cell theory postulates

1. Postulates of the Cell Theory

2. Explain the postulates of
the cell theory.
STEM_BIO11/12-Ia-c-1.

3. Pre-Activity:
Did You Know?
What is the smallest unit of
Life?

4. Did You Know?
How many cells make up an
average human being?
 The average human
being is composed of
around 100 Trillion
individual cells!!!
 It would take as many
as 50 cells to cover the
area of a dot on the
letter “i”

5. Did You Know?
 What is the type of cell that can no longer regenerate
once used up?

6. Did You Know?
 What type of cell can carry Oxygen and supplies it
through the body?

7. Did You Know?
 What is the smallest cell in nature?

8. Did You Know?
 What is the biggest cell in nature?

9. The Cell Theory

10. Discovery of Cells
 1665- English Scientist, Robert Hooke, discovered
cells while looking at a thin slice of cork.
 He described the cells as tiny boxes or a honeycomb
 He thought that cells only existed in plants and fungi

11. Anton van Leuwenhoek
 1673- Used a handmade microscope to observe
pond scum & discovered single-celled organisms
 He called them “animalcules”
 He also observed blood cells from fish, birds,
frogs, dogs, and humans
 Therefore, it was known that cells are found in
animals as well as plants

12. 1827-33 - Robert Brown
R- Robert Brown the
noticed that pollen grains in water jiggled around
called “Brownian motion”
-discovered
nucleus
Nucleus
Human Cheek Cell

13. 1838 - Matthias Schleiden
A botanist who concluded that all plants are made of cells.
Typical Plant
Cell

14. 1839 - Theodor Schwann
A zoologist who concluded that all animals are made of
cells.
Nerve Cells

15. 1855 - Rudolph Virchow
A physician who did
research on cancer cells
and concluded
“Omnis cellula e
cellula”.
“All cells are from other
pre-existing cells.”

16. The 3 Basic Components of the Cell Theory :
1. All organisms are composed of one or
more cells.
(Schleiden & Schwann)(1838-39)

17. 2. The cell is the basic unit of life in all living
things. (Schleiden & Schwann)(1838-39)

18. 3. All cells are produced by the
division of preexisting cells.
(Virchow)(1858)

19. The Cell Theory Complete
 The 3 Basic Components of the Cell Theory
were now complete:
 1. All organisms are composed of one or more
cells. (Schleiden & Schwann)(1838-39)
 2. The cell is the basic unit of life in all living
things. (Schleiden & Schwann)(1838-39)
 3. All cells are produced by the division of
preexisting cells. (Virchow)(1858)

20. STEM CELL RESEARCH
The research started simple question “How can the
various parts of the human body began forming and
how may it be possible to replicate the processes.

21. Modern Cell Theory

22. Modern Cell Theory
 Modern Cell Theory contains 4 statements, in
addition to the original Cell Theory:
1. The cell contains hereditary information(DNA) which
is passed on from cell to cell during cell division.
2. All cells are basically the same in chemical
composition and metabolic activities.
3. All basic chemical & physiological functions are
carried out inside the cells.(movement, digestion,etc)
4. Cell activity depends on the activities of sub-cellular
structures within the cell(organelles, nucleus, plasma
membrane)

23. Some Parting Thoughts
Humans are just an intricately
designed community of cells, which
must work together to survive

24. Application:
Explain the Cell Theory in your
own words
How has the knowledge of Cell
Theory help you understand life.

25. Cell Organelles
Unit 2: Cells
Ch. 7-2

26. Let’s Review!
Two cell types
 Prokaryotes (Prokaryotic
Cells)
 Eukaryotes (Eukaryotic Cells)

28. Prokaryotes - Bacteria
 No Nucleus
 No Membrane bound
organelles.

29. Eukaryotes
 Have a nucleus
 Have membrane bound
organelles
Nucleus

30. Two Types of Eukaryotic Cells
1. Animal Cell
2. Plant Cell
 Both cells
function
similarly

31. “Typical” Animal Cell
http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif

32. http://waynesword.palomar.edu/images/plant3.gif
“Typical” Plant Cell

33. Animal vs. Plant Cells – Chloroplasts Are a Big Part of
the Difference

34. Cells In a Leaf

35. Two Other Unique Features of Plant Cells
The central
vacuole may
occupy 90%
of a plant
cell.

36. Cellular Anatomy

37. Cell Organelles
Organelle = “little organs”
 Specialized structures that
perform specific jobs in the
cell
Found only in eukaryotic
cells
Many are “membrane-
bound” (a membrane surrounds
the organelle)
Cytosol: watery matrix that
organelles float in
Cytoplasm: Everything in a
cell except the nucleus

38. Cell Membrane
Surrounds the cell and
decides what comes in
and out
Semi-permeable: allows
nutrients in and waste
products out
Made of a phospholipid
bilayer
Also called Plasma
Membrane

39. Factory Part:
 Gates or Doors
Found in:
 Plant cells
 Animal cells
 Prokaryotic cells

40. Nucleus
Control center of the cell
Stores DNA
(chromosomes)
Surrounded by the nuclear
membrane
 Pores let material in and out
Also contains the
Nucleolus, which makes
ribosomes

