Biology 2120 Recitation

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Biology 2120 Recitation

• Week 5

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Todays schedule

• Review lecture notes/material from last week
• Review key figures/drawings on the exam
• (Practice midterm, if you have one and want to
  use it)
• The research papers what do we need to know?

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• Phospholipids are the basic building blocks of
  cellular membranes
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• Phospholipids contain three structural elements
  Fig. 7-6
• Glycerol is a three carbon sugar-alcohol
• The lipid portion of a phospholipid can vary
  widely in structure
• Polar head groups confer additional specificity
  on the structure of phospholipids
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• The amphipathic nature of phospholipids allows
  them to form lipid bilayers in aqueous solution
• Individual phospholipids can diffuse freely
  within a single layer Fig. 7-10, 7-11
• Lipid bilayers are asymmetrical
• Phospholipid bilayers are semi-permeable
  barriers Fig. 8-5
• Maintaining a chemical imbalance across a
  membrane is essential for life

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• The fluid mosaic model explains how phospholipids
  and proteins interact within a cellular membrane
  Fig. 7-5
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• Membrane proteins associate with membrane
  phospholipids in at least four different ways
  Fig. 7-19, 7-20
• Transmembrane proteins typically use alpha
  helices to cross the lipid bilayer Fig. 7-21
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• Cellular membranes are both fluid and static
• Membrane fluidity is sensitive to at least four
  different variables
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• The length and saturation of lipid tails affects
  their fluidity Table 7-2, Figure 7-14
• Cholesterol interacts with lipid tails Fig. 7-15
• Temperature and atmospheric pressure affect the
  motion of membrane constituents

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• Membrane components can form large molecular
  complexes with little or no mobility
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• Cell-cell and cell-matrix junctions on the cell
  surface are relatively immobile Figs. 17-7,
  17-2, 17-3, 17-8
• Lipid rafts are highly stable regions on
  membranes
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• The smooth endoplasmic reticulum builds
  eukaryotic cellular membranes
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• Phospholipids are built at the cytosolic face of
  the SER membrane
• Flippases transport phospholipids from one
  phospholipid layer to the other
• Membrane vesicles transport new membrane from the
  endoplasmic reticulum to other organelles in the
  endomembrane system
• Fatty acid binding proteins carry phospholipids
  to peroxisomes, mitochondria, and chloroplasts

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Figure 7-10 Movements of Phospholipid Molecules
Within Membranes
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Figure 7-5c
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Figure 7-19
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Figure 7-21
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Figure 7-14 The Effect of Unsaturated Fatty Acids
on the Packing of Membrane Lipids
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Figure 7-15
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• Lecture 6 Cytoskeleton I intermediate filaments
  and microtubules
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• A The cytoskeleton is represented by three
  functional classes of proteins Tables 15-1, 15-2
• AIntermediate filaments are the strongest, most
  stable elements of the cytoskeleton Fig. 15-23,
  15-25
• BIntermediate filaments are formed from a
  family of related proteins Table 15-4
• CThe intermediate filament genes in humans are
  classified into six groups
• CIntermediate filament expression is largely
  cell- and tissue-specific
• BThe primary building block of intermediate
  filaments is a filamentous subunit Fig. 15-24
• CA central alpha helical domain confers
  tremendous tensile strength to intermediate
  filament subunits
• BIntermediate filament subunits form
  coiled-coil dimers
• BHeterodimers overlap to form filamentous
  tetramers
• BAssembly of a mature intermediate filament
  from tetramers occurs in three stages
• BIntermediate filaments form specialized
  structures
• CLamins form a strong cage inside the nucleus
  Fig. 18-31
• CEpithelial intermediate filaments form strong
  attachment sites at the cell surface Fig. 17-22

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• AMicrotubules organize movement inside a cell
• BMicrotubule assembly begins at a microtubule
  organizing center (MTOC) Fig. 15-9
• CThe MTOC contains the gamma tubulin ring
  complex (gTuRC) which nucleates microtubule
  formation Fig. 15-10
• CThe primary building block of microtubules is
  an alpha-beta tubulin dimer Fig 15-2
• CMicrotubules are hollow "tubes" composed of 13
  protofilaments Fig. 15-3, 15-4
• CGTP binding and hydrolysis regulate
  microtubule polymerization and disassembly
• BThe growth and shrinkage of microtubules is
  called dynamic instability Fig. 15-8
• CSome microtubules rapidly grow and shrink in
  cells Fig. 15-7
• CCells can regulate the rate of microtubule
  growth and shrinkage
• CSome microtubules exhibit "treadmilling" Fig.
  15-6
• CDynamic instability allows cells to "explore"
  their cytosol

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• AActin filaments control the movement of cells
• BThe building block of actin filaments is the
  actin monomer Fig. 15-13
• CATP binding and hydrolysis regulate actin
  filament polymerization and disassembly
• BActin polymerization occurs in three stages
  nuclei?elongation?steady state
• BActin filaments have structural polarity
• CActin filaments undergo treadmilling
• BSix classes of proteins bind to actin to
  control its polymerization and organization Fig.
  15-15, 15-17
• CMonomer-binding proteins regulate actin
  polymerization
• CNucleating proteins regulate actin
  polymerization
• CCapping proteins affect the length and
  stability of actin filaments
• CSevering and depolymerizing proteins control
  actin filament disassembly
• CCrosslinking proteins organize actin filaments
  into bundles and networks Fig. 15-21, 15-22,
  15-16

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Figure 15-24 A Model for Intermediate Filament
Assembly In Vitro
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Figure 15-10 ?-Tubulin Ring Complexes (?-TuRCs)
Nucleate Microtubules
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Figure 15-6 Treadmilling of Microtubules
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Figure 15-7 The GTP Cap and Its Role in the
Dynamic Instability of Microtubules
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Figure 15-13
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Figure 15-21b
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Your Quiz (if you so choose)
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What do I need to know about the papers?

• Know the definition of hypothesis, and explain
  the hypothesis of either paper in everyday
  language.
• Know the format of a Logical Argument, and be
  able to cite an example.
• Be able to translate any research papers title
  into everyday English.