Chapter 9 Cellular Reproduction

1
Chapter 9 Cellular Reproduction

• 9.1 Cellular Growth

2
Cells Come in Different Sizes

• Red Blood Cell 8 um in diameter
• Nerve Cell 1 m in length with very small diameter
• Yolk of ostrich egg 8 cm
• Most cells are 2-200 um
• 1000 um 1 mm

3
Limits to Cell Size

1. Diffusion
2. DNA
3. Surface to volume ratio

4
Diffusion Limits Cell Size

• Within the cell nutrients must diffuse to all
  parts
• Diffusion is based on random movement of
  particles
• Diffusion is too slow for a large cell
• When cells reach maximum size they die or divide

5
DNA Limits Cell Size

• DNA contains all the instructions for
  synthesizing proteins (including enzymes)
• Large cells would need more proteins
• More copies of the DNA instructions would be
  needed for a large cell
• Most cells contain only one set of DNA

6
Surface Area to Volume Ratio Limits Cell Size

• As the size of a cell increases the volume
  increases faster than the surface area
• If the cell size is doubled then need eight times
  more nutrients but plasma membrane is only four
  times larger
• Cells divide before they become too large to
  function properly

7
Volume Increases Faster than Surface Area
What are the surface area to volume ratios?
8
The Cell Cycle

• Sequence of growth and division of a cell
• Two main periods
• Growth also called interphase
• Division also called mitosis and cytokinesis

9
Cell Cycle
10
Interphase

• NOT part of mitosis, rather the time between one
  mitosis and the next
• Stages of interphase
• G1 phase rapid growth and metabolic activity
• S phase synthesis of DNA (additional copy is
  made)
• G2 phase centrioles and other organelles
  replicate cell prepares for division

11
Chromosomes and Chromatin

• Both are DNA
• Chromosomes are the condensed form of DNA that is
  visible as individual strands.
• Chromatin is the relaxed very thin form of DNA
  that is not visible as individual strands.
• During interphase DNA is in the chromatin form.

12
Chromosomes and Chromatin
Chromatin DNA form
Chromosome DNA form
Chromatin DNA form
13
(No Transcript)
14
Cell Reproduction

• Process of producing new cells from preexisting
  cells
• Three Types
• Fission bacteria
• Meiosis sex cells
• Mitosis body cells
• Needed for growth
• Needed for repair

15
Bacteria Reproduce by Fission

• Prokaryotes do not have a nucleus
• They divide the cell contents then divide

16
Chapter 9 Cellular Reproduction

• 9.2 Mitosis and Cytokinesis

17
Eukaryote Cell Reproduction is Mitosis and
Cytokinesis

• Mitosis is division of the nucleus producing two
  genetically identical daughter cells from one
  parent cells
• Needed for growth
• Needed for repair
• Cytokinesis is division of the cell contents
• Usually they happen simultaneously

18
Phases of Mitosis

• Prophase
• Metaphase
• Anaphase
• Telophase

19
Chromosome Structure

• Chromosome is two sister chromatids connected by
  a centromere
• Chromosomes are made of DNA and contain genes
  (hereditary units)
• Chromosomes are the condensed form of chromatin

20
Prophase

• Chromatin coils into visible chromosomes
• Nuclear membrane disintegrates
• Nucleus disappears
• Centrioles migrate to opposite ends of cell
• Spindle fibers form

21
Prophase
22
Metaphase

• Much shorter amount of time than prophase
• Spindle fibers attach to centromere
• Chromatids line up at the cells equator

23
Metaphase
24
Anaphase

• Centromeres split
• Spindle fibers shorten to pull chromatids to each
  end of cell
• Sister chromatids separate

25
Anaphase
26
Telophase

• Starts when chromatids get to opposite poles
• Chromosome uncoil and become chromatin
• Spindles breakdown
• Nuclear membrane reforms
• Nucleus becomes visible

