Unit 4- Analytical Techniques

Question 1

Define isoelectric point.

Answer 1

pH at which the amino acid has a net charge of zero (aka as a zwitterion).

Question 2

Describe three features of the structure of DNA that X- ray crystallography helped Rosalind Franklin identify.

Answer 2

Any of: DNA forms a double helix, DNA is double stranded, Twists very 3.4 nm, 10 basepairs/twist. phosphate grps on the outside of double helix

Question 3

Gel electrophoresis separates proteins on the basis of what two factors?

Answer 3

Size and charge

Question 4

A hexagon shape present in X-ray crystallography indicates?

Answer 4

Benzene ring

Question 5

Identify two factors that affect the overall charge on a protein

Answer 5

The type of amino acids in the polypeptide chain and the pH of the chemical environment

Question 6

In chromatography, what is the mobile phase?

Answer 6

A liquid or gas that carries the sample molecules along the column or TLC plate

Question 7

In chromatography, what is the stationary phase?

Answer 7

Solid particles to which the sample molecules adsorb

Question 8

In mass spectroscopy, what does the M+1 peak indicate?

Answer 8

The presence of carbon 13 isotopes.

Question 9

In mass spectroscopy, what does the M+2 peak indicate?

Answer 9

The presence of a halogen.

Question 10

In mass spectroscopy, what does the M peak indicate?

Answer 10

Molecular mass of the molecular ion.

Question 11

The key information gained from IR spectroscopy is?

Answer 11

Functional groups present

Question 12

Name the two types of stretching vibration modes in IR spectroscopy

Answer 12

Symmetric and antisymmetric stretching

Question 13

True or false? A cationic exchange column has a negatively charged stationary phase (solid support)

Answer 13

TRUE

Question 14

True or False? All bond types, polar and non-polar, will give
rise to a band in an IR

Answer 14

FALSE. IR active bonds must be polar

Question 15

True or FALSE? A substance to be
separated by TLC that is strongly attracted to the stationary phase will travel more slowely than a substance that is not strongly attracted.

Answer 15

TRUE

Question 16

True or False? Electron density maps can not be created from X-ray diffraction patterns.

Answer 16

FALSE

Question 17

True or False? Strongly polar bonds produce weak bands in an IR spectrum

Answer 17

FALSE

Question 18

TRUE or FALSE? The longer the protein sample is in the chromatography column the higher the retention time.

Answer 18

TRUE

Question 19

True or False? The strength with which proteins bind to the solid support in a cationic exchange column is determined by the relative degree of negative surface charge on each different protein.

Answer 19

TRUE

Question 20

True or False? Weakly polar bonds produce weak bands in an IR spectrum.

Answer 20

TRUE

Question 21

What does a peak at 15m/z in mass spectroscopy indicate?

Answer 21

Methyl fragment CH3+

Question 22

What does a peak at 29 m/z in mass spectroscopy indicate?

Answer 22

Ethyl fragment CH3CH2+ or aldehyde CHO+

Question 23

What is the amino acid charge if the pH<pI?

Answer 23

Negative

Question 24

What is the amino acid charge if the pH>pI

Answer 24

Positive

Question 25

Where is the fingerprint region of an IR spectrum located?

Answer 25

From around 1500 -1600 cm