Chapter 5 – Cell Growth and Division
5.1 The Cell Cycle
Key Concept: Cells have distinct phases of growth, reproduction and normal functions.
Main Ideas:
The cell cycle has four (4) main stages.
Cells divide at different rates.
Cell size is limited.
Vocabulary:
Cell cycle
mitosis
cytokinesis
Objectives:



Describe the stages of the cell cycle.
Compare rates of cell division in different cell types.
Identify factors that limit cell growth.
The cell cycle has four main stages
1.
2.
The cell cycle is the regular pattern of growth, DNA replication, and cell division that occurs in eukaryotic cells.
See page 134 Fig. 5.1 – Cell Cycle
DIRECTIONS: Use the phases below to label the cell cycle diagram on the right. Then, place the number for each event
listed in the appropriate phase of the diagram.
ANAPHASE
CYTOKINESIS
G1-PHASE
G2-PHASE
INTERPHASE
METAPHASE
MITOSIS
PROPHASE
S-PHASE
TELOPHASE
CELL EVENTS:
1. A LINE OF SISTER CHROMATIDS FORMS AT THE EQUATOR OF THE CELL
2. CELL WOULD BE ABLE TO MAKE PROTEINS
3. CHROMOSOMES “SUPER-COIL”
4. COPIES OF ORGANELLES ARE BEING MADE
5. DNA REPLICATION WOULD BE OCCURRING
6. GENETIC TRANSCRIPTION MIGHT BE HAPPENING
7. IDENTICAL COPIES OF EACH CHROMOSOME ARE MADE
8. IDENTICAL COPIES OF EACH CHROMOSOME MIGRATE TO OPPOSITE POLES OF THE CELL
9. MOST SPINDLE FIBERS ARE SHORTENING
10. NUCLEAR ENVELOPE DISAPPEARS
11. NUCLEAR ENVELOPE REAPPEARS
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
ONE CELL BECOMES TWO IDENTICAL CELLS
PAIRS OF SISTER CHROMATIDS ARE MOST EASILY SEEN
SETS OF IDENTICAL CHROMOSOMES EXIST AT EACH POLE OF THE CELL (with organelles too)
SISTER CHROMATID PAIRS ARE CREATED
SPINDLE (APPARATUS) FORMS
SPINDLE (APPARATUS) DISAPPEARS
SPINDLE FIBERS ATTACH TO SISTER CHROMATID PAIRS (AT CENTROMERE)
THE CELL MEMBRANE DIVIDES TO FORM TWO CELL MEMBRANES
THE CHROMOSOMES THAT MAKE UP A SISTER CHROMATID PAIR BECOME SEPARATED
THE SPINDLE’S FIBERS PULL ON CENTROMERES OF SISTER CHROMATID PAIRS & MOVE THEM TO THE
CELL’S EQUATOR
22. TRANSLATION MIGHT BE OCCURRING IN CELL
3.
There are four (4) main stages:

Gap 1 (G1)
The cell carries out the normal functions of the cell

Synthesis (S)
Chromosomes are duplicated. By the end of S stage cell has 2 identical copies of DNA

Gap(G2)
Last check point to be sure all functions and materials are accurate for mitosis. Normal cell activity.

Mitosis (M)
Includes 2 processes, consists of both mitosis and cytokinesis.
Mitosis is the division of the cell nucleus and its contents.
Cytokinesis is the division of the cytoplasm.
Cells divide at different rates
1.
2.
3.
4.
5.
Rate of division is based on your body’s needs.
Prokaryotes divide much faster than eukaryotes because they lack organelles.
Children and embryos rate of cell cycle is faster than in adults.
S, G2 and M stages usually last about 12 hours in humans.
Cells that divide rarely like neurons (nerve cells) enter a stage called G0. The cells are either highly unlikely to divide or stay in a
permanent G0 stage like nerve cells.
Cell size is limited
1.
2.
3.
4.
5.
Cells have both an upper and lower limit in size.
The cell must be large enough to house enough organelles to survive.
It cannot grow too large or the ability to distribute nutrients is impaired.
The decision to divide therefore is based on the surface area to volume of the cell contents.
See (pg. 137 – Fig.5.3)
5.2 Mitosis and Cell Division
Key Concepts:
Cells divide during mitosis and cell division
Main Ideas:
Chromosomes condense at the start of mitosis.
Mitosis and cytokinesis produce two (2) genetically identical daughter cells.
Vocabulary:
Chromosomes
histones
chromatin
chromatids
centromere
Telomere
prophase
metaphase
anaphase
telophase
Objectives:


