process that occurs after cell division where the newly formed cells are. structurally modified so that they can perform their function efficiently. and effectively. • Cell modification is features or structure of the cell that makes it different. from another type of cell and at the same time enables it to carry out.

1. CELL
CELL
MODIFICATION
MODIFICATION
Group 3

2. • Cell specialization (or modification or differentiation) is
actually a process that occurs after cell division where the
newly formed cells are structurally modified so that they
can perform their function efficient and effectively.
• Cell modification is features or structure of the cell that
makes it different from another type of cell and at the
same time enables it to carry out unusual functions.
WHAT IS CELL MODIFICATION?

3. WHAT IS CELL MODIFICATION?
• Cell modification are specialized or modifications re-
acquired by the cell after cell division.

4. • Plant and animal cells are specialized to be able to
carry out their tasks efficiently.
• They have particular adaptation to their structure to
suit its function.
WHAT IS CELL MODIFICATION?

5. • Basal Modification (bottom)
• Apical Modifications (top)
• Lateral Modification (sides)
KINDS OF CELL
MODIFICATION

6. Apical modification occurs in the apical surface. Under
the APICAL MODIFACTION are:
• Microvilli
• Cilia
• Stereocilia
• Flagella
APICAL MODIFICATION

7. STRUCTURE,
STRUCTURE,
LOCATIONS AND
LOCATIONS AND
FUNCTIONS
FUNCTIONS

8. • Microvilli are microscopic cellular membrane
protrusions that increase the surface area for
diffusion and minimize any increase in volume, and
are involved in a wide variety of functions, including
absorption, secretion, cellular adhesion, and
mechanotransduction.
• Microvilli, in the most simplistic terms, are tiny little
projections that exist in, on, and around cells.
MICROVILLI

9. • The tissue has small fingerlike extensions called villi
which are collections of cells, and those cells have
many microvilli to even further increase the available
surface area for the digestion process.
• Microvilli are covered in plasma membrane, which
encloses cytoplasm and microfilaments. Though these
are cellular extensions, there are little or nocellular
organelles present in the microvilli.
MICROVILLI

10. • Thousands of microvilli form a structure called the
brush border thatis found on the apical surface of
some epithelial cells, such as the small intestines.
• Microvilli should not be confused with intestinal villi,
which are made of many cells. Each of these cells has
many microvilli. Microvilli are observed on the plasma
surface of eggs, aiding in the anchoring of sperm cells
that have penetrated the extracellular coat of egg
cells.
MICROVILLI

11. • Microvilli are most often found in the small
intestine, on the surface of egg cells, as well as on
white blood cells.
• In the intestine, they work in conjunction with villi
to absorb more nutrients and more material because
they expand the surface area of the intestine.
MICROVILLI

12. • They also play a role in egg cells as they help in
anchoring the sperm to the egg, thus allowing for
easier fertilization. In white blood cells, the microvilli
again act as an anchoring point.
• Microvilli are extremely important because they
increase the surface area of the cell that they are
found on.
MICROVILLI

13. • Microvilli function as the primary surface of nutrient
absorption in the gastrointestinal tract. Because of this vital
function, the microvillar membrane is packed with enzymes that
aid in the breakdown of complex nutrients into simpler
compounds that are more easily absorbed. For example, enzymes
that digest carbohydrates called glycosidases are present at high
concentrations on the surface of enterocyte microvilli. Thus,
microvilli not only increase the cellular surface area for
absorption, they also increase the number of digestive enzymes
that can be present on the cell surface.
MICROVILLI

14. • A cilium, or cilia (plural), are small hair-like
protuberances on the outside of eukaryotic cells.
• They are primarily responsible for locomotion, either
of the cell itself or of fluids on the cell surface. They
are also involved in mechanoreception.
• There is even a class of microorganisms named for
these small structures.
CILIA

15. • Ciliates are protozoans that possess cilia which they
use for both locomotion and feeding.
• Cilia can be grouped into two categories. First, there
are motile cilia, which are always moving in a single
direction. They help the cell move around in the cellular
fluids and help move fluids past the cell. Motilecilia are
found together on cells and coordinate their movements
to be most effective, making up for their small size.
CILIA

