Parts of the Cells
The Nucleus – the main office of the factory
 Control center of the cells
 Contains nearly all of the cell’s DNA and,
with it, the coded instructions for making
proteins and other important molecules
 Surrounded by a nuclear envelope compose of
two membranes
o Chromatin – the threadlike chromosomes
that are spread throughout the nucleus
 A complex DNA bound to proteins.
 The site of cell division – cells
breaking up to become a new cell.
 Chromosomes – contain the genetic
information that is passed from one
generation to the next.
o Nucleolus – assembly of ribosomes begins
 On the nuclear envelope you have nuclear
pores
o Allow material to move into and out of
the nucleus (the door to the main office)
o Think about like messages, instructions,
and blueprints moving in and out of the
main office, a steady stream of proteins,
RNA, and other molecules move through
the nuclear pores to the rest of the cell.
Organelles that Store, Clean Up, and Support
Vacuoles = store materials like water, salts,
proteins, and carbohydrates
 Large, saclike, membrane-enclosed structures
 Plants cells – a single, large central vacuole
filled with liquid. The pressure of the central
vacuole in these cells increases their rigidity,
making it possible for plants to support heavy
structures such as leaves and flowers.
o Paramecium (unicellular organism)
contains an organelle called a contractile
vacuole.
 Pumps excess out of the cell because
it contracts rhythmically.
 Eukaryotic cells contain smaller membraneenclosed structures called vesicles.
o Store and move materials between cell
organelles, as well as to and from the cell
surface.
Lysosomes = break down lipids, carbohydrates,
and proteins into small molecules that can be used
by the rest of the cell.
 Help break down organelles that have outlives
their usefulness
 Cleanup Crew – cleans up the clutter and
accumulated “junk” in the cell
Cytoskeleton= helps maintain its shape and is also
involved in movement.
 Network of protein filaments
 Certain parts help transport materials
between different parts of the cell
o Much like conveyer belts that carry
materials from one part of the factory to
another.
 Microfilaments and microtubules
o Two principle protein filaments that
make up the cytoskeleton.
Microfilaments
 Threadlike structures made up of protein
called actin
 Form extensive networks in some cells and
produce a tough, flexible framework that
supports cells.
 Also help the cell move.
 Microfilament assembly and disassembly is
responsible for the cytoplasmic movements
that allow cells, such as amoebas, to crawl
along surfaces.
Microtubules
 Hollow structures made up of proteins known
as tubulins.
 Critical in maintaining cell shape
 Also important in cell division, form a
structure called the mitotic spindle, which
helps separate chromosomes.
 Help build projections from the cell surface
known as cilia and flagella, that enable cells to
swim rapidly through liquids.
 Arrange in a “9+2” pattern
 Small cross-bridges between microtubules in
these organelles use chemical energy to pull
on, or slide along, the microtubules, allowing
cells to produce controlled movements.
In animal cells, centrioles are also formed from
tubulins
 Located near the nucleus and help to organize
cell division.
 NOT found in plant cells!!!
Organelles That Build Proteins
Ribosomes – where proteins are assembled
 Small particles of RNA and protein found
throughout the cytoplasm in all cells.
 Produce proteins by following coded
instructions that come from DNA.
Endoplasmic Reticulum (ER) – where proteins are
made
 Eukaryotic cells
 Lipid components are also assembled in the
ER
 Rough ER
o May be released, or secreted, from the
cell
o May be membrane proteins
o Or proteins destined for lysosomes and
other specialized locations within the cell
 Smooth ER
o Ribosomes are not found on the smooth
ER
o Contains collections of enzymes that
perform specialized tasks
 Synthesis of membrane lipids
 Detoxification of drugs.
Golgi apparatus – modifies, sorts, and packages
proteins and other materials from the
endoplasmic reticulum for storage in the cell or
release outside the cell
 Proteins come here after they are produced in
the rough ER
 Appears to be a stack of flattened membranes
 Proteins are bundled into tiny vesicles that
bud from the ER and carried into the Golgi
apparatus.
 It is the customization shop, where the
finishing touches are put on proteins before
they are ready to leave the “factory”
 From the Golgi apparatus, proteins are
“shipped” to their final destination inside or
outside the cell.
Organelles That Capture and Release Energy
 All living things require a source of energy.
Most cells are powered by food molecules that
are built using energy from the sun.
 Chloroplasts – capture energy from the
sunlight and convert it into food (glucose
molecules) that contains chemical energy in a
process called photosynthesis.
Sunlight + H2O + CO2  C6H12O6 + O2
 Mitochondria – convert chemical energy
stored in food into compounds that are more
convenient for the cells to use in a process
called cellular respiration
C6H12O6 + O2  H2O + CO2 + ATP
Chloroplasts and mitochondria are both involved
in energy conversion processes within the cell.
Chloroplasts
 Plants and some other organisms (Protistssuch as Euglena) contain chloroplasts.
 Biological equivalents of solar power
 Use photosynthesis
 Surrounded by membranes
 Inside of chloroplasts are large stacks of other
membranes, which contain green pigment
chlorophyll
Mitochondria
 Nearly all eukaryotic cells, including plants,
contain mitochondria.
 Power plants of the cell
 Contains two membranes
o An outer – protecting the folded inner
membrane
o An inner – folded up inside of the
organelle
o Interesting thing about mitochondria is
the way that they are inherited
 In humans nearly all of our
mitochondria come from the
cytoplasm of the ovum, or egg cell.
You get your mitochondria from
Mom!!
Chloroplasts and mitochondria contain their own
genetic information in the form of small DNA
molecules.
Endosymbiotic Theory – suggests that
chloroplasts and mitochondria may have
descended from independent microorganisms.