Download Biology Chapter 10 Mitosis Notes 3-13

Chapter 10: Cell Growth, Division and Reproduction
Most cells are very small and can’t be observed with the naked
eye.
 Bacteria are the smallest cells <10 µm
o Mycoplasmas, range 0.1 to 0.25 µm in diameter
o Epulopiscium fishelsoni is 250 micrometers (µm) long
and visible to the naked eye
 Eukaryotic cells are larger, most between 10-100 µm
o Bird eggs are large cells
o Colossal Squid - nerve cells over 12 m (40 ft)
o Muscle cells and nerve cells are very long
 Human motor neuron 1.3 m (over 4 feet)
What limits cell size?
 Function
o Minimum size must be large enough to contain DNA,
proteins and internal structures needed for survival
and reproduction
 Resource needs
o Maximum size must be based on the supply of
nutrients and oxygen to the cell, as well as waste
removal. How do these substance get in/out?
Surface Area = 96 mm2
Volume = 64 mm3
What is the relationship between Surface Area and Volume?
Surface Area = Length X Width X 6 (Number of sides)
Volume = Length X Width X Depth
Conclusions:
 Large cells have more surface area and volume than
smaller cells
 Smaller cells, however, have larger surface area to
volume ratios
Is it better to be made out of 1 big cell or many smaller cells?
Many small cells
Larger cell has greater volume, which means:
 More chemical reactions
 Greater need for resources
 Greater waste production
 Greater heat production
Smaller SA/V ratio makes it difficult to acquire necessary
resources while removing waste and heat.
http://www.youtube.com/watch?v=xuG4ZZ1GbzI
Cells give rise to more cells (part of Cell Theory)
 Asexually reproducing organisms produce identical or
nearly identical “daughter” cells to themselves.
Strawberry
Hydra
 Sexually reproducing organisms produce “daughter”
cells/organisms that are much more varied.
Why?
Dog breeds display particular traits from a wide variety of traits
found in the species.
Cell Division
Why do cells divide?
1. Asexual reproduction for some unicellular and multicellular
organisms.
(Binary Fission or Mitosis)
2. Growth – multicellular organisms only
(Mitosis)
3. Repair/renewal – multicellular organisms only
(Mitosis)
4. Formation of sex cells: sperm and eggs
(Meiosis)
Prokaryotic Cell Division – Binary Fission
Why don’t we call
this type of
division Mitosis?
Bacteria reproduce asexually.
 Cell grows in size
 The chromosome is duplicated (copied)
 Copies are separated from each other and moved to
opposite sides of cell.
 Plasma membrane and cell wall pinches inward to form
two separate cells.
Eukaryotic Cell Genetic Material and Chromosome
Duplication
 Eukaryotic cells are generally larger than prokaryotic cells.
 Eukaryotic cells have many more genes than prokaryotic
cells and they are located on more than one chromosome.
 Genetic material located in the nucleus.
Genetic Material Terms:
Chromatin – diffuse mass of long, thin fibers of DNA and
proteins.
 Genetic material spends most of its time in this state.
Sister Chromatids – two copies of the same DNA molecule
connected by a centromere (narrow portion).
 Connected chromatids are identical right after duplication.
Chromosomes – supercoiled, compact chromatin
 DNA wound around proteins.
 Prior to and during cell division.
 Visible under a light microscope, often stained.
1 = Magnified portion of a DNA molecule
2 = Less magnified portion of a DNA molecule, proteins visible
3 = Chromatin, unreplicated
4 = Replicated chromatin (made of sister chromatids)
5 = Replicated chromosome (made of sister chromatids)
Cell Cycle
The “life-history” of cells.
 Once mature, an organism maintains a fairly constant cell
number.
o Humans – 100 trillion cells
 Millions of cells dividing/sec in your body.
 Some divide 1/day (skin)
 Some less often (liver/kidney)
 Some not at all once mature (nerve/muscle)
Cell Cycle – ordered sequence of events that starts from cell
formation to cell division.
 Two Phases: Interphase and Mitotic phase (M phase)
o Each with its own subphases
Interphase – 90% of cell cycle
o Perform daily function
o Cell growth
o Organelle/DNA doubling
Subphases:
o G1 (Gap phase 1) – Cell grows, doubles building
blocks (?) to make more DNA.
o S phase (synthesis) – Cell grows, Copies/Replicates
DNA molecules
o G2 (Gap phase 2) – Cell grows, doubles organelles
needed for a second cell to survive.