41. Factory Part:
 Manager’s Office
Found in:
 Plant cells
 Animal cells

42. Nuclear Membrane
• Surrounds nucleus
• Made of two layers
• Openings allow
material to enter and
leave nucleus
http://library.thinkquest.org/12413/structures.html

43. Chromosomes
• In nucleus
• Made of DNA
• Contain instructions
for traits &
characteristics
http://library.thinkquest.org/12413/structures.html

44. Nucleolus
• Inside nucleus
• Contains RNA to build
proteins
http://library.thinkquest.org/12413/structures.html

45. Ribosome
Smallest organelle
NOT surrounded by a
membrane
Makes proteins according
to DNA instructions.
Two Types:
 Free ribosomes: float free in
cytosol
 Bound ribosomes: attached
to rough ER
That looks familiar…what is a
polypeptide?

46. Factory Part:
 Machines
Found in:
 Plant cells
 Animal cells
 Prokaryotic cells

47. Endoplasmic
Reticulum
Transport system for
materials in cell
Two Types:
Rough ER: covered
with ribosomes; site of
protein synthesis
Smooth ER: NO
ribosomes; it makes
hormones & lipids

48. Factory Part:
 Conveyor Belts
Found in:
 Plant cells
 Animal cells

49. Golgi Apparatus
Delivery system of
the cell
Collects, modifies,
and packages
molecules in the cell
Distributes and
transports
molecules in
vesicles

50. Factory Part:
 Post office or
Mail Room
Found in:
 Plant cells
 Animal cells

51. Golgi Bodies
• Protein 'packaging
plant'
• Move materials within
the cell
• Move materials out of
the cell
http://library.thinkquest.org/12413/structures.html

52. Lysosomes
Trash Disposal of
the cell
Contain digestive
enzymes that break
down waste

53. Factory Part:
 Janitors
Found in:
 Plant cells
 Animal cells

54. Lysosome
• Digestive 'plant' for
proteins, fats, and
carbohydrates
• Transports undigested
material to cell
membrane for removal
• Cell breaks down if
lysosome explodes
http://library.thinkquest.org/12413/structures.html

55. Mitochondria
“Powerhouse” of the
cell
Site of cellular
respiration
Converts energy stored
in food into energy the
cell needs – ATP
Sugar + Oxygen Carbon dioxide + Water + ATP
ATP = Adenosine triphosphate

56. Factory Part:
 Power Plant /
Electrical Room
Found in:
 Plant cells
 Animal cells

57. The Mitochondrion
A class of diseases that causes
muscle weakness and
neurological disorders are due
to malfunctioning
mitochondria.
Worn out mitochondria may be an important factor in aging.

58. Chloroplast
Found only in plant
cells and algae
Contains green
pigment, chlorophyll
Changes sunlight
(solar energy) into
food like glucose
(chemical energy)
Sunlight + Carbon Dioxide + Water Sugar + Oxygen

59. Factory Part:
 Solar Powered
Energy Panels
Found in:
 Plant cells

60. The Chloroplast
Think of the chloroplast as the solar panel of the plant cell.
Only plants have chloroplasts, but animals reap the benefits too.

61. Cell Wall
Rigid, protective
barrier (maintains
cell shape)
Found in plant and
bacterial cells
Located outside of
the cell membrane
Made of cellulose
(Carbohydrate fiber)

62. Factory Part:
 Factory Gates
Found in:
 Plant cells
 Some Prokaryote
cells

63. Vacuoles
Large central
vacuole usually in
plant cells
Many smaller
vacuoles in animal
cells
Storage container
for water, food,
enzymes, wastes,
etc
Supports cell
shape in plants

64. Factory Part:
 Storage room
Found in:
 Plant cells
 Animal cells
(smaller)

65. The name is misleading. The
cytoskeleton is the skeleton
of the cell, but it’s also like
the muscular system, able to
change the shape of cells in a
flash.
The Cytoskeleton
An animal cell cytoskeleton

66. A Cytoskeleton Gallery

67. A white
blood cell
using the
cytoskeleton
to “reach
out” for a
hapless
bacterium.
The
Cytoskeleton
in Action

68. The Cytoskeleton in Action
Cilia on a protozoan Beating sperm tail at fertilization
Smoker’s cough is due to destruction of cilia linking the airways.

