1. Cell Division & Specialization

2. The Cell Cycle
The cell cycle is an ordered set of events including cell growth & division into new cells; it is the period of time from the beginning of one cell division to the beginning of the next.

3. The Cell Cycle The cell cycle describes the stages of a
single cell’s life.
The length of each part of the cycle varies, and not all cells move through the entire cycle at the same rate. Bone marrow cells, skin cells, and cells of the digestive tract may pass through a cycle in a few hours. Other cells take much longer.

4. The Prokaryotic Cell Cycle
The prokaryotic cell cycle is a regular pattern of growth, DNA replication, and cell division.
Most prokaryotic cells begin to replicate, or copy, their DNA once they have grown to a certain size.
When DNA replication is complete, the cells divide through a process known as binary fission.

5. The Prokaryotic Cell Cycle
Binary fission is a form of asexual reproduction during which two genetically identical cells are produced.
For example, bacteria reproduce by binary fission.

6. The Eukaryotic Cell Cycle
The eukaryotic cell cycle consists of four phases.

7. Phases of the Cell Cycle
G1 Gap 1 S Synthesis G2 Gap 2 M Mitosis and Cytokinesis

8. Gap 1 (G1) Phase
-intense cell growth -RNA is produced -protein synthesis occurs -G1 Checkpoint is activated to ensure that everything is ready for DNA synthesis

9. S Phase
-DNA replication occurs (new DNA is synthesized when the chromosomes are replicated)

10. Gap 2 (G2) Phase
-preparation for division -many of the organelles and molecules required for cell division are produced -at the end of this stage is another control checkpoint— the G2 Checkpoint—to determine if the cell can proceed to the M phase and divide G1, S, and G2 all are part of interphase.

11. M Phase -cell growth & protein synthesis stops
-all of the cell’s energy is focused on division into two daughter cells (mitosis and cytokinesis)

12. M Phase
-the metaphase checkpoint ensures that the cell is ready to complete cell division
-this phase takes place quickly in comparison to interphase

14. Various Stages of Mitosis

15. Most of the time….
Most of the cell cycle is spent in Interphase, preparing for nuclear <mitosis> and cytoplasmic <cytokinesis> division so that the cell is ready to undergo the next stage as soon as new cells are needed.

16. 2 Major Events of the Cell Cycle
1. DNA is Copied (duplicated)
-the copying of the chromosomes
that contain the cell’s genetic information
-occurs during S Phase

17. 2 Major Events of the Cell Cycle
2. Cell Division- after the nucleus is replicated, the cell divides into two independent cells—daughter cells
-the M phase of the cell cycle

18. “Fifth” Phase of the Cell Cycle
Gap 0 Phase ( G0 )
-occurs when G1 of the next cycle would be occurring
-a cell would leave the cycle & stop dividing
-may be a temporary rest period or more permanent

19. G0
-non-dividing cells are not considered to be in the cell cycle. Ex> a cell that has reached the end stage of development and will no longer divide enters G0
(ex. Neurons and most muscle cells)

21. How is the cell cycle regulated?
If cells are grown in a lab, they will continue to divide until they come into contact with each other. If the neighboring cells are scraped away, the remaining cells resume dividing until they make contact again. This proves that cell growth and division can be turned on and off, or regulated.

22. How is the cell cycle regulated?
The cell cycle is controlled by regulatory proteins both inside and outside the cell.

23. Cyclins
-group of proteins that regulate timing of the cell cycle -help to start & stop the cycle

24. Fluctuating Cyclin Levels
Cyclin production peaks to stimulate cell division and declines during interphase to stop division.

25. The controls on cell growth and division can be turned on and off.
Ex> when an injury such as a broken bone occurs, cells are stimulated to divide rapidly and start the healing process; the rate of cell division slows when the healing process nears completion

26. 2 types of Cell Cycle Regulatory Proteins
Internal regulators are proteins that respond to events inside a cell. They allow the cell cycle to proceed only once certain processes have happened inside the cell. Ex.> checkpoints
External regulators are proteins that respond to events outside the cell. They direct cells to speed up or slow down the cell cycle.
Ex>Growth factors are external regulators that stimulate the growth and division of cells. They are important during embryonic development and wound healing.
Other external regulatory proteins on cell surfaces cause the cycle to stop or slow down to prevent excessive growth and keep body tissues from disrupting each other.

27. Cell Death
As new cells are produced everyday in multicellular organisms, other cells die. They can die because of damage or injury, but they can also be “programmed” to die in advance.

