1. The Cell Growth and Division

2. Copy the questions and answer them directly below your drawings.
Make a drawing of a cell that has the following dimensions: 5cm X 5cm X 5cm.
Make a second drawing of another cell about half the size of the first cell.
Compare the drawings.
Copy the questions and answer them directly below your drawings.
How much longer do you think it would take to get from the cell membrane to the center of the big cell than from the cell membrane to the center of the smaller cell?
What is the advantage of cells being small?

3. THINK ABOUT IT When a living thing grows, what happens to its cells?
What is there about growth that requires cells to divide and reproduce themselves?

4. Limits to Cell Size
What are some of the difficulties a cell faces as it increases in size?
The larger a cell becomes, the more demands the cell places on its DNA.
A larger cell is less efficient in moving nutrients and waste materials across its cell membrane.

5. Information “Overload”
Living cells store critical information in DNA.
As a cell grows, that information is used to build the molecules needed for cell growth.
As size increases, the demands on that information grow as well. If a cell were to grow without limit, an “information crisis” would occur.

6. Information “Overload”
A growing cell makes greater demands on its genetic “library.” If the cell gets too big, the DNA would not be able to serve the needs of the growing cell.

7. Exchanging Materials
Food, oxygen, and water enter a cell through the cell membrane. Waste products leave in the same way.
The rate at which this exchange takes place depends on the surface area of a cell.
The rate at which food and oxygen are used up and waste products are produced depends on the cell’s volume.
The ratio of surface area to volume is key to understanding why cells must divide as they grow.

8. Ratio of Surface Area to Volume
As the length of the sides of a cube increases, its volume increases faster than its surface area, decreasing the ratio of surface area to volume.
If a cell gets too large, the surface area of the cell is not large enough to get enough oxygen and nutrients in and waste out.

9. Traffic Problems
A cell that continues to grow would experience “traffic” problems. If the cell got too large, it would be more difficult to get oxygen and nutrients in and waste out.

10. Division of the Cell
Before a cell grows too large, it divides into two new “daughter” cells in a process called cell division.
Before cell division, the cell copies all of its DNA.
It then divides into two “daughter” cells. Each daughter cell receives a complete set of DNA.
Cell division reduces cell volume. It also results in an increased ratio of surface area to volume, for each daughter cell.

11. Asexual Reproduction
Asexual reproduction is reproduction that involves a single parent producing an offspring. The offspring produced are, in most cases, genetically identical to the single cell that produced them.
Asexual reproduction is a simple, efficient, and effective way for an organism to produce a large number of offspring.
Both prokaryotic and eukaryotic single-celled organisms and many multicellular organisms can reproduce asexually.

12. Examples of Asexual Reproduction
Bacteria reproduce by binary fission.
Kalanchoe plants form plantlets.
Hydras reproduce by budding.

13. Sexual Reproduction
In sexual reproduction, offspring are produced by the fusion of two sex cells – one from each of two parents. These fuse into a single cell before the offspring can grow.
The offspring produced inherit some genetic information from both parents.
Most animals and plants, and many single-celled organisms, reproduce sexually.

14. Comparing Sexual and Asexual Reproduction

15. Chromosomes What is the role of chromosomes in cell division?
Chromosomes make it possible to separate DNA precisely during cell division.

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

17. Prokaryotic Chromosomes
Most prokaryotes contain a single, circular DNA molecule, or chromosome, that contains most of the cell’s genetic information.

18. Eukaryotic Chromosomes
In eukaryotic cells, chromosomes are located in the nucleus, and are made up of chromatin.
Chromatin is composed of DNA and histone proteins.
DNA coils around histone proteins to form nucleosomes.
The nucleosomes interact with one another to form coils and supercoils that make up chromosomes.

19. DNA Chromatin - uncoiled DNA Chromosomes - tightly coiled DNA
Homologous chromosome – pair of identical chromosomes
Chromatid – ½ of a replicated chromosome
Centromere - place where chromatids attach

22. The Cell Cycle What are the main events of the cell cycle?
During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells.

23. 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.

24. The Eukaryotic Cell Cycle
The eukaryotic cell cycle consists of four phases: G1, S, G2, and M.
Interphase is the time between cell divisions. It is a period of growth that consists of the G1, S, and G2 phases. The M phase is the period of cell division.

25. G1 Phase: Cell Growth
In the G1 phase, cells increase in size and synthesize new proteins and organelles.

26. S Phase: DNA Replication
In the S (or synthesis) phase, new DNA is synthesized when the chromosomes are replicated.

27. G2 Phase: Preparing for Cell Division
In the G2 phase, many of the organelles and molecules required for cell division are produced.