69. Cilia and flagella are protein
microtubule extensions of the
plasma membrane
1. Cilia: short and numerous
2. Examples: within oviducts to move eggs,
filter-feeding in invertebrates, movement
of particles out of respiratory system

70. Flagella: longer and fewer

71. Quick Review
Which organelle is the control center of the cell?
Nucleus
Which organelle holds the cell together?
Cell membrane
Which organelles are not found in animal cells?
Cell wall, central vacuole, chloroplasts
Which organelle helps plant cells make food?
Chloroplasts
What does E.R. stand for?
Endoplasmic reticulum

72. Cell City Analogy
Cell Organelles City Analogies
Cell Membrane City border
Cell Wall City Wall
Cytoplasm Lawns
Endoplasmic Reticulum Highway or road system
Ribosomes Lumber or brick yard
Golgi Bodies Post Office or UPS
Chloroplasts Solar Energy Plants
Nuclear Membrane City Hall Fence with security guard
Mitochondria Energy Plants
Nucleus City Hall
DNA Original Blueprints or the city
RNA Copies of Blueprints
Nucleolus Copy Machine
Lysosomes Waste Disposal/ Recyclers
Vacuole Warehouses, water towers or garbage dumps
Protoplasm Air or atmosphere
Chromosomes Rolled up blueprints
Proteins Lumber or bricks

73. Cells: Prokaryote vs
Eukaryote

74. Cell Types
 Two categories:
1. Prokaryotic cells
- Unicellular organisms such as bacteria
are examples of prokaryotes.
2. Eukaryotic Cells
- All other cells are these.

75. 75
Prokaryotic Cells
 Lack a membrane-bound nucleus
 Structurally smaller and simpler than eukaryotic
cells (which have a nucleus).
 Most ancient and abundant type of cells
 Prokaryotic cells are placed in two taxonomic
domains:
 Bacteria
 Archaea
 Live in extreme habitats

76. Prokaryote cells are smaller and
simpler
Commonly known as bacteria
10-100 microns in size
Single-celled(unicellular) or
Filamentous (strings of single cells)

77. These are
prokaryote
E. coli bacteria
on the head of
a steel pin.

78. 78
The Structure of Bacteria
 Extremely small - 1–1.5 μm wide and 2–6 μm long
 Occur in three basic shapes:
 Spherical coccus,
 Rod-shaped bacillus,
 Spiral spirillum (if rigid) or spirochete (if flexible).
coccus
spirillum
spirochete
bacillus

80. Prokaryote cells are simply built
(example: E. coli)
capsule: slimy outer
coating
cell wall: tougher middle
layer
cell membrane: delicate
inner skin

81. cytoplasm: inner liquid filling
DNA in one big loop
pilli: for sticking to things
flagella: for swimming
ribosomes: for building
proteins
Prokaryote cells are simply built
(example: E. coli)

82. Prokaryote lifestyle
unicellular:
single-celled
colony: in group
filamentous:
forms a chain of
cells

83. 3 Types of Prokaryotes
based on Feeding
Photosynthetic: energy from sunlight
Disease-causing: feed on living things
Decomposers: feed on dead things

84. Eukaryotes are bigger and more
complicated
Have organelles
Have chromosomes
can be multicellular
include animal and plant cells

85. Organelles are
membrane-bound cell
parts
Mini “organs” that have
unique structures and
functions
Located in cytoplasm

86. Cell membrane
delicate lipid
and protein
skin around
cytoplasm
found in all
cells
Cell Structures

87. Nucleus
a membrane-bound
sac evolved to
store the cell’s
chromosomes(DNA
)
has pores: holes

88. Nucleolus
inside nucleus
location of
ribosome
factory
made or RNA

89. mitochondrion
makes the
cell’s energy
the more
energy the cell
needs, the
more
mitochondria it
has

90. Ribosomes
build proteins
from amino acids
in cytoplasm
may be free-
floating, or
may be attached
to ER
made of RNA

91. Endoplasmic
reticulum
may be smooth:
builds lipids and
carbohydrates
may be rough:
stores proteins
made by
attached
ribosomes

92. Golgi Complex
takes in sacs
of raw
material from
ER
sends out
sacs
containing
finished cell
products

93. Lysosomes
sacs filled with
digestive
enzymes
digest worn out
cell parts
digest food
absorbed by cell

94. Centrioles
pair of bundled
tubes
organize cell
division

95. Cytoskeleton
made of
microtubules
found throughout
cytoplasm
gives shape to cell
& moves
organelles around
inside.

96. Structures found in
plant cells
Cell wall
very strong
made of
cellulose
protects cell
from rupturing
glued to other
cells next door

97. Vacuole
huge water-
filled sac
keeps cell
pressurized
stores starch

98. Chloroplasts
filled with
chlorophyll
turn solar
energy into
food energy

99. How are plant and animal cells different?

100. Structure Animal cells Plant cells
cell membrane Yes yes
nucleus Yes yes
nucleolus yes yes
ribosomes yes yes
ER yes yes
Golgi yes yes
centrioles yes no
cell wall no yes
mitochondria yes yes
cholorplasts no yes
One big vacuole no yes
cytoskeleton yes Yes

101. Eukaryote cells can be
multicellular
The whole cell can be specialized for
one job
cells can work together as tissues
Tissues can work together as organs

102. Advantages of each kind of cell
architecture
Prokaryotes Eukaryotes
simple and easy to grow
have specialized function
on organelles
fast reproduction multicellularity
all the same can build large bodies