28. Apoptosis
Apoptosis is a process of programmed cell death.
It is a series of controlled steps starting with chromatin shrinking, cell membrane destruction, and final clean up by other cells.

29. Apoptosis in Development
Apoptosis plays a role in development by shaping the structure of tissues and organs in plants and animals.

30. For example, the foot of a mouse is shaped the way it is partly because the toes undergo apoptosis during tissue development.

31. Unregulated Apoptosis
Apoptosis can lead to disease…..
Ex> if apoptosis occurs too frequently, too many cells die too rapidly, such as in Parkinson’s Disease and AIDS

32. Mitosis &Cell Division

33. M Phase: Cell Division Mitosis is the division of the nucleus.
In eukaryotes, cell division occurs following interphase: it is the M phase and includes mitosis and cytokinesis.
Mitosis is the division of the nucleus.
Cytokinesis is the division of the cytoplasm.

34. Chromosomes
Every cell must copy, or duplicate, its genetic information before cell division begins. Each daughter cell gets its own copy of that genetic information.
The genetic information that is passed on from one generation of cells to the next is carried by chromosomes.
Cells of every organism have a specific number of chromosomes.

35. Careful Packaging Even a small cell, such as a
bacterial cell, contains a tremendous amount of genetic information. If the bacterial DNA was stretched out, it would be 1.6 mm, which is 1,000 times longer than the cell itself. This would be like stuffing a 300 meter rope into a backpack.
Cells must therefore carefully package this genetic information.

36. Prokaryotic Chromosomes
Prokaryotic cells lack nuclei. Instead, their DNA molecules are found in the cytoplasm.
Most prokaryotes contain a single, circular DNA molecule, or chromosome, that contains most of the cell’s genetic information.

37. Eukaryotic Chromosomes
In eukaryotic cells, chromosomes are located in the nucleus, and are made up of chromatin.

38. Chromatin is composed of DNA and histone proteins.

39. DNA coils around histone proteins to form nucleosomes.

40. The nucleosomes interact with one another to form coils and supercoils that make up chromosomes.

41. What is the role of chromosomes in cell division?
Chromosomes make it possible to separate DNA precisely during cell division.
Separating chromatin would be difficult.

42. Chromatin, chromosomes, duplicated chromosomes, and chromatids

43. Mitosis
Process in which a cell’s replicated nucleus is divided in preparation for division of the cell

44. Mitosis is vital for:
1. Growth 2. Repair & replacement of damaged or worn out cells 3. Asexual reproduction (Reproduction without eggs & sperm)

45. Growth
In the cells of the adult human body, mitosis occurs about 25 million times per second.

46. Repair Mitosis continues in full grown organisms as a means of maintaining the organism— Ex> replacing dying skin cells

47. Asexual Reproduction
Mitosis is the sole mode of reproduction for many single-celled organisms.

48. Asexual Reproduction

49. The life cycle of eukaryotic cells is a continuous process typically divided into three main phases: 1. interphase-G1, S, G2 2. mitosis (division of the nucleus) 3.cytokinesis (division of the cytoplasm)

50. Interphase -occurs before mitosis
-includes G1, S, and G2 phases of the cell cycle
- it is the longest of the 3 main phases
-chromosomes are not clearly visible here

52. Mitosis occurs in 4 continuous phases
Prophase Metaphase Anaphase Telophase

53. Timing of Mitosis
Depending on cell type, mitosis may last several minutes to several days. Prophase is the longest phase of mitosis.

54. 1. Prophase
-chromatin condenses and duplicated chromosomes become visible as DNA coils up; duplicated chromosomes are attached to each other at a place called the centromere; each DNA strand of a duplicated chromosome is called a chromatid

55. 1. Prophase
-the centrioles, tiny structures located in the cytoplasm of animal cells, move to opposite sides of nucleus; they will radiate thin, hollow, proteins called microtubules that help organize the spindle, a fanlike structure that will help separate the chromatids

56. Prophase -the nucleolus disappears and nuclear envelope breaks down
-final digestion of the membrane marks the beginning of metaphase

58. Metaphase
-spindle fibers attach to duplicated chromosomes at the centromeres so they line up at the equatorial plate of the cell, halfway between the poles

59. Metaphase
-one chromatid faces one pole of the cell while its partner faces the opposite pole

61. Chromosomes

62. Anaphase
-the centromeres split and the paired chromatids separate to become individual chromosomes which move along the shortening spindle fibers to opposite poles of the cell, forming two groups near the poles of the spindle

