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Cell Diversity
*Prokaryotic - cells which lack a nucleus and membrane
bound organelles
Pro - before Karyot – nucleus
Ex. Bacteria
*Eukaryotic - cells which contain a nucleus and membrane
bound organelles
Eu - true
Karyot - nucleus
Ex. Fungi, Protista,
Plants & Animals
Prokaryotic vs. Eukaryotic
Prokaryotic cells…..
• do not enclose their genetic material within a
nucleus
• are generally smaller and simpler then eukaryotic cells - always
unicellular
• do not have membrane-bound organelles
• DNA is circular
• Ribosomes are small
• Moves by rotating flagellum
• Cell division by binary fission
Staphylococcus epidermidis
Escherichia coli
Prokaryotic vs. Eukaryotic
Eukaryotic cells…..
• use their nucleus to enclose the genetic material from the
rest of the cell
• are generally larger and more complex then prokaryotic
cells –multicellular
• have membrane-bound organelles
• DNA is linear
• Ribosomes are large
• Moves by waving cilia or flagellae
• Cell division by mitosis or meiosis
Prokaryotic &
Eukaryotic Similarities:
• Enclosed by plasma membranes
• Contain DNA as their genetic material
• Have Ribosomes
• Filled with cytoplasm
Eukaryotic Organelles “ little organs”
We will spend the next section discussing the different organelles
found in Eukaryotic Cells
Organelles found in a cell are dependent on the cell’s
particular function in the organism.
All cells have organelles which are necessary for the cells
own survival needs like:
*Food intake
*Conversion of food to Cellular Energy
*Waste Removal
*Reproduction
*No matter how cells differ from one another the majority of
Eukaryotic cells have these Three Main Components:
1. Cell membrane - outer boundary of the cell
2. Cytoplasm - liquid portion inside the cell membrane
3. Nucleus - contains the cells DNA
1. Cell Membrane
*The cell membrane is also known as the Plasma Membrane.
A. Functions:
1. Separates the cell from its external surroundings or
environment
2. Gives the cell its shape and flexibility
3. Regulates what enters and exits the cell.
 Selectively permeable/ Semi-permeable
*to permeate - to pass through
2. Cytoplasm
*Also called Cytosol - a gelatin-like aqueous fluid which
bathes the organelles which is found
between the cell membrane & the
nucleus
*Aqueous fluid which contains:
Salt (0.85%)
Organic molecules (? Proteins, Carbohydrates + Lipids)
Minerals (K Mg Na Fe )
*The cytoplasm is in constant motion as particles and organelles
move around inside the cell called Cytoplasmic Streaming
3. Nucleus
A. Function:
* directs cellular activity
* contains most of the cells DNA
* site of nucleic acid synthesis ( RNA & DNA)
B. Structure:
* spherical organelle with thousands of nuclear pores
* surrounded by a double membrane =Nuclear Envelope
*contains a spherical body called the Nucleolus,
where ribosomes are produced
* it is porous, so small substances can pass in and out
*filled w/ a dense liquid =Nucleoplasm
4. Ribosomes
A. Function:
* site of Protein Synthesis
*most abundant organelle in the cell
B. Structure:
*consists of 2 spheres (upside down snowman)
* smallest organelle (15 - 20 nm)
*not membrane bound
*made in the nucleus by the nucleolus
C. Location:
* 2 locations of Ribosomes:
1. Free Floating in the Cytoplasm
- makes proteins for the Cell’s Own Use,
to be used inside the cell Ex. Cellular Enzymes
2. Attached to the Endoplasmic Reticulum
- makes proteins to be exported from the cell to
be used in other areas of the organism
Ex. Insulin Gastric Enzymes
5. Endoplasmic Reticulum (ER)
A. Structure:
*a system of highly folded membranes forming pouches
and tunnels
*lipid/proteins components are assembled
B. Functions:
*the function of the endoplasmic reticulum depends on
whether it has ribosomes attached or not.
2 Types of ER:
1. Rough ER - covered with ribosomes resulting in
a bumpy or rough appearance
a. site of synthesis of exported proteins
b. intracellular pathway
2. Smooth ER - has no ribosomes on its surface so it
appears smooth
a. intracellular pathway
b. storage area for proteins waiting to be exported
c. synthesis of steroids in Gland Cells
d. Regulates Ca levels in Muscle Cells
e. Breakdown of toxic substances in Liver Cells
6. Golgi Apparatus
*also called Golgi Bodies
A. Structure:
*a stack of membranes and fluid filled sacs
*fluid contains dissolved substances to be added to
proteins before they are exported
B. Function:
* processing packaging and secreting of proteins
* like an assembly line in a manufacturing plant:
1. Proteins are made in Rough ER
*Car gets body, wheels, frame etc.