27
Telophase
28
Cytokinesis

• Division of the cytoplasm
• Plants form a cell plate, the beginning of a cell
  wall
• Animals have cleavage furrow where the plasma
  membrane pinches in

29
Animal and Plant Cytokinesis
30
Results of Mitosis

• Mitosis allows for genetic continuity in each
  generation of daughter cells
• Same chromosomes
• Same genes
• Same exact DNA

31
Levels of Organization

• In unicellular organisms one organism undergoes
  mitosis to make two organisms
• In multicellular organisms one cell undergoes
  mitosis to make two cells that form tissues
• Tissues of different types functioning together
  form organs
• Organs functioning together form systems
• Systems functioning together form organisms

32
Chapter 9 Cellular Reproduction

• 9.3 Cell Cycle Regulation

33
(No Transcript)
34
Length of Cell Cycle

• Each cell type has a specific growth and
  reproduction time table
• Frog embryo cell cycle of less than one hour
• Cells lining your intestine 24-48 hours
• Mature nerve cells do not divide

35
Normal Control of the Cell Cycle

• Much that science does not fully understand
• Enzymes control the cell cycle
• Many enzymes needed
• Most enzymes are used at just one point in the
  cycle
• Loss of a functional enzyme can cause the cell
  cycle to be out of control

36
Normal Control of the Cell Cycle

• Signaling molecules made of a cyclin bound to a
  CDK kick off the cell cycle and drive it through
  mitosis.
• Checkpoints monitor the cell cycle for errors and
  can stop the cycle if an error occurs

CDK are enzymes, cyclins are proteins
37
Genes and Proteins

• Genes located on DNA are responsible for giving
  direction about what proteins (enzymes) to
  produce
• A defective gene would produce a faculty enzyme
  that would not function correctly

38
Key Time for Control of the Cell Cycle

• Key control of the cell cycle is just prior to S
  phase during interphase
• If new DNA is synthesized then the cell will
  continue on with mitosis

39
Cancer

• A cell out of control of the cell cycle
• Mistake in the Cell Cycle
• Too fast rate of mitosis
• Result of changes in one or more genes that
  produce enzymes that are involved in controlling
  the cell cycle

40
Cancer Cells
41
Cancer Cells

• Cancer cells form tumors
• Tumors are masses of cells that interfere with
  normal functioning
• Metastasis cancer cells break off the tumor and
  travel to other locations to form tumors

42
Causes of Cancer

• Both genetic and environmental
• When people move from one country to another
  their rate of cancer is that of the country they
  are now living
• Example Rate of breast cancer is high in US and
  low in Japan when people move from Japan to US
  their rate of breast cancer increases

43
Environmental Causes of Cancer
Smoking
UV Light
Diet
Air Pollution
44
Environmental Causes of Cancer
Viruses Cervical Cancer
Water Pollution
45
Cancer Prevention

• Clear link between healthy lifestyles and
  incidence of cancer
• Low fat, high fiber diet reduces risk
• Daily exercise reduces risk
• No tobacco in any form reduces risk

46
Apoptosis

• Programmed cell death
• All animal cells have a death program
• Fetal human tail cells have undergone apoptosis
  programmed cell death at the appropriate time
• Plant leaves undergo apoptosis in autumn when the
  leaves are falling
• Apoptosis can help protect organisms from
  developing cancerous growths.

47
Stem Cells

• Stem cells are unspecialized cells that can
  develop into specialized cells under the right
  conditions

48
Embryonic Stem Cells

• After a sperm fertilizes an egg the cell divides
  until there is 100-150 cells
• Each of these cells can develop into a wide
  variety of specialized cells
• Much controversy exists due to the ethical
  concerns about the source of these embryonic stem
  cells

49
Adult Stem Cells

• Present in adults (and newborns) to produce the
  same type of cell
• Not pluripotent (cant become any cell type)
• In 2000 adult stem cells ere used to restore lost
  brain tissue in mice
• Less controversy exists to the use of adult stem
  cells