Transcript Biol 178 Lecture 4

Bio 178 Lecture 4
The Chemical Building Blocks of Life
Outline
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Macromolecules
Proteins
Nucleic Acids
Lipids (Mon)
Carbohydrates (Mon)
Reading
•
Chapter 3
Quiz Material
•
Questions on P 60
•
Chapter 3 Quizzes on Text Website
(www.mhhe.com/raven7)
Chemistry of Carbon - Organic Molecules
• Biological molecules are composed primarily of C atoms bonded to
H, O, N, & S.
• Hydrocarbons - Store a lot of energy!
Functional Groups
• The part of a molecule responsible for its chemical properties.
• Organic molecules
Have a C based core with attached functional groups.
Functional Groups
Macromolecules
Types
Carbohydrates, lipids, proteins, & nucleic acids.
Polymer
A long chain of similar molecules.
Making and Breaking Macromolecules
• Dehydration synthesis
• Hydrolysis
Proteins
Composition
Polymers of amino acids.
Carboxyl Group
Amino Acids
Amino Group
Functional groups can be polar,
non-polar, electrically charged,
aromatic, or have unique
properties.
Protein Synthesis
Protein Structure
Bonds that stabilize Protein Structure
• Hydrogen bond
• Disulfide bridge
• Ionic bond
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Fig. 3.7b(TE Art)
O
C
N
H
H
C C S S C C
H
H
O
N
C
2
Disulfide
bridge
Levels of Protein Structure
• Primary
• Secondary
• Motifs
• Tertiary
• Domains
• Quaternary
Primary Structure
• Unique aa seq of a protein
• Determined by genetic information
Secondary Structure of a Protein
Coiling or folding of the polypeptide
chain as the result of hydrogen bonds
at regular intervals along the
polypeptide backbone
Motifs (Supersecondary structure)
A distinctive, usually recurrent structural element
(secondary protein structures) such as a simple protein
motif consisting of two alpha helices.
Examples:
•  turn 
•
•  barrel
Tertiary Structure
• The overall 3D shape of the polypeptide chain.
Hydrophobic regions will be on the inside.
• Due to interactions between the R groups.
• Stability of tertiary structure is determined by how well
non-polar R groups (will be different sizes) fit into the
protein interior.
Domains
• Portion of a polypeptide chain that folds independently of
the rest of the polypeptide chain (can be excised and still
fold correctly).
• Domains often have different functions within the protein
(eg. DNA binding region).
Quaternary Structure
The spacial arrangement of the polypeptide chains
(subunits) when a protein is composed of 2 or more
polypeptide chains.
Protein Folding
Chaperone Proteins
• Enable new proteins to fold correctly.
• Example - heat shock proteins.
• Scientific evidence suggests that the primary function of
chaperones is to prevent protein aggregation (of
incompletely folded proteins).
Chaperone Proteins and Disease
• Can chaperones prevent protein misfolding diseases?
• Why do these defense mechanisms fail in patients with
these diseases?
Human Brain with Spongiform
Encephalopathy
Normal Protein Folding is Critical to Function
Normal (Good) PrPC
Prion (Bad) PrPSc
Protein Denaturation
A change in the shape of the protein.
Caused by a change in temperature or polarity of the
protein’s environment.
Protein Functions
Function
Class
Examples
Use
Enzyme
catalysis
Enzymes
Proteases
Break down
protein
Defense
Transport
Transport
Mark foreign
Immunoglobulins Antibodies
substances
Long distance
transporters
Hemoglobi Transport O2
n
and CO2
Short distance
transporters
Transports
protons
across
membranes
Proton
pump
Protein Functions
Function
Support
Motion
Class
Fibers
Collagen
Muscle
Actin &
Myosin
Regulation Hormones
Storage
Examples
Ion
Binding
Use
Forms
cartilage
Muscle
Contraction
Insulin
Glucose
Transport
Ferritin
Calmodulin
Stores Iron
Binds
Calcium
Structural Proteins
Fig. 3.4
Nucleic Acids
Composition
Polymers of nucleotides (5-C sugar, phosphate group, &
nitrogenous base).
Types
• DNA (deoxyribonucleic acid)
• RNA (ribonucleic acid)
Functions
DNA - Genetic instructions. Occurs in the nucleus.
RNA - Direct protein synthesis. Made in the nucleus,
travels to the cytoplasm.
A Nucleotide is a monomer of a nucleic acid
Nitrogenous Bases