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Control center of the cell
Contains the genes (genetic materials)
 DNA – molecule in the cell that is used to construct
proteins
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Interesting facts about the nucleus
 The shape of the nucleus will conform to the shape of
the cell
 Absolutely necessary for cell reproduction. A cell
that has lost or ejected its nucleus is only
programmed to die
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Nuclear Envelope – double membrane barrier
around the nucleus
Nucleoli (plural of nucleolus)– small, darkstaining round bodies where ribosomes are
assembled
Chromatin – DNA that is combined with
protein to form a loose network of bumpy
threads and is scattered throughout the
nucleus. During replication, this will coil and
condense to form chromosomes
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Fragile, transparent barrier
Consists of two lipid layers arrange “tail to
tail”
Protein molecules float around in the
membrane. Example include:
 Enzymes
 Receptors for hormones
 Protein channels (tiny pores)
 Carriers (carry wanted materials into the cell)
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Microvilli – tiny finerlike projections that greatly
increase the surface area for faster absorption
Membrane Junctions
 Tight Junctions – impermeable junctions that bind
cells together into “leak proof sheets”
 Desmosomes – anchoring junctions that prevent
cells from being pulled apart
 Gap Junctions – allow communication in between
cells. The two cells are connected by connexons
(hollow cylinders that span width of the membranes)
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The cellular material outside the nucleus and
inside the plasma membrane
Three major elements
 Cytosol – semitransparent fluid that suspends the
other parts
 Organelles – means little organs, these are the
specialized compartments that are designed for
specific tasks inside the cell
 Inclusions – extra chemical substances in the cell
Mitochondria – bean shaped cellular power plants
Ribosomes – tiny, bilobed, dark bodies that are the
protein making factories of the cell
 Endoplasmic Reticulum (ER)– serves as a minicirculatory system and provides a network of channel to
carry substances
 Rough ER – covered with ribosomes (makes it rough).
So it takes the newly made proteins, allows them to
finish folding into their normal shape, and then ships
them to other parts of the cell
 Smooth ER – lipid metabolism and detoxification
takes place here.
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• Golgi Apparatus – post office, it receives
proteins from the rough ER, modifies them,
and then packages them in secretory vesicles.
– These vessels travel to the plasma membrane,
fuse with it, and then eject its contents out of the
cell
• Lysosomes – “breakdown bodies,” sacs filled
with digestive enzymes capable of digesting
old cells or foreign materials
• Peroxisomes –detoxify the cell of poisonous
materials and deactivate free radicals using
oxidase enzymes
• Cytoskeleton – network of proteins that for
the “bones and muscles” of the cell. It
consists of:
– Intermediate filaments – “wires” that help to
resist pulling forces on the cell
– Microfilaments – involved in cell movement and in
producing changes in cell shape
– Microtubules – determines the overall shape of
the cell and distribution of organelles
• Centrioles – rod shape bodies near the
nucleus that help direct cell division
Don’t forget, the next memory check is
going to be…
Homework
• Complete the Cell Diversity Worksheet