63. Anaphase

65. Telophase
-a new nuclear membrane forms around each new group of chromosomes

66. Telophase
-spindle fibers break down and newly formed chromosomes begin to unwind and spread out into a tangle of chromatin -a nucleolus becomes visible in each daughter nucleus

67. Telophase

69. Duplicated, but not divided
Mitosis accomplishes division of the nucleus, but the cell has yet to divide.

70. Cytokinesis
-final phase of the cell cycle -timing varies depending on cell type Ex>It can begin during anaphase and finish in telophase, or it can follow telophase

71. Results in two cells that are genetically identical (daughter cells)
Cytokinesis
Results in two cells that are genetically identical (daughter cells)

72. Cytokinesis
-the cell’s cytoplasm, organelles, and plasma membrane separate in half with each half containing one nucleus
-The process of cytokinesis is different in animal and plant cells.

74. Cytokinesis in animal cells
The cell membrane pinches in, creating a cleavage furrow, until the mother cell is pinched in half.

75. Cytokinesis in Plant Cells
In plants, the cell membrane is not flexible enough to draw inward because of the rigid cell wall.

76. Cytokinesis in Plants
Cellulose & other materials that make up the cell wall are transported to the midline of the cell and a new cell wall is constructed.

77. Cytokinesis in Plants

78. End Results
The processes of DNA replication, mitosis, and cytokinesis result in two new cells that are genetically identical.

79. The new cells enter interphase, and the cell cycle begins again.
What Next?
The new cells enter interphase, and the cell cycle begins again.

82. The Phases of the Cell Cycle

84. Levels of Organization

85. Atoms -smallest units that possess
the characteristics of a particular element
Ex. a sample of any element from the periodic table would be composed of the same type of atom

86. Molecules
-structures made up of two or more atoms covalently bonded together
Ex. small molecules like H2O or macromolecules like DNA

87. Organelles
-groups of molecules organized to perform specific cellular functions Ex. Mitochondria, ER, Lysosome

88. Cells
-smallest units that can carry out all of life’s processes A single cell can be a complete organism (ex. bacteria) or part of a larger organism (ex. bone cells).

89. Differentiation in cells
Eukaryotic cells themselves are tiny systems with organelles that allow them to carry out life processes.

90. Differentiation
Individual cells of a multicellular organism do not have to carry out every life function; instead, different cells perform different jobs. These cells are differentiated, or specialized to a particular function.

91. Structure- an arrangement of parts function- specific activity or role of parts
Structure impacts function

92. Structure Impacting Function
Ex> A red blood cell is specialized to deliver oxygen to body tissues- its shape allows it to move easily through narrow blood vessels; in contrast, nerve cells have long thin branches extending from the main part of the cell that help deliver information from one part of the body to another.

93. Structure Impacting Function
Ex>Capillaries are the narrowest blood vessels having walls only one cell thick; this allows substances in blood to move across the capillary walls easily, into and out of the cells.

94. Tissues -groups of similarly structured cells organized to carry out a
particular
function

95. Tissues in Action
Ex> Muscle cells are made of long thin cells that can contract or shorten; groups of these cells work together to move the body. Muscle tissue can be under voluntary control, such as any muscle controlled at will, or involuntary control, such as the smooth muscle lining the stomach.

96. Epithelial tissue
Epithelial tissues cover body surfaces in animals; the tissue is composed of small, flat, interlocking cells that enclose and protect the organism. Epithelial tissue can have one or many layers.

97. Connective tissue
Connective tissue holds organs in place and attaches epithelial tissue to other tissues.
Ex>fat, bones, blood (liquid tissue)
Bone cells in your body form bone tissue, a strong solid tissue that gives you shape & support.
Blood cells in your body are part of blood tissue, a liquid responsible for transporting food and oxygen throughout the body.

98. Tissue

99. Organs
-groups of tissues organized to carry out a particular function; each type of tissue performs an essential task to help the organ function
Ex. Heart made up of muscle tissue, blood tissue, & nerve tissue

100. Organs

101. Cells, Tissues, and Organs

102. Functions of Organs
Ex>The stomach digests food; muscle tissues in the stomach help mix food with gastric juices secreted by glands in epithelial tissue in the stomach lining; the gastric acid has a pH of 1 to 3. Mucus must be secreted by other tissues to protect the stomach from being harmed by the acid. Blood supplies oxygen to the stomach tissue.

