Section 2: Inside the Eukaryotic Cell
Bell Ringer
During lab when you used a light microscope to view a slide of a eukaryotic cell and
found the nucleus of the cell, how did you know that the structure was the nucleus?
The Framework of the Cell
Eukaryotic cells have an intricate network of protein fibers called the
______________which provides the interior framework of the cell.
The cytoskeleton helps the cell ___________, keep its shape, and organize its
parts.
There are three different kinds of cytoskeleton fibers: microfilaments,
microtubules, and intermediate fibers.
Cytoskeleton
Directing Cellular Activity
________ contains instructions for making proteins which control most of the
activity of the cell.
The DNA of eukaryotic cells is stored in the _______________.
DNA instructions are copied as ______________ messages, which leave the
nucleus. In the cytoplasm, ribosomes use the RNA messages to assemble
proteins.
Nucleus
A double membrane called the ________________________envelope surrounds the
nucleus.
Nuclear pores located on the nuclear envelope act as channels to allow certain
molecules to move in and out of the nucleus.
The___________________ is a structure within the nucleus where ribosome parts
are made.
These ribosome parts are transported out of the nucleus into the cytoplasm
where they are assembled to form a complete ribosome.
Ribosomes
Each ribosome in a cell is made of ___________ and many different proteins.
Ribosomes that are suspended in the cytosol are called “____________” ribosomes.
Free ribosomes make proteins that remain inside the cell.
Ribosomes that are attached to the membrane of another organelle are called
“___________” ribosomes.
Bound ribosomes make proteins that are exported from the cell.
Ribosomes can switch between being bound or free, depending on what proteins
the cell needs to make.
Protein Processing
Some proteins that a cell manufactures are needed _______________ the cell that
makes them.
Proteins that are sent outside the cell are packaged in vesicles.
_______________are small, membrane-bound sacs that enclose the proteins and
keep them separate from the rest of the cytoplasm.
The __________________________ and Golgi apparatus are organelles involved in
preparing proteins for extracellular export.
Endoplasmic Reticulum
The endoplasmic reticulum, or ER, is an extensive system of internal
membranes that moves proteins and other substances through the
______________.
The membranes of the ER are connected to the outer membrane of the nuclear
________________.
The endoplasmic reticulum is divided into two portions: _____________ER and
______________ ER.
The portion of the ER with attached ribosomes is called rough ER because it has
a __________________ appearance when viewed with an electron microscope.
The portion of the ER with no attached ribosomes is called smooth ER because it
has a smooth appearance when viewed with an electron microscope.
The ribosomes on the rough ER make proteins that are packaged into
_______________. Enzymes of the smooth ER make lipids and break down
________________substances.
Golgi Apparatus
The Golgi apparatus is a set of flattened, membrane-bound sacs.
The Golgi apparatus helps __________, sort, and _____________________ cell
products for distribution.
Making and Exporting Proteins
The ribosomes located on the rough ER make proteins which then cross into the
________________________ of the ER. The ER membrane then pinches off and
forms a vesicle around the proteins.
Vesicles transport the proteins from the rough ER to the Golgi apparatus, where
they are modified by ___________________and repackaged in new vesicles.
These new vesicles transport the modified proteins to the cell membrane to be
released outside the cell.
Lysosomes
Vesicles help maintain ____________________ by storing and releasing a variety
of substances as the cell needs them.
A lysosome is a vesicle produced by the Golgi apparatus that contains enzymes
that break down large molecules.
Lysosomes ________________ old or damaged organelles and digest food particles
to provide nutrients for the cell.
Vacuoles
A vacuole is a fluid-filled ___________________ found in the cytoplasm of many
plant cells.
Plant cells contain a large compartment called the __________________________,
which stores water, ions, nutrients, and wastes.
When water fills the central vacuole, the cell becomes rigid, allowing the plant to
stand up (turgor pressure increased). When the vacuole loses water, the cell
shrinks, and the plant wilts.
Other Vacuoles
Some protists have _____________________vacuoles which pump excess water out
of the cell in order to control the concentration of salts and other substances.
A _________________ vacuole is another type of vacuole. It is formed when the
cell membrane surrounds food particles outside the cell and pinches off to form a
vesicle inside the cell.
Energy Production
Cells need a constant source of __________________.
The energy for cellular functions is produced by chemical reactions that occur in
the mitochondria and chloroplasts.
In both organelles, chemical reactions produce
_______________________________________ (ATP), the form of energy that fuels
almost all cell processes.
Chloroplasts
A ____________________ is an organelle found in plant and algae cells that uses
light energy to make carbohydrates from carbon dioxide and water.
Chloroplasts are surrounded by ___________ membranes and have several stacks
of flattened sacs where energy production takes place.
________________ cells may have several chloroplasts.
Mitochondria
Mitochondria are cell organelles that use _________________ from organic
compounds to make ATP.
Most of the _____________needed by a cell is produced inside mitochondria. Both
animal and plant cells contain mitochondria.
A smooth outer membrane and a folded inner membrane surround a
mitochondrion. ATP is produced by _______________ on the folds (cristae) of the
inner membrane.
Summary
The cytoskeleton helps the cell move, keep its shape, and organize its parts
DNA instructions are copied as RNA messages, which leave the nucleus. In the
cytoplasm, ribosomes use the RNA messages to assemble proteins.
The endoplasmic reticulum and Golgi apparatus are organelles involved in
preparing proteins for extracellular export.
Vesicles help maintain homeostasis by storing and releasing a variety of
substances as the cell needs them.
The energy for cellular functions is produced by chemical reactions that occur in
the mitochondria and chloroplasts.