16. • The second type of cilia is non-motile cilia, and these
are responsible for sensing the surrounding
environment. They are also called primary cilia. Whereas
motile cilia are found in groups on cells, each cell
usually has just one non-motile cilium.
• A cilium is made up of microtubules coated in plasma
membrane.
CILIA

17. • The microtubules are small hollow rods made of the protein
tubulin. Each cilium contains nine pairs of microtubules
forming the outside of a ring, and two central microtubules.
• Cilia attach to the cell at a basal body. The basal body is
made up of microtubules arranged as nine triplets. The
triplets are formed as the doublets from the cilia are joined
by an additional microtubule from the cell . The two central
microtubules end before entering the basal body.
CILIA

18. • Cilia are very small structures – measuring approximately
0.25 μm indiameter and up to 20 μm in length. Where present
they are found inlarge numbers on the cell surface. The cilia
act like oars, beating back and forth to create movement.
• Cilia play an important role in locomotion. This can include
movement of the cell itself, or of other substances and objects
past the cell.
CILIA

19. • In some organisms known as ciliates, cilia are responsible for
movement of the organism as a whole. For example, in the
unicellular protist Paramecium, cilia cover the surface of the
organism and are responsible for movement as well as feeding.
In addition to covering the outside of the organism, cilia also
line the oral groove, moving food into the organism’s “mouth”.
CILIA

20. • Cilia can help to remove contaminants from organs or tissue
by helping to move fluids over the cell. The lining of the
nasopharynx and the trachea are covered in cilia. These
ciliated epithelial cells removemucus, bacteria, and other
debris from the lungs.
CILIA

21. • Stereocilia are non-motile apical modifications of the cell,
which are distinct from cilia and microvilli, but closely related
to the latter.
• Long microvilli that function in increasing absorption.
• Found in sensory cells in ear and male reproductive tract.
• Does not have the true characteristic of true cilia or
flagella.
STEREOCILIA

22. • Stereocilia are the mechanosensing organelles of hair cells,
which respond to fluid motion in numerous types of animals
for various functions, including hearing and balance. They
are about 10–50 micrometers in length and share some similar
features of microvilli. The hair cells turn the fluid pressure
and other mechanical stimuli into electric stimuli via the
many microvilli that make up stereocilia rods. Stereocilia
existin the auditory and vestibular systems.
STEREOCILIA

23. • The stereocilia are located in the otolithic organs and the
semicircular canals. Hair cells in the vestibular system are
slightly different from those in the auditory system, in that
vestibular hair cells have one tallest cilium, termed the
kinocilium.
STEREOCILIA

24. • The stereocilia of the epididymis are long cytoplasmic
projections that have an actin filament backbone. These
filaments have been visualized at high resolution using
fluorescent phalloidin that binds to actin filaments. The
stereocilia in the epididymisare non-motile. These membrane
extensions increase the surface area of the cell, allowing for
greater absorption and secretion. It has been shown that
epithelialsodium channel that allows the flow of Na+ ions
into the cell is localized onstereocilia.
STEREOCILIA

25. • A flagellum is a microscopic hair-like organelle used by cells
and microorganisms for movement.
• The word flagellum in Latin means whip, just like the
whipping motion flagella (plural) often use for locomotion.
• Specialized flagella in some organisms are also used as
sensory organelles that can detect changes in temperature
and pH.
FLAGELLA

26. • Eukaryotes have true flagellum, almost half the human
population produces cells with them in the form of sperm.
• This is the only cell in the human body with flagellum, and
for good reason. In order to move through the vaginal tract
to meet the egg, sperm must be able to swim, or move, very
long distances (incomparison of cell to body size). Without
the flagellum, there would be very little chance of
fertilization or population stability.
FLAGELLA

27. • A flagellum can be comprised of different structures
depending on the organism, especially when flagellum from
eukaryotes and bacteria are compared. Since eukaryotes are
usually complex organisms, the attached flagellum is more
complex as well. The flagellum is made up of microtubules
composed from a protein called tubulin.
FLAGELLA

