protein 3

Question 1

Proteins in wheat flour are extracted using H2O, NaCl and
ethanol as solvent. What is the mode of action of these
solvents?

Answer 1

• H2O: protein with a polar surface are extracted
• NaCl: salting in –> at low ionic strength ions increase the
  solvation of charged groups at the protein surface
• Ethanol: organic solvent –> more apolar solvent, increased
  solubility of hydophobic groups

Question 2

how do globular proteins occur?

Answer 2

as soluable, monomeric or multimeric proteins
combination of alpha&beta- sheet

Question 3

what are fibrous proteins?

Answer 3

muscle protein –> are tipically associated into larges complexes

Question 4

what are random coil protein

Answer 4

these are neither globular or fibrillar
and do not have a fixed secondairy or tertiary structure

Question 5

what does the solubility of protein influence?

Answer 5

• appearance
• teture
• digestibility
• foam/ emulsion properties

Question 6

what happens to the solubility if you add salt ions around the pI?

Answer 6

normally the proteins wil aggregate; so not solubule

but by adding salt, they neutralize; increased solubility

Question 7

what are chemical reactions that can happend?

Answer 7

• hydrolysis of peptide bonds
• formation of lysino-alanyl derivatives
• formation or reshuffling of S-S bridges
• deamidation of decarboxylation
• maillard reaction

Question 8

what is the sweetening power of aspartame?

Answer 8

• 180 times that of sucrose

Question 9

peptides are often bitter; what is the rule of thumb:

Answer 9

1. Amino acids in a peptide are more bitter than free amino acids
2. Non-terminal amino acids are more bitter than terminal amino acids
3. A peptide is bitter when the average hydrophobicity >1400 Cal/mole
4. Peptides > 6000 Da are not bitte

Question 10

what is the advantage and disadvantage of total N content of protein?

Answer 10

• fast
• also insoluble materials
• measures all nitrogen, also non protein

Question 11

that is the advantage and disadvantage of spectrophotometric?

Answer 11

• fast
• cheap
• only for soluble protein
• influenced by other compounds

Question 12

how does SDS work?

Answer 12

1. Unfolding of protein and dissociate
   complexes
2. Separation of proteins on a gel under
   influence of an electric field
3. Separation distance on gel relates with
   molecular weight
4. Calculate molecular weight by
   comparison with marker (contains
   protein of known Mw)

Question 13

what is strecker degration ?

Answer 13

• Combination of decarboxylation and deamination
• Removal of alpha-carboxylic acid and alpha-amino group:
  Results in:
• Formation of aldehydes (aroma compounds)

Question 14

In big apolar group is L or D bitter or sweet?

Answer 14

L: bitter; D: sweet

Question 15

in polar/ small apolar group is L or D bitter or sweet?

Answer 15

L: sweet natural, D: neutral