Kingdom Monera. They are the most
abundant microorganisms. Bacteria occur almost everywhere. Hundreds of
bacteria are present in a handful of soil. They also live in extreme habitats
forms can survive. Many of them live in or on other organisms as parasites.
Bacteria are grouped under four categories based on their shape: the spherical
Coccus (pl.: cocci), the rod-shaped Bacillus (pl.: bacilli), the comma-shaped
Vibrium (pl.: vibrio) and the spiral Spirillum (pl.: spirilla).
Though the bacterial structure is very simple, they are very complex in
behavior. Compared to many other organisms, bacteria as a group show the
most extensive metabolic diversity. Some of the bacteria are autotrophic
they synthesis their own food from inorganic substrates. They may b
photosynthetic autotrophic or chemosynthetic autotrophic. The vast majority
of bacteria are heterotrophs, i.e., they do not synthesis their own food but
depend on other organisms or on dead organic matter for food.
Draw all the organisms and label any organelles you were able to see on
your science book.
The fungi constitute a unique kingdom of heterotrophic organisms. They show
a great diversity in morphology and habitat. When your bread develops a
mould or your orange rots it is because of fungi. The common mushroom you
eat and toadstools are fungi. White spots seen on mustard leaves are due to a
parasitic fungus. Some unicellular fungi, e.g., yeast are used to make bread
and beer. Other fungi cause diseases in plants and animals; wheat rust-causing
Puccinia is an important example. Some are the source of antibiotics, e.g.,
Penicillium. Fungi are cosmopolitan and occur in air, water, soil and on
animals and plants. They prefer to grow in warm and humid places. With the
exception of yeasts, which are unicellular, fungi, are filamentous. Their bodies
consist of long, slender thread-like structures called hyphae.
Animals are Eukaryotic, multicellular organisms that form the biological
kingdom Animalia. Animals are motile (able to move), heterotrophic
(consume organic material), reproduce sexually, and their embryonic
development includes a blastula stage. The body plan of the animal derives
from this blastula, differentiating specialized tissues and organs as it develops;
this plan eventually becomes fixed, although some undergo metamorphosis at
some stage in their lives. Animals are divided by body plan into vertebrates
and invertebrates. Vertebrates—fishes, amphibians, reptiles, birds, and
mammals—have a vertebral column (spine); invertebrates do not. All
vertebrates and most invertebrates are bilaterally symmetrical (Bilateria).
These invertebrates include arthropods, molluscs, roundworms, ringed
worms, flatworms, and other phyla in Ecdysozoa and Spiralia.
Is categorized into three phylum's:
Round worms, Round in cross section; Separate sexes; Complete digestive
tract; 500,000 species only a few parasitic to man e.g.- Ancylostoma