The document outlines the cell cycle, highlighting its significance in cell division, growth, and reproduction, while detailing the phases of mitosis and cytokinesis. It discusses various reproductive methods, describes the roles of chromosomes and chromatin, and emphasizes the regulation of the cell cycle by external and internal factors. Additionally, it addresses apoptosis, cancer development due to cell cycle disruption, and standard treatment options for cancer.

1. Cell Cycle

2. Learning Objectives
 Infer the significance of cell division.
 Differentiate a DNA molecule, a chromosome, and a
chromatid.
 Characterize the phases of the cell cycle and their control
points.
 Describe the major events associated with stages of mitosis.
 Explain the process of cytokinesis.
 Describe the role of apoptosis in the life cycle of a cell.
 Relate cancer as a result of the malfunction of the cell
during the cell cycle.

3. Values
Uphold the importance of cell cycle
and reproduction especially in the
perpetuation of generation of
species.
Advocate preservation of life

4. Why must cells divide?

6. Cell division plays
important roles in the
lives of organism

7. Growth and Development
Cell division is associated with
growth and development.
Humans are products of numerous
cellular divisions, as life begins
with only a single cell from the
fusion of parent’s sex cells.

8. How come bacteria and other minute organisms
reproduce faster and live in almost everywhere
on Earth?
 Reproduction is common process among life forms to
make new organism from one or two parent organism.
 Sexual Reproduction- involves two specialized cells,
called gametes, coming from the parents that will
result to a unique offspring.

9. Asexual Reproduction
 Is the production of offspring from single parent
without the involvement of gametes.
 The offspring is genetically identical with each other
and to the single parent.
 Most Bacteria and other unicellular organisms,
reproduction involves a simple cell division.
 Binary Fission- the cell pinches apart, splits into two ,
then new cell wall forms between two daughter cells.

11. Where do cells get the information
they need to function?
 The cell’s genetic material is organized in
tightly-coiled structures called
chromosomes.
 A chromosome is simply a long, continuous
thread of DNA wounded together by DNA-
associated proteins, referred as histones.

12. DNA is loosely
organized like
scattered
spaghetti on a
plate.

13. Chromatin
efficiently packages
the DNA into small
volume and fits
inside the nucleus.
Chromatin
undergoes further
condensation,
forming the
chromosome

14.  The complex set of macromolecules that contain
loose DNA, proteins, and RNA is called chromatin.
 Chromatin is responsible for packaging the DNA
efficiently into smaller volume so that it fits the
nucleus of a cell to protect the DNA structure and
sequence, to prevent DNA damage, to control gene
expression and DNA replication, and to reinforce
the DNA molecule to allow mitosis and meiosis

15.  Chromatid refers to each
strand of the duplicated
chromosomes.
 Together they are called sister
chromatids, which are held
together by centromere – a
region of condensed
pinched chromosomes.
 Located at the centromere is
a group of proteins called
kinetochore, which is
attached to the spindle fibers
during cell division.

16.  At the ends of the DNA molecules are structures
referred as telomeres that contain repeated
nucleotides, which contain genetic information that
do not translate into pairs.
 Their role is to prevent the ends of chromosomes from
accidentally attaching to one another and prevent the
loss genes.

17.  Main Idea: Cell have distinct phases fro growth,
reproduction, and normal operations.
 EQ: How do healthy cells decide when to
divide?

18. THE CELL
CYCLE
Cells follow
definite stages
of growth,
duplication,
and division
known
collectively as
the cell cycle.

19. STAGES OF CELL CYCLE

21. INTERPHASE
 Interphase is the growth period in the cell cycle and is
divided into three parts

22. Gap 1 (G1)
 Gap 1 is the first part of the cell cycle wherein the cell
carries out its normal metabolic functions.
 During Gap 1 phase , an intestinal cell performs its
primary function to absorb nutrients, while a red
blood cells shuttles oxygen to the rest of the body.
 During this phase, cells also increase their size, as
their organelles increase in number.
 Cells have a required size limit.

23. Synthesis (S)
Synthesis is the second part of cell
cycle, which refers to the time that the
cell makes a copy of the genetic
material in the form of nuclear DNA.
During S phase, the cell spends
considerable amount of time and
energy to make copies of its
chromosomes.

24. Gap 2 (G2)
 During this stage, cells continue to carry out
their normal functions and also undergo
further growth.
 This stage contain a critical checkpoint
before transitioning to the next stage.
 The cell make sure that everything is in
order, including growing to its correct size
and duplicating DNA without damage.

25. Mitosis (M)
 Mitosis involves the division of the nucleus and the
genetic material.
 Parts of Mitosis
o Prophase
o Metaphase
o Anaphase
o Telophase
During M stage, the hereditary materials of parent cell is
given to the daughter cells.

26.  This leads to the formation of two daughter
cells conataining the identical genetic
materials.
 The goal of Mitosis is to distribute an
identical set of genetic instructions- one
copy of each chromosome to the two
daughter cells.
 In M stage the cell’s nuclear membrane
disintegrates, while the DNA condensed,
forming two nuclei.

27. Cytokinesis
Cytokinesis is basically divides the
cytoplasm of the cell.
Cytokinesis early during telophase and
continues after the nuclei have formed
in the daughter cells.

28. Rate of Cell Division
 Growth rates vary widely in different organism and
even in the different tissues within an organism.
Common Cell Life Span
Cell Type Approximate Life Span
Skin Cell 14 days
Red Blood Cell 12odays
Liver cell 300-500 days
Internal lining of
intestine
4-5 days
Smooth muscles of
intestine
16 years

29.  Some parts of the body where cell divides
are rarely believed by scientists to have
entered a stage known as gap zero or G0.
 In this stage, cell are unlikely to divide but
still continue to perform normal function.
 Such cells, like neuron cells and heart
muscle cell that are highly differentiated or
specialized and that body cannot easily
replace, are said to be permanently in G0.