103. Examples of specialized
eukaryotic cells
liver cell:
specialized to
detoxify blood
and store
glucose as
glycogen.

104. Mesophyll
cell
specialize
d to
capture
as much
light as
possible
inside a
leaf

105. How do animal cells
move?
Some can crawl with pseudopods
Some can swim with a flagellum
Some can swim very fast with cilia

106. Pseudopods
means “fake feet”
extensions of cell
membrane
example:
ameoba

107. Flagellum/flagella
large whiplike tail
pushes or pulls
cell through water
can be single, or a
pair

108. Cilia
fine, hairlike
extensions
attached to cell
membrane
beat in unison

109. Prokaryotes vs. Eukaryotes
Prokaryotes
No
organelles
Unicellular
Bacteria
Eukaryotes
organelles
Defined
Nucleus
Multi or
Unicellular
Reproduce
Grow
metabolize
Maintain
Homeostasis!

110. Seatwork
Make your own Venn
diagram to show the
similarities and
differences of
prokaryotic and

111. Rubrics
There are 15 or more
similarities and
differences
10 points
There are less than 10
similarities and
differences
8 points
There are less than 5 6 points

112. THE CELL CYCLE AND CELL DIVISION
Presented by:
Fasama Hilton Kollie
Lecturer, Department of Biology
Mother Patern College of Health
Sciences

114. CHAPTER OUTLINE
1. Cell Division
2. Importance of Cell Division
3. Prokaryotic and Eukaryotic Cell
Division
4. Cell Cycle
5. Regulation of the Cell Cycle

115. LESSON OBJECTIVES
• By the end of this session, the learners will be able to;
1. Define cell division and cell cycle
2. Identify the purpose of cell division
3. Describe cell division in prokaryotic and Eukaryotic
cell
4. Describe the cell cycle

116. CELL DIVISION
• It’s the process by which a cell divides to form two new
cells
• Three types of cell division or cell reproduction in
organism
• Prokaryotes (bacteria)
— Binary fission
• Divides forming two new identical cells

117.  Eukaryotes
— Mitosis (somatic cell)
• Cell or organism growth
• Replacement or repair of damaged
cells
— Meiosis (sex cells, germ cell, gametes)
• formation of sex cells, or gametes

118. WHY DO CELLS DIVIDE?
• Cells divide for growth, development, repair of worn-out tissues
• To facilitate the exchange of materials
• To control DNA overloading

119. PROKARYOTIC CELL DIVISION
1. Binary Fission
• Three (3) major steps;
• DNA Replication
DNA is copied resulting into two identical chromosomes
• Chromosome Segregation
Chromosomes separate and move towards ends (poles)
of cell
• Cytokinesis (Separation)
Cytoplasm divides forming two (2) cells
• Each new daughter cell is Genetically Identical to parent
cell

120. Prokaryotic Cell
Division

121. EUKARYOTIC CELL DIVISION
• Cell division that results in two daughter cells each having the
same number and kind of chromosomes as the parent cell
1. MITOSIS
• Two (2) main steps:
1. Mitosis
Fours steps; [Prophase>Metaphase>Anaphase>Telophase]
2. Cytokinesis
Cytoplasm divides forming two new daughter cells
• Each daughter cell is Genetically Identical to parent cell

123. Prophase

124. Prophase

129. Eukaryotic Cell Division Cont.
• Cell division that results in four daughter cells
2. MEIOSIS
• Two (2) major steps:
1. Mitosis
Four steps;
[Prophase>Metaphase>Anaphase>Telophase]
2. Cytokinesis
Cytoplasm divides forming two new daughter cells
• Each daughter cell is NOT Genetically Identical to
parent cell

132. CELL CYCLE

133. THE CELL CYCLE
• The sequence of events from the time a cell first arises as a result of cell
division until the time when that cell itself divides.
• Arise – Divide
• This consist of periods of;
•Growth and Development
•DNA Replication
•Preparation For Division
•Cell Division
• Cell after division begins a new cycle

134. The Cell Cycle
• Consist of two(2)
main periods;
I. Interphase
II. Mitotic
Phase
M phase
G2
phase
S
phase
G1 phase

135. CELL CYCLE - Interphase
• Interphase: period of growth and
DNA replication between cell
divisions
• Three (3) phases:
• G1 Phase
‒ Cell increases in size
• S
Phase
‒ Replication of
DNA
‒
Two sister strands of DNA called
chromatids
are
produced
• G2 Phase
‒ Organelles double
‒ New cytoplasm forms
‒ All other structures needed for mitosis
form
Centrioles
Nuclearmembrane
Nucleolus
Chromosomes

137. M phase
G2 phase
S phase
G1 phase
CELL
CYCLE

138. CELL CYCLE – Mitotic Phase
• Mitotic phase is the stage when a cell divides
• Mitosis – the division of a single nucleus into two
genetically identical daughter nuclei
• This division involves two(2) processes;
‒ Division of the nucleus
‒ Separation of the cytoplasm and the new nuclei into
daughter cells

139. Mitotic Phase
• Divided into two (2) mitotic phases
• 1st MP contain four stages(P-MAT)
‒ Prophase, metaphase, anaphase and telophase
• 2nd MP is cytokinesis

