Download Basic information on cell

Basic information on cell:
cell membrane and its function,
organelles, general types of tissues of
human origin
CEAC514
Assoc. Prof. Dr. Yasemin G. İşgör
Typical Animal Cell
MEMBRANE STRUCTURE
 Similar to any container, the first noticeable thing is the presence of
boundaries around the cells or in biological terminology;
MEMBRANES.
 Biological membranes consist of phospholipid bilayers with various
sorts of PROTEINS interspersed in them and located on the
membrane surfaces according to the widely accepted FLUID
MOSAIC MODEL of membrane structure
Fluid mosaic model of biological membranes
MOVEMENT OF MATERIALS ACROSS MEMBRANES
 All materials (including the cellular solvent: H2O) move across membranes
through highly regulated mechanisms.
 A membrane is said to be “permeable” to a substance if it allows free
passage of that substance.
 It is often stated that cellular membranes are SEMIPERMEABLE,
meaning solvents but not solutes may cross.
 The living cell membranes “is not openly permeable” to any substance,
including, H2O, although H2O may cross more freely than most other
substances.
 Of these mechanisms, three shall be mentioned due to their importance in
culturing of cells:
1.
Osmosis:
2.
Simple Diffusion
3.
Active Transport
Hypotonic, hypertonic and isotonic Solutions
 When a solute is more concentrated on one side of a membrane than
the other, a concentration gradient exists.
 If a solvent is capable of traversing a membrane it will move from the
side where the solute is more dilute (hypotonic: free water is high),
to the side of solute concentration is high (hypertonic: free water is
less).
 Solvent molecules continue to move until the concentrations are
equal across both sides of the membrane (isotonic) .
1.Osmosis:
 The process by which a solvent crosses a membrane in response to a
concentration gradient is known as OSMOSIS and the force with which
the solvent is drawn from dilute solute side to the concentrated side is the
OSMOTIC PRESSURE.
2. Simple Diffusion
 Many solutes are dissolved in the
cellular solvent which is H2O
 Dissolved solute across membranes by
moving from a higher concentration
(of
solute)
side
to
the
lower
concentration side by the involvement
of special membrane proteins.
• This is called simple diffusion and actually it is moving down a
concentration
gradient
from
high
to
low
solute
concentrations.
• The rate of diffusion through a membrane is known as flux.
3. Active Transport
 Unlike diffusion, active transport is able to achieve a net movement of a solute “UPHILL”
against a concentration gradient. To accomplish this task the cell must use ATP as the
energy source
 Nearly all cells (either prokaryotic or eukaryotic) use active transport to pull valuable
molecules like sugars.
 in a resting human body, for example, 30-40% of all energy used goes in to active transport
and the percentage may be much higher in certain organs such as brain and kidneys.
PROKARYOTIC CELL STRUCTURE
Ribosomes
Flagella
Cytoplasm
Chromosome
Cell wall Cell membrane
EUKARYOTIC CELL STRUCTURE
 Eukaryotic cells are characterized by internal membrane systems and by
compartmentalization that subdivides the chemical activities.
 These membrane bound structures within eukaryotic cells are called
ORGANELLES
EUKARYOTIC CELL STRUCTURE: NUCLEUS-1
 . The cell’s nucleus is surrounded
by
the
NUCLEAR
ENVELOPE
which consists of two layers of
membranes with a narrow space
between them.
 Macromolecules
(mRNA,
rRNA,
nuclear proteins etc) can exit or
enter the nucleus through PORES,
which
provide
communication
routes
for
with
the
surrounding cytoplasm.
EUKARYOTIC CELL STRUCTURE: NUCLEUS-2
 Within the nucleus, DNA is organized in linear arrays of NUCLEOSOMES
.
EUKARYOTIC CELL STRUCTURE :ENDOPLASMIC RETICULUM-1
 ER is a network of flattened tubes surrounding the nucleus
 is actually of two types: 1) rough endoplasmic reticulum (RER) and 2)
smooth endoplasmic reticulum (SER).