30. The Mechanism of Cell Division
Mitosis and cytokinesis produce
genetically identical daughter cells.
How is information passed to new cells
during cell division?

31. Mitosis
 Is the division of nucleus into two genetically identical
nuclei containing the same full set of DNA.
 Mitosis occurs in body cells, except the sex cells.
 Mitosis prepares the cells for cytokinesis.
Phases of Mitosis
Prophase
Metaphase
Anaphase
telophase

32. Prophase: Start of Mitosis
Prophase (pro means “before”).
During prophase, several distinct events
occur.
In prophase, the nucleus disppears.
Chromatin condenses into chromosomes
and the mitotic spindles is formed.
 Spindle fibers are organized microtubles.

33. Metaphase: Chromosomes at the
Center
 Metaphase (meta means “near”, the spindle fibers
attached to the kinetochore of sister chromatids
facilitates the movement of chromosomes toward the
middle of the cell.
 During metaphase, chromosomes align at the
metaphase plate.

34. Anaphase: Chromatids to
opposites Poles
 Anaphase ( ana means “up” or “back”), sister
chromatids are tightly paired due to the centromere
and protein cohesion, which is responsible for holding
DNA molecules together in its entire length.
 In anaphase, chromatids separated toward opposite
poles.

35. Telophase: reformation of Nuclei
 Telophase (telo means “end”), the two complete sets of
identical chromosomes are now positioned at each
pole of the cell, and the reverse of the major events in
prophase happen.
 In telophase, new nuclear envelope forms.
Chromosomes unfold back into chromatin, the nucleoli
reappear, and the cell continues to elongates.

36. Love of Lab
 Locating the Stages of Mitosis on page 96A.

37. Cytokinesis
 This stage involves splitting of the
cytoplasm into two cells and completes the
entire cytoplasm divides.
 Cytokinesis typically starts to occur in late
anaphase or telophase.
 It also differs in plants and animal cell
because of some differences in cellular
structure.

38.  In animals cells, cytokinesis starts with the formation
of cleavage furrow or trench that is pulled inward by
tiny strands of protein actin called microfilaments like
a drawstring
 Slowly membrane begins to pinch roughly in half and
close off, forming a separate cell around each nucleus.
 Daughter cells receive equal portions of parents cell’s
plasma content.

39.  In plants cell the membrane cannot pinch
off because of the presence of cell wall.
 Instead cell plate form midway between the
two daughter cells’ nuclei.
 This Cell plate is made by the golgi
apparatus, while vesicles supply the new
cells wall material and lipids to form plasma
membrane to the cell plate.
 Cytoplasm is equally divided between both
plants and animal cell.

40. Cell cycle must be regulated for
healthy cell growth.
Both internal
and external
factors work
together to
regulate cell
division
Group of proteins
active in
controlling cell
cycle & in
initiating DNA
synthesis
Any various enzymes that
catalyze the transfer of
phosphate group from high
energy phosphate.

41. External Factors
 External factors from outside the cell that are in the
form of message from nearby cells or from remote
parts of the organism’s body.
 Physical and Chemical External factor help regulate
the cell cycle.
 Physical signs, such as cell-to-cell contact, exist
between cells.
 Mammalian cells experiments grown in in vitro
laboratory steup grow until a single layer covers the
entire surface of the culture dish.

42.  When cell touches another cell, it stops
dividing- a phenomenon called contact
inhibition.
 Another study shown cell that shown cell only
grow if surface is available and stop dividing
when detached from the culture dish – a
phenomenon called anchorage dependent.
 One explanation for this is there are receptors
found in neighboring cell binding each other
and causing the cell’s cytoplasm to form
structures that can block the signal, stopping
the continuous division.

43. Chemical signals
 Released by the cell such as growth factors
provide instructions for other cells to grow.
 Growth factor are proteins that stimulates
cell division, which have the ability to
activate specific genes to trigger cell growth.

44. Internal factor
 Come from inside the cell that include several types of
molecules in its cytoplasm.
 The most well-studied internal factors in eukaryotic
cell cycle are kinases and cyclins.
 Kinase is an enzyme that transfers a phosphate group
from one molecule to the target molecules.
 Cyclins are group of proteins active in controlling cell
cycle & in initiating DNA synthesis.

45. Apoptosis
 Orderly programmed cell death t or suicide.
 Apoptosis is needed by the body to ensure
proper cell functioning.
 Apoptosis occurs in body’s webbed fingers
during embryonic period to allow
detachment of fingers and thumbs before
baby is born.

46. What happens to the
body when there is
uncontrolled cell growth?

47. CANCER: Growing Out Of Control
 Cancer refers to a group of diseases
characterized by uncontrolled and
abnormal cell division. It occurs when there
is a disruption in the cell cycle.
 Instead of stopping and starting at
appropriate points, cancerous cell divide
continuously until a disorganized solid mass
of cells called tumor is formed.

48.  Tumors can be categorized as benign or malignant.
 Benign Tumors are cancer cells that remain clustered
together which may be harmless or not and can
probably be cured when removed out of the body.
 Tumors that break away or metastasize are called
malignant tumors. Their ability to break away from
their present location allows them to be transported to
the bloodstream of the lymphatic system to other parts
of the body parts to form more tumors.

49. Standard cancer treatment option
Local
surgery
radiation
Systematic
chemotherapy
immunotherapy
Involves removal
of the cancerous
body part
Involves exposure
to X-rays to kill
cancer cell and
shrink the tumor
cells
Uses certain
drug to kill
actively
dividing
cells
Uses substances
either from the
body or laboratory
to improve the
body’s defense to
fight cancer