Cell Size The size of cell is related to its function Ex. rbc, wbc, nerve, etc.

Cell Size Comparison

Chapter 9 Cellular Reproduction 9.1 Cellular Growth As the cell grows, its volume increases much more rapidly than the surface area.

Ratio of Surface Area to Volume Chapter 9 Cellular Reproduction 9.1 Cellular Growth Ratio of Surface Area to Volume

What are the problems with this?

The cell might have difficulty supplying nutrients and expelling enough waste products. Diffusion over large distances is slow and inefficient. (Small cells maintain more efficient transport systems)

Chapter 9 Cellular Reproduction Cell size affects the ability of the cell to communicate instructions for cellular functions.

How do cells avoid these problems? A few types will stop growing Most cells will divide (mitosis)

Chapter 9 Cellular Reproduction 9.1 Cellular Growth 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.

Cell Cycle Mitosis is only one phase of a cell’s “life” The cell’s entire “life” is called the cell cycle

Cell Cycle

The cell cycle consists of three major phases:

Chapter 9 Cellular Reproduction 9.1 Cellular Growth 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 is divided into three smaller phases G1 S G2

The Stages of Interphase Chapter 9 Cellular Reproduction 9.1 Cellular Growth The Stages of Interphase The first stage of interphase, G1 The cell is growing, carrying out normal cell functions.

The cell copies its DNA in preparation for cell division. Chapter 9 Cellular Reproduction 9.1 Cellular Growth The Second Stage of Interphase, S (synthesis) The cell copies its DNA in preparation for cell division.

The Third Stage of Interphase, G2 Chapter 9 Cellular Reproduction 9.1 Cellular Growth The Third Stage of Interphase, G2 The cell prepares for the division of its nucleus.

Interphase

The Stages of Mitosis

Prophase The Stages of Mitosis Chapter 9 Cellular Reproduction 9.2 Mitosis and Cytokinesis The Stages of Mitosis Prophase The cell’s chromatin condenses to form chromosomes Chromatin: a strand of protein molecules wrapped in DNA

Prophase Chromatin changes from thread-like structure to a rod-like structure They condense and replicate to form chromosomes

Chromosome Structure

Chromosomes consist of two identical sister chromatids Chromatids are held together at a central location called the centromere At the tips of the chromosomes are telomeres

Chromosome Parts

Prophase The nuclear envelope disappears. Chapter 9 Cellular Reproduction Prophase The nuclear envelope disappears. Centrioles appear and begin to move to the opposite ends of the cells (poles)

Prophase Spindle fibers form between the centrioles Spindle fibers: cluster of microtubules that assist with chromosome division

Prophase

Prophase in Plant Cells

Metaphase Chromosomes attach to the spindle fibers at the centromere Chromosomes line up in the middle of the cell (the equator)

Metaphase

Metaphase

Metaphase in an Animal Cell

Anaphase The microtubules of the spindle apparatus begin to shorten. Chapter 9 Cellular Reproduction Anaphase The microtubules of the spindle apparatus begin to shorten. The sister chromatids separate. The chromosomes move toward the poles of the cell.

Notice: the chromosomes move in the direction of the “arrow”

Anaphase in a Plant Cell

Chapter 9 Cellular Reproduction Telophase The chromosomes arrive at the poles and revert back into chromatin (thread-like) Two new nuclear membranes begin to form and the nucleoli reappear. The spindle apparatus disassembles.

Telophase in an Animal Cell

Chapter 9 Cellular Reproduction Cytokinesis In animal cells, microfilaments constrict, or cleave, the cytoplasm. In plant cells, a new structure, called a cell plate, forms.

Cytokinesis in an Animal Cell

Cytokinesis in a Plant Cell

Beginning of Cytokinesis in an Animal Cell

Make an acronym to help you remember the phases of mitosis!!

Onion Root Tip Mitosis Lab