Proteins- Basics Flashcards
Amino Acid Structure
Peptide Bond
Covalent
Link AA’s together
Levels of structure in a protein
- Primary protein structure: Sequence of a chain of amino acids
- Secondary: local folding of polypeptide chain into helices or sheets–> regular and repeating
- Tertiary structure: 3-d folding pattern of a protein due to side chain interactions
- Quaternary Protein Structure: protein consisting of more than one amino acid chain
Secondary structures in proteins are:
- a-helices
- b-pleated sheets
- regular repeating patterns
- maximize hydrogen boding
What is the difference between tertiary and quaternary structure?
- Tertiary = 3d folding of a single polypeptide chain via H-bonds, ionic bonds, and van der waals
- Quaternary= for multi-subunit complexes- 3d analysis
- ex. Hemoglobin- 4 subunits that contain a heme molecule
What are the primary function of proteins in the body?
- Structural support
- Enzymes
- Signaling processes
What is the primary difference between globular and fiborous proteins?
Globular Proteins:
- Spheroidal shape
- Soluable
- Catalysts, transporters and signal transducers
Fibrous:
- Large, rod-like
- Structural role
- ex. collagen, keratin
Describe how the deficiency of vitamin C causes scurvy?
Collagen composition: glycine, proline, and hydroxyproline
Vitamin C is required to hydroxyproline formation from proline
No vitamin C = no collagen = no support for the skin
What is the primary role of enzymes?
To catalyze the rate of reaction
Enzymes work to lower the energy needed to form the transition state
If a reaction is favorable, then what does it require?
Favorable RXN:
- Requires keq >1
- delta G < 0
Unfavorable RXN:
- keq < 1
- delta G > 0
Do enzymes effect the delta G of the reaction? How do they effect the transition state?
- Enzymes don’t influence the delta G of the reaction
- Enzymes lower the energy needed to reach the transition state
Reactions relating to the free energy of all involved molecules
The delta G of enezyme catalysis by carbonic anhydrase is -700kcal/mole. Effect of enzyme on the thermodynamics of the reaction.
- Delta G < 0 –> favorable reaction
- Carbonic anhydrase (enzyme) doesn’t effect delta G
- Carbonic anhydrase will lower the energy of the transition state
Two primary models of enzyme function
Lock and key mechanism:
- Enzymes only bind 1 substrate
- Complementarity with active site of the enzyme
- enzyme + substrate = rigid bind
- Important for fast enzymes to quickly form substrate and then the product
Induced-fit model:
- Substrate binding changes the active site conformation of an enzyme
- Enzyme binds to substrate to form a complex
How do temperature and pH effect the rate of enzymatic reactions?
- Increased temperature = increased frequency of collisions
- Temp. too high = denaturation of enzymes ~ 45C
- Most enzymes have an optimal pH that they function at
