Cell Growth and Division

Why Cells Divide DNA overload Small cell – information stored in DNA meets all the cells needs Cell growth without limits leads to “information crisis”

Why Cells Divide Exchange of materials Nutrients and waste leave the cell through the cell membrane Rate of exchange depends on surface area of cell Rate at which nurtrients are used and waste products produced depends on volume of cell

Why Cells Divide Ratio of surface area to volume As a cell increases in size, volume increases much more rapidly than surface area Ratio of surface area to volume decreases Decrease in ratio causes problems for the cell

Ratio of Surface Area to Volume

Cell Division To avoid decreasing ratio of surface area to volume, cells divide before they become too large Each daughter cell has increased the ratio of surface area to volume

The rate at which materials enter and leave through the cell membrane depends on the cell’s a. Volume b. Weight c. Mass d. Surface area

Cell Cycle and Mitosis Genetic information that is passed from one generation to the next is carried by chromosomes Chromosomes are made up of DNA and protein Cells of every organism have a specific number of chromosomes

Chromosomes are not visible in most cells except during cell division At beginning of cell division, chromosomes condense Before cell division, each chromosome is copied Each chromosome consists of two identical “sister” chromatids attached at a centromere

Chromosomes Replicated chromosome Consists of 2 sister chromatids Exact copies of each other Connected by a centromere Cell division separates chromatids Each new cell gets one copy of each chromosome

Genetic information that is passed on from generation to generation is carried by ____________ Chromosomes.

Chromosomes are made up of _______________ DNA and proteins

Pairs of identical chromatids are attached to each other at an area called the a. Centriole b. Centromere c. Spindle d. chromosome

The Cell Cycle The cell cycle is the series of events that cells go through as they grow and divide During the cell cycle a cell… Grows Prepares for division Divides to form two daughter cells

The Cell Cycle G1 – cell growth S – chromosomes are replicated; synthesis of DNA molecules G2 – organelles and molecules required for cell division are produced M – mitosis and cytokinesis

Interphase The cell grows and replicates its DNA and centrioles

4 Phases of Mitosis Prophase Metaphase Anaphase Telophase

Prophase Chromatin condenses into chromosomes Centrioles separate Spindle begins to form Nuclear membrane breaks down

Metaphase Chromosomes line up across center of cell (the “metaphase plate”) Each chromosome is connected to a spindle fiber at its centromere

Anaphase Sister chromatids separate into individual chromosomes and are moved apart

Telophase Chromosomes gather at opposite ends of the cell Two new nuclear membranes form

Cytokinesis in animal cells

Cytokinesis in plant cells

The cell cycle is the a. Series of events that cells go through as they grow and divide b.Period of time between the birth and death of a cell c.Time from prophase until cytokinesis d.Time it takes for one cell to undergo cytokinesis

Which of the following is a phase of the cell cycle? a. G1 phase b. G2 phase c. M phase d. All of the above

Which of the following is NOT a correct statement about the events of the cell cycle? a. Interphase is usually the longest phase b. DNA replicates during the S phase c. Cell division ends with cytokinesis d. The cell grows during the G2 Phase

The two main states of cell division are called a. Mitosis and interphase b. Synthesis and cytokinesis c. The M phase and the S phase d. Cytokinesis and mitosis