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FDSC251 > protein 2 > Flashcards

protein 2 Flashcards

1
Q

What is the name of the proteins that are made of only amino acids

A

simple proteins

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2
Q

Complete : albumins are soluble in _____

A

neutral distilled water

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3
Q

Complete : globulins are soluble in _____ and insoluble in ____

A

neutral dilute salt water

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4
Q

Glutelins are proteins that are soluble in _____ but not in _____

A

acid or base insoluble in neutral solutions

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5
Q

prolamines are proteins that are soluble in ____ and insoluble in _____

A

50-90% ethanol water

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6
Q

histones are proteins that are soluble in ____ and precipitated by ______

A

soluble in water precipitated by ammonia

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7
Q

What are the proteins that are the most interest from the food science perspective

A

albumins and globulins

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8
Q

What are the two major amino acids compose the histones

A

arginine and lysine

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9
Q

Scleroproteins are proteins that are insoluble in _____ and in _____ and resistant to ____

A

water and neutral salts resistant to enzymatic hydrolysis

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10
Q

What are conjugated proteins?

A

proteins that contain a non-amino acid part (prostetic group)

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11
Q

What are the 4 classes of conjugated proteins seen in class

A
  1. metalloproteins ** 2. phosphoproteins 3. glycoproteins 4. lipoproteins
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12
Q

What is a prosthetic group?

A

group attached to a protein that is not an amino acid.

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13
Q

In the case of glycoproteins. what is the amino acid that the sugar will be attached ti if it forms a o-glycosidic bond

A

serine, tyrosine (but aromatic doesn’t favor tyrosine) threonine

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14
Q

T or F : lipoproteins can make great emulsifiers

A

true, because they are often attached to phospholipids

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15
Q

In the case of glycoproteins. what is the amino acid that the sugar will be attached ti if it forms a n-glycosidic bond

A

asparagine

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16
Q

What are the two amino acid that can link the phosphate for the phosphoproteins

A

OH group of serine and threonine

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17
Q

T or F : the more the protein are susceptible to their environment and the more they can be complex

A

true

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18
Q

T or F : proteins are more sensitive to their environment than lipids and carbohydrates

A

true

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19
Q

What is the definition of denaturation

A

change in the structure or the conformation of a protein because of the distruction of the forces between a.a. Does not involve breaking the peptide bond

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20
Q

What are the interactions that denaturation disrupt?

A
  1. hydrogen bonds 2. electrostatic bonds 3. hydrophobic bonds 4. van der waals 5. covalent bonds (only the S-S not the peptidic)
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21
Q

what are the variables of the sensitivity to denaturation?

A
  1. chain length 2. amino acid composition 3. complexity of structure 4. prosthetic groups 5. environmental conditions
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22
Q

T or F : denaturation can be reversible if it the bonds didn’t destroy in the 2˚ structure

A

true

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23
Q

When the conformation of a protein is changed, many of its _____ properties are also changed

A

physical

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24
Q

(2) Denaturation of protein generally results in a reduction in its _____

A

solubility

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25
Q

Why do we digest food more easily when we cook it?

A

because we make the peptides bonds more accessible by the denaturation

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26
Q

What is the most important factor contributing to denaturation

A

heat

27
Q

why does caseins don’t denature easily

A

because they have little to no secondary structure.

28
Q

What are the factors that can lead to denaturation

A
  1. changes in pH 2. changes in ionic strength (hydrogen bond breakers) 3. chemical agents (ethanol/acetone, urea) 4. Detergents 5. organic solvents 6. surface forces 7. combination of the above
29
Q

Proteins with significant quantities of _____(3 amino acid) are especially susceptible to changes in pH

A

aspartic acid, glutamic acid and lysine

30
Q

Why does urea can denature proteins?

A

because the NH2 compete with the peptide linkage for hydrogen bonds that can readuly disrupt the 3˚ and 2˚ structures.

31
Q

how does acetone and alcohol works to disrupt the h-bonds in a protein

A

partial dehydration of the protein.