103. Organ Systems
-groups of organs designed to carry out a particular task
Ex. digestive system

104. Digestive System Organs

105. Organ Systems
Organ systems function to meet the needs of cells throughout the body; although cells are specialized, they cannot carry out all life functions on their own; they rely on the body’s systems to meet some of their needs, such as: Exchanging materials with the environment Transporting materials to and from cells Allowing movement Storing nutrients for later use Responding to stimuli In a unicellular organism, a single cell would carry out all of these functions.

106. Digestive System in Action
The digestive system includes the mouth, esophagus, stomach, intestines, gallbladder, liver, and pancreas; these organs all work together to break down food into small molecules. After food is digested, blood vessels in the intestines absorb useful molecules that are transported to cells everywhere in the body to be used for energy and as raw materials to repair and build new cells.

107. Digestive System

108. Human Organ Systems Nervous Endocrine Skeletal Muscular Integumentary
Immune
Circulatory
Respiratory
Digestive
Urinary
Reproductive

109. Interrelated organ systems
Organ systems can have a single function or share multiple functions with other systems. Ex> the respiratory system brings oxygen to the body and removes carbon dioxide produced by cells; this is accomplished by the diaphragm contracting to expand the lungs; air passes through the nose and into the trachea and bronchi, ending up in the alveoli of the lungs; in the alveoli, oxygen in the air moves into capillaries as carbon dioxide moves from capillaries into the alveoli and is exhaled; this process is called gas exchange

110. Interrelated organ systems
While capillaries have a role in the respiratory system, they are part of the circulatory system, including the heart, blood, arteries and veins. The circulatory system transports oxygen, nutrients, carbon dioxide, and metabolic wastes throughout the body.
Veins carry blood toward your heart, while arteries carry blood away from your heart.
Capillaries are a good example of the interrelatedness of the circulatory and respiratory systems.

111. Interrelated organ systems
Another example is the muscular system, consisting of organs that contract in response to nerve signals from the nervous system. These muscles exert forces on bones, part of the skeletal system, and cause movement. Muscles work in pairs, where one muscle causes motion in one direction around a joint by contracting, and the partner muscle acts in the opposite direction.
Skeletal muscle tissue is under voluntary control, as you can decide whether to move the muscle or not.

112. Plants
Even plants have specialized structures in leaf cells tissues, and organs that carry out specific functions. Ex> vascular tissue is made of differentiated cells that stack together to form tube like structures that allow transport of food, water, and minerals throughout the plant; without vascular tissue, plants could grow no taller than moss Ex>inner leaf plant cells carry out photosynthesis; the upper layer of a leaf is transparent to allow light to pass to cells below; a wax cuticle traps water in the leaf, underside cells contain stomata that allow water vapor and gases in and out

113. Multicellular Organism
-groups of organ systems working together The smooth functioning of a complex organism is the result of all its various parts working together.

114. Levels of Organization

115. Cancer

116. Directions to Divide
Cells divide only when they receive the proper signals from growth factors that circulate in the bloodstream or from a cell they directly contact.

117. Directions to Divide
For example, if a person loses blood, a growth factor called erythropoietin which is produced in the kidneys circulates in the bloodstream and tells the bone marrow to manufacture more blood cells.

118. Normally…..
When a cell receives the message to divide, it goes through the cell cycle which includes several phases for the division to be completed. Checkpoints along each step of the process make sure that everything goes the way it should.

119. A “Hiccup” in the process
Many processes are involved in cell reproduction and all these processes have to take place correctly for a cell to divide properly. If anything goes wrong during this complicated process, a cell may become cancerous .

120. Cancer Uncontrolled Cell Growth
Cancer is a disorder in which body cells lose the ability to control cell growth.

121. Cancer Cells
Cancer cells do not respond to the signals that regulate the growth of most cells. As a result, the cells divide uncontrollably.
Cancer cell- cell that grows out of control; they ignore signals to stop dividing, to specialize, or to die and be shed

122. Cancer cells have defects in normal cellular functioning
Growing in an uncontrollable manner and unable to recognize its own natural boundary, the cancer cells may spread to areas of the body where they do not belong. In a cancer cell, several genes change (mutate) and the cell becomes defective.

123. metastasis
-the process of transmission of cancerous cells from an original site to one or more sites elsewhere in the body
Cancer cells absorb nutrients needed by other cells, block nerve connections, and prevent organs from functioning.