2. Travel through the Rough ER and /or Smooth ER
*Assembly line
3. Placed in a membrane vesicle
*Car carrier takes the car to the next station
4. Travels to the Golgi to get the extras
*Options are added: CD, AC, Navigation etc
5. Placed into another vesicle
*Another car carrier
6. Travels to the Cell Membrane to be exported
*Out the factory doors
7. Vesicles
A. Function:
*Stores or transports substances within a cell
*most have specialized functions depending on what
material they contain
B. Structure:
*Small, intracellular membrane-enclosed sac
8. Mitochondria
A. Function:
*the power house of the cell
*where compounds are broken down through the process of
Cellular respiration
B. Structure:
*a large organelle composed of 2 membranes:
1. Outer Membrane - separates the mitochondria from
its surroundings
2. Inner membrane - highly folded membrane across
which respiration takes place
called the Cristae
What is the advantage of having the Cristae highly folded?
> Surface Area, > amount of energy produced
What type of cells have high numbers of Mitochondria?
Muscle Cells 2500/cell
*Theory of Endosymbiosis:
1.
2.
3.
4.
* Notice the shape of the Mitochondria.
Does it remind you of any cells we have discussed before?
Scientists believe that mitochondria were once rod shaped
Prokaryotic Bacteria that were engulfed by other bacteria.
The inner bacteria provided energy and the outer cell
provided protection.
This was a Symbiotic Relationship in which both bacteria
benefited .
Over time they became so dependent on each other that they
could not live apart and developed into the first Eukaryotic Cells.
9. Lysosomes
A. Structure:
* small spherical organelles which contain over 40
digestive enzymes
B. Function:
* digest food particles like: carbohydrates, proteins,
lipids, DNA & RNA into their monomers so cell
can use them for energy or reuse them to make
molecules needed
* also digests foreign invaders like Viruses and Bacteria
to protect the cell
10. Cytoskeleton, Microtubules & Microfilaments
A. Function:
*Cells need a support system = called a Cytoskeleton
*The cytoskeleton helps the cell maintain its shape and is
involved in moving “spider web-like”
B. Structure:
*There are 2 types of proteins involved:
1. Microtubules - long hollow tubes made
of tubulin (protein) used to make Spindle fibers
which pull apart chromosomes during cell division
2. Microfilaments - threadlike structures made of actin
(protein) their assembly and disassembly are responsible for
cytoplasmic streaming
11. Centrioles
A. Function:
*help to organize cell division
B. Structure:
*located near nucleus, made from the protein
tubulin
* not in plants
12. Cilia & Flagella
A. Function:
*responsible for cellular movement
1. Cilia - short hair-like structures which extend
from the cell
*usually in high numbers
*surround the cell
*beat in synchronized strokes
Functions of Cilia:
Unicellular organisms
a. locomotion
Ex. paramecium
Multicellular organisms
a. move substances along the digestive tract
b. filter out dirt and debris in the respiratory tract
Ex. Nose
2. Flagella - long whip-like structures
*usually found in singles or pairs
Functions of Flagella:
Unicellular organisms
a. locomotion
Ex. Giardia lamblia
Multicellular organisms
a. locomotion
Ex. sperm
The Next 3 Organelles are Found Primarily in Plants
13. Cell Wall
A. Function:
* a rigid covering that surrounds the cell membrane
which is inflexible
B. Structure:
* made primarily of a polysaccharide =Cellulose
* contains pores to allow substances to enter which are
then regulated by the semi-permeable cell membrane
14. Central Vacuole
A. Structure:
*a fluid filled space located in the center of a plant cell
*can take up as much as 90% of the cells volume.
B. Function
*stores enzymes and metabolic wastes
(The plant needs to eliminate its waste but the cell
wall limits this.
By placing the metabolic waste in the vacuole
with enzymes, the waste products can be broken
down into usable substances)
*location of plant poisons
****There are vacuoles in animal cells too!!
-Smaller, sac-like membrane enclosed structures
-Store materials like water, salts, proteins and carbs
-Play a role in the release of cellular waste
15. Chloroplast
A. Structure:
* green organelle which contains the
pigment Chlorophyll
* contains flattened sacs called thylakoids
B. Function:
* where photosynthesis takes place
Staphylococcus epidermidis
Escherichia coli
Onion
Elodea
Human Cheek
Gram staining is a
microbiological procedure that
categorizes bacteria based on the
physical and chemical structure
of their outer surface.
Gram-negative bacteria have
an additional outer membrane
whose properties resist
acetone/alcohol-dehydration
and result in loss of the crystal
violet stain. A counterstain,
made up of fuchsin, stains these
bacteria red or pink.
Gram-positive bacteria have a
thick layer made up of polymers
of protein-sugar molecules called
peptidoglycan. Gram staining of
the peptidoglycan layer (a.k.a.
the cell wall) with a chemical
called crystal violet results in
purple coloration of the grampositive bacteria. Addition of
acetone or alcohol dehydrates the
bacteria, causing it to retain the
purple color.