Cell Growth & Division

Limits to Cell Growth DNA “Overload”: if a cell gets to big, DNA cannot serve the increasing needs of the growing cell. Exchanging Material: If a cell gets to big, food, oxygen, water, cannot get in quick enough and wastes cannot get out quick enough. Ratio of Surface Area to Volume: Volume increases much more rapidly than surface area

Cell Size Surface Area (length x width x 6) Volume (length x width x height) Ratio of Surface Area to Volume

Chromosomes Contain the genetic information (DNA) They are not visible except during cell division. Humans have 46 Fruit flies have 8 Carrots have 18 Sister Chromatids Centromere

includes is divided into Concept Map Cell Cycle M phase (Mitosis) Interphase G 1 phaseS phaseProphaseG 2 phaseMetaphaseTelophaseAnaphase

M phase G 2 phase S phase G 1 phase Cell Cycle

The Cell Cycle Interphase: the “in-between” period of growth; longest & busiest phase of the cell cycle During the cell cycle, a cell grows, prepares for division, and divides into 2 daughter cells, then each begin the cycle again.

Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Mitosis and Cytokinesis

Interphase: Cell Growth G 1 cells are growing, synthesizing proteins and organelles. S: chromosomes are replicated G 2 : organelles and other molecules required for cell division are produced

Mitosis It is divided into 4 phases Prophase Metaphase Anaphase Telophase

Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Mitosis and Cytokinesis

Prophase First and longest phase. Centrioles separate and move to opposite sides of the nucleus. Centrioles help to organize the spindle fibers Chromatin condenses into chromosomes Nuclear envelope breaks down.

Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Mitosis and Cytokinesis

Metaphase The chromosomes line up across the middle of the cell (at the equator). Each chromosome is connected to the spindle fiber by the centromere.

Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Mitosis and Cytokinesis

Anaphase The sister chromatids separate into individual chromosomes and are moved apart to opposite poles.

Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Mitosis and Cytokinesis

Telophase Chromosomes begin to untangle. Two nuclear envelopes will form Spindle begins to break down. Nucleolus becomes visible.

Centrioles Chromatin Interphase Nuclear envelope Cytokinesis Nuclear envelope reforming Telophase Anaphase Individual chromosomes Metaphase Centriole Spindle Centriole Chromosomes (paired chromatids) Prophase Centromere Spindle forming Mitosis and Cytokinesis

Cytokinesis The cytoplasm pinches in half. Each daughter cell has an identical set of duplicate chromosomes. In plants the cells do not separate but form a cell plate between the 2 nuclei and the cell wall starts to form.

Results of Cell Division 2 daughter cells with same number of chromosomes as the original (parent) cell. Ex. 24 → 2 cells each with 24 All of our body cells go through mitosis. Mitosis is used for growth and development, healing, & when cells die from old age.