EUKARYOTIC CELL STRUCTURE :ENDOPLASMIC RETICULUM-2
1) Rough Endoplasmic Reticulum (RER)
 surface is studded with ribosomes. This is the place where proteins
are synthesized by translation of the mRNA.
2) smooth endoplasmic reticulum (SER)
 do not contain ribosomes and do not function in protein synthesis.
 SER contains phospholipids, neutral fats, sterols and other lipids that
it is the site for lipid biosynthesis.
EUKARYOTIC CELL STRUCTURE :GOLGI APPARATUS
 In most eukaryotic cells, one or more GOLGI BODIES (Apparatus) are present in
the form of membranous sacs (transfer vesicles)
 Membranous sacs (transfer vesicles) from RER and SER bring proteins and lipids
to the golgi body, where they are repackaged into secretory vesicles. These
vesicles then move to the plasma membrane where their contents are expelled
from the cell (Exocytosis)
 Golgi bodies also carry on synthesis. In them, proteins from the RER are converted
to glycoproteins, polysaccharides of various sorts and mucoproteins which form the
mucus are synthesized.
• Golgi
bodies
also
carry
on
synthesis. In them, proteins from
the
RER
are
converted
to
glycoproteins, polysaccharides of
various sorts and mucoproteins
which
form
synthesized.
the
mucus
are
EUKARYOTIC CELL STRUCTURE : LYSOSOMES
 . membrane-bound organelles that contain a variety of powerful hydrolytic enzymes
which catalyze the breakdown of large biological molecules
 The separation of hydrolytic enzymes from the cytoplasm by the lysosome’s
membrane protects the normal working components of a living cell from random
destruction (digesting itself).
• Lysosomes
vary
in
size
and
appearance, and probably derived
either from the ER or Golgi bodies
(or from both).
EUKARYOTIC CELL STRUCTUR E: MITOCHONDRIA
 act as power plants in the energy
system of eukaryotic cells. The output
of this energy production is the high
compound called ATP (Adenosine
triphosphate)
 Mitochondria have double membrane
system; the outer one is fairly typical,
unspecialized unit membrane, but the
inner one is highly specialized for ATP
production.
 Elaborate
folds
of
this
inner
membrane (CRISTA) extend into the
mitochondria’s interior gel-like matrix
(STROMA)
RECALLING THE BASIC TISSUE-CELL KNOWLEDGE -1
 Over 200 Cell types in the human body are assembled to form variety of
tissues such as: Epithelia, Connective tissue, Muscle, and Nervous tissue
 Most of these tissues contain mixtures of cell types (non-homogeneous).
 Epithelia is the sheets of cells that forms the inner and outer lining of the
organs and surface of the body.
 Some has main function to increase absorption (absorptive cells), some have
transport function to facilitate the transport of substances (such as mucus)
over the epithelial sheet (ciliated cells) and some have function to secrete
substances out of cell (secretory cells).
Absorptive cells
Ciliated cells
Secretory cells
RECALLING THE BASIC TISSUE-CELL KNOWLEDGE-2
 Connective tissue is in between the organs and tissues to create more
interaction, provide strength, and as the name implies connects the solid
structures (between bones).
 It is mainly composed of a strong fibrous protein network (collagen and
elastin)
in polysaccharide gel. This forms a structure called extracellular
matrix secreted mainly by fibroblasts.
 Also bone cells (osteoclasts) secrete to extrtacellular matrix, and these
secretion becomes a crytal of calcium phosphates and keep bone cells
together in solid matrix structure.
osteoclasts
Osteoclasts in calcium
phosphate deposited
matrix.
OTHER TYPE OF CELLS THAT FORMS THE BODY STRUCTURE
 Nerve tissue: is made of nerve cells called neurons.
Muscle cells
Blood cells