140. 1. Prophase
2. Metaphas
e
3. Anaphase
4. Telophase
• P-
MAT
Interphase 1 2
3
4
Cytokinesis
Mitosis

141. Interphase:
Centrioles
Nuclear membrane
Nucleolus
Chromatids

142. Early Prophase:
• Chromatids condense
becoming chromosomes
• Nucleolus
disappears
• Centrioles separate and start
moving to opposite ends of the
cell
• Spindlebegins to
form
Chromatids
connected by
a
centromere.
Centrioles
Spindle madeof
microtubules

143. Late Prophase:
• The nuclear membrane
fragments and the
microtubules invade the
nuclear area
• Centrioles have moved to
the opposite poles
• The spindle is completely
formed
centrioles
Microtubules
form a
complete
spindle
chromatids
centrioles

144. Metaphase:
In metaphase;
•The chromosomes are aligned
at the metaphase plate
•Centrioles move at polar ends
and projects spindle fibers to
connect each chromosome
Centrioles
Chromosomes
Spindle
composed
of
microtubule
s

145. Anaphase:
In anaphase;
•The paired chromosomes
(sister chromatids) separate
•Separated chromatids move to
opposite pole
•Partial division of cytoplasm
begins
Chromatids are
being pulled to
opposite sides
of the cell.
Shortening of
the
microtubules

146. Telophase:
In telophase;
•Chromosomes are at the
poles
•Chromosomes uncoil-turn
chromatin
• Nuclear envelops
reforms
• Spindle fiber disappear
Nuclear
membrane
is
returning

147. Cells return to interphase
Cytokinesis:
• Occurs at the end of mitosis
• Animal cells: a cleavage furrow
separates the daughter cells
• Plant cell: a cell plate separates the
daughter cells
• Daughter cells are genetically
identical

148. Mitosis
Animation

149. 1. Name the phases
starting at the top.
Mitosis
SELF QUIZ
Design an Education Game from
Here
A
B
C
D
E

150. Name the phases:
1. Identify W
Sister
Chromatid
2. Identify X
Spindle fibre
3. Identify Y
Centriole
4. Identify Z
Centromere
SELF QUIZ
z
w

151. Name this phase
and provide brief
description
Telopha
se

152. CONTROL OF THE CELL C
• Regulatory proteins called cyclins control the cell cycle at
checkpoints:
• G1 Checkpoint—decides whether or not cell will divide
• S Checkpoint—determines if DNA has been properly
replicated
• Mitotic Spindle Checkpoint—ensures chromosomes are
aligned at mitotic plate

153. REFERENCE
• Nabor, Murray W., INTRODUCTION TO BOTANY. Copyright 2004
Pearson
Education, Inc., Publilshing as Benjamin Cummings, 1301 Sansome
St., San Francisco, CA 94111.
www.aw-bc.com
• CK – 12
https://www.ck12.org/biology/cell-division/lesson/Cell-Division-BIO/
• Image Attributions [Prokaryotic cell division]
Credit: Mariana Ruiz Villarreal (LadyofHats) for CK-12 Foundation
Source: CK-12 Foundation
License: CC BY-NC 3.0

156. Mitosis allows organisms
to reproduce asexually,
grow and repair of worn-
out or damaged tissues.
Meiosis on the other hand,
is important in sexual
reproduction and genetic
diversity among sexually
reproducing organism.

157. Many of the steps of meiosis
closely resemble corresponding
steps in mitosis. Meiosis, like
mitosis, is preceded by the
duplication of chromosomes.
However, this single duplication is
followed by not one but two
consecutive cell divisions called
meiosis I and meiosis II. These two
divisions result in four daughter
cells (rather than the two
daughter cells of mitosis), each
with only half as many
chromosomes as the parent cell—
one set, rather than two.

158. Meiosis reduces the
amount of genetic
information
resulting to its
importance in
sexual reproduction
and genetic
diversity among
sexually
reproducing
organism.

159. The overview of meiosis
shows for a single pair of
homologous chromosomes in
a diploid cell, that both
members of the pair are
duplicated and the copies
sorted into four haploid
daughter cells.

160. Recall that sister chromatids
are two copies of one
chromosome,
closely associated all along
their lengths; this association
is called
sister chromatid.

161. MEIOSIS I: Separates
homologous
chromosomes

166. MEIOSIS II:
Separates sister
chromatids

172. Through the process of meiosis, rapid
generation of new genetic combinations
happen to sex cells during their
development. There are three
mechanisms that contribute to this
genetic variation: independent
assortment, crossing-over, and random
fertilization.

173. 1. Independent Assortment
The random distribution of homologous chromosomes during
meiosis is called independent assortment. In metaphase I, maternal and
paternal chromosomes lined up at the equator of the cell, but eventually,
these are pulled apart randomly at opposite poles in anaphase I. Each
of the 23 pair segregates or separates independently. Each daughter
cell gets one chromosome from each homologous pair. Independent
assortment is shown in Figure 3 with just four pairs of homologous
chromosomes for simplified illustration. With four pairs of homologous
chromosomes, you may come up with 24 or 16 possible combinations.
Thus, 223 (about eight million) with different gene combinations can be
produced from one original cell by this mechanism alone for humans.

