Transcript Cytology * The Study of Cells

Cytology – The Study of Cells
Discovery of The Cell
 Robert Hooke (mid 1600s) – looked at thin slice of
cork (plant material)
 Saw that cork was made of thousands of tiny, empty
chambers
Reminded him of the monastery’s
tiny rooms called cells
Many Observations Later
• 1838 German botanist, Matthias Schleiden,
concluded all plants were made of cells
• 1855 German physician, Rudolf Virchow, concluded
that news cells could be produced by existing cells
• THE CELL THEORY
The Cell Theory States:
1.) All living things are composed of cells
2.) Cells are the basic unit of structure and
function in living things
3.) New cells are produced
by preexisting cells
2 Types of Cells
Two main types of cells:
• Prokaryotes
• Eukaryotes
Prokaryotes
1. Cells that do not contain a nucleus (control center
of the cell)
2. Smaller and simpler
3. No membrane-bound organelles (small structures
within the cell)
3. Genetic material is NOT contained in the nucleus
Example: bacteria
Eukaryotes
1.) Contains a nucleus (control center)
2.) Larger / More Complex
3.) Contain dozens of tiny membrane bound
structures called organelles
4.) Many structures are highly specialized
5.) Genetic material IS contained in a nucleus
Eukaryotes Continued:
• Some eukaryotes are single-celled organisms
• Some are multicellular (many cells) – plants,
animals, fungi, and protists
Differences and Similarities
Prokaryotes
Similarities
Eukaryotes
No nucleus
Contain DNA as genetic
material ( may be in
different forms)
Nucleus
No membrane-bound
organelles ( mitochondria,
ER, etc.)
Cell membrane
Contains many membrane
bound organelles
Unicellular organisms –
bacteria and archaea
Both contain ribosomes
Multicellular organisms –
plants, animals, fungi,
protists
1-10 um
Both very diverse
10-100 um
DNA floats freely
DNA contained in nucleus
The Wacky History of Cells
Eukaryotic Cell Structure
• Think of a Factory: Mechanisms buzz and clatter,
people are moving quickly, in different directions ---Cells are like Factories
• Many structures in eukaryotic cells act like
specialized organs so they were given the name
“organelles”
Eukaryotic Cell Parts
• Two major parts
1.) Nucleus
2.) Cytoplasm
The Cytoplasm
• - portion of the cell outside the nucleus
• The cytoplasm and the nucleus wok together
in the business of life
The Nucleus
• The same way a main office controls the factory, the
nucleus is the control center of the cell.
• Contains nearly all of the cell’s DNA
• Coded instructions for making proteins
The Nucleus
• The nucleus is surrounded by the nuclear envelope
-Contains thousands of tiny pores – allows
materials to move in and out of cell
-like messages moving in and out of an office,
there is a steady stream of information ( proteins, RNA, and
other molecules moving into and out the nucleus)
The Nucleus
• The granular material you can see in the nucleus is
called chromatin
• Chromatin is DNA bound to protein.
• Chromatin is spread throughout the nucleus
• When a cell divides, chromatin condenses to form
chromosomes
Ribosomes
• One of the most important jobs in a cellular “factory” is
making proteins
•
Proteins are assembled on ribosomes
•
Ribosomes are small particles of RNA and protein found
throughout cytoplasm
Ribosome
• Ribosomes produce polypeptide chains which are
then folded into proteins by following the coded
instructions given to them by the nucleus (the boss)
Endoplasmic Reticulum
• Known as the internal membrane system
• Nickname is the “ER”
• Found close to the nucleus
•
Where lipid components of the cell membrane are
assembled along with proteins
Endoplasmic Reticulum
Two types:
Rough ER – involved with the synthesis of proteins
(contains ribosomes along surface – why it looks “rough”
Smooth ER – contains enzymes that perform special tasks
( synthesis of lipids ); NO RIBOSOMES
Liver cells – detoxifying drugs, often contain lots of smooth ER
Golgi Apparatus
• The “mailroom” of the cell
• Proteins produced in the rough ER move here
• Appears as a stack of pancakes
•
Modifies, sorts, and packages proteins from the ER for
storage in the cell or secretion outside of the cell
• From the Golgi Apparatus, proteins are “shipped” to
their final destinations
Lysosomes
•
Cleanup crew of a factory
•
•
Small organelles filled with enzymes
Function is to digest ( breakdown) lipids, carbohydrates, and
proteins into smaller molecules for the rest of the cell to use
•
Serious human diseases like Tay-Sachs disease, can be traced
to lysosomes that fail to function properly
Vacuoles
•
Storage room of the cell
• Store materials such as water, salts, proteins, and
carbohydrates
•
In plant cells, there is a single, large central vacuole filled
with liquid (the pressure of this vacuole allows the plant to
support heavy structures like leaves and flowers)
Vacuoles Continued
•
Paramecium ( single-celled organism) contains a contractile
vacuole
• By contracting, it is able to pump excess water out of the cell.
This allows the paramecium to maintain homeostasis – a
controlled internal environment
Mitochondria
•
All living things require an energy source. Factories are
hooked up to a power company but what about cells?
•
Nearly all eukaryotic cells (including plants) contain
mitochondria
•
Mitochondria convert chemical energy stored in food into
compounds more convenient for the cell to use
Mitochondria
•
Enclosed by two membranes: an outer membrane and an
inner membrane
• The inner membrane is folded up inside the organelle
Mitochondria – Interesting Facts
• All, or nearly all, of our mitochondria comes from
the cytoplasm of the ovum, or egg cell
• This means that all of the mitochondria you possess
in your body came from your mom!
Chloroplasts
• Also considered the energy source within cells – the
Solar Power Plant
• Found in plants and some other organisms
• Capture energy from sunlight and convert it into
chemical energy in a process called photosynthesis
Chloroplasts
• Like mitochondria, surrounded by two membranes
• Inside the organelle are large stacks of other
membranes, which contain the green pigment
chlorophyll
Organelle DNA
• Chloroplasts and mitochondria are the ONLY organelles that
contain their own DNA besides the nucleus
•
Lynn Margulis, an American biologist, suggested that
mitochondria and chloroplasts are actually descendents of
ancient prokaryotes
•
Suggests that the prokaryotic ancestors of the organelles
developed a symbiotic relationship with early eukaryotes
taking up residence within them.
Cytoskeleton
• A factory building is supported by steel or cement beams and
by columns that support its walls and roof
•
A network of protein filaments that helps the cell maintain its
shape
•
It is also involved in movement
Cell Membrane
•
A factory has a fence surrounded the premises to keep
unauthorized personal out of the area
•
Just like a factory, the cell has a thin, flexible barrier
surrounding it known as the cell membrane.
Cell Membrane Continued
• Regulates what enters and leaves the cell
• Also provides protection and support
• The cell membrane is double layered and is made up of
phospholipids : phospholipid bilayer
Cell Membrane Continued
• In addition, the phospholipid bilayer also contains proteins
and other molecules
•
“Mosaic of Different Molecules”
Cell Wall
•
Present in many organisms like plants, algae, fungi, and many
prokaryotes
• Animal cells DO NOT contain a cell wall, however, both plant
and animal cells have cell membranes
•
Provides support and protection for the cell