Period 7
10.1 Cell Growth, Division, and Reproduction
Limits to cell size -The larger a cell becomes, the more demands the cell places on its DNA. Also, a larger cell is less efficient in moving nutrients and waste materials across the cell membrane.

Information “Overload” -Living cells store critical information in a molecule known as DNA. AS the cell grows the information is used to build the necessary molecules needed for cell growth. -As a cell increases in size its DNA does not. If a cell were to grow too large, an “information crisis” would occur.

Exchanging Materials -Cell size is limited because food, oxygen, and water enter a cell through its cell membrane. Waste products leave the cells in the same way. -That rate at which this exchange takes place depends on the surface area of the cell. -The rate at which food and oxygen are used up and waste products are produced depends on the cell’s volume. -The surface area does not increase as fast as the volume does. -If a cell got too large, it would be difficult to get sufficient amounts of oxygen and nutrients in and waste products out.

Division of the Cell -Cell division is the process by which a cell divides into two new daughter cells. -Before cell division begins the cell must replicate its entire DNA so that each new daughter cell gets a complete copy of genetic information.

Asexual Reproduction -The production of genetically identical offspring from a single parent is known as asexual reproduction. -For many single-celled organisms, cell division is the only form of reproduction. -It many also occur in multicellular organisms by the process of budding.

Sexual Reproduction -In sexual reproduction, offspring are produced by the fusion of special reproductive cells formed by each of the two parents. -Offspring produced by sexual reproduction inherit some of their genetic information from each parent. -Produces genetic diversity.

10.2 The Process of Cell Division
Chromosomes -Chromosomes are genetic information that is bundled into packages of DNA.

Prokaryotic Chromosomes -Since prokaryotes lack nuclei their DNA molecules are found in the cytoplasm along with most of the other contents of the cell.

Eukaryotic Chromosomes -Eukaryote cells have much more DNA than prokaryotes have, and therefore contain multiple chromosomes. -Chromatin is the complex of chromosome and a protein, known as histones. -DNA tightly coils around the histones, and together, the DNA and histone molecules form beadlike structures called nucleosomes. -Chromosomes make it possible to separate DNA precisely during cell division.

The Cell Cycle -The cell cycle is a serious of events that cells go through as they grow and divide. -During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells.

Prokaryotic Cell Cycle -DNA replication and cell division take place very rapidly under ideal conditions. -The process of cell division in prokaryote is a form of asexual reproduction known as binary fission.

Eukaryotic Cell Cycle -Interphase is the “in-between” period of growth, and the longest.
-This cell cycle consists of four phases: G1, S, G2, and M. -G1 Phase (Cell Growth): Cells increase in size and synthesize new proteins and organelles. -S Phase (DNA Replication): New DNA is synthesized when the chromosomes are replicated. The cell has twice as much information as it did at the beginning of the phase. -G2 Phase (Preparing for Cell Division): Usually the shortest of the three phases of interphase. Many of the organelles and molecules required for cell division are produced. -M Phase (Cell Division): Follows interphase and produces two daughter cells. This process usually takes place quite quickly. Cell division occurs in two main stages, mitosis, and cytokinesis. Mitosis is the division of the cell nucleus. Cytokinesis is the division of the cytoplasm.

Prophase -The