Cell Growth and Division Chapter 10

Why would we need new cells???

GrowthRepair Cell death

Limits of cell growth Why cells stay small…and divide DNA Overload DNA Overload Larger cells mean more demand of DNA Exchange of material Exchange of material Service area effects exchange rate Surface area Surface area Volume increase more than surface area

Before the cell becomes too large, it divides into two “daughter” cells in a process called Cell Division

Cell division

Cell Division All cells come from preexisting cells Prokaryotes Binary Fission Binary FissionEukaryotes Mitosis Mitosis Meiosis Meiosis

Cell Cycle Series of events that that cells go through as they grow and divide Cell grows Prepares for division Divides into 2 daughter cells

InterphaseMitosisCytokinesis

INTERPHASE- 3 phase G 1 phase Monitor environment and cell size Monitor environment and cell size Checks for DNA damage Checks for DNA damage increase in mass increase in mass Organelles prep for cell division Organelles prep for cell division Cell spends most of its life in Interphase Cell spends most of its life in Interphase

S phase DNA is copied DNA is copied

G 2 phase Intracellular components replicated Intracellular components replicated Last chance for growth prior to division Last chance for growth prior to division

Cytokinesis Division of the cytoplasm Division of the cytoplasm

Chromosomes Compact, coiled DNA Sister Chromatids One half of the chromosome One half of the chromosomeCentromere Between the two chromatids Between the two chromatids holds them together holds them together

Mitosis How all cells divide EXCEPT reproductive cells The cytoplasm and nucleus both divide Results in two cells that are genetically identical

Prophase Prophase DNA is shortened and tightened into chromosomes Nucleolus & nuclear membrane break down & disappear Two centrosomes appear Animals also have centrioles Centrosomes move to opposite poles of cell Spindle fibers radiate from centrosomes

Metaphase Metaphase Spindle fibers move chromosomes to the center of cell

Anaphase Anaphase Chromatids separate at the centromere and are pulled to opposite poles of cell by spindle fibers

Mitosis - Telophase Spindle fibers break down Chromosome loosens up Nuclear envelope forms around each set of chromosomes Cleavage furrow forms Nucleolus forms

Cytokinesis

Cytokinesis Cell membrane pinches inward creating a cleavage furrow Eventually leads to two cells

Cell Plate Only in plants Cell plate forms between two nuclei Cell plate forms between two nuclei

In Animal Cells Cell membrane pinches inward to form a cleavage furrow

Mitosis animation Mitosis animation Mitosis/cell cycle Video Mitosis/cell cycle Video Mitosis /Cell cycle 3D Mitosis /Cell cycle 3D

Regulation of the cell cycle

Not all cells divide at the same time Cell typeLife span Esophagus2-3 days can divide Small intestine1-2 days can divide Large intestine6 days can divide Red blood cells<120 days cannot divide White blood cells0 hrs – decades many do not divide Smooth muscleLong lived can divide Heart muscleLong lived cannot divide Nerve cellsLong lived most do not divide Stomach cells5 days Nerve cells in brainAs old as you are Liver1-1.5 years Adult skeleton7-10 years Outer layer of skin2 weeks

Changes in mitosis AgingCancermutations

AGING Mitosis begins after fertilization and continues until death. All living things age. The rate of mitosis slows down with age. As a result of a slowing mitosis rate in humans these things can happen: hair loss, wrinkled skin, loss of calcium in bones and muscle weakness,

CANCER how does it happen?

Mutations?? What can cause mutations

Control of the Cell Cycle

Cyclins Proteins that regulate the a cell’s progression through the cell cycle

An abnormal cell should not be able to pass checkpoint

When Control is Lost: Cancer Cancer results if cells do not respond to control mechanisms and start growing uncontrollably

CANCER – Cells mutate and grow, passing checkpoints Normally a mutant cell is destroyed or self destructs. Apoptosis Apoptosis This does not occur in cancer cell

Cancer cell division Unlike normal cells, cancer cells continue to divide indefinitely, even if they become densely packed. Cancer cells will also continue dividing even if they are no longer attached to other cells.

Metastasis A cancer tumor grows and spreads to other parts of body

Cancer animation Cancer animation

Causes of Cancer 1)carcinogen - Any substance that can induce or promote cancer. 2) Mutagens – A substances that cause mutations.

KINDS OF CANCER Carcinomas- tumors grow in the skin and lining of organs. Ex. Lung and breast cancer Sarcomas- tumors that grow in bone and muscle tissue. Lymphomas- tumors that grow in the lymph and blood. Ex. Leukemia.

Cellular Reproduction Stem Cells- another way to produce new cells  Unspecialized cells that can develop into specialized cells when under the right conditions

Cellular Reproduction Embryonic Stem Cells  After fertilization, the resulting mass of cells divides repeatedly until there are about 100–150 cells. These cells have not become specialized.

Cell differentiation the process by which a less specialized cell becomes a more specialized cell type.

Cellular Reproduction Adult Stem Cells  Found in various tissues in the body and might be used to maintain and repair the same kind of tissue  Less controversial because the adult stem cells can be obtained with the consent of their donor