Cellular Reproduction 9

The Big Idea Cells go through a life cycle that includes interphase, mitosis, and cytokinesis.

Section 9.1: Cellular Growth Main Idea #1 Cells grow until they reach their size limit, then they either stop growing or divide.

What Limits Cell Size? As the cell grows, its volume increases much more rapidly than the surface area. The cell might have difficulty supplying nutrients and expelling enough waste products.

What Limits Cell Size? Transport of Substances Substances move by diffusion or by motor proteins. Diffusion over large distances is slow and inefficient. Small cells maintain more efficient transport systems. Cell Communication The need for signaling proteins to move throughout the cell also limits cell size. Cell size affects the ability of the cell to communicate instructions for cellular functions.

The Cell Cycle Cell division prevents the cell from becoming too large. It also is the way the cell reproduces so that you grow and heal certain injuries. Cells reproduce by a cycle of growing and dividing called the cell cycle.

The Cell Cycle Interphase is the stage during which the cell grows, carries out cellular functions, and replicates. Mitosis is the stage of the cell cycle during which the cell’s nucleus and nuclear material divide. Cytokinesis is the method by which a cell’s cytoplasm divides, creating a new cell.

Interphase The first stage of interphase, G1 The cell is growing, carrying out normal cell functions, and preparing to replicate DNA.

Interphase The second stage of Interphase, S The cell copies its DNA in preparation for cell division.

Interphase The third stage of Interphase, G2 The cell prepares for the division of its nucleus.

Cells Alive On laptops, go to Click on Interactive Cell Cycle Complete Worksheet - “Cells Alive”

Section 9.2: Mitosis and Cytokinesis Main Idea #2 Eukaryotic cells reproduce by mitosis, the process of nuclear division, and cytokinesis, the process of cytoplasm divisions.

Cell Division – Intro Cell division in prokaryotes occurs by binary fission. A prokaryote cell copies its DNA. The cell begins to divide. Two identical haploid cells are produced that contain identical DNA. Eukaryotic cell division is much more complex; there are two types. Mitosis - results in new cells with genetic material that is identical to the original cell Meiosis - reduces the chromosome number by half in the new cells; ex - sex cells

Mitosis Mitosis is the division of the nucleus during cell division. Mitosis is a continuous process that is divided into four phases: Prophase, Metaphase, Anaphase, Telophase

Prophase DNA begins to shorten and tightly coil into the rod-shaped chromosomes. The nucleolus and nuclear membrane begin to disappear. Centrosomes and centrioles begin to appear and start to move to the opposite ends of the cell.

Prophase As the centrosomes separate, spindle fibers begin to form and create a structure known as the mitotic spindle. The mitotic spindle helps to divide the chromatids into equal halves. There are two types of fibers within the mitotic spindle: kinetochore and polar fibers.

Metaphase This is the easiest phase to see the chromosomes. Sister chromatids are pulled along the spindle apparatus toward the center of the cell. They line up in the middle of the cell.

Anaphase The microtubules of the spindle apparatus begin to shorten. The sister chromatids separate. The chromosomes move toward the poles of the cell.

Telophase The chromosomes arrive at the poles and begin to relax. Two new nuclear membranes begin to form and the nucleoli reappear. The spindle apparatus disassembles.

Cytokinesis In animal cells, microfilaments constrict, or pinch, the cytoplasm. The part that pinches in and eventually separates is called the cleavage furrow. In plant cells, a new structure, called a cell plate, forms.

Mitosis Internet Lesson http://www.biologycorner.com/workshee ts/mitosis.html#.Unb7qBahClL

Section 9.3 Cell Cylce Regulation Main Idea #3 The normal cell cycle is regulated by cyclin proteins.

Abnormal Cell Cycle: Cancer Cancer is the uncontrolled growth and division of cells. Cancer cells can kill an organism by crowding out normal cells, resulting in the loss of tissue function.

Causes of Cancer The changes that occur in the regulation of cell growth and division of cancer cells are due to mutations. Various environmental factors can affect the occurrence of cancer cells. Factors that can cause cancer are called carcinogens. Examples include smoke, sunlight, chemicals, radiation, etc.

Apoptosis Apoptosis is programmed cell death. Cells going through apoptosis actually shrink and shrivel in a controlled process.

Stem Cells Stem cells are unspecialized cells that can develop into specialized cells when under the right conditions. After fertilization, the resulting mass of cells divides repeatedly until there are about 100–150 cells. These cells have not become specialized. Adult stem cells are found in various tissues in the body and might be used to maintain and repair the same kind of tissue. Adult stem cells are less controversial because the adult stem cells can be obtained with the consent of their donor