Name: ____________________________________ Cells and the Cell Theory I. Tools of the Cytologist: Methods Used in the Study of Cells A. Compound Light Microscope: Most influenced the development of the cell theory. 1. Can view living or dead specimens 2. Measurement: 1000 micrometer (micron) = 1 mm 3. Can magnify 40 to 500 times The Compound Light Microscope

A. Used to observe microscopic samples. B. The term “Compound” means there are more than one

lens . The term “Light” means that light is used to create an image.

C. Parts of the Compound Light Microscope: 1. Lenses

Objective lenses: Closest to the specimen

Low power: Shorter lens, less magnification (10x)

High power: Longer lens, more magnification (40x)

Ocular lens or eyepiece is 10X Magnification or magnifying power: how

many times the image seems to be enlarged. Equation: (power of objective)X(power of

ocular)=magnification

Example)

Objective lens magnification = 40X

Ocular lens magnification = 10X

Total magnification= (40x) X (10x)= 400X 2. Light Source: Produces the image 3. Body Tube: Holds the lenses. 4. Nosepiece: Rotates the objective lenses. 5. Stage: Platform on which specimen is mounted 6. Clips: Hold the slide into position 7. Diaphragm: Controls the amount of ligh t

passing through the specimen 8. Arm: Holds the tube and stage 9. Base: Supports the microscope 10. Adjustments: Used to focus the image.

D. Microscopy Terms: 1. Coarse Adjustment is used to find a specimen under

low power. NEVER USE UNDER HIGH POWER Fine Adjustment is used to focus on a specimen under high power.

2. Resolution : The ability of a microscope to show two points together as separate images

3. Inversion: The image the microscope produces is inverted (upside down and backwards or rotated 180 degrees) Therefore, when one moves the slide to the

right, the image appears to move to the left 4. Microns or micrometers: The metric unit used with

the microscope. 1 micron or micrometer = 1/1000 of a millimeter

(mm)

1000 micrometers = 1 millimeter (mm)

*micrometers are 1000 times smaller than millimeters*

Conversions:

mm to micrometers o mm x 1000 = micrometers

micrometers to mm o micrometers/1000 = mm

B. Electron Microscope: Beam of electrons gives great detail and magnification.

1. Specimen being looked at must be thin, dry, and in a vacuum chamber (non-living)

2. Can magnify 750,000 times 3. Used to view-micro structures like ribosomes or the inside

of large structures like a chloroplast C. Microdissection Apparatus: used to perform operations in living cells (example: remove a nucleus from a cell) D. Dissecting Microscope (stereomicroscope): 6 to 50X

magnification 1. Provides a 3-dimensional image of a specimen 2. Used to study the external structure of small plants and

animals (Ex. Dissect a fly) E. Ultracentrifuge: Used to separate very light particles from

one another by their densities F. Staining Techniques: Used to see details when looking at cells

under the microscope 1. Two stains: Methylene blue and Lugol’s iodine

II. Cell Theory Cell : The basic unit of structure and function in organisms Cell Theory

Cells are the structural units of all living things o All living things are made up of one or more cells

Cells are the functional units of all living things o All living things carry out their own life activities

Cells arise from preexisting, living cells o This is through reproduction and cell division

Exceptions to the Cell Theory

Mitochondria and Chloroplasts Contain their own genetic material (DNA) and can duplicate themselves o Evidence that they are descendants of primitive

bacteria

Viruses Consist of DNA surrounded by a protein coat. o Viruses can only reproduce indie

cells, but are not cells themselves

Where did the first cell come from?

Animal cell Plant cell

II. Cellular Organization As organisms become more complex , their structures are organized in more complex ways. A. Cells: the basic unit of structure and function in organisms

– Unicellular : A complete living organism that is made of only one cell • Example- Amoeba, paramecium, euglena

– Multicellular : A complete living organism that is made up of many cells • Example- Dog, human, palm tree

B. Tissue : A group of cells in an organism that are alike in

structure and activity.

Example- Muscle tissue, blood, blood vessels, nerve tissue, bone, cartilage, etc.

C. Organ : A group of tissues that work together to

perform a specific function.

Example- Stomach (made of nerves, muscles and blood vessels)

D. Organ System : A group of organs that work together

to perform a specific function.

Example- Digestive System (includes mouth, esophagus, stomach, intestines, liver, etc.)

E. Organism : A living thing Example- Cat, sunflower, paramecium

IV. Cell Structure Purpose of Cells:

• Cells have particular structures to perform particular jobs. • These structures perform the actual work of the cell-they

are called organelle s (little organs) A. Cell (plasma) membrane: Separates the interior of the cell from the surrounding environment.

1. Membrane regulates the chemical composition of the cell by allowing only certain molecules to pass into and out of the cell o Large molecules must first be broken down outside

the cell which allows them to pass through. They are then built into large molecules inside the cell.

2. The cell membrane maintains homeostasis

3. The cell membrane is a two-layered structure of lipids with proteins embedded in them.

B. Nucleus : A Large, round, dense body that serves as the

control center for cell metabolism and reproduction

Nuclear membrane/envelope which controls what goes in and out of the nucleus.

The nucleus contains the DNA in a eukaryotic cell. DNA is hereditary information in the form of chromosomes.

C. Cytoplasm: Watery material in that contains many of the substances involved in cell metabolism.

Place where most of the cell’s chemical reactions take place

D. Endoplasmic Reticulum (ER): System of fluid-filled canals forming a continuous network throughout the cytoplasm.

Used to transport materials throughout the cell.

Rough endoplasmic reticulum (RER) has ribosomes attached.

Smoot h endoplasmic reticulum (SER) has no ribosomes attached to it.

E. Golgi complex : Stack of membranes that serve as the

packaging and storage center of the cell.

Like UPS headquarters: “shipping & receiving department t”

Animals have one while plants have many

F. Lysosomes : Small organelle structures that contain

strong hydrolytic (digestive) enzymes. 1. Break down worn out organelles 2. Disease fighters (eat bacteria) 3. Found only in animal cell s

G. Mitochondria : Slipper-shaped organelle surrounded by membranes.

Inner membrane is highly folded forming christae.

Site of cellular respiration, “POWERHOUSE ” of the cell.

H. Centriole s: Pair of cylindrical structures located near the

nucleus which are involved in cell division . 1. Only found in animal cells I. Vacuole : Fluid filled organelles which function as storage

sites. 1. Plants have 1 large vacuole 2. Animals have few small ones

J. Chloroplast: Double membrane bound organelle that is

found only in plants. It serves as the site of photosynthesis . 1. Contains chlorophyll 2. Contains its own DNA and can replicate itself.

K. Cell Wall: Rigid, non-living structure which gives the cell its shape and provides protection .

1. Composed of cellulose. 2. Only found around plant cells. L. Ribosomes: Site of protein synthesis within the cell. M. Cell Receptors: Molecules on the surface of the cell that

allow cells to communicate with each other