175. Another factor that contributes to genetic
variation is crossing-over. This occur during
prophase I of meiosis, where chromosomes line up
in the process called synapsis, while sections of
their DNA are exchanged. DNA exchange during
crossover adds more recombination probabilities to
the assortment of chromosomes that occur later in
meiosis. The number of genetic combinations in
the gametes is practically unlimited. In addition,
because the zygote that forms a new individual is
created by the random fusion of two gametes,
fertilization squares the number of possible
outcomes (223 x 223 = 64 trillion).

177. Random fertilization refers to the fact
that if two individuals mate, and each is
capable of producing over 8million potential
gametes, the random chance of any one
sperm and egg coming together is a product
of these two probabilities - some 70 trillion
different combinations of chromosomes in a
potential offspring

180. Activity 1
Match Me: Define the prefixes in column A with the meaning in
column B.
Write the letter of your choice before the number.

181. CELL DIVISION
is a very important process in all
living organisms. During the
division of a cell, DNA
replication and cell growth also
take place. All these processes,
example cell division, DNA
replication, and cell growth,
hence, have to take place in a
coordinated way to ensure
correct division and formation
of progeny cells containing
intact genomes.

182. The sequence of events
by which a cell
duplicates its genome,
synthesizes the other
constituents of the cell
and eventually divides
into two daughter cells
is termed

183. Although cell growth (in terms of
cytoplasmic increase) is a continuous
process, DNA synthesis occurs only
during one specific stage in the cell
cycle. The replicated chromosomes
(DNA) are then distributed to daughter
nuclei by a complex series of events
during cell division.

184. M is the phase of
the cell cycle in
which the
microtubular
apparatus assembles,
binds to the
chromosomes, and
moves the sister
chromatids apart.

185. M is called mitosis, this process is the
essential step in the separation of the two
daughter genomes. Although mitosis is a
continuous process, it is traditionally
subdivided into five stages:
Prophase
Prometaphase
Metaphase
Anaphase
Telophase

187. During prophase, changes
occur in both the nucleus and
the cytoplasm. Within the
nucleus, the chromatin fibers
become more tightly coiled
and folded, forming discrete
chromosomes that can be
seen with the light
microscope.

188. Each duplicated chromosome
appears as two identical sister
chromatids joined together,
with a narrow “waist” at the
centromere. In the cytoplasm,
the mitotic spindle begins to
form as microtubules rapidly
grow out from the centrosomes,
which begin to move away from
each other.

189. The completion of prophase can thus be
marked by the following characteristic
events:
Chromosomal material condenses to
form compact Mitotic chromosomes.
Chromosomes are seen to be composed
of two chromatids attached together
at the centromere.
Initiation of the assembly of mitotic
spindle, the microtubules, the
proteinaceous components of the cell

190. The nuclear envelope breaks into fragments
and disappears. Microtubules emerging from
the centrosomes at the poles (ends) of the
mitotic spindle reach the chromosomes, now
highly condensed. At the centromere region,
each sister chromatid has a protein structure
called a kinetochore (shown as a black dot).
Some of the spindle microtubules attach to the
kinetochores, throwing the chromosomes into
agitated motion. Other spindle microtubules
make contact with microtubules coming from
the opposite pole. Forces exerted by protein
“motors” associated with spindle microtubules
move the chromosomes toward the center of the
cell.

191. The complete disintegration of the
nuclear envelope marks the start of the
second phase of mitosis; hence the
chromosomes are spread through the
cytoplasm of the cell. The key features
of metaphase are:
*Spindle fibers attach to kinetochores
of chromosomes.
*Chromosomes are moved to spindle
equator and get aligned along
metaphase plate through spindle fibers
to both poles.

192. At the onset of anaphase, each
chromosome arranged at the
metaphase plate is split
simultaneously and the two daughter
chromatids, now referred to as
chromosomes of the future daughter
nuclei, begin their migration towards
the two opposite poles. Key events:
*Centromeres split and chromatids
separate.
*Chromatids move to opposite poles.

193. the chromosomes that have reached their
respective poles decondense and lose their
individuality. The individual chromosomes
can no longer be seen, and chromatin
material tends to collect in a mass in the
two poles. This is the stage which shows
the following key events:
*Chromosomes cluster at opposite spindle
poles and their identity is lost as discrete
elements.
* Nuclear envelope assembles around the
chromosome clusters.
*Nucleolus, Golgi complex and ER reform

194.  The eukaryotic cell has
partitioned its replicated genome
into two nuclei positioned at
opposite ends of the cell. While
mitosis was going on, the
cytoplasmic organelles, including
mitochondria and chloroplasts (if
present), were reassorted to areas
that will separate and become the
daughter cells. The phase of the
cell cycle when the cell divides is
called cytokinesis. It generally
involves the cleavage of the cell
into roughly equal halves.

