Download Cell Membranes - Enrico Fermi High School

7.2 Cell Structure
Cell Organization
 The eukaryotic cell can be divided into two major
parts: the _________________ and the ___________________.
 The cytoplasm is the fluid portion of the
cell______________ the nucleus.
Cell Organization
Many cellular structures act as if they are specialized organs. These
structures are known as __________________,
literally “little organs.”
The Nucleus
 The nucleus is the _____________
center of the cell.
 The nucleus contains nearly all the cell’s _________ and, with it, the
coded instructions for making proteins and other important
molecules. This DNA is passed from one _________________ of cells
to the next.
 Most of the time, the threadlike chromosomes are spread
throughout the nucleus in the form of______________a complex of
DNA bound to proteins. When a cell
divides,
its_________________________
condense.
 The nucleus is surrounded by a nuclear ____________ composed of
two membranes.
 The nuclear envelope is dotted with
thousands of nuclear ______________, which allow
material to move into and out of the nucleus.
 Most nuclei also contain a small, dense
region known as the _________________.
 The nucleolus is where the assembly of ___________ begins.
Organelles That Store, Clean Up, and Support
Vacuoles and Vesicles
 Many cells contain large, saclike, membrane-enclosed structures called
___________________that store materials such as water, salts, proteins, and
carbohydrates.
 In many plant cells, there is a _____________, _______________ central
vacuole filled with liquid. The pressure of the central vacuole in these cells
increases their rigidity, making it possible for plants to support
_________________structures such as leaves and flowers.
 Vacuoles are also found in some __________________organisms and in
some ___________________.
 Nearly all ____________________ cells contain smaller membraneenclosed structures called _______________. Vesicles are used to store
and move materials between cell organelles, as well as to and from the cell
surface.
Lysosomes
 __________________ are small organelles filled with _______________
that function as the cell’s cleanup crew. Lysosomes perform the vital
function of removing _______________ that might otherwise accumulate
and clutter up the cell.
 One function of lysosomes is the breakdown of ___________,
_________________, and __________________ into small molecules that
can be used by the rest of the cell.
 Lysosomes are also involved in breaking down organelles that have
_______________ their usefulness.
The Cytoskeleton
 Eukaryotic cells are
given their shape and internal
organization by a network of
protein filaments known as
the______________________.
 Certain parts of the cytoskeleton also help to transport
____________________between different parts of the cell.
 ______________________and _____________________ are two of
the principal protein filaments that make up the cytoskeleton.
Microfilaments
 They form extensive networks in some cells and produce a tough,
flexible framework that _______________ the cell.
 Microfilaments also help cells ___________________.
Microtubules .
 Microtubules are hollow structures made up of proteins known as
____________.
 They play critical roles in maintaining cell ________________________.
 In animal cells, structures known as _____________ are also formed from
tubilins.
 _________________________are
located near the nucleus and help to
organize cell division.
 __________________________are not
found in plant cells.
Organelles That Build Proteins
Cells need to build new molecules all the time, especially _____________, which
catalyze chemical reactions and make up important structures in the cell.
Because ______________ carry out so many of the essential functions of
living things, a big part of the cell is devoted to their production and distribution.
Proteins are synthesized on _____________, sometimes in association with
the rough endoplasmic reticulum in eukaryotes.
Ribosomes
 __________________ are small particles of RNA and protein found
throughout the cytoplasm in all cells.
 _____________produce _____________by following coded
instructions that come from DNA.
Endoplasmic Reticulum
 Eukaryotic cells contain an internal membrane system known as the
_____________ _______________ or ER.
 The endoplasmic reticulum is where lipid components of the cell
membrane are assembled, along with _____________ and other
materials that are exported from the cell.
 The portion of the ER involved in the synthesis of proteins is called
__________ endoplasmic reticulum, or rough ER. It is given this name
because of the ______________found on its surface.
 The other portion of the ER is known as _________________
endoplasmic reticulum (smooth ER) because _____________ are
___________found on its surface.
Golgi Apparatus
 Proteins produced in the rough ER move next into the __________
_____________which appears as a stack of flattened membranes.
 The Golgi apparatus modifies, __________, and packages proteins
and other materials from the ER for storage in the cell or release
outside the cell.
 From the Golgi apparatus, proteins are _____________ 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 ___________.
____________________ and ____________________ are both involved in
energy conversion processes within the cell.
Chloroplasts
 ________________ and some other organisms contain chloroplasts.
 _______________________ are the biological equivalents of solar
power plants. They capture the ___________ from sunlight and
convert it into food that contains chemical energy in a process called
photosynthesis.
 Inside the organelle are large stacks of other membranes, which
contain the _______________pigment ___________________.
Mitochondria
Nearly all eukaryotic cells, including plants, contain ___________________.
________________________ are the _____________ _____________of
the cell. They convert the chemical energy stored in food into compounds that are
more convenient for the cell to use.
Cellular Boundaries
Similarly, cells are surrounded by a barrier known as the cell
____________.
Many cells, including most prokaryotes, also produce a strong supporting
layer around the membrane known as a _________________.
Cell Walls
 The main function of the cell wall is to provide _________and
_______ for the cell.
 Prokaryotes, plants, algae, fungi, and many prokaryotes _______ cell
walls. Animal cells do _________ have cell walls.
 Cell walls lie outside the cell membrane and most are __________
enough to allow _____________, ____________, carbon dioxide and
certain other substances to pass through easily.
Cell Membranes
 All cells contain a cell membrane that regulates what _______________
and ______ _____________the cell and also ______________ and
___________________ the cell.
 The composition of nearly all cell membranes is a double-layered sheet
called the _____ _______, which gives cell membranes a ________
_____________________structure and forms a strong barrier between the
cell and its _________________.
The Properties of Lipids
 Many ______ ______________have oily fatty acid chains attached to
chemical groups that _______________ strongly with ______________.
 The fatty acid portions of such a lipid are ___________________, or
“water-hating,” while the opposite end of the molecule is
_______________________, or “water-loving.”
 When such lipids are mixed with ________________, their hydrophobic
fatty acid “_______________” cluster together while their hydrophilic
“_______________” are attracted to water. A lipid ________________ is
the result.
 The ____ ___________groups of lipids in a bilayer are _________________
to water, while the fatty acid tails form an oily layer ______
___________the membrane from which water is excluded.
The Fluid Mosaic Model
 Most cell membranes contain _________________ molecules that
are embedded in the lipid bilayer. __________ ______molecules are
attached to many of these proteins.
 Because the proteins __________ _________in the lipid bilayer can
move around and “______________” among the lipids, and because
so many different kinds of molecules make up the cell membrane,
scientists describe the cell membrane as a “______ _______.”
 Some of the proteins form _______________ and ______
____________that help to move material _________________ the
cell membrane.
 Many of the carbohydrate molecules act like chemical ____________
_____, allowing individual cells to identify one another.
 Although many substances can cross _____________________
membranes, some are too ___________________ or too
________________ charged to cross the lipid bilayer.
 If a substance is able to cross a ______________________, the membrane
is said to be _______________________ to it.
 A membrane is ____________ to substances that cannot
________________ across it.
 Most biological membranes are _________ ___________, meaning that
some substances _______________ pass across them and others
________. Selectively permeable membranes are also called
____________________ ___________ membranes.