Mitotic Phase (M phase) – 10% of cell cycle
o Nuclear and Cellular Division
Subphases:
o Mitosis – Nuclear division; nucleus and genetic
material divide and reform into two nuclei with
identical genetic material.
 Prophase
 Metaphase
 Anaphase
 Telophase
o Cytokinesis – cellular division, cytoplasm divided
Mitosis is very accurate.
o 1 error in 100,000 cell divisions
Reorganize
this diagram
into a flow
chart.
 Interphase IS NOT part of Mitosis
Mitotic Phase (M phase)
Mitosis and Cytokinesis
Mitosis
 Prophase
Pro = before
o Replicated chromatin supercoils into replicated
chromosomes; Centromere visible
o Nucleoli (nucleolus) disappear
o Nuclear envelope breaks down
o Spindle fibers (microtubules) begins to form
o Some spindle fibers attach to the centromere of each
replicated chromosome
o Other spindle fibers connect to fibers from the other
centrosome (centrioles)
 Metaphase – Middle
Meta = between/after
o Replicated chromosomes line-up along the metaphase
plate
 Imaginary plane between the poles
 Anaphase – Separate
Ana = back
o Sister chromatids separate
 Pulled by spindle fibers to opposite poles
 Now each an Unreplicated Chromosome
o Spindle-Spindle interactions elongate the cell
 Telophase – reverse prophase
Telo = end
o Nuclear envelopes reform around genetic material
o Unreplicated chromosomes uncoil to unreplicated
chromatin
o Nucleoli reform
o Spindle fibers disappear
Cytokinesis – Cellular Division
 Division of cytoplasm to both new cells
 Usually begins during telophase
End Result:
 Two identical daughter cells
 Both identical to parent cell
 Possible uses:
o Growth
o Wound Repair/Replacement
o Asexual Reproduction
Animal vs. Plant Cytokinesis
Animal Cells
 Divide from the outside-in
o Cleavage furrow – groove in the cell surface caused
by the cytoskeleton (microfilaments).
 Deepens to pinch the cell into two
Plant Cells
 Divide from the inside-out
o Cell plate – vesicles containing cell wall material
accumulate/gather in the center of the cell
 Membranes and cell wall components fuse to
form a new cell wall
Growth Factors
Organisms must be able to regulate cell division
 Different tissues divide at different rates in an organism
o Skin and digestive tract frequently divide
Density-Dependent Inhibition – a single layer of cells form
when grown in a Petri dish
 Growth Factors – secreted proteins that stimulate division
o Chemical cues regulate division, not physical contact
o Over stimulated cells smaller and more numerous
Cell Cycle – ordered sequence of events that starts from cell
formation to cell division.
Regulated by:
Internal signals – Growth factors
External signals – Environmental conditions
Growth factors and environmental conditions signal the CCCS
(Cell Cycle Control System)
o Molecules that trigger and coordinate events in the cell
cycle
o Stop signals prevent the cell cycle
o Go-ahead signals override stop signals
Tumors – Diseases of the cell cycle
Benign tumors – masses of unregulated cell growth that stay in
one location
o Problematic based on location
Malignant tumors – normal cell changes into cancer cell
o Divide uncontrollably
 Don’t need growth factors
 Some produce their own growth factors
 “Immortal” – divide indefinitely (normal <50X)
o Invade other tissues – metastasis
o Recruit new blood vessels to “feed” cells
Cancers named based on the organ or tissue from which they
originated (Not Tested)
o Carcinomas – originate from external/internal covering
of the body
o Ex. Skin or lining of intestines
o Sarcomas – originate from tissues that support the body
o Ex. Bone or muscle
o Leukemias – originate from the bone marrow and spleen
o Lymphomas – originate from lymph nodes
Tumor Treatment
o Surgery – cut out cells and surrounding tissue if possible
o Radiation – high energy radiation
o Damages DNA of rapidly dividing cells
 Side-effects: sterility (harms ovaries and testes)
o Chemotherapy – Drugs that disrupt specific steps in the cell
cycle
o Paclitaxel (Taxol) – “freezes” mitotic spindle fibers
o Vinblastin – prevents spindle fiber formation
 Side-effects: hair loss, digestive issues, lowers
immune system
o Endostatin – prevents the recruitment of new blood
vessels (angiogenesis)