Chapter 5 - Key Concepts & Review Points Flashcards
In theory, the size and composition of a polypeptide chain are ____________.
unlimited
In cells, the potential polypeptide variety is limited by the efficiency of _____________ and by the ability of the polypeptide to fold into a ____________.
protein synthesis
functional structure
Environmental conditions such as ______ and _____________ affect a protein’s stability during purification.
pH
temperature
A(n) __________ based on a protein’s chemical or binding properties may be used to quantify a protein during purification.
assay
____________ procedures take advantage of a protein’s unique structure and chemistry in order to separate it from other molecules.
fractionation
____________ the salt concentration causes selective “salting out” (precipitation) of proteins with different solubilities.
increasing
A protein’s ionic charge, polarity, size, and ligand-binding ability influence its ____________ behavior.
chromatographic
The overall size and shape of macromolecules and larger assemblies can be assessed through ____________.
ultracentrifugation
To be sequenced, a protein must be separated into individual ____________ that can be cleaved into sets of overlapping ____________.
polypeptides
fragements
The amino acid sequence can be determined by ____________, a procedure for removing N-terminal residues one at a time.
Edman degradation
Mass spectrometry can identify amino acid sequences from the __________________ of gas-phase protein fragments.
mass-to-charge ratio
Protein sequence data are deposited in ____________.
online databases
Sequence comparisons reveal the ________________ between proteins.
evolutionary relationships
Protein families evolve by the ___________ and ____________ of genes encoding protein domains.
duplication
divergence
The rate of evolution ________ from protein to protein.
varies
The properties of proteins depend largely on the ________ and ____________ of their polypeptides.
sizes
sequences
Protein purification requires controlled conditions such as ________ and ____________, and a means to quantify the protein (a(n) ________).
pH
temperature
assay
Fractionation procedures are used to purify proteins on the basis of:
- ____________
- ____________
- ____________
- ____________
- ____________
solubility charge polarity size binding affinity
Difference in ____________ permit proteins to be concentrated and purified by salting out.
solubility
Chromatography, the separation of soluble substances by their rate of movement through an insoluble matrix, is a technique for purifying molecules by ____________, _____________, and ____________. Binding and elution often depend on the salt concentration and pH.
charge (ion exchange chromatography) hydrophobicity (hydrophobic interaction chromatography) binding specificity (affinity chromatography)
Electrophoresis separates molecules by ________ and ________; SDS-PAGE separates them primarily by ________. 2D electrophoresis can resolve thousands of proteins.
charge
size
size
A macromolecule’s rate of sedimentation in an ultracentrifuge is related to its ________.
mass
Analysis of a protein’s sequence begins with ____________, to determine the number of difference subunits, and the cleavage of ____________.
end group analysis
disulfide
Polypeptides are cleaved into fragments suitable for sequencing by ____________, in which residues are removed, one at a time, from the N-terminus. Peptides can also be sequence by ____________.
Edman degradation
mass spectrometry
A protein’s sequence is reconstructed from the sequences of ____________ and from information about the location of ____________. The sequences of numerous proteins are archived in publicly available databases.
overlapping peptide fragments
disulfide bonds
Proteins evolve through changes in ____________. Protein sequences can be compared to construct ____________ and to identify essential amino acid residues.
primary sequence
phylogenetic trees
New proteins arise as a result of the ____________ of genes or gene segments specifying protein domains, followed by their divergence.
duplication
