Centrioles

1
Centrioles

• Found in pairs perpendicular to one another.
• Small, hollow cylinders composed of
  __________________.
• Visible during cell division near nuclear
  envelope in the ________________ (cell center).
  Help to organize spindle fibers during cell
  division.
• Form the base of cilia and flagella (known as
  __________ _________).

2
Nucleus

• Control center of the cell.
• Contains the DNA of the cell
• Cell may have one nucleus, be multi-nucleated, or
  anucleated.
• Anatomy is divided into four parts
• Nuclear Envelope/Membrane
• Nucleoplasm
• Chromatin
• Nucleoli

3
Nuclear Envelope and Nucleoplasm

• Nucleus is separated from cytosol by a nuclear
  ________________ composed of two lipid bilayers
• Outer layer is continuous with the ER.
• Covered in ___________________.
• Contains nuclear __________ - channels through
  envelope.
• Pores are large enough to allow protein in and
  RNA out of nucleus, but DNA cannot fit through.
• _________________ - gelatinous substance that
  fills the nucleus and is similar to cytosol.

4
Nucleoli

• Small, dark, spherical patches contained within
  the nucleus.
• Not bound by a membrane.
• Where _____________ _____________ are made
  (before they are sent to the cytoplasm and become
  functional).
• Contain DNA that governs synthesis of __RNA.

5
DNA, RNA and Chromatin

• _____________ - made up of DNA and globular
  proteins called histones.
• DNA winds around 8 histone molecules to form a
  ________________.
• Nucleosomes are joined together by linker DNA.
• The chromatin condenses into super-coiled
  x-shaped structures called ________________
  during cell division.
• Two chromatids held together by a protein called
  a centromere.

6
Life Cycle of the Cell

• Two major periods
• _______________
• Begins immediately after a cell has divided into
  two new cells.
• New cell is growing, maturing, and
  differentiating.
• DNA replication occurs here.
• Cells spend majority of time in this phase.
• ________________ phase
• When cell is actively dividing into two equal
  daughter cells.

7
Interphase

• Three subphases
• ___________ 1 (G1)- intense metabolic activity
  and cell growth cell size and number of
  organelles doubles
• _____________ (S)- DNA replication
• ___________ 2 (G2)- very brief synthesis of
  proteins needed for mitosis

8
DNA Replication

• DNA must be replicated before the cell can divide
  into two identical copies.
• During S phase of Interphase
• Chromatin uncoils, histones separate from DNA,
  and a helicase enzyme separates the helix into 2
  nucleotide chains
• DNA polymerase III matches free floating
  nucleotides with the exposed nucleotides on the
  unwrapped DNA chain
• Histones wrap around each new strand. The strands
  supercoil into a chromosome held together by a
  centromere.

9
Mitosis Prophase

• Spindle apparatus appears
• Centrioles have just finished replicating and
  each pair moves from being near the nucleus
  (centrosome) to being at opposite poles of the
  cell.
• Microtubules called spindle fibers extend from
  centrioles to the center of the cell
• Nuclear envelope disintegrates

10
MitosisMetaphase

• Chromosomes are lined up in center of cell
  (equator) to form the metaphase plate.
• Centromere of each chromosome is attached to a
  spindle fiber.

11
MitosisAnaphase

• Centomeres split apart and sister chromatids
  separate as the spindle fiber pulls them away
  from each other toward the centrioles.
• Cell elongates and cytoplasm begins to constrict
  along metaphase plate.

12
MitosisTelophase

• Final stage of mitosis
• Begins when chromosomal movement stops and
  chromatin unraveling begins
• New nuclear envelope appears as well nucleoli.
• Spindle fibers disassemble
• ------------------------------------------------
• CYTOKINESIS (division of cytoplasm) occurs after
  Telophase.
• New daughter cells enter interphase.

13
TRANSCRIPTION

• Process of making mRNA
• Occurs in the nucleus
• Helicase separates the double helix into single
  strands of DNA
• RNA polymerase connects free floating RNA
  nucleotides to their coordinating DNA
  nucleotides.
• Once transcription ends, RNA polymerase detaches,
  mRNA is released, and the DNA forms a double
  helix again.

14
Translation

• Process of building protein. Occurs in the
  cytoplasm.
• Information on mRNA is translated from
  nucleotides to amino acids.
• A ribosome wraps around the strain of mRNA.
• rRNA on the ribosome has an active site where
  tRNA can attach.
• As each codon of mRNA is read, tRNA with a
  corresponding anticodon brings the appropriate
  amino acid to the mRNA.
• A peptide chain is formed as amino acids link
  together and is eventually released.

15
Membrane Processes

• In order to maintain homeostasis, a cell must
  select what it needs from the ________cellular
  fluid and bring it into ________cellular
  environment.
• Electrolytes, fatty acids, vitamins, amino acids,
  hormones, gases
• Must excrete waste products or transport
  resources needed in other parts of the body to
  the extra cellular environment.
• Processes may be _______________ (do not require
  ATP) OR _____________ (do use ATP).

16
Passive Membrane Processes

• Diffusion
• Facilitated Diffusion
• Osmosis
• Filtration
• NO ENERGY REQUIRED

17
Diffusion

• Movement of molecules from an area of _________
  concentration to _____________concentration
• Driven by a ____________ ____________- the
  difference between the concentration of one area
  and the concentration of another.
• Will continue until the molecule is evenly
  dispersed throughout the solution

18
Facilitated Diffusion

• Proteins assist in movement of molecules from an
  area of high to low concentration
• Speed of facilitated diffusion is limited by the
  ______________ of carrier molecules.

19
Osmosis

• Passive movement of ___________ through a
  semi-permeable membrane from a dilute solution to
  a concentrated solution.
• Similar to diffusion, but here, we are referring
  to the movement of water molecules rather than
  solute.

20
Osmosis/TonicityTerminology

• ___________________ Cytoplasm (inside) of cell
  is more concentrated than extracellular (outside)
  fluid
• __________________ Extracellular fluid is more
  concentrated than cytoplasm
• __________________ Extracellular fluid has same
  concentration of dissolved substances as
  intracellular fluid

21
Filtration

• The passage of a fluid/small molecules through a
  semipermeable membrane that does not allow cells/
  large molecules to pass through.
• Fluid/small molecules are pushed through the
  membrane when the pressure on one side of the
  filter is greater than on the other side.
• The force that pushes the liquid is the
  _______________ pressure.

22
Active Membrane Processes

• Active Transport
• Cytosis
• Endocytosis, Exocytosis
• REQUIRE ATP
• Some molecules are unable to enter the cell via
  passive routes because
• Molecules are not lipid soluble, too large for
  protein pores, or are on the wrong side of the
  concentration gradient
• Do not require a concentration gradient

23
Active Transport

• Active movement of molecules by a specific
  carrier protein with a binding site for ATP
  molecules may move against concentration
  gradient.
• __________ system substances are moved in the
  same direction
• __________ system substances are moved in
  opposite directions

24
Endocytosis

• Importing substances from the extracellular space
  to the intracellular environment.
• ____________________
• Cell engulfs
• ____________________
• Cells invaginates
• ___________-___________ endocytosis
• Specialized protein receptors bind to ligands.
• Ligand-small molecules that bind to receptors or
  larger molecules.

25
Exocytosis

• Exporting substances from the intracellular to
  the extracellular environment
• Excretion of waste products and secretion of
  manufactured substances.
• Packaged in secretory vesicles which fuse with
  cell membrane and are ejected to extracellular
  space.
• _____________- exocytosis of wastes
• _____________- exocytosis of manufactured
  molecules