Golgi Apparatus

1
Golgi Apparatus

• Stacked and flattened membranous sacs
• Functions in modification, concentration, and
  packaging of proteins
• Transport vessels from the ER fuse with the cis
  face of the Golgi apparatus
• Proteins then pass through the Golgi apparatus to
  the trans face
• Secretory vesicles leave the trans face of the
  Golgi stack and move to designated parts of the
  cell

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Golgi Apparatus
Figure 3.20a
3
Role of the Golgi Apparatus
Figure 3.21
4
Lysosomes

• Spherical membranous bags containing digestive
  enzymes
• Digest ingested bacteria, viruses, and toxins
• Degrade nonfunctional organelles
• Breakdown glycogen and release thyroid hormone
• Breakdown nonuseful tissue
• Breakdown bone to release Ca2
• Secretory lysosomes are found in white blood
  cells, immune cells, and melanocytes

5
Endomembrane System

• System of organelles that function to
• Produce, store, and export biological molecules
• Degrade potentially harmful substances
• System includes
• Nuclear envelope, smooth and rough ER, lysosomes,
  vacuoles, transport vesicles, Golgi apparatus,
  and the plasma membrane

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Endomembrane System
Figure 3.23
7
Peroxisomes

• Membranous sacs containing oxidases and catalases
• Detoxify harmful or toxic substances
• Neutralize dangerous free radicals
• Free radicals highly reactive chemicals with
  unpaired electrons (i.e., O2)

8
Cytoskeleton

• The skeleton of the cell
• Dynamic, elaborate series of rods running through
  the cytosol
• Consists of microtubules, microfilaments, and
  intermediate filaments

9
Cytoskeleton
Figure 3.24
10
Microtubules

• Dynamic, hollow tubes made of the spherical
  protein tubulin
• Determine the overall shape of the cell and
  distribution of organelles

11
Microfilaments

• Dynamic strands of the protein actin
• Attached to the cytoplasmic side of the plasma
  membrane
• Braces and strengthens the cell surface
• Attach to CAMs and function in endocytosis and
  exocytosis

12
Intermediate Filaments

• Tough, insoluble protein fibers with high tensile
  strength
• Resist pulling forces on the cell and help form
  desmosomes

13
Motor Molecules

• Protein complexes that function in motility
• Powered by ATP
• Attach to receptors on organelles

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Motor Molecules
Figure 3.25a
15
Motor Molecules
Figure 3.25b
16
Centrioles

• Small barrel-shaped organelles located in the
  centrosome near the nucleus
• Pinwheel array of nine triplets of microtubules
• Organize mitotic spindle during mitosis
• Form the bases of cilia and flagella

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Centrioles
Figure 3.26a, b
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Cilia

• Whiplike, motile cellular extensions on exposed
  surfaces of certain cells
• Move substances in one direction across cell
  surfaces

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Cilia
Figure 3.27a
20
Cilia
Figure 3.27b
21
Cilia
Figure 3.27c
22
Nucleus

• Contains nuclear envelope, nucleoli, chromatin,
  and distinct compartments rich in specific
  protein sets
• Gene-containing control center of the cell
• Contains the genetic library with blueprints for
  nearly all cellular proteins
• Dictates the kinds and amounts of proteins to be
  synthesized

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Nucleus
Figure 3.28a
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Nuclear Envelope

• Selectively permeable double membrane barrier
  containing pores
• Encloses jellylike nucleoplasm, which contains
  essential solutes
• Outer membrane is continuous with the rough ER
  and is studded with ribosomes
• Inner membrane is lined with the nuclear lamina,
  which maintains the shape of the nucleus
• Pore complex regulates transport of large
  molecules into and out of the nucleus

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Nucleoli

• Dark-staining spherical bodies within the nucleus
• Site of ribosome production

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Chromatin

• Threadlike strands of DNA and histones
• Arranged in fundamental units called nucleosomes
• Form condensed, barlike bodies of chromosomes
  when the nucleus starts to divide

Figure 3.29
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Cell Cycle

• Interphase
• Growth (G1), synthesis (S), growth (G2)
• Mitotic phase
• Mitosis and cytokinesis

Figure 3.30
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Interphase

• G1 (gap 1) metabolic activity and vigorous
  growth
• G0 cells that permanently cease dividing
• S (synthetic) DNA replication
• G2 (gap 2) preparation for division