*
Melanie
Pd. 8
*
*Cytoplasm
*Cytosol
*Organelles
*Extracellular fluid
*What the cell
floats in.
*
*
* The cell membrane forms the outer boundary of the cell.
* The most important components of the cell membrane
include:
* Phospholipids
* Proteins
* Glycolipids
* Cholesterol.
* The cell membrane is also called the plasma membrane,
or sometimes even plasmalemma.
* All parts of the cell must work together to maintain
homeostasis at the tissue, organ, and system levels.
* All communication and coordination activities involve the
cell membrane, because it forms the interface between
each cell and its surroundings.
* The cell membrane regulates the dynamic exchange
between the intracellular and extracellular fluids. It is very
important to maintain regulation between the two fluids,
because each is different from the other, and in order to
preserve homeostasis.
*
* Cell Membrane- Lipid bilayer, containing phospholipids, steroids, and
proteins. Isolation, protection, sensitivity, organization.
* Cytosol- Fluid component of cytoplasm. Distributes materials by diffusion.
* Cytoskeleton (microtubules, microfilaments)- Proteins organized in fine
filaments or slender tubes. Strength, movement of cellular structures and
materials.
* Microvilli- Membrane extensions containing microfilaments. Absorption of
extracellular materials.
* Cilla- Membrane extensions containing microtubules in 9 X 2 arrangement.
Movement of materials over surface.
* Centrioles- Two centrioles, at right angles; each composed of microtubules
in 9 X 3 array. Movement of chromosomes during cell division.
* Ribosomes- RNA + proteins; fixed ribosomes bound to endoplasmic
reticulum, free ribosomes scattered in cytoplasm. Protein synthesis.
* Mitochondria- Double membrane, with inner folds (cristae) enclosing
important metabolic enzymes. Produce 95% of the ATP required by the cell.
*
* Nucleus- Nucleoplasm containing nucleotides, enzymes, and
nucleoproteins; surrounded by double membrane or “nuclear
envelope”
* Nucleolus- Dense region in nucleoplasm. Site of RNA synthesis.
* Endoplasmic reticulum- Network of membranous channels extending
throughout the cytoplasm. Synthesis of secretory products;
intracellular storage and transport.
* Rough ER- Ribosomes attached to membranes. Secretory protein
synthesis.
* Smooth ER- Lacks attached ribosomes. Lipid and carbohydrate
synthesis.
* Golgi apparatus- Series of stacked, flattened membranes (saccules)
containing chambers (cisternae). Storage, alteration, and packaging of
secretory products and lysosomes.
* Peroxisomes- Vesicles containing degradative enzymes. Neutralization
of toxic compounds.
*
*
* Cells obtain 95% of their necessary energy from a
Membranous Organelle inside the cell named, Mitochondria.
* The Mitochondria is composed of Double Membrane, with
inner folds (cristae) enclosing important metabolic enzymes.
* The Mitochondria produces 95% of the ATP required by the
cell.
* The Nucleus is composed of Nucleoplasm containing
nucleotides, enzymes, and nucleoproteins; surrounded by
double membrane or “nuclear envelope”.
* It controls the metabolism of the cell.
* It also controls storage and processing of genetic information.
*
*
* The cell-division cycle is a essential process where a singlecelled organism splits to make another organism.
* In cells with a nucleus, the cycle is divided into two periods:
* Interphase:
* The cell grows, accumulates nutrients needed for mitosis and
duplication its DNA.
* Mitosis (M) Phase:
* The cell splits itself in two, which are often called “daughter cells”
* Cytokinesis- where the cell is completely divided.
*
* Many cell functions that involve the cell membrane, such
as secretion or ciliary movement, involve changes in the
transmembrane potential.
* Also, because the transmembrane potential can magnify a
stimulus in this way, it greatly increases the cell’s
sensitivity to its environment.
* Two factors, one passive and one active, maintain the
transmembrane potential.
* The passive factor- is that the membrane permaebilties for sodium
and potassium are quite different, thus causing the cell to lose
positive charge faster than it can gain them.
* Because these molecules are too large to pass through the
membrane, the interior of the cell develops an excess of negative
charges.
* The active factor- is the presence of the sodium potassium exchange
pump in the membrane surface. Again the potassium ions diffuse out
of the cell much faster than sodium ions enter it, and the exchange
pump cannot prevent the net loss of positive charges.
* But because the rate is precisely balanced by the activity of the
sodium-potassium exchange pump, the transmembrane potential is
stabilized at this value.
*
*
*Most cells in the body attach to other cells or to
extracellular protein fibers.
*The attachment occurs at cell junctions, that are not
involved in membrane flow.
*There are four different types of cell junctions:
* Gap Junction
* Tight Junctions
* Intermediate Junctions
* Desmosomes
* In Gap junction, two cells are held together by an
interlocking of membrane proteins.
