Chapter 11 - Review

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11.1 Cell Growth, Division, and Reproduction The _larger_ a cell becomes, the more demands the cell places on its _DNA._ In addition, a larger cell is less _efficient_ in moving nutrients and waste materials across the _cell_membrane._ The process of cell division solves this problem. Asexual reproduction is the production of genetically _identical_ offspring from a _single_ parent. Offspring produced by _sexual_ reproduction inherit some of their genetic information from _each_ parent. Sexual reproduction produces genetic _diversity_ and may help a species to survive in a _changing_ environment. 11.2 The Process of Cell Division Genetic information is bundled into packages of DNA known as _chromosomes._ Prokaryotic cells have a single _circular_ chromosome. Eukaryotic cells have _multiple_ chromosomes enclosed in the _nucleus._ Cell division in prokaryotes is a form of asexual _reproduction_ known as _binary_ fission. The eukaryotic cell _cycle_ consists of four stages: cell _growth,_ _DNA_ replication, preparing for cell division, and cell _division._ Mitosis is the division of the cell _nucleus._ During mitosis, chromosomes _duplicate_ and condense into sister _chromatids,_ which line up and then _separate._ In the final phase of mitosis, the separated chromosomes _cluster_ and form duplicate _nuclei._ After mitosis, _cytoplasm_ divides in the process known as cytokinesis, forming _two_ daughter cells. 11.3 Regulating the Cell Cycle Cell cycles are regulated by _internal_ proteins such as _cyclin_ and _external_ proteins such as _growth_ factors. Other external regulatory proteins cause cells to slow down or stop their cell cycles. _Apoptosis_ is a process of programmed cell death, which shapes the structure of tissues and _organs._ Cancer results in _uncontrolled_ cell growth and division. Cancer cells form _tumors,_ which invade and destroy surrounding _healthy_ tissue. Rapidly growing cancer cells can be targeted by _radiation_ or chemotherapy or by _surgically_ removing the tumor. 11.4 Cell Differentiation _ Differentiation_ is the process by which cells become specialized. The differentiation process can be mapped in _simple_ organisms but the process is more complicated in more _complex_ organisms. A _zygote,_ the fertilized egg, is _totipotent,_ in that it will develop into any type of cell for the organism, including cells that make up the extra-embryonic membranes and placenta. Embryonic stem cells are _pluripotent,_ which means they are able to produce every type of cell. Adult stem cells are _multipotent,_ so they are capable of replacing cells in the _tissues_ where they are found. The use of embryonic stem cells for research raises many _ethical_ concerns, but stem cell research has made promising advances in _repairing_ or _replacing_ damaged cells and tissues.