Compare and contrast binary fission and mitosis.
Describe how some eukaryotes reproduce through mitosis.
Chromosomes condense at the start of mitosis
1. A chromosome is a long continuous thread of DNA that consists of numerous genes along with regulatory information.
Mitosis and Cytokinesis produce two genetically identical daughter cells
1.
The combined process of mitosis and cytokinesis produce two genetically identical daughter cells.
See page 147 – Figure 5.7 - http://www.youtube.com/watch?v=Q6ucKWIIFmg (Mitosis and cell Division)
2.
3.
Mitosis is the division of the nucleus and its contents.
Cytokinesis is the division of the cytoplasm.
Interphase
1.
2.
The cell is not undergoing cell division. Normal cell activities.
By the end of interphase:

Chromosomes have duplicated.

Organelles have been produced in large numbers.

It is large enough to divide.
Prophase
1.
2.
Chromosomes become coiled and start to move toward the equator.
Each chromosome is made up of identical sister chromatids.
3.
4.
5.
The nuclear membrane breaks down.
The nucleolus disappears.
The centrioles begin to move toward the poles and form the spindle fibers.
Metaphase
1.
The chromosomes attach to the spindle and arrive at the center or equator of the cell.
Anaphase
1.
2.
The sister chromatids separate from each other.
The spindle fibers shorten and the chromatids begin to move toward opposite poles.
Telophase
1.
2.
3.
4.
5.
The complete set of identical chromosomes is positioned at each pole.
The nuclear membrane reforms.
The nucleolus reappears.
The spindle fibers start to fall apart and disappear.
The chromosomes start to uncoil.
Cytokinesis
1.
2.
3.
4.
Cytokinesis divides the cytoplasm into two daughter cells.
Cytokinesis is a separate process not part of mitosis.
In animal cells, a pinching in of the cell membrane occurs and microfilaments pull the cells apart.
In plant cells, a cell plate forms between the daughter cells.
Single-celled organisms use mitosis for reproduction.
Multi-celled organisms use mitosis for growth, repair and development.
5.3 Regulation of the Cell Cycle
Key Concepts
Cell Cycle regulation is necessary for healthy growth
Main ideas
Internal and external factors regulate cell division
Cell division is unregulated (controlled) in cancer.
Vocabulary
Growth factor
apoptosis
cancer
benign
malignant
metastasize
Objectives
Identify internal and external factors that regulate cell division.
Explain cancer in terms of the cell cycle.
Internal and external factors regulate cell division
External factors
1. Growth factors are a broad group of proteins that stimulate cell division.
2. Hormones like human growth hormone also can regulate cell division. (HGH)
carcinogen
tumor
Internal Factors
1.
2.
3.
4.
5.
Kinases and Cyclins are two (2) very important internal factors.
A kinase is an enzyme that when activated transfers a phosphate group from one molecule to a specific target molecule.
This either changes the shape of the target molecule or increases the energy of the target molecule.
Cyclins are proteins that activate kinases that help regulate the cell cycle.
Cyclins are rapidly produced and destroyed depending on the needs of the cell.
Apoptosis
1.
2.
Apoptosis is programmed cell death.
Apoptosis and cell division must be balanced at different stages of the cell cycle to maintain the health of the organism.
Cell division is uncontrolled in cancer
1.
2.
3.
4.
Cancer is uncontrolled cell division.
A tumor is a disorganized cluster of cells.
Two types of cancer:
1. Benign tumors – cancer cells typically remain clustered together and are harmless.
2. Malignant tumors – the cancers cells break away (metastasize) spread though out the body in the lymph or circulatory
systems.
Carcinogens are substances that are known to produce or promote the development of cancer cells.
Bell Ringer 5.3 page 147 Questions 1-5
5.4 Asexual Reproduction
Key Concept
Many organisms reproduce by cell division.
Main ideas
Binary fission is similar in function to mitosis.
Some eukaryotes reproduce through mitosis.
Vocabulary
Asexual reproduction
binary fission
Objectives
Compare and contrast binary fission and mitosis
Describe how some eukaryotes reproduce through mitosis
Binary fission is similar in function to mitosis
1.
2.
3.
Asexual reproduction is the creation of a new offspring from a single parent without the joining of gametes. ( sex cells )
The offspring are genetically identical to the parent cell.
Asexual reproduction is more rapid and provides less genetic diversity than sexual reproduction.
Binary Fission and Mitosis
1.
2.
Most eukaryotes reproduce through binary fission.
Binary fission is the asexual reproduction of a single celled organism by division into two parts.
http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter10/animation_-_cell_division.html (Binary Fission)
www.Classzone.com – Binary Fission
Advantages and Disadvantages of Asexual Reproduction
1.
2.
3.
4.
5.
6.
In conditions that are constant and don’t change asexual reproduction may be more of an advantage since the organism is well
adapted to the environment.
In changing conditions, sexual reproduction may be more of an advantage because it allows for genetic variation and
adaptation.
Asexual reproduction produces organisms that can all reproduce. Sexual reproduction produces only ½ of reproductive
efficiency because ½ will be male and the other ½ female.
Asexual reproduction does not require a mating partner. Sexual reproduction requires time, energy and resources to locate
and secure a breeding partner.
Asexual reproduction is more rapid and can build population increase in shorter time periods.
Fragmentation (starfish) and budding (yeast, hydra) are other examples of asexual reproduction.
Bell Ringer 5.4 – page 150 Questions 1-4
5.5 Multicellular Life
Key concepts
Cells work together to carry out complex functions.
Main Ideas
Multicellular organisms depend on interactions among different cell types.
Specialized cells perform specific functions
Stem cells can develop into different cell types.
Objectives:
Describe the specialization in multicellular organisms
Identify different types of stem cells.
Vocabulary
Tissue
organ
organ system
cell differentiation
stem cell
Multicellular organisms depend on interactions among different cell types
1.
2.
3.
4.
Tissues are a group of cells that perform a specific function.
Group of tissues that perform a specific function are called organs.
Group of organs that perform a specific function are called organ systems.
http://www.youtube.com/watch?v=wdJFTC44meI&feature=related (levels of organization)
Specialized cells perform specific functions
1.
Cell differentiation is the process which unspecialized cells develop into their mature forms and functions.
Stem cells can develop into different cell types
1.


