CELL STRUCTURE BIOLOGY 1010: CHAPTER 4

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CELL STRUCTURE
BIOLOGY 1010 CHAPTER 4

• the cell is as fundamental to biology as the
  atom is to chemistry.

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The Cell

• is the smallest unit of living matter !

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I. Eukaryotic Cells versus Prokaryotic Cells

• Eu true karyo nucleus
• cells having an organized true nucleus
• possessed by higher organisms
• Protists,
• Fungi,
• Plants,
• Animals

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Eukaryotic Cells versus Prokaryotic Cells

• Pro before karyo nucleus
• cells lacking an organized nucleus
• includes the Monerans
• bacteria and blue-green algae

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Eukaryotic Cells versus Prokaryotic Cells

• Eukaryotic
• 1. organized nucleus
• 2. nuclear membrane
• 3. DNA and histones
• 4. linear chromosomes
• 5. mitosis

• Prokaryotic
• 1. no organized nucleus
• 2. no nuclear membrane
• 3. DNA only
• 4. one circular chromosome
• 5. simple division fission

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Prokaryotic Cells (Figure 4.4)

• Bacterial cells
• Outer boundary
• Cytoplasm
• Nucleoid

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II. The Cell Protoplasm

• PROTOPLASM
• Proto first plasm substance
• background substance filling the cell
• entire cells contents (includes nucleus)
• colloid composed of water, salts, dissolved and
  undissolved substances, lipids, proteins,
  carbohybrates, and cellular organelles

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A. The Cell Cytoplasm

• cyto - cell plasm substance
• 90 water
• heterogeneous colloid
• includes everything between the cell and
  nuclear membrane except the nucleus

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1. Organelles made of Membrane

• a. Plastids -- exclusive to plants
• 1. amyloplast -- starch storage
• 2. chloroplast --photosynthesis
• 3. chromoplast - auxiliary pigments such as
  carotenes

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The chloroplast (Figure 4.16)
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1. Organelles made of Membrane

• b. Vacuoles - single membrane bound spheres named
  for content or function
• water vacuole
• food vacuole
• excretory vacuole
• secretory vacuole
• contractile vacuole

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1. Organelles made of Membrane

• c. Lysosomes digestive enzymes for
• digestion of contents of food vacuoles
• autolysis - self-digestion suicide bags

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1. Organelles made of Membrane

• d. peroxisones
• an organelle containing enzymes that
• transfer hydrogen from various substrates
• to oxygen, producing and then degrading
• hydrogen peroxide.

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The formation and function of lysosomes
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1. Organelles made of Membrane

• d. Endoplasmic reticulum- membrane canals that
  function in internal transport and protein
  synthesis
• smooth E.R. - transport only
• rough E.R. - transport and protein synthesis
• ribosomes - small, nonmembrane structures made of
  protein and RNA

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Endoplasmic reticulum (Figure 4.10)
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1. Organelles made of Membrane

• e. Golgi apparatus
• - cellular packaging center
• Cell products are synthesized in the rough E.R.
  and transported by the smooth E.R. to the Golgi
  apparatus. There the products are then packaged
  into secretory vacuoles or transport vesicles.

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For example

• A glycoprotein is a protein covalently bonded
  to a carbohydrate. They are the main ingredients
  of the ECM (Extracellular Matrix) secreted by the
  cell.
• The ECM is the fingerprint by which self
  cells are distinguished from pathogens.

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The Golgi apparatus (Figure 4.13)
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Relationships among endomembranes
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1. Organelles made of Membrane

• f. Mitochondrion
• largest organelle
• most numerous
• powerhouse
• site of cellular respiration (where ATP is made)
• clustered where energy requirements are high

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The mitochondrion (Figure 4.17)
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2. Organelles Not Made of Membrane

• a.The Cytoskeleton -- page 77
• 1. Microtubules - hollow tubes consisting of
  13 columns of the protein tubulin
• 2. Microfilaments - two intertwined strands of
  actin filaments
• 3. Intermediate Fibers - fibrous proteins
  supercoiled into thicker cables

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2. Organelles Not Made of Membrane

• a.The Cytoskeleton -- page 72

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Structure and Function of Cytoskeleton
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Cytoskeletal Specifics
b. Centrioles and Asters (Figures 4.15) 1.
Centrosome -region of microtubules near the
nucleus -the centrosome of animal cells
contains a pair of centrioles - each centiole
is composed of 9 sets of triplet
microtubules
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Centrioles (Figure 4.19)
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Cytoskeletal Specifics (Figure 4.20)

• 2. Cilia and flagella
• - 9 2 arrangement
• - anchored in the cell by a basal body which is
  structural like a centriole

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ULTRASTRUCTURE OF EUKARYOTIC FLAGELLUM OR CILIUM
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Dyneinwalking moves cilia and flagella
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Motion of flagella
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Motion of cilia
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B. The Nucleus - cellular control center

• 1. Nuclear Membrane
• encloses contents of nucleus separating its from
  the cytoplasm
• continuous with endoplasmic reticulum
• double membranes fused at the nuclear pores

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The nucleus and its envelope (Figure 4.7)
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B. The Nucleus

• 2. Nuclear Pores
• - regulate the entrance and exit of
  macromolecules into and out of the nucleus
• 3. Karyoplasm
• -contents of the nucleus
• -matrix is a colloid much like the cytosol

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B. The Nucleus

• 4. Nucleolus
• - ribosomal RNA stored here
• - ribosomes assembled here
• 5. Chromatin
• - threads of genetic material
• - composed of DNA and highly specialized proteins
  called histones
• - condense coil to become visible chromosomes
  during cell division

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B. The Nucleus

• 4. Nucleolus
• - ribosomal RNA stored here
• - ribosomes assembled here
• - number varies from species to species but is
  constant within cells of some species
• 5. Chromatin
• - threads of genetic material
• - composed of DNA and highly specialized proteins
  called histones
• - condense coil to become visible chromosomes
  during cell division

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III.Cell Connections

• Many cells of an animal or plant are integrated
  into one functional unit.
• Neighboring cells often adhere, interact, and
  communicate through special patches of direct
  physical contact.

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Plant Cell Connections...

• 1.Middle Lamella - composed of pectin
• cements adjacent plant cell walls together
• 2.Plasmodesmata- cytoplasmic strands between
  adjacent plant cells which permit communication
  between cells

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Plant cell walls
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B. Animal Cells

• Whereas plant cells are cemented together by
  pectins in the middle lamella, animal cells are
  cemented together by hyaluronic acid.

Cement
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The cell is a living unit greater than the sum of
its parts.

• Organelles do not function in isolation!
• At the cellular level, life emerges from these
  complex interactions of a cells parts.

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There are 3 animal cells connections

• 1. Desmosomes - hold cells of tissue together
  interwoven protein fibers from cell to hyaluronic
  acid
• 2. Tight Junctions - prevent leakage and occur
  where adjacent cell membranes are fused
• 3. Gap Junctions - small channels allowing
  passage of macromolecules between adjacent cells

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Intercellular junctions in animals