* Because these are channel proteins, the result is a
narrow passageway that lets small molecules and ions
pass from cell to cell.
* Gap Junctions are most common in:
* Cardiac muscle
* Smooth muscle tissue.
* Occasionally found between nerve cells.
*
*
* At tight junctions there is a partial fusion of the lipid
portions of the two cell membranes.
* Because the membranes are fused together, tight junctions
are the strongest intercellular connections.
* Tight junctions also provide mechanical strength, block
the passages of water or solutes between the cells.
* They are often found:
* Where cells are exposed to fluids whose composition is very
different from that of normal extracellular fluid.
* At intermediate junctions the opposite cell membrane are
held together by a thick layer of proteoglycans.
* This Proteoglycan layer is called, intercellular cement.
* Hyaluronic acid is the most important proteoglycan involved.
* The cytoplasm at one of these junctions contains a dense
network of microfilaments that anchor the junction to the
cytoskeleton. This arrangement adds strength and helps
stabilize the shape of the cell.
*
*
* At desmosomes these is a very thin proteoglycan layer
between the opposing cell membranes, reinforced by a
network of intermediate filaments that lock the two cells
together.
* Desmosomes are very strong and the connection can resist
stretching and twisting.
* These intercellular connections are most abundant between
the cells in the superficial layers of the skin.
*
* Cytology- the study of the structure and function of
cells.
* Transmission electron microscopy- when electrons pass
through an ultrathin section to strike a photographic
plate.
* Scanning electron microscopy- when electrons bouncing
off exposed surfaces create a scanning electron
micrograph.
* Extracellular fluid- a watery medium our cells float in.
* Cell membrane or Plasma membrane- the outer boundary of
the cell.
* Cell membrane is also called a phospholipid bilayer, because they
form two layers.
* Peripheral proteins- attached to the inner membrane
surface.
* Integral proteins are embedded in the membrane.
* Some of these proteins form channels that let water molecules,
small water-solution compounds, and ions into and out of the cell.
* Cytosol or intracellular fluid- contains dissolved nutrients,
ions, soluble and soluble proteins and waste products.
* The membrane also separates the cytosol from the surrounding
extracellular fluid.
* Organelles- structures that preform specific functions within
the cell.
* Inclusions- masses of insoluble materials sometimes found in
the cytosol.
* Nonmembranous organelles- cellular organelles that are
always in contact with the cytosol.
* Membranous organelles- cellular organelles that are
surrounded by lipid membranes that isolate them from the
cytosol.
* Cytoskeleton- is an internal protein framework that gives the
cytoplasm strength and flexibility.
* Microfilaments- slender protein strands, usually composed of
the protein actin.
* Myosin- protein component of the thick myofilaments.
* Neurofilaments- found in nerve cells, where they provide
structural support and provably assist in the movement of
materials within the cytoplasm.
* Thick filaments- are relatively massive strands composed of
myosin protein subunits.
* Microtubules- found in all our cells are hollow tubes built from
the globular protein tubulin.
* Microvilli- small, finger-shaped projections of the cell
membrane.
* Centriole- is a cylindrical structure composed of short
microtubules.
* Centrosome- is the cytoplasm surrounding the pair.
* Cilia- contains nine parts of microtubules surrounding a central
pair.
* Basal body- a compact situated just beneath the cell surface
which the cilla are anchored to.
* Flagella- resemble cilla but are much larger.
* Ribosomes- are small, dense structure that cannot be seen
clearly with the light microscope.
* Free ribosomes- scattered throughout the cytoplasm, they
product proteins that enter the cytosol.
* Fixed ribosomes- are attached to the endoplasmic reticulum , a
membranous organelle.
* Mitochondria- small organelles that have an unusual double
membrane.
* Cristae- numerous folds in the inner membrane.
* Matrix-the fluid contents of the mitochondrion.
* Respiratory enzymes-attached to the cristae produce most of
the ATP generated by mitochondria.
* Nucleus- the control center for cellular operations.
* Nuclear envelope- surrounds the nucleus and separates it from
the cytosol.
* Peri-nuclear space- a narrow passage in the double membrane
in the nuclear envelope.
* Nuclear pores- chemical communication between the nucleus
and cytosol occurs here.
* Nucleoplasm- the fluid contents of the nucleus.
* Chromosomes- complex structures formed by the DNA.
* Histones- chromosomes that contain DNA strands bound to
special proteins.
* Nucleosome-DNA strands wind around the histones at intervals,
forming a complex known as Nucleosome.
* Chromatin- in cells that are not dividing, when chromosomes
are loosely coiled, forming a tangle of fine filaments.
* Nucleoli- one to four dark-staining areas found in the nucleoli.
* Endoplasmic reticulum- a network of intracellular membranes.
* Cisternae- round chambers formed by the ER.
* Rough endoplasmic reticulum- used as a combination workshop
and shopping depot.