Protein Stability Flashcards
These are spherical proteins that serve functional roles and are generally water-soluble
Globular proteins
These proteins are typically elongated (sheet-like) and hydrophobic. They serve structural roles
Fibrous proteins
These proteins are attached to plasma membrane
Membrane proteins
Which has a higher entropy unfolded or folded protein?
Unfolded
Hydrophilic solvents lose entropy when they form a ____________ _________ around hydrophobic side chains
Solvation layer
Therefore, minimal contact = maximum entropy
Protein folding is driven by what interactions?
Hydrophobic interactions
After protein folding, this has minimal interaction with external environment
Hydrophobic core
After protein folding, this interacts with the external environment and is composed of polar amino acids and side chains
Hydrophilic shell
Protein folding is favorable despite the decrease in entropy of the folded protein because
The increase in entropy of the solvents (surroundings) is much greater
In proteins, the unfolding or loss of higher-level structure is known as what?
Denaturation
Loss of non-primary protein structure
Protein denaturation
Non- primary: secondary, tertiary, and quartenary
Denatured protein has what structure
It is a primary protein- existing as a linear chain of amino acids
Denatured protein has what structure
It is a primary protein- existing as a linear chain of amino acids
T or F. Denaturation breaks the primary, secondary, tertiary, and quartenary structure until all is left is a linear chain of amino acids
Denaturation breaks proteins to its primary level which is a linear chain of amino acids
Amino acids are held by what bonds? Which atoms are bound by this bond?
Peptide bonds between Carbon and Nitrogen
Which are stronger? Intermolecular bonds or intramolecular bonds
Intramolecular bonds
What type of bonds can be found in primary, secondary, and tertiary/ quaternary protein structures
Primary: covalent (peptide) bonds
Secondary: hydrogen bonds
Tertiary/ quaternary:non-covalent side-chain interactions, disulfide bonding
Example of denaturing agents
Temperature, pH Extremes, Detergents, and Reducing Agents, specific compounds (ex. Urea)
Effect on proteins by high temperatures
Disrupt the non-primary interactions that hold a folded protein together
Effect of proteins by low temperatures
Can decrease protein activity or enzyme activity
Most human proteins are designed to optimally function at what temperature
Around body temp: 37.6 C or 98.6 F
pH extremes effect on proteins
Can disrupt charge-based interactions in tertiary and quaternary structure such as salt bridges
These denaturing agents are part-polar, part-nonpolar. It can disrupt hydrophobic interactions- largely stripping the protein of its higher-level protein folding
Detergents
Give a well known detergent used in a lab technique.
SDS (sodium dodecyl sulfate) used in SDS PAGE
T or F. Denaturation of proteins are reversible
False. Some are reversible (denaturing agent: urea) some are irreversible (denaturing agent: heat)
These break apart protein primary structure by catalyzing the hydrolysis of peptide bonds
Proteases
These denaturing agents disrupt covalent bonds between sulfur atoms (disulfide bonds)
Reducing agent
*remember that disulfide bonds are formed via oxygenation and therefore is broken via reduction
These proteases use the hydroxyl group of a serine residue to catalyze protein cleavage. Give an example
Serine proteases
Ex. Digestive enzyme trypsin
Trypsin cleave at what terminal
C
Aminopeptidases cleave from what terminal?
N-terminal
Carboxypeptidases cleave at which terminal
C terminal