124. What is a tumor? There are 2 types of tumors:
A mass of cells is called a tumor.
There are 2 types of tumors:

125. Benign A benign tumor is noncancerous.
-tumors that do not grow in an unlimited, aggressive manner, do not invade surrounding tissue, and do not metastasize
A benign tumor is noncancerous.

127. malignant
-not self-limited in its growth and is capable of invading into adjacent tissues
A malignant tumor is cancerous. It invades and destroys surrounding healthy tissue and can spread to other parts of the body.

128. Metastasis

129. What causes cancer?
Cancers are caused by defects in genes that regulate cell growth and division. Some sources of gene defects are smoking tobacco, radiation exposure, and viral infection.
A damaged or defective p53 gene is common in cancer cells. It causes cells to lose the information needed to respond to growth signals.

130. Treatment Some localized tumors can be removed by surgery.
Treatment will vary depending on many different factors associated with both the type of cancer & the patient.
Some localized tumors can be removed by surgery.
Many tumors can be treated with targeted radiation.
Chemotherapy is the use of compounds that kill or slow the growth of cancer cells.

131. Naming Cancer
Cancer is named for its site of origin.
Ex>breast cancer that spreads to the lungs and forms a metastatic tumor is metastatic breast cancer, not lung cancer.

132. Stem Cells

133. Early Stages
All organisms start life as just one cell, a zygote.
Most multicellular organisms later pass through an early stage of development called an embryo, which gradually develops into a fetus and then an adult organism.

134. During development, an organism’s cells become differentiated and specialized for particular functions.
For example, a plant has specialized cells in its roots, stems, and leaves.

135. Defining Differentiation
The process by which cells become specialized is known as differentiation.
During development, cells differentiate into many different types and become specialized to perform certain tasks.
Differentiated cells carry out the jobs that multicellular organisms need to stay alive.

136. Mapping Differentiation
In most organisms, a cell’s role is determined at a specific point in development.
For example, in the worm C. elegans, daughter cells from each cell division follow a specific path toward a role as a particular kind of cell.

137. Differentiation in Mammals
Cell differentiation in mammals is controlled by a number of interacting factors in the embryo.
Adult cells generally reach a point at which their differentiation is complete and they can no longer become other types of cells.

138. One of the most important questions in biology is HOW all of the specialized, differentiated cell types in the body are formed from just a single cell.
Biologists say that such a cell is totipotent, literally able to do everything, to form all the tissues of the body. These cells are capable of producing an entire organism.
Only the fertilized egg and the cells produced by the first few cell divisions leading to embryonic development are truly totipotent.

139. After about four days of development, the dividing cells takes the form of a blastocyst, a hollow ball of cells with a cluster of cells inside known as the inner cell mass.
The cells of the inner cell mass are said to be pluripotent, which means that they are capable of developing into nearly all of the body's cell types, but not an entire organism.

140. Stem Cells
Stem cells are these unspecialized cells from which differentiated cells develop.
There are two types of stem cells: embryonic and adult stem cells.

141. Embryonic Stem Cells
Researchers have grown stem cells isolated from human embryos in culture. Their experiments confirmed that embryonic stem cells have the capacity to produce most cell types in the human body.

142. Adult Stem Cells
Adult organisms contain some types of stem cells.
Adult stem cells are multipotent. They can produce many types of differentiated cells, but adult stem cells of a given organ or tissue typically produce only the types of cells that are unique to that tissue.

143. Frontiers in Stem Cell Research
What are some possible benefits and issues associated with stem cell research?
Stem cells offer the potential benefit of using undifferentiated cells to repair or replace badly damaged cells and tissues.

144. Potential Benefits
Stem cell research may lead to new ways to repair many types of cellular damage that results from heart attack, stroke, burns to the skin, and spinal cord injuries.
One example is the approach to reversing heart attack damage illustrated below.

145. Bone marrow transplants are the most well known and most common stem cell treatments.

146. Controversy
Human embryonic stem cell research is controversial because the arguments for it and against it both involve ethical issues of life and death.

147. Ethical Issues
Most techniques for harvesting, or gathering, embryonic stem cells cause destruction of the embryo.
Government funding of embryonic stem cell research is an important political issue.

148. Ethical Issues
Groups seeking to protect embryos oppose such research as unethical.
Other groups support this research as essential to saving human lives and so view it as unethical to restrict the research.