Proteins Flashcards
What is the primary structure?
Amino acid sequence
What is the secondary structure?
α helixes, beta sheets, beta turns
What is the tertiary structure?
3D shape
What is the quaternary structure?
Protein forms complexes with other proteins
What are proteins made up of?
Polypeptide chains
What are the 6 functions of proteins?
Enzymes Signalling Transport Antibodies Structural Transcription factors
What do enzymes do?
catalyse chemical reactions
What is signalling?
Required for information processing within cells
What is a proteins function determined by?
It’s structure
Explain the example of the Ras protein?
It is a signalling enzyme called GTPase
It converts GTP (on) to GDP (off)
The active site of GTPase binds to GTP and Mg2+
Which techniques can you use for protein purification?
- Ultracentrifugation
- Gel filtration chromatography
- Ion-exchange chromatography
- Affinity chromatography
- Gel electrophoresis
What is ultracentrifuation?
Seperates biological macromolecules based on their relative buoyancy by spinning them at high speeds
What are proteins separated by in gel filtration chromatography?
Seperated on the basis of their size
How does gel-filtration chromatography work?
The protein mixture is run through a column contatining beads of a hydrophilic polymer
Large proteins do not enter the pores in the beads and so pass through quickly
Smaller proteins pass through the beads and so run much more slowly
What are proteins separated by in affinity chromatography?
Separated on the basis of a specific interaction with another molecule bound to a column of beads
How does affinity chromatography work?
Proteins that interact stick to the beads, others do not and are washed off.
Purified protein is then released from the column
What are proteins separated by in ion exchange chromatography?
Separated on the basis of their net charge by exchange chromatography
How does ion exchange chromatography work?
Proteins with a net positive charge bind to a column of beads containing carboxylate groups (negatively charged proteins do not)
In ion exchange chromatography, what are the proteins eluted with?
Increasing concentrations of sodium chloride solution
In ion exchange chromatography, which proteins elute first?
Least charge elute first
In ion exchange chromatography, which proteins elute last?
Highly charged proteins
What is electrophoresis?
Charged molecules moving in an electric field
What does the velocity of migration depend on?
Field strength
Net charge on the protein
Radius of the sphere
Viscosity of the medium
What medium is used in gel electrophoresis?
PolyAcrylamide Gel
What can gel electrophoresis be used to separate?
DNA
RNA
Proteins
Which proteins are the slowest in gel electrophoresis?
Larger proteins
