Download CHAPTER 1 - The Cell Cycle (part 1) - GSCS

CHAPTER 1 - The Cell Cycle (part 1)
 How do organisms grow?
 How do broken bones mend?
 How do people age?
 What is cancer?
 How do organisms make more of themselves?
The basic unit of life
Cell Theory
 Technological advancements such as improved microscopes have helped to study
living things in detail
 Cell theory are:
Inside the basic unit of life – the cell
 Numerous membrane bound organelles, that perform specific functions
 Nucleus – bounded by double-layered porous membrane = nuclear membrane
keeps the cell’s genetic material (DNA – deoxyribonucleic Acid)
 DNA – forms long strands of chromatin throughout nucleus
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Nucleolus –
 Jelly-like material = cytoplasm enclosded by cell membrane – supports nucleus
and other organelles
 Endoplasmic reticulum –
 Mitochondria transform energy for cell
 Golgi bodies –
 Vacuoles –
 Lysosomes –
So what’s the difference?
 Plant cells –
 Plant cells –
Understanding the Cell Cycle
 Humans begin as a single cell
 Adults –
 One cell – divided into two – two becomes four and so on
 Each new cell must have a complete nucleus (complete set of DNA) = mitosis
 Before it can begin, nucleus must make a copy of itself (chromatin) = 2 sets of
DNA = replication
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 After replication –
The Cell Cycle (part 2)
Phases of Mitosis in an Animal Cell
 Prophase –
 Metaphase –
 Anaphase –
 Telophase – complete set of chromosomes at each pole of cell, spindle fibers
disappear, nuclear membrane forms around each set of chromosoms
 Nucleolus appears within each nucleus, single stranded chromosomes uncoil into
thin strands of chromatin = 2 nuclei in one cell (itself ready to divide)
Cell division
 At the end of mitosis = 1 cell with 2 identical nuclei
 Animal cells – the cell membrane pinches in near the middle of the cell, dividing
the cytoplasm into 2 new cells
 Plant cells –
 In both – each new division is an exact copy of the original
 Number of chromosomes in nucleus of each cell is the same number in the
original cell
Interphase
 Greater portion of time spent for a cell is called interphase (between)
 Used to be thought as an inactive period however now we know differently

The Cell Cycle (part 3)
 Cell cycle ensures that number of chromosomes in nuclei of your body remains
constant
 Chromosomes vary from species to species
 Dogs = 78 chromosomes, tomato plants have 24, humans have 46
 While growing, mitosis and cell division add to total number of cells in body
Regeneration and Aging
 Cut skin – usually heal in short amount of time
 Bone breaks – take longer
 This is because of mitosis – capable of repairing injured tissue
 Repair of injured cells or making of lost body parts = regeneration
Aging
 Collect several product advertisements from magazines that use the word “aging”
 What do the advertisements claim the products will do?
 Base on what you know about aging, assess the credibility of each ad
 Do some have any scientific merit?
 Make a poster to display your results
Cancer – the cell way out of control



 Cells begins to divide uncontrollably = cancer
 Interferes with surrounding cells and disrupts their ability to function, stock piles
on top of others which results in a tumour or lump in one area
 Some cases, the cancerous cells move to other parts of body and grow and divide
uncontrollably, consume all of the oxygen and nutrients
 Tobacco, asbestos, chemicals, some viruses, radioactivity and ultraviolet radiation
have all been linked to cancer in humans
Asexual Reproduction in Bacteria, Protists, Fungi and Animals
 Mitosis and cell division are the basis for asexual reproduction
 Asexual reproduction –
 Bacteria – kindgom Monera, unicellular organisms without a true nucleus
– Reproduce asexually through binary fission – parent cell divides so that
each new cell contains a single chromosome carrying complete DNA
identical to that of the parent
 Unicellular organisms in kingdom Protista, for example the amoeba

 Molds, yeasts, mushrooms are a part of the Fungi kingdom
 Bodies consist of many thin hyphae which grow over the surface and other
organisms to receive food
 Fragmentation –
 Budding –
 Spore – moulds do this in which a spore (reproductive cell) grows into a new
individual through mitotic division
– Spores are stored in sporangium case and when they are mature, take on
certain colors
Asexual Reproduction in Animals
 Kingdom Animalia – animals divided into vertebrates (with backbones) or
invertebrates (without backbones)
 Invertebrates –
 Most invertebrates –
 Flatworm –
 Some animals – sponges or hydras reproduce by budding where a cell near the
base undergoes mitosis to produce a new group of cells (bud) which completes
development, breaks a part and becomes a new individual
The Cell Cycle (part 4)
Asexual Reproduction in Plants
 Ability of plants to reproduce asexually and to repair themselves = mitotic cell
division
 Asexual reproduction ensures that each new branch has same DNA as parent
 Meristem –
 Certain times – meristematic cells specialize into cells that make up roots, stems,
leaves in plant
 Once plant structures mature –
 Cuttings are lengths of parent stem – used to establish offspring that are exact
copies of parent = cloning (process by which identical offspring are produced
from single cell or tissue)
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 New plants from roots – meristem cells in roots divide mitotically to produce
stems, leaves and other roots – dandelions, weeds
 New plants from stems – meristematic cells in stem divide to produce cells that
will become a new plant – strawberries have runners in which new plants grow
from the tips
 Layering –
 Branch of parent plant is bent down to ground and part of it covered with soil =
roots will grow from the buried stem and exposed tip will grow a new shoot
 Grafting –
 Stems from plants with desirable qualities can be attached or grafted to rooted
stock of similar plant
 Used with apples, grapes, roses