A Tour of the Cell
I.
Microscopes provide windows to the world of the cell
a. LIGHT MICROSCOPE  work by passing visible light
through a specimen; lenses bend the light to magnify the image
i. MICROGRAPH  a picture taken through a microscope
ii. Light microscopes max out @ 1,000X magnification
b. MAGNIFICATION  the increase in the apparent size of an
image
c. RESOLVING POWER  the clarity of the image; the ability
to show to objects as separate
d. CELL THEORY  all living things are composed of cells and
all cells come from other cells
e. ELECTRON MICROSCOPE  uses a beam of electrons;
1,000X better than a Light Microscope
i. Two types
1. SCANNING E.M.  shows structural surface
2. TRANSMISSION E.M.  shows internal
structure
II.
Cell size vary with their function
a. Bird eggs are big because they contain a large amount of
nutrient for young
b. Nerve cells are long to expedite signal transmission
c. Blood cells are smaller to fit through vessels easily
III.
Natural laws limit cell size
a. Minimum  must be able to house DNA, proteins
b. Maximum  surface area to volume ratio
IV.
Prokaryotic cells are small and structurally simple
a. PROKARYOTIC CELLS  consist of bacteria and archaea
i. NO MEMBRANE BOUND ORGANELLES
ii. Usually smaller than eukaryotic cells (2–8 micrometers
in length)
iii. NUCLEOID (nucleus-like) region  DNA coiled here
iv. RIBOSOMES  assemble amino acids into polypeptides
v. PLASMA MEMBRANE  surrounds the contents of the
cell; separating it from its environment
vi. PROKARYOTIC CELL WALL  protects the cell and
helps maintain shape
vii. CAPSULE  sticky out coat; protective
viii. PILI  short projections used to attach to surfaces
ix. PROKARYOTIC FLAGELLA  propel the cell through
aquatic environment
V.
Eukaryotic cells are partitioned into functional compartments
a. EUKARYOTIC CELLS  animals, plants, protests, fungi
i. MEMBRANE BOUND NUCLEUS
ii. More complex than prokaryotes
iii. CYTOPLASM  fluid-filled region between the nucleus
and plasma membrane
iv. ORGANELLES  the structures in the cytoplasm, help
perform cell activities
v. CELLULAR METABOLISM  chemical activities of
the cell
vi. MEMBRANE BOUND ORGANELLES INCREASE
VOLUME AND ALLOW MULTIPLE ACTIVITIES TO
OCCUR SIMULTANEOUSLY
vii. Animal cells and plant cells have overlapping organelles
1. LYSOSOMES, CENTRIOLES ONLY IN
ANIMAL CELLS
2. CELL WALLS, CHLOROPLASTS ONLY IN
PLANT CELLS
VI.
The nucleus is the cell’s genetic control center
a. NUCLEUS  genetic control center of the eukaryotic cell
b.
c.
d.
e.
i. DNA is the hereditary blueprint
CHROMATIN  nuclear DNA attached to proteins forming
long fibers
CHROMOSOME  fibers of chromatin
NUCLEAR ENVELOPE  double membrane with pore that
control the flow of materials in and out
NUCLEOLUS  dense part inside nucleus; DNA + protein +
RNA = ribosome production
VII. Overview: Many cell organelles are related through the
endomembrane system
a. ENDOMEMBRANE SYSTEM  network of organelles that
work together in the synthesis, storage and export of important
molecules
VIII. Rough endoplasmic reticulum makes membrane and proteins
a. ROUGH E.R.  network of interconnected flattened sacs,
covered with ribosomes, with two main functions
i. Make more membrane
ii. Make proteins secreted by the cell
b. GLYCOPROTEIN  protein with a sugar attached
c. TRANSPORT VESSICLE  tiny membranous sac to move
secretory proteins
IX.
Smooth endoplasmic reticulum has a variety of functions
a. SMOOTH E.R.  continuous with rough E.R. but lacks
ribosomes
i. FUNCTIONS
1. Synthesis of lipids (fatty acids, phospholipids,
steroids)
2. In liver the smooth ER
a. Controls the amount of sugar
b. Breakdown/detoxify drugs and other
harmful substances
i. Can lead to higher tolerance to drugs
from increased smooth ER amounts
3. Storage of calcium ions
a. Muscle tissue needs this for muscle
contraction
X.