28. • The flagellar structure consists of three different parts:
rings embedded in the basal body, a hook near the surface
of the organism to keep it in place, and the flagellar protein
filaments. Every flagellum has these three things in common,
regardless of organism. However, there are four distinct
types of bacterial flagellum based on location.
FLAGELLA

30. • A. Monotrichous
A single flagellum at one end of the organism or the other .
• B. Lophotrichous
Several flagellum on one end of the organism or the other .
• C. Amphitrichous
A single flagellum on both ends of the organism.
• D.Peritrichou:
Several flagellum attached all over the organism.
FLAGELLA

31. • A. Monotrichous
Monotrichous, amphitrichous, and lophotrichous flagellum are
considered polar flagellum because the flagellum is strictly located on
the ends of the organism. These flagella can rotate both clockwise and
counterclockwise. A clockwise movement propels the organism (orcell)
forward, while a counterclockwise movement pulls the organism
backwards.
FLAGELLA

32. • B. Peritrichous
Peritrichous flagella are not considered polar because they are located
all over the organism. When these flagella rotate in a counterclockwise
movement, they form a bundle that propels the organism in one
direction. If a few of the flagellum break away and begin rotating
clockwise, the organism then begins a tumbling motion. During this
time, the organism cannot move in any real direction.
FLAGELLA

33. • If any flagellum stops rotating—regardless of polarity—the
organism will change direction. This is caused by Brownian motion
(constant movement of liquid particles) and fluid currents
catching up with the organism and spinning it around. Some
organisms that cannot change direction on their own rely on
Brownian motion and fluid currents to do it for them.
FLAGELLA

34. • Flagella are filamentous protein structures found in bacteria,
archaea, and eukaryotes, though they are most commonly found
in bacteria.
• They are typically used to propel a cell through liquid (i.e.
bacteria and sperm). Flagella have many other specialized
functions. Some eukaryotic cells use flagellum to increase
reproduction rates.
FLAGELLA

35. • Other eukaryotic and bacterial flagella are used to sense
changes in the environment , such as temperature or pH
disturbances.
• Flagella may also be used as a secretory organelle according to
the recent work of the green alga Chlamydomonas Reinhardtii.
• Stereocilia (along with the entirety of the hair cell) in mammals
can be damaged or destroyed by excessive loud noises, disease, and
toxins and are not regenerable.
FLAGELLA

36. • Abnormal structure/organization of a bundle of stereocilia
can also cause deafness and in turn create balance problems
for an individual. In other vertebrates, if the hair cell is
harmed, supporting cells will divide and replace the damaged
hair cells.
FLAGELLA

37. • Basal Infoldings
• Hemidesmosome
BASAL MODIFICATION

38. BASAL INFOLDINGS
• Often found in epithelium that are known to transport fluid
(kidney).
• Will often see mitochondria in the basal infoldings; suggests
thatactive transport is occurring.
• Very important in epithelial polarization and stability.
•Support the epithelium and also functions as a passive molecular
sieve or ultra filter.

39. BASAL INFOLDINGS
• Infoldings of the basolateral region of the plasma membrane
are commonly found in cells engaged in active transport of fluids
and ions. These infoldings increase the surface area available for
transport.
• The infoldings of the plasma membrane which surround
individualmitochondria; this portion of the membrane is involved
in energy-intensive ion exchange, part of the kidney filtration
process.

40. BASAL INFOLDINGS
• If basal lamina is destroyed (trauma, infections, burns), the
epithelium will not be repaired but substituted with a scar
(connective tissue).

