Cell Cycle Interphase Mitosis Cancer and Cell Size

Cell Cycle Interphase, Mitosis, Cancer, and Cell Size © Pic. Science LLC 2011

What is cell division? division • cell divides and creates 2 identical daughter cells; cell reproduction Three types: 1. Prokaryotes – for reproduction 2. Eukaryotes – for growth and repair 3. Gametes – makes sex cells

How do the types of division differ? Mitosis Binary fission Diploid cell DNA replication Meiosis S S-phase Chromosome segregation gametes Cytokinesis + zygote Prokaryotic division-cells reproduce by binary fission: Cell’s genetic information (chromosomes) is copied, cell divides in two, each cell is identical to parent cell Eukaryotic division-parent cell makes copy of its chromosomes before it divides. Gametes made by meiosis.

Let’s look more closely at eukaryotic division… division Cell Cycle—sequence of growth and division that a eukaryotic cell undergoes Two parts: 1) Interphase 2) Mitosis Interphase— 1 st phase; busiest and most time consuming part of cell cycle

1) Interphase 3 phases: G 1 phase- cell growth, protein G 2 S Mitosis In te rp ha se G 1 production S phase-chromosomes copied (DNA synthesis), creates 2 sister chromatids G 2 phase-cell prepares to divide, new organelles form

2) Mitosis • Mitosis-nucleus of cell divides to form 2 nuclei ▫ -ensures that each new cell will have a copy of every chromosome • Cytokinesis- division of cell cytoplasm, follows mitosis

Mitosis • 4 main phases: ▫ ▫ Prophase Metaphase Anaphase Telophase Let’s see what happens in each phase… Prophase Metaphase Anaphase In te rp Telephase ha se

The Cell Centrioles Chromatin Nucleolus

Prophase Chromatin condenses/coils Centrioles creating chromosomes Chromatin Nucleolus Sister chromatids are held together by centromere

Prophase The nuclear membrane/envelope breaks down Spindle fibers form between centrioles

Metaphase Chromosomes (sister chromatids) line up at center of cell at the metaphase plate

Metaphase Chromosomes (sister chromatids) line up at center of cell at the metaphase plate Each chromosome is attached to spindle fiber at centromere

Anaphase-sister chromatids pulled apart by spindle fibers

Telophase Chromosomes reach opposite poles of cell and unravel to form chromatin Nuclear envelope reforms and chromosomes, plasma membrane begins to form around nucleus

The result of mitosis is 2 identical cells produced through cytokinesis.

Summary G 1 Interphase S G 2 Cell division Prophase Metaphase Mitosis Anaphase Telephase

What happens if cells divide too much? • Cancer-uncontrolled dividing of cells form failure to produce certain enzymes---controlled by genes. ▫ Enzymes-organic catalysts that control the rate of chemical reaction within the cell

Cancer • Form masses of cells called tumors which deprive normal cells of nutrients • Spread freely because they lack surface proteins • Have abnormal size, shape, and abilities Normal Large cytoplasm Single nucleus Single nucleolus Fine chromatin Small cytoplasm Multiple nuclei Multiple and large nucleoli Coarse chromatin

Cancer • Invade tissues by traveling through the blood stream replacing healthy cells • 2 nd leading cause of death in U. S. • Some causes of cancer: environmental influences viruses

Cell Size • Cells come in all sizes from very small to very large • Examples: • nerve cell 1 micrometer (millionth of a meter) • Ostrich yolk 8 cm in width

Why is cell size limited? • 1. ) the smaller the cell the easier and less time it takes for diffusion of substances such as oxygen O 2 to reach the mitochondria; site of cellular respiration and production of ATP can occur O 2

• 2. ) cells DNA also limits the size of the cell. If a cell doesn’t have enough DNA to program its metabolism (all the chemical reactions that occur in an organism) it cannot live. Large cells often have more than one nucleus providing more DNA.

• 3. ) as cell size increases, volume increases much faster than surface area • See p. 202 -203 Surface area = length (L) X width (W) X # of sides Volume= L x W x height (H) • Example: A. B. C. D. 1 mm x 6 mm = 6 mm² 1 cm x 1 cm = 1 cm³ 2 mm x 6 mm =24 mm² 2 cm x 2 cm = 8 cm³

Review • 1. ) Which of the following occurs during binary fission? • A. ) two genetically identical cells are produced • B. ) a cell grows as large as it can • C. ) The nucleus of as cell divides into two nuclei • D. ) a cell develops a second cell membrane Binary fission occurs with prokaryotic cells that do not have a true nucleus.

Review • 2. ) In which phase of the eukaryotic cell cycle is the genetic material duplicated? • A. ) G 1 phase • B. ) S phase • C. ) G 2 phase • D. ) M phase DNA synthesis occurs and creates 2 sister chromatids

Review • 3. ) Which 2 phases of the cell cycle make up cell division? • A. ) telophase and cytokinesis • B. ) mitosis and cytokinesis • C. ) interphase and mitosis • D. ) cytokinesis and interphase Mitosis and cytokinesis b/c mitosis is the process of a nucleus dividing to make 2 and cytokinesis is the actual splitting of the cytoplasm

Review • • • 4. ) What happens in prophase? A. ) sister chromatids line up at center of the cell B. ) sister chromatids start to separate C. ) sister chromatids are formed D. ) the cell splits in two Chromatin condenses to form chromosomes

Review • 5. ) What are masses of cancerous uncontrollable cell growth called? • A. ) cysts • B. ) nodules • C. ) tumors • D. ) T cells Tumors are the result of cancer growing…they steal vitamins and nutrients from surrounding cells

Review • • • 6. ) cancer spreads easily b/c they lack A. ) mitochondria B. ) cell membranes C. ) inhibitor growth genes D. ) surface proteins They can grow almost anywhere and the cells divide quickly b/c they lack growth controlling enzymes