The Golgi apparatus finishes, sorts, and ships cell produces
a. GOLGI APPARATUS  series of flattened sacs; NOT
INTERCONNCETED like the E.R.
i. Function  serves as a molecule warehouse and shipping
factory
ii. Receives transport vesicles from the E.R., chemically
modifies the glycoproteins, then ships them to their
respective destinations
XI.
Lysosomes digest the cell’s food and wastes
a. LYSOSOMES  “breakdown body”; contain hydrolytic
enzymes
i. Digest tiny food particles, bacteria, busted organelles
ii. ENZYMES MUST BE KEPT WITHIN MEMBRANE
TO PREVENT “SELF-DIGESTION”
XII. Abnormal lysosomes can cause fatal diseases
a. LYSOSOMAL STORAGE DISEASES  hereditary disorder
that impedes the enzyme function of lysosomes
b. POMPE’S disease  harmful amounts of glycogen build in the
liver
c. TAY-SACH’S  lipids accumulate that damage the nerve cells
XIII. Vacuoles function in the general maintenance of the cell
a. VACUOLES  membranous sacs that have various functions
and comes in various shapes and sizes
i. May store excess water, chemicals, wastes
b. CONTRACTILE vacuole  removes excess water
i. Found in paramecium
XIV. A review of the endomembrane system
XV. Chloroplasts convert solar energy to chemical energy
a. CHLOROPLASTS  photosynthesizing organelles that
convert light energy to chemical energy
XVI. Mitochondria harvest chemical energy from food
a. MITOCHONDRIA  convert chemical energy (as in sugar)
into a usable form (ATP)
XVII. The cell’s internal skeleton helps organize its structure and
activities
a. CYTOSKELETON  a supportive structure of fine fibers
i. Fibers are also involved in cell movement
b. 3 kinds of fibers
i. MICROFILAMENTS  thinnest fiber
ii. MICROTUBULES  thickest fiber
iii. INTERMEDIATE FILAMENTS
XVIII.
Cilia and flagella move when microtubules bend
a. CILIA  short, numerous, hair-like projections that are
involved in propulsion
b. FLAGELLA  longer, and fewer in number
c. BASAL BODY  anchoring structure; may act as foundation
for growth
d. DYNEIN ARMS  protein knobs attached to each microtubule
doublet
i. Using ATP, exert a force which causes tubules to bend
XIX. Cell surfaces protect, support, and join cells
a. CELL JUNCTIONS  structures that connect one cell to
another
i. 3 types of animal cell junctions
1. TIGHT JUNCTIONS
2. ANCHORING JUNCTIOINS
3. COMMUNICATING JUNCTIONS
b. PLASMODESMATA  channels between adjacent plant cells
that form a circulatory and communication system
c. EXTRACELLULAR MATRIX  sticky layer of glycoproteins
that cells are embedded
XX. Eukaryotic organelles comprise four functional categories
a. GENERAL FUNCTION : MANUFACTURE
i. Nucleus
ii. Ribosomes
iii. Rough ER
iv. Smooth ER
v. Golgi Apparatus
b. GENERAL FUNCTION : ENERGY PROCESSING
i. Chloroplasts
ii. Mitochondria
c. GENERAL FUNCTION : BREAKDOWN
i. Lysosomes
ii. Peroxisomes
iii. Vacuoles
d. GENERAL FUNCTION: SUPPORT, MOVEMENT, AND
COMMUNICATION BETWEEN CELLS
i. Cytoskeleton
ii. Cell Walls
iii. Extracellular Matrix
iv. Cell Junctions
XXI. Extraterrestrial life forms may share features with life on Earth
a. All life-forms on Earth share fundamental features
i. Consist of cells, membrane bound and separate from
environment
ii. Have DNA as genetic material
iii. Carry out metabolic processes
*OTHER LIFE FORMS MAY NOT HAVE EXACT
STRUCTURE OR MATERIAL, BUT FUNDAMENTAL
CONCEPTS OVERLAP