197. Mitosis, a process of cell
duplication, or
reproduction, during
which one cell gives rise
to two genetically
identical daughter cells.
The newly formed
daughter cells are
genetically identical to
the parent cell and to
each other.

198. Strictly applied, the term
mitosis is used to describe the
duplication and distribution of
chromosomes, the structures
that carry the genetic
information. During the
mitosis process, the cell’s
nucleus along with the
chromosome is divided to form
two new daughter cell nuclei.
The daughter nuclei inherit the
same number of chromosomes
as that of the parent nucleus.

199. Mitosis is important to
multicellular organisms
because it provides new
cells for growth and for
replacement of worn-out
cells, such as skin cells.
Many single-celled
organisms rely on mitosis
as their primary means
of asexual reproduction.

201. Mitosis helps in the splitting of
chromosomes during cell division and
generates two new daughter cells.
Therefore, the chromosomes form from the
parent chromosomes by copying the exact
DNA. Therefore, the daughter cells formed
as genetically uniform and identical to the
parent as well as to each other. Thus,
mitosis helps in preserving and
maintaining the genetic stability of a
particular population.

202. You are to build a
model of the stages
of Mitosis using
materials that are
recyclable or
indigenous. Follow
the rubrics below in
making your model.

204. A cell’s DNA is
replicated during the
M phase of the cell
cycle.

205. The stage in which a
cell divides is called
the mitotic phase.

206. In meiosis, cellular
division occurs three
times.

207. ___5. Plant and animal
cells have many
differences. One
difference is the plant
cells have a cell plate.

208. ___6. Meiosis usually
results in the
formation of four
genetically identical
cells.

209. ___7. Chromosome
number is not changed
during mitosis.

210. ___8. Crossing-over
rarely occurs in
meiosis because
homologous

211. ___9. Cells divide to
repair tissues, to grow
and to reproduce.

212. ___10. Two members of
a pair are called
homologous
chromosomes.

216. All cells are surrounded by
a cell membrane also
known as plasma
membrane.

217. The membrane is a
physical barrier that
separates a cell from its
surrounding
environment. It also
regulates exchange of
materials inside the cell
with its surroundings
and gets rid of the
wastes.

218. The fluid mosaic
model is the currently
accepted concept
describing the
structure of plasma
membrane. According
to this model, the
membrane is a mosaic
of protein molecules
bobbing in a fluid
bilayer of
phospholipids.

219. It describes the
plasma membrane
having a fluid
consistency wherein
individual molecules
are just floating in a
fluid medium, and
they are all capable of
moving sideways
sliding past each
other within the
membrane.

220. Mosaic refers to
something that
contains many
different parts. The
plasma membrane is
a mosaic of
phospholipids,
cholesterol
molecules, proteins,
and carbohydrates

222. The plasma membrane is
composed of four different
types of molecules:
Phospholipids
Proteins
Cholesterol
Carbohydrates

223. It is made up
primarily of a
bilayer of
phospholipids with
embedded proteins,
carbohydrates,
glycolipids, and
glycoproteins, and,
in animal cells,
cholesterol.

225. The bulk of the membrane structure is composed of
two back-to-back layers of phospholipid molecules.
A phospholipid molecule has two different regions:
a hydrophilic region and a hydrophobic region.
Because of this difference in the properties, the
molecule is called amphipathic.

227. The head end contains a phosphate group
and is hydrophilic which means that it
likes or is attracted to water molecules.
They are in contact with aqueous fluid both
inside and outside the cell.

228. The tail end is made up of fatty acid chains. Fatty acids are long
chains that are mostly made up of hydrogen and carbon which are
hydrophobic, or do not like to mingle with water molecules. Just like
what happens when you pour cooking oil in water. The oil will not
mix with the water. The hydrophobic tails are attracted to each
other while being repelled by water hence face inward where there
is no water.

229. Integral proteins
Peripheral
proteins

230. Integral proteins embed in the lipid bilayer
while peripheral proteins are loosely attached
to the membrane surface. Most integral
proteins are transmembrane proteins, which
span the membrane; other integral proteins
extend only partway into the hydrophobic
interior. Some integral membrane proteins
form a channel that allows ions or other small
molecules to pass.

232. Peripheral proteins on the other hand are
not embedded in the lipid bilayer at all,
instead they are loosely bound to the surface
of the membrane. The functions of
membrane proteins include transport,
enzymatic activity, signal transduction, cell-
cell recognition, intercellular joining, and
attachment to the cytoskeleton and
extracellular matrix.

234. Short chains of carbohydrates or sugars
(may consist of 2–60 monosaccharide units
and may be either straight or branched) can
be found attached to proteins (forming
glycoproteins) and lipids (forming
glycolipids) on the outside of a cell
membrane. Together, these carbohydrates
form the glycocalyx. The glycocalyx cushions
and protects the plasma membrane, and it is
also important in cell recognition.

