Cell Growth and Division Chapter 5 Mr. Scott

Cell Growth Limits to cell growth Limits to cell growth The bigger a cell is, the more demands the cell places on its DNA. The cell has trouble moving enough nutrients and wastes across the cell membrane

Cell Growth DNA “overload” DNA – provides information that controls the cell’s funtions Small cells have less need for that information than big cells Big cells may need so much information that the single copy of DNA cannot provide it to all areas of the cell

Cell Growth Exchanging materials Surface area of a cell determines the amount of material exchanged Oxygen, water, and food Total area of the cell membrane Volume of a cell determines how fast these materials are produced (waste) or used (food and oxygen)

Cell Growth Ratio of surface area to volume Surface area / volume Surface area Length X Width X Number of sides units 2 Volume Length X Width X Height units 3

Cell Growth If the length of the cell doubles what happens to the ______? Volume Surface Area Ratio SA / V What does this do to the cell?

Cell Growth Division of the cell Division of the cell Cell division The process by which a cell divides forming two new daughter cells This occurs when the cell becomes too big Before a cell divides, it replicates its DNA.

Cell Division Chromosomes Chromosomes Carries the cells genetic information from one generation to the next. Made of DNA and proteins Each cell contains a specific number of chromosomes Humans – 46 Apes - 48 Flies - 8 Carrot – 18 Dog - 78

Cell Division Chromatin – DNA and histone proteins wrapped together Chromatin – DNA and histone proteins wrapped together Keeps the DNA compacted Keeps the DNA compacted Spends 90% of its time in this stage Spends 90% of its time in this stage

Cell Division Chromatids One of two identical “sister” parts of a duplicated chromosome Centromeres Area where the chromatids of a chromosome are attached

Cell Division Telomeres – End caps of DNA strands Telomeres – End caps of DNA strands Do not code for genes Do not code for genes Keep DNA from attaching to other pieces Keep DNA from attaching to other pieces Small portion lost each time DNA replicates Small portion lost each time DNA replicates

Cell Division The cell cycle The cell cycle Interphase Period of the cell cycle between cell divisions Cell cycle During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells, each of which then begins the cycle again

Cell Division Events of the cell cycle Events of the cell cycle G 1 phase Cell growth S phase DNA replication G 2 phase Preparation for mitosis M phase Cell division (mitosis and cytokinesis)

Cell Division Mitosis Mitosis Division of the cell nucleus Four phases (PMAT) Prophase, metaphase, anaphase, and telophase

Cell Division Prophase 1 st phase Longest phase Chromosomes become visible Nuclear envelope dissolves Centrioles separate Spindles begin to form

Cell Division

Metaphase Chromosomes line up across the center of the cell Each chromosome is connected to a spindle fiber

Cell Division

Anaphase Sister chromatids separate into individual chromosomes Chromosomes move toward opposite poles

Cell Division

Telophase Chromosomes gather at the poles and lose their shape New nuclear envelopes surround each set of chromosomes

Cell Division

Cytokinesis Cytokinesis Division of the cytoplasm Each daughter cell has an identical set of chromosomes

Cell Division

Regulating the Cell Cycle Controls of cell division Controls of cell division Cell growth can be turned on or off On Injury Off Cells become crowded

Regulating the Cell Cycle Cell cycle regulators Cell cycle regulators Something that tells the cell when it is time to divide, duplicate their chromosomes, or enter another phase Cyclin Protein that cause spindles to form Regulate the timing of the cell cycle in eukaryotic cells Kinases Enzymes that increase molecular energy Initiates cellular division

Regulating the Cell Cycle Internal regulators Proteins that respond to events inside the cell Allow the cell to proceed only when certain processes have happened

Regulating the Cell Cycle External regulators Proteins that respond to events outside the cell Direct the cell to speed up or slow down the cell cycle Ex. Growth factor

Regulating the Cell Cycle Uncontrolled cell growth Uncontrolled cell growth Cancer Cancer cells do not respond to the signals that regulate the growth of most cells Benign – tumor cells clustered; good tumor Malignant – Cells can metastasize; bad tumor Metastasize – tumor spreads Carcinogens – cancer causing agents

Regulating the Cell Cycle Apoptosis – Programmed cell death Apoptosis – Programmed cell death Nucleus shrinks and break apart Nucleus shrinks and break apart Other cells take in the cell remains Other cells take in the cell remains

Asexual Reproduction Binary fission is similar in function to mitosis. Binary fission is similar in function to mitosis. Asexual reproduction is the creation of offspring from a single parent. Asexual reproduction is the creation of offspring from a single parent. Binary fission produces two daughter cells genetically identical to the parent cell. Binary fission produces two daughter cells genetically identical to the parent cell. Binary fission occurs in prokaryotes. Binary fission occurs in prokaryotes. parent cell DNA duplicates cell begins to divide daughter cells

Asexual Reproduction Environment determines what form of reproduction is most advantageous. Environment determines what form of reproduction is most advantageous. Asexual reproduction is an advantage in consistently favorable conditions. Sexual reproduction is an advantage in changing conditions.

Asexual Reproduction Some eukaryotes reproduce through mitosis. Some eukaryotes reproduce through mitosis. Budding forms a new organism from a small projection growing on the surface of the parent.

Asexual Reproduction Fragmentation is the splitting of the parent into pieces that each grow into a new organism. Fragmentation is the splitting of the parent into pieces that each grow into a new organism. Vegetative reproduction forms a new plant from the modification of a stem or underground structure on the parent plant.

Multicellular Life Multicellular organisms depend on interactions among different cell types. Multicellular organisms depend on interactions among different cell types. Tissues are groups of cells that perform a similar function. Tissues are groups of cells that perform a similar function. Organs are groups of tissues that perform a specific or related function. Organs are groups of tissues that perform a specific or related function. Organ systems are groups of organs that carry out similar functions. Organ systems are groups of organs that carry out similar functions.

Multicellular Life Specialized cells perform specific functions. Specialized cells perform specific functions. Cells develop into their mature forms through the process of cell differentiation. Cells develop into their mature forms through the process of cell differentiation. Cells differ because different combinations of genes are expressed. Cells differ because different combinations of genes are expressed. A cell’s location in an embryo helps determine how it will differentiate. A cell’s location in an embryo helps determine how it will differentiate. Outer: skin cells Middle: bone cells Inner: intestines

Multicellular Life Stem cells are unique body cells. Stem cells are unique body cells. Stem cells have the ability to: Stem cells have the ability to: divide and renew themselves divide and renew themselves remain undifferentiated in form remain undifferentiated in form develop into a variety of specialized cell types develop into a variety of specialized cell types

Multicellular Life Stem cells are classified into three types. Stem cells are classified into three types. totipotent, or growing into any other cell type pluripotent, or growing into any cell type but a totipotent cell multipotent, or growing into cells of a closely related cell family

Multicellular Life Stem cells come from adults and embryos. Stem cells come from adults and embryos. Adult stem cells can be hard to isolate and grow. The use of adult stem cells may prevent transplant rejection. The use of embryonic stem cells raises ethical issues Embryonic stem cells are pluripotent and can be grown indefinitely in culture.

Multicellular Life The use of stem cells offers many currently realized and potential benefits. The use of stem cells offers many currently realized and potential benefits. Stem cells are used to treat leukemia and lymphoma. Stem cells may cure disease or replace damaged organs. Stem cells may revolutionize the drug development process.