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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
Why do we digest food more easily when we cook it?
because we make the peptides bonds more accessible by the denaturation
26
What is the most important factor contributing to denaturation
heat
27
why does caseins don't denature easily
because they have little to no secondary structure.
28
What are the factors that can lead to denaturation
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
Proteins with significant quantities of \_\_\_\_\_(3 amino acid) are especially susceptible to changes in pH
aspartic acid, glutamic acid and lysine
30
Why does urea can denature proteins?
because the NH2 compete with the peptide linkage for hydrogen bonds that can readuly disrupt the 3˚ and 2˚ structures.
31
how does acetone and alcohol works to disrupt the h-bonds in a protein
partial dehydration of the protein.
32
T or F : casein can be denatured by heat
false
33
How can you take all the protein out of solution of milk?
with boiling (whey proteins) and acid (casein)
34
Which one is the more severe in the structure modification : urea or acteone/alcohol
urea
35
How does detergents work in denaturing proteins
they have both hydrophilic and hydrophobic parts so they open the structure of the protein.
36
Complete : SDS is a ____ and results in the opening of the structure of the protein
detergents
37
How does organic solvent works to denature proteins?
they turn the environment hydrophobic so the protein's hydrophobic region can be exposed
38
T or F : in a organic solvent, lipase can add FFA to glycerol
True in some cases
39
How does surface force denature proteins?
air bubbles are incorporated into the proteins. The hydrophobic part is is facing the air and this change in arrangement cause denaturation. (foaming)
40
What are the protein reactions seen in class
1. non-enzymatic browning 2. cross-linking 3. formation of lysinoalanine 4.racemization of a.a
41
What is the definition of hygroscopic
substance tending to absorb moisture from the air.
42
Which amino acids participate in non-enzymatic browning ?
the major one is lysine. Other that can react at high temperature are arginine, glutamine, asparagine, histidine and tryptophan.
43
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
aldehyde (R-CH=O) group reducing sugar amino group
44
The first product of the maillard reaction is a :
glycosylamine and water
45
The second product of the maillard reaction is :
amadori compound
46
What is the problem with the maillard reaction
'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
Roasted cereals would make the PER ___ (decrease or increase)
PER is the weight gain by wt protein consumed. Since lysine is not present, the PER will decrease because less weight gain
48
What explains the brown color in the maillard reactions
the formation of melanoidin
49
What is cross-linking?
amide bonds forming between the NH2 and and COOH of SIDE CHAINS of amino acids
50
What are the two carboxylic amino acids that can participitate in cross-linking reactions
aspartic acid and glutamic acid
51
What is the indigestible product of the cross-linking and of the maillard reaction ?
cross-linking : hexapeptide (X1-X2-X3 l X4-X5-X6) maillard : tripeptide (A-L-A)
52
In the formation of lysinoalanine, what are the starting amino acids?
Cystine and lysine
53
The formation of lysinoalanine occurs under alkaline or acidic conditions?
alkaline conditions (OH deprotonate the H from the cystine).
54
What are the conditions to have a racemization?
alkaline conditions
55
What are the degradative reactions of proteins?
1. proteolysis (break in the peptidic linkage) 2. putrefaction (deaminase and decarboxylase)
56
At lower pHs, the ______ are the most active, while at higher pHs the ______ are the most active.
decarboxylase deaminases
57
Why does the putrefaction release odors?
because the decarboxylation and deamination lowers the molecular weight of the proteins and can make them volatile
58
Complete : cadaverine and putrescine are by-product of \_\_\_\_\_\_
putrefaction (decarboxylation)
59
What is the reaction by wich there is a fishy smell produced in old fish
The enzyme trimethylamine-N-oxide reductase is produced by enzymes
60
What can you add in bread to make it more moist?
milk proteins
61
What are the three water form?
1. bound water 2. hydrate water 3. free water
62
T or F : freezing can cause denaturation
true because of the salt being concentrated.
63
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FDSC251 (22 decks)

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