Cell Growth and Division Chapter 10

Why would we need new cells???

Growth Repair Cell death

Does cell size Matter? Comparison of cells to everyday items we see with our eyes with ones that need a microscope. Write down two observations or reactions to the cell size comparisons.

Which type of cell is more efficient? Why?

Limits of cell growth Why cells stay small…and divide DNA Overload Larger cells mean more demand of DNA Exchange of material Surface area affects exchange rate 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

How is prokaryotic and eukaryotic cell division different?

Cell Division Prokaryotes Binary Fission Eukaryotes Mitosis Meiosis

Cell Cycle Series of events that that cells go through as they grow and divide

3 parts of the cell cycle: Interphase Mitosis Cytokinesis

INTERPHASE- 3 phase G1 phase Monitor environment and cell size Checks for DNA damage grows Organelles prep for cell division Cell spends most of its life in Interphase

S phase DNA is copied

G2 phase Intracellular components replicated Last chance for growth prior to division

Mitosis Division of the nuclear material 4 phases

Cytokinesis Division of the cytoplasm

Internet activity Cell Plate activity

Mitosis animation

Chromosomes Compact, coiled DNA Sister Chromatids Centromere One half of the chromosome Centromere Between the two chromatids 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 DNA is shortened and tightened into chromosomes Nucleolus & nuclear membrane break down & disappear Two centrosomes appear Spindle fibers appear

Metaphase Spindle fibers move chromosomes to the center of cell

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

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

Cytokinesis

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

Cell Plate Only in plants Cell plate forms between two nuclei

Mitosis/cell cycle Video

Regulation of the cell cycle

Not all cells divide at the same time Cell type Life span Esophagus 2-3 days can divide Small intestine 1-2 days can divide Large intestine 6 days can divide Red blood cells <120 days cannot divide White blood cells 0 hrs – decades many do not divide Smooth muscle Long lived can divide Heart muscle Long lived cannot divide Nerve cells Long lived most do not divide Stomach cells 5 days Nerve cells in brain As old as you are Liver 1-1.5 years Adult skeleton 7-10 years Outer layer of skin 2 weeks

Changes in mitosis Aging Cancer mutations

AGING Mitosis begins after fertilization and continues until death. The rate of mitosis slows down with age.

Control of the Cell Cycle

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

CDKs (cyclin dependent kinases)- proteins that stop cells from progressing through the cell cycle P53 – stops at G1 to; activates DNA repair if needed; triggers cell death if damage If this is absent can cause cancer P27- blocks entry into the S phase Breast cancer diagnosis is determined by p27 levels

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 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

Causes of Cancer 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.

Cell Differentiation

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

Embryonic Stem Cells – unspecialized cells Cellular Reproduction Embryonic Stem Cells – unspecialized 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

stem cells