Transcript Molecular Representations - West Chester University of

The
World
of the
Cell
Wayne M. Becker
Lewis J. Kleinsmith
Jeff Hardin
Gregory Paul Bertoni
Seventh Edition
Chapter 2
The Chemistry
of the Cell
Pages 18-40
Copyright © 2009 Pearson Education, Inc..
Five Principles
The Importance of:
1. Carbon
2. Water
3. Selectively Permeable Membranes
4. Synthesis by Polymerization of Small Molecules
5. Self-Assembly
Nature of Phospholipids
-Amphipathic molecules
Structure of Phospholipids
-Polar Head Groups
-Nonpolar tails
Lipid Bilayer
What defines the specific function of a membrane?
Major Intracellular Compartments
Membrane Structure
-Different Regions
-Protein Function
-Sugars
-Others
Protein Channel Types
Macromolecules
• Important Theme:
– Small molecular repeat units “condense” to form
macromolecules
– Macromolecules “self-organize” to mature
biological dstructure
– Repeat Units - “monomers”
– Repeat Units condense:
•
•
•
•
2 repeat units - “dimer”
3 repeat units - “trimer”
Several repeats units - “oligomer”
Many repeat units - “polymer”
Assembly of
Cellular
Structures
Families of Macromolecules
Macromolecule Formation
Monomers condense - water is released
- Condensation often releases water
-“Dehydration condensation”
Reverse = “degradation”
– Water is added
– “Hydrolysis”
Simple Sugar Structure
Glucose
Formation of a Disaccharide
Which reaction
requires energy?
Monomers  Polymers
Macromolecules
• Recurring Theme…
• Monomers condense to polymers..
• Polymers “self-organize” into mature
macromolecules..
Self Assembly
• Polymers must
assume exact final 3D shape and structure
• How “molded” into
final 3-D shape?
• Biological “casting
structure”?
How do macromolecules
assume their final 3-D shape?
How do macromolecules
assume their final 3-D shape?
• Casting mold?
Anfinsen Expt
• 1920s
• Functional Enzyme – “Pancreatic Ribonuclease”
• “Denature” (disrupt 3D
shape - usually only
break non-covalent
bonds)
• Loose biological
functionality
Denaturation
• Disrupt 3D structure
(mainly through noncovalent bonds)
• Leave sequence of
condensed
monomers intact..
Anfinsen Expt
• Remove denaturation
agent
• Molecule spontaneously
refolds to original 3D
shape!
• Biological functionality
recovered..
Anfinsen Expt
Means:
– No “casting” mold
necessary
– All information needed to
define 3D shape already
present in “sequence” of
amino acids
– “3° structure is defined by
1° structure…”
– How……?
Defines 3D Structure:
• “Non-Covelent” Bonds:
– H-Bonds
– Ionic bonds
– VDW Bonds
– “Hydrophobic” Bonds
“Hydrophobic Interactions”
UNFAVORABLE!!
“Hydrophobic Interactions”
Hydrophobic Interactions
Hydrophilic – Water loving
-can form hydrogen bonds
-dissolve in water
Hydrophobic – Water hating
-cannot from hydrogen bonds
-does not dissolve in water
Hydrophobic force is caused by a pushing of
nonpolar surfaces out of the hydrogen-bonded
water network bringing nonpolar surfaces
together
Noncovalent Interactions
of Macromolecules
Final 3-D structure:
• Final Trade-Off:
– Maximize total
number of
favorable
Noncovalent
interactions
– Minimize total
number of
unfavorable
Noncovalent
interactions