32
Q

T or F : casein can be denatured by heat

A

false

33
Q

How can you take all the protein out of solution of milk?

A

with boiling (whey proteins) and acid (casein)

34
Q

Which one is the more severe in the structure modification : urea or acteone/alcohol

A

urea

35
Q

How does detergents work in denaturing proteins

A

they have both hydrophilic and hydrophobic parts so they open the structure of the protein.

36
Q

Complete : SDS is a ____ and results in the opening of the structure of the protein

A

detergents

37
Q

How does organic solvent works to denature proteins?

A

they turn the environment hydrophobic so the protein’s hydrophobic region can be exposed

38
Q

T or F : in a organic solvent, lipase can add FFA to glycerol

A

True in some cases

39
Q

How does surface force denature proteins?

A

air bubbles are incorporated into the proteins. The hydrophobic part is is facing the air and this change in arrangement cause denaturation. (foaming)

40
Q

What are the protein reactions seen in class

A
  1. non-enzymatic browning 2. cross-linking 3. formation of lysinoalanine 4.racemization of a.a
41
Q

What is the definition of hygroscopic

A

substance tending to absorb moisture from the air.

42
Q

Which amino acids participate in non-enzymatic browning ?

A

the major one is lysine. Other that can react at high temperature are arginine, glutamine, asparagine, histidine and tryptophan.

43
Q

Complete : maillard reaction involves the reaction of an _____ of a ______ and a free ____of an amino acid or the free amino group on a peptide or protein

A

aldehyde (R-CH=O) group
reducing sugar
amino group

44
Q

The first product of the maillard reaction is a :

A

glycosylamine and water

45
Q

The second product of the maillard reaction is :

A

amadori compound

46
Q

What is the problem with the maillard reaction

A

‘Bound’ lysine causes steric hindrance that limits enzymatic digestion of the protein. The enzyme will not hydrolyse the peptide linkage between the lysine and other neighboor a.a. and you’ll be left with a-L-a that won’t be digested

47
Q

Roasted cereals would make the PER ___ (decrease or increase)

A

PER is the weight gain by wt protein consumed. Since lysine is not present, the PER will decrease because less weight gain

48
Q

What explains the brown color in the maillard reactions

A

the formation of melanoidin

49
Q

What is cross-linking?

A

amide bonds forming between the NH2 and and COOH of SIDE CHAINS of amino acids

50
Q

What are the two carboxylic amino acids that can participitate in cross-linking reactions

A

aspartic acid and glutamic acid

51
Q

What is the indigestible product of the cross-linking and of the maillard reaction ?

A

cross-linking : hexapeptide (X1-X2-X3
l
X4-X5-X6)
maillard : tripeptide (A-L-A)

52
Q

In the formation of lysinoalanine, what are the starting amino acids?

A

Cystine and lysine

53
Q

The formation of lysinoalanine occurs under alkaline or acidic conditions?

A

alkaline conditions (OH deprotonate the H from the cystine).

54
Q

What are the conditions to have a racemization?

A

alkaline conditions

55
Q

What are the degradative reactions of proteins?

A
  1. proteolysis (break in the peptidic linkage)
  2. putrefaction (deaminase and decarboxylase)
56
Q

At lower pHs, the ______ are the most active, while at higher pHs the ______ are the most active.

A

decarboxylase
deaminases

57
Q

Why does the putrefaction release odors?

A

because the decarboxylation and deamination lowers the molecular weight of the proteins and can make them volatile

58
Q

Complete : cadaverine and putrescine are by-product of ______

A

putrefaction (decarboxylation)

59
Q

What is the reaction by wich there is a fishy smell produced in old fish

A

The enzyme trimethylamine-N-oxide reductase is produced by enzymes

60
Q

What can you add in bread to make it more moist?

A

milk proteins

61
Q

What are the three water form?

A
  1. bound water
  2. hydrate water
  3. free water
62
Q

T or F : freezing can cause denaturation

A

true because of the salt being concentrated.

63
Q
A
64
Q
A

FDSC251 (22 decks)

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