Stem cells are a unique body cell that has the ability to:
Divide and renew themselves for a long period of time
Develop into a variety of specialized cell types.
Stem Cell Classification


Totipotent stem cells can grow into any other cell type. Only a fertilized egg and the cells produced by the first few divisions of the
embryo are totipotent.
Pluripotent stem cells can grow and develop into any type of cell except for totipotent stem cell.

Multipotent stem cells can only grow into cell type of a related cell family.
http://www.youtube.com/watch?v=9xdEsuroJaE (stem cell classification)
http://actcells.com/stem-cells-101/stem-cell-diagram/ (stem cell harvesting)
Adult stems cells
1.
2.
3.
4.
5.
6.
Partially differentiated cells located among the specialized tissues and organs in the body.
They are found all over the body
Also found in children and umbilical cord blood. ( somatic stem cell is more accurate)
Major advantage is the non-rejection when transplanted back into the patient.
Disadvantage is they are few in number, difficult to isolate and tricky to grow.
They can also contain more genetic abnormalities than embryonic stem cells.
Embryonic Stem cells
1.
2.
3.
4.
Taken at a clinic from a cluster of undifferentiated cells in a 3-5 day old embryo.
Do not have any characteristics of specific cell type.
Can grow into any of the 200 cell types in the body
Disadvantage is they can be rejected by the body since the patient’s immune system doesn’t recognize it.
Research and Treatment Hope
1. Offer a huge potential for hope to patients with leukemia, lymphoma..
2. Potential for injuries to the spinal cord and damaged organs.
3. many ethical issues depending on culture, religion and educational background.
Bell Ringer 5.5 page 155 Questions 1-6