41. • Hemidesmosomes are very small stud-like structures found in
keratinocytes of the epidermis of skin that attach to the
extracellular matrix.
• Hemidesmosomes are found in epithelial cells connecting the
basalepithelial cells to the lamina lucida, which is part of the
basal lamina.
HEMIDESMOSOME

42. • Protein filaments interlock with filaments of the adjacent cell
which forms a dense intermediate line between the cells.
• Found beneath the zonula adherens.
• Cytoplasmic face is connected to microfilaments extending
into the cytoplasm.
HEMIDESMOSOME

43. • Tight Junctions (Zonula Occludens)
• Adhering Junctions (Zonula Adherens)
• Gap Junctions
• Desmosome (Macula Adherens)
LATERAL MODIFICATION

44. • Tight junctions are areas where the membranes of
two adjacent cells join together to form a barrier.
• The cell membranes are connected by strands of
transmembrane proteins such as claudins and
occludins.
• Tight junctions bind cells together, prevent molecules
from passing in between the cells, and also help to
maintain the polarity of cells.
TIGHT JUNCTIONS

45. • Tight junctions are often found at epithelial cells,
which are cells that line the surface of the body and
line body cavities. Not only do epithelial ial cells
separate the body from the surrounding environment,
they also separate surfaces within the body. Therefore,
it is very important that the permeability of molecules
through layers of epithelial cells is tightly controlled.
TIGHT JUNCTIONS

46. • If molecules are blocked by tight junctions and
physically unable to pass through the space in between
cells, they must enter through other methods that
involve entering the cells themselves. They could pass
through special proteins in the cell membrane, or be
engulfed by the cell through endocytosis. Using these
methods, the cell has greater control over what
materials it takes in and allows to pass through.
TIGHT JUNCTIONS

47. • Another function of tight junctions is simply to hold
cells together. The branching protein strands of tight
junctions link adjacent cells together tightly so that
they form a sheet. These strands are anchored to
microfilaments, part of the cell’s cytoskeleton that is
made up of long strands of actin proteins.
• Microfilaments are located inside the cell, so the
combination of microfilaments and sealing strands
anchors the cells together from the inside and the
outside.
TIGHT JUNCTIONS

49. • Tight junctions are a branching network of protein
strands on the surface of a cell that link with each
other throughout the surface of the membrane.
• The strands are formed by transmembrane proteins
on the surfaces of the cell membranes that are
adjacent to each other.
TIGHT JUNCTIONS

50. • There are around 40 different proteins at tight
junctions. These proteins can be grouped into four
main types.
• Transmembrane proteins are wedged in the middle of
the cell membrane and are responsible for adhesion
and permeability. Scaffolding proteins organize
transmembrane proteins.
TIGHT JUNCTIONS

51. • Claudins are important in forming tight junctions,
while occludins play more of a role in keeping the
tight junction stable and maintaining the barrier
between cells that keeps unwanted molecules out.
TIGHT JUNCTIONS

52. • The Adherens junction and Tight junction provide
important adhesive contacts between neighboring
epithelial cells.
• Although these junctions comprise different proteins,
there are similarities in the roles of specialized
transmembrane proteins informing extracellular
adhesive contacts between cells, and intracellular links
to the actin cytoskeleton and signaling pathways
including the regulation of gene transcription.
ADHERENS JUNCTION

53. • Adherens junctions are protein complexes that occur
at cell–cell junctions in epithelial and endothelial
tissues usually more basal than tight junctions.
• They can appear as bands encircling the cell (zonula
adherens) or as spots of attachment to the
extracellular matrix (adhesion plaques). Adherens
junctions uniquely disassemble in uterine epithelial cells
toallow the blastocyst to penetrate between epithelial
cells.
ADHERENS JUNCTION

54. •Gap junctions are a type of cell junction in which
adjacent cells are connected through protein channels.
• These channels connect the cytoplasm of each cell
and allow molecules, ions, and electrical signals to pass
between them. Gap junctions are found in between the
vast majority of cells within the body because they are
found between all cells that are directly touching
other cells.
GAP JUNCTIONS

55. • Exceptions include cells that move around and do not
usually come into close contact with other cells, such as
sperm cells and red blood cells. Gap junctions are only
found in animal cells; plant cells are connected by
channels called plasmodesmata instead.
GAP JUNCTIONS

56. • The main function of gap junctions is to connect cells
together so that molecules may pass from one cell to the
other. This allows for cell-to-cell communication, and
makes it so that molecules can directly enter neighboring
cells without having to go through the extracellular fluid
surrounding the cells.
GAP JUNCTIONS