236. Cholesterol molecules are often
found stuck between
phospholipid molecules in the
plasma membranes of animal
cells. They have a role in
maintaining the fluid
consistency of the plasma
membrane. Cholesterol
molecules keep the
phospholipid tails from coming
into contact and solidifying.
This ensures that the cell
membrane stays fluid and
flexible. They also strengthen
the membrane by preventing
some small molecules from
crossing it.

237. 1. It encloses every cell and maintains cellular
integrity, thus keeping all contents of the cell
from spilling out.
2. It is a selective barrier that separates the
external from the internal environment of the
cell (compartmentalization).
3. It provides many of the unique functional
properties of specialized cells.

238. The plasma membrane’s
lipid bilayer has a
hydrophobic region
which creates a barrier
for some polar
molecules. This hinders
the movement of certain
materials through the
membrane. In other
words, not all
substances can pass
through the cell
membrane.

239. However, some substances
can pass through it with
ease, like gases, water,
and other fatty
substances, while others,
particularly larger
molecules (i.e., glucose,
fatty acids, amino acids,
and glycerol), have
difficulty in passing
through the cell
membrane.

240. This property makes the cell membrane semi-permeable or
selectively permeable. The membrane functions more like a
bag of tightly woven cotton fabric than like a concrete wall.

241. Nonpolar molecules, such as hydrocarbons, carbon dioxide,
and oxygen, are hydrophobic and can dissolve in the lipid
bilayer of the membrane and cross it rapidly. Remember
that phospholipids are lipid in nature, thus the concept
―like dissolves like‖ applies.

242. Polar molecules on the other hand such as glucose
and other sugars pass only slowly through a lipid
bilayer, and even water, a very small polar molecule,
does not cross very rapidly.

243.  Ions such as sodium and potassium must have a special means of
penetrating plasma membranes. Cell membranes allow these ions and a
variety of polar molecules while avoiding meeting the lipid bilayer. This
can be done by passing through transport proteins called channel
proteins used by certain molecules or ions as tunnels through the
membrane

244.  Substances moving across the selectively
permeable plasma membrane can be
either ―passive—i.e., occurring without
the input of cellular energy —or
―active—i.e., its transport requires the
cell to expend energy. Plasma
membranes must allow certain
substances to enter and leave a cell,
while preventing harmful materials or
wastes from entering and essential
material from leaving. If plasma
membranes were to lose this selectivity,
the cell would no longer be functioning
well, and it would be destroyed. The cell
employs various transport mechanisms
involving cell membranes.

245. Functions of the cell
membrane
Transport
enzymatic activity
Signal Transduction
cell-cell recognition
intercellular joining
attachment to the
cytoskeleton and
extracellular matrix.

246. GENETIC
DISORDERS

247. A change in the
number or structure
of chromosomes can
dramatically change
the traits of an
organism and can
cause serious
problems.

248.  Abnormal chromosomes most
often happen as a result of an
error during cell division.
Chromosome abnormalities
often happen due to one or
more of these:
 ➢ Errors during dividing of sex
cells (meiosis)
 ➢ Errors during dividing of
other cells (mitosis)
 ➢ Exposure to substances that
can cause birth defects
(teratogens)

250. is the process by which photographs of
chromosomes are taken in order to
determine the chromosome
complement of an individual, including
the number of chromosomes and any
abnormalities.

251. Numerical abnormality also called
aneuploidy, a condition which occurs
when an individual has a missing
chromosome from a pair (monosomy)
or has more than two chromosomes
of a pair (trisomy, tetrasomy, etc.).
NUMERICAL
ABNOMALITY
Aneuploidy

253. Down Syndrome (Trisomy 21)
Turner Syndrome (45, XO)
Klinefelter Syndrome (47, XXY)
Trisomy X Syndrome (47, XXX)
Patau Syndrome (Trisomy 13)
Edward Syndrome (Trisomy 18)

254. occur when the chromosome’s structure is altered, which
can take several forms such as:
Deletion – a portion of a chromosome is missing or
deleted;
Duplication – segment of a chromosome is repeated
twice;
Translocation – transfer of a section of one chromosome
to non-homologous chromosome;
Inversion – a section of the chromosome becomes
changed by rotation at 180 degrees.

255. Cri-du-chat
Syndrome (5p
minus syndrome)

257. ✓ The most common disorder of
trisomy is Down syndrome, wherein
the 21st chromosome has three
instead of two chromosomes.
✓ Most cases of Down syndrome are
not due to inheritance but on random
mistakes during formation of
reproductive cells of the parents.
✓ Physical manifestations: Short neck,
with excess skin at back of the neck.
Flattened facial profile and nose.
Small head, ears, and mouth. Upward
slanting eyes.

258. ✓ A condition that affects only
female as a result of one of the X
chromosomes (sex chromosome) is
missing or partially missing.
✓ Physical manifestations: Webbed
neck, short stature, swollen hands
and feet. Some have skeletal
abnormalities, kidney problems,
and/or congenital heart defect.

261. ✓ A condition resulting from two or more X
chromosomes in males
✓ Manifestations are typically more severe if
three or more X chromosomes are present as
in (48, XXXY) or (49, XXXXY).