day 1 Flashcards
Some proteins can switch between two or more conformations. The switch often involves :
noncovalent binding of another molecule
weak bonds
noncovalent bonds
Types of noncovalent interactions
ionic, polar, LDF’s, hydrophobic exclusions
of amino acids essential for humans
9
polypeptide chain: Formation of peptide bond by energy-requiring ___ rxn
condensation
Hydrogen bonding is not involved in forming which level of protein structure?
primary
Proper folding of a newly synthesized protein is accomplished by:
the hydrophobic effect
electrostatic attractions and repulsions
Van der Waals attraction
help from chaperone proteins
Functioning proteins change between conformations when
a small molecule binds noncovalently
combustion: exer or endergonic?
exergonic
which things contribute to a proteins function?
shape
order of amino acids in primary sequence
positioning of R groups
secondary struture
The R group of which amino acid would form a covalent bond with another R group?
cysteine
Which of the following defines the polypeptide backbone?
anything that’s not an R group
how would you calculate an isoelectric point and what does it mean
- take the average of the pKa’s of its various forms
- its the point at which it stops migrating in an electric field which is equal to its average pH
aspartic acid vs serine; which is more water solube and why?
aspartic acid. COO- >> OH. ionic wins
Enzymes differ from chemical catalysts because they lose activity at high temperature or extremes of pH. This difference can be explained by
the loss of the 3-D shape of the enzyme
the loss of the shape of the active site
the loss of noncovalent interactions
the loss of ionic bonds
name an amino acid with an R group capable of hydrogen bonding
serine, threonine, tyrosine
If a crystal of NaCl is dropped into a beaker of polar solvent such as methanol, how would the electrostatic attraction of Na+ for Cl- in the salt bridge change?
The electrostatic attraction is weaker
DNA Polymerase is the enzyme involved in
Replication
are hydrophobic exclusions a true type of bond? where do they exist and what do they mainly depend on? give an example
- Not a true bond. Only exists in water
- Depends on entropy more than any binding
- Benzene: nonpolar molecule.
If you put benzene in water, benzene clusters together
T/F: membrane formation is powered by the hydrophobic effect
T
entropy of protein folding
disorder -> order
name some hydrophobic R groups
hydrophobic R groups: alanine, leucine, isoleucine
ways to denature a protein
Since proteins are held together with these weak forces, they can be unfolded fairly easily.
- Heat up to 50 degrees celcius,
- Detergent also denatures protein. (amphipathic molecule- highly polar salt bridge on one side, long hydrophobic tail on other side. Surrounds molecule- unfolds the molecule)
- Urea: has a lot of polar properties (2 dipoles) .
- Changing the pH of the system. Changes the molecules ability to ionize- titrates amino acids- lowering pH means adding H+ to the system. Swamping your negative R groups with positively charged hydrogen.
T/F: protein folding occurs via hydrogen bonding between backbone atoms and weak interactions of the R groups
True