28. M Phase: Cell Division
In eukaryotes, cell division occurs in two stages: mitosis and cytokinesis.
Mitosis is the division of the cell nucleus.
Cytokinesis is the division of the cytoplasm.

29. Important Cell Structures Involved in Mitosis
Chromatid – each strand of a duplicated chromosome
Centromere – the area where each pair of chromatids is joined
Centrioles – tiny structures located in the cytoplasm of animal cells that help organize the spindle
Spindle – a fanlike microtubule structure that helps separate the chromatids

30. Prophase
During prophase, the first phase of mitosis, the duplicated chromosome condenses and becomes visible.
The centrioles move to opposite sides of nucleus and help organize the spindle.
The spindle forms and DNA strands attach at a point called their centromere.
The nucleolus disappears and nuclear envelope breaks down.

31. Metaphase
During metaphase, the second phase of mitosis, the centromeres of the duplicated chromosomes line up across the center of the cell.
The spindle fibers connect the centromere of each chromosome to the two poles of the spindle.

32. Anaphase
During anaphase, the third phase of mitosis, the centromeres are pulled apart and the chromatids separate to become individual chromosomes.
The chromosomes separate into two groups near the poles of the spindle.

33. Telophase
During telophase, the fourth and final phase of mitosis, the chromosomes spread out into a tangle of chromatin.
A nuclear envelope re-forms around each cluster of chromosomes.
The spindle breaks apart, and a nucleolus becomes visible in each daughter nucleus.

34. Cytokinesis: division of the cytoplasm
Plant Cells
In plants, the cell membrane is not flexible enough to draw inward because of the rigid cell wall.
Instead, a cell plate forms between the divided nuclei that develops into cell membranes.
A cell wall then forms in between the two new membranes.
Animal Cells
Cleavage Furrow: The cell membrane is drawn in until the cytoplasm is pinched into two equal parts.
Each part contains its own nucleus and organelles

36. The Stages of the Cell Cycle

38. Cell Division Animation

39. Questions to think about???????
How is the cell cycle regulated?
The cell cycle is controlled by regulatory proteins both inside and outside the cell.

40. Regulating Cell Growth
The controls on cell growth and division can be turned on and off.
For example, 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.

41. The Discovery of Cyclins
Cyclins are a family of proteins that regulate the timing of the cell cycle in eukaryotic cells.
This graph shows how cyclin levels change throughout the cell cycle in fertilized clam eggs.

42. 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.
External regulators are proteins that respond to events outside the cell. They direct cells to speed up or slow down the cell cycle.
Growth factors are external regulators that stimulate the growth and division of cells. They are important during embryonic development and wound healing.

43. Apoptosis Apoptosis is a process of programmed cell death.
Plays a role in development by shaping the structure of tissues and organs in plants and animals.
For example, the foot of a mouse is shaped the way it is partly because the toes undergo apoptosis during tissue development.

44. Cancer: Uncontrolled Cell Growth
How do cancer cells differ from other cells?
Cancer cells do not respond to the signals that regulate the growth of most cells. As a result, the cells divide uncontrollably.

45. Cancer is a disorder in which body cells lose the ability to control cell growth.
Cancer cells divide uncontrollably to form a mass of cells called a tumor.

46. A benign tumor is noncancerous.
It does not spread to surrounding healthy tissue.
A malignant tumor is cancerous.
It invades and destroys surrounding healthy tissue and can spread to other parts of the body.
The spread of cancer cells is called metastasis.
Cancer cells absorb nutrients needed by other cells, block nerve connections, and prevent organs from functioning.

47. 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, defective genes, 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.

48. Treatments for Cancer 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.

49. THINK ABOUT IT
The human body contains hundreds of different cell types, and every one of them develops from the single cell that starts the process. How do the cells get to be so different from each other?

50. From One Cell to Many
How do cells become specialized for different functions?
During the development of an organism, cells differentiate into many types of cells.
All organisms start life as just one cell.
Most multicellular organisms pass through an early stage of development called an embryo, which gradually develops into an adult organism.
During development, an organism’s cells become more differentiated and specialized for particular functions.
For example, a plant has specialized cells in its roots, stems, and leaves.

51. 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.
Stem Cells are cells that are not terminally differentiated and have the ability to become many different types of cells.

52. From Simple to Complex Atoms: are the smallest chemical units
Molecules:
are a group of atoms working together
Organelles:
are a group of molecules working together
Cells:
are a group of organelles working together
Tissues:
are a group of similar cells working together
Organs:
are a group of different tissues working together
Organ systems:
are a group of organs working together
Organism:
is an individual