Proteins

Question 1

What is the primary structure?

Answer 1

Amino acid sequence

Question 2

What is the secondary structure?

Answer 2

α helixes, beta sheets, beta turns

Question 3

What is the tertiary structure?

Answer 3

3D shape

Question 4

What is the quaternary structure?

Answer 4

Protein forms complexes with other proteins

Question 5

What are proteins made up of?

Answer 5

Polypeptide chains

Question 6

What are the 6 functions of proteins?

Answer 6

Enzymes 
Signalling 
Transport 
Antibodies 
Structural 
Transcription factors

Question 7

What do enzymes do?

Answer 7

catalyse chemical reactions

Question 8

What is signalling?

Answer 8

Required for information processing within cells

Question 9

What is a proteins function determined by?

Answer 9

It’s structure

Question 10

Explain the example of the Ras protein?

Answer 10

It is a signalling enzyme called GTPase
It converts GTP (on) to GDP (off)
The active site of GTPase binds to GTP and Mg2+

Question 11

Which techniques can you use for protein purification?

Answer 11

• Ultracentrifugation
• Gel filtration chromatography
• Ion-exchange chromatography
• Affinity chromatography
• Gel electrophoresis

Question 12

What is ultracentrifuation?

Answer 12

Seperates biological macromolecules based on their relative buoyancy by spinning them at high speeds

Question 13

What are proteins separated by in gel filtration chromatography?

Answer 13

Seperated on the basis of their size

Question 14

How does gel-filtration chromatography work?

Answer 14

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

Question 15

What are proteins separated by in affinity chromatography?

Answer 15

Separated on the basis of a specific interaction with another molecule bound to a column of beads

Question 16

How does affinity chromatography work?

Answer 16

Proteins that interact stick to the beads, others do not and are washed off.
Purified protein is then released from the column

Question 17

What are proteins separated by in ion exchange chromatography?

Answer 17

Separated on the basis of their net charge by exchange chromatography

Question 18

How does ion exchange chromatography work?

Answer 18

Proteins with a net positive charge bind to a column of beads containing carboxylate groups (negatively charged proteins do not)

Question 19

In ion exchange chromatography, what are the proteins eluted with?

Answer 19

Increasing concentrations of sodium chloride solution

Question 20

In ion exchange chromatography, which proteins elute first?

Answer 20

Least charge elute first

Question 21

In ion exchange chromatography, which proteins elute last?

Answer 21

Highly charged proteins

Question 22

What is electrophoresis?

Answer 22

Charged molecules moving in an electric field

Question 23

What does the velocity of migration depend on?

Answer 23

Field strength
Net charge on the protein
Radius of the sphere
Viscosity of the medium

Question 24

What medium is used in gel electrophoresis?

Answer 24

PolyAcrylamide Gel

Question 25

What can gel electrophoresis be used to separate?

Answer 25

DNA
RNA
Proteins

Question 26

Which proteins are the slowest in gel electrophoresis?

Answer 26

Larger proteins