57. • Gap junctions are especially important during
embryonic development , a time when neighboring cells
must communicate witheach other in order for them to
develop in the right place at the right time. If gap
junctions are blocked, embryos cannot develop normally.
GAP JUNCTIONS

58. • Gap junctions make cells chemically or electrically
coupled. This means that the cells are linked together
and can transfer molecules to each other for use in
reactions.
• Electrical coupling occurs in the heart, where cells
receive the signal tocontract the heart muscle at the
same time through gap junctions.
GAP JUNCTIONS

59. • It also occurs in neurons, which can be connected to
each other byelectrical synapses in addition to the
well-known chemical synapses that neurotransmitters
are released from.
• When a cell starts to die from disease or injury, it
sends out signals through its gap junctions. These
signals can cause nearby cells to die even if they are
not diseased or injured. This is called the “bystander
effect”, since the nearby cells are innocent bystanders
that become victims.
GAP JUNCTIONS

61. • In vertebrate cells, gap junctions are made up of
connexin proteins. (The cells of invertebrates have
gap junctions that are composed of innexin proteins,
which are not related to connexin proteins but
perform a similar function.)
• Groups of six connexins form a connexon, and two
connexons are put together to form a channel that
molecules can pass through.
GAP JUNCTIONS

62. • Other channels in gap junctions are made up of
pannexin proteins. Relatively less is known about
pannexins; they were originally thought only to form
channels within a cell, not between cells.
• Hundreds of channels are found together at the
site of a gap junctionin what is known as a gap
junction plaque. A plaque is a mass of proteins.
GAP JUNCTIONS

63. • Desmosomes are a type of anchoring junction in animal
tissues that connect adjacent cells.
• Anchoring junctions are button-like spots found all
around cells that bind adjacent cells together.
DESMOSOMES

64. • Desmosomes have intermediate filaments in the cells
underneath that help anchor the junction, while the other
type of anchoring junction, an adherens junction, is anchored
by microfilaments.
• Intermediate filaments and microfilaments are two
different componentsof a cell’s cytoskeleton.
DESMOSOMES

65. • The function of desmosomes is to adhere cells together.
• They are found in high numbers in tissues that are subject to
a lot of mechanical forces.
• For example, many are found in the epidermis, which is the
outer layerof skin, and the myocardium, which is muscle tissue
in the heart.
DESMOSOMES

66. • They are also found in between squamous epithelial cells, which
form the lining of body parts like the heart, blood vessels, air
sacs of the lungs, and esophagus.
• There are three components in desmosomal adhesion: the
intermediate filaments inside the cell, the bond between
intermediate filaments and desmosomal adhesion molecules, and
the bond provided by the desmosomal adhesion molecules.
DESMOSOMES

67. •The intermediate filaments and their link to the desmosomal
adhesion molecules are both located inside the cell, while the
bonds of the desmosomal adhesion molecules themselves are on
the outside of the cell.
• Specifically, desmoglein and desmocollin are the two proteins
thatbind cells at desmosomes.
DESMOSOMES

68. • They are transmembrane proteins and are both members of
the cadherin family of proteins.
• All three components of desmosomal adhesion are necessary
for desmosomes to properly function in binding adjacent cells
together, so if one of the components fails, the desmosomes
cannot bind cells properly.
DESMOSOMES

70. SPECIALIZED MODIFICATION
• Nerve cells, or neurons are very specialized cells of the nervous
system. Since ancelectrical signal needs to travel relatively long
distances to parts of the body, nerve cells have specialized
structures called dendrites, which receive an electrical signal from
another neuron, and axons, which transmit an electrical signal to
another person.
• Muscle cells are made up primarily of a pair of special proteins
called actin and myosin which allows the muscle to contract.

71. SPECIALIZED MODIFICATION
• Red blood cells are anucleate, and thus are produced from
bone marrow, but contain large amounts of hemoglobin to
transport oxygen throughout the body.
• Sperm cells are haploid and contain flagellum in order to
swim through the vagina.

72. SPECIALIZED MODIFICATION
• Plant cells have large amounts of the organelle chloroplast,
which allows the cell to undergo photosynthesis. Plant cells
are also covered by a cell wall.