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FDSC251 > Proteins > Flashcards

Proteins Flashcards

1
Q

What are the various nutritional roles of proteins?

A
  1. provide amino acids 2. give nitrogen 3. give energy (debatable)
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2
Q

Complete : nutritionist approach proteins for their ___ while food scientist approach protein for their ___

A
  1. nutritional value 2. functionality
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3
Q

What is a protein functionality?

A

the function or property the protein give in a food product.

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4
Q

What is one function of the protease in food processing

A

tenderize meat

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5
Q

What is one function of the lipases in food processing

A

flavor development in cheeses

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6
Q

What is one function of the amylases in food processing

A

to manufacture corn syrup/sugars

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7
Q

What is one function of the glucose oxidase in food processing

A

to remove the head space oxygen from food packages.

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8
Q

What is the amino acid you loose when roasting cereals?

A

lysine

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9
Q

What is surimi?

A

crab meat analog made from pollock

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10
Q

T or F : Only compounds that have an amino (NH2) and a carboxylic acid (COOH) group attached to the same carbon (the alpha-carbon) are considered to be amino acids.

A

T

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11
Q

complete : at low pH, the amino acid is ____

A

protonated (COOH/NH3)

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12
Q

Complete : since amino acid have both a base and an acid they are ___

A

ampholytes or amphoteric

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13
Q

T or F : structure at the isoelectric point is neutral

A

false, it is a zwitterion but it is not neutral.

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14
Q

What is the form of the amino acid glycine at neutral pH

A
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15
Q

What is the form of the aa glycine at low pH ?

A
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16
Q

What is the form of the aa glycine at high pH ?

A
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17
Q

Can a zwitterion be neutral?

A

Zwitterions are simultaneously electrically charged and electrically neutral.

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18
Q

What are the three physical properties of amino acids at the pI

A
  1. decompose at high temperatures
  2. soluble in water
  3. have a crystalline structure
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19
Q

What is the only amino acid that doesn’t have a asymetric carbon?

A

Glycin (2H)

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20
Q

What are optical isomers?

A

mirror images of a compound. They are not superimposable (cannot be flipped over to superimpose unpon one another.

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21
Q

Complete : since the alpha carbon is asymetric, the a.a. show _____ and rotate ____

A

optical isomerism
plane-polizired light in opposite directions

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22
Q

What is the reference compound that was determined to give the configurations D and L?

A

Glyceraldehyde.

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23
Q

The glyceraldehyde is L, when the OH is on the ____, the aldehyde is on the ____ and the alcohol is on the ___

A

OH on the left
aldehyde on the top
alcohol on the bottom

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24
Q

In L amino acid, the ___ is on the left, the ___ is on the top, and the ___ is on the bottom

A

NH3 on the left
Carboxylic on the top
R group on the bottom

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25
Q

What enamtiomer is this glyceraldehyde?

A

L

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26
Q

Which enamtiomer of amino acid is this?

A

L-amino acid

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27
Q

which enamtiomer of amino is this?

A

L

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28
Q

T or F : all proteins are synthesized from the D amino acids

A

false, in the L form

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29
Q

What amino acid supplement should you buy (assume same price), synthetic or the ones from protein hydrolysis

A

The one from protein hydrolysis because if you take synthetic 50% of the amino would be in the D-form (unusable). (racemic mixture)

30
Q

What is a racemic mixture?

A

In chemistry, a racemic mixture, or racemate (/reɪˈsiːmeɪt, rə-, ˈræsɪmeɪt/), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule.

31
Q

What are the 7 categories of amino acids?

A

(1) Amino acids that have aliphatic side chains
(2) Amino acids that have hydroxylic side chains
(3) Amino acids that have carboxylic side chains
(4) Amino acids that have basic side chains
(5) Amino acids that have aromatic side chains
(6) Sulfur-containing amino acids
(7) Imino acids

32
Q

What are the three amino acids with OH groups

A
  1. serine
  2. threonine
  3. tyrosine
33
Q

What are diester linkages?

A

linkage with one phosphate group in between two hydroxyl amino acids (either serine threonine or tyrosine). These bonds play a role in the 3D structure of proteins and make them less susceptible to denaturation.

34
Q

Why are casein stable to heat?

A

because of the presence of diester linkages.

35
Q

Which are the three amino acids that can be glycolysated or phosphorylated?

A

the ones with an OH group (hydroxyl group). Threonine, tyrosine and serine

36
Q

What is the linkage between a sugar and a serine ?

A

o-glycosidic linkage

37
Q

Complete : proteins that contains significant amounts of aspartate and glutamate will have a ____ isoelectric point

A

low

38
Q

T or F: At pH 7 and above, most of these free carboxyl groups would be negatively charged - affects protein conformation as a function of pH.

A

under certain conditions, when the amino acids are burried inside the proteins, the proteins structure can sheild the COOH from ionization.

39
Q

what are the two amino acids from which an NH2 can be added to form two new amino acids

A

glutamatic acid —> glutamine
asparatic acid –> asparagine

40
Q

What are the amino acids that can participate in the non-enzymatic browning?

A

all the amino acids with a amine in their side chain. (lysine, glutamine, asparagine, histidine, arginine)

41
Q

What are the two conditions that can cause the asparagine or glutamine to be hydrolyse into aspartic or glutamic acids

A

heat and acidic contions.

42
Q

What is the reaction by which the asparagine become aspartic acid?

A
43
Q

What is the reaction by which the glutamine become glutamate?

A
44
Q

Which one is more polar : positive polar amino acids or negative polar amino acids

A

the positive (amide groups) are more water solulble

45
Q

What is the link between the sugars and the amide bonds in the maillard reactions

A

N-glycosidic bonds

46
Q

Which group of amino acids have has higher pka value?

A

the amino groups.

47
Q

What is the name of the very basic group on the amino acid arginine

A

guanidino group

48
Q

what is the name of the group in the histidine

A

imidazole

49
Q

What is the name of the group that is particular in proline and hydroproline

A

imino.

50
Q

What is the function of the proline and hydroxyproline (imino amino acids)

A

interrrupt the natural tendency of the alpha helix.

51
Q

What are the two reactions responsible for the odors in putrefaction?

A

deamination and decarboxylation of free amino acids

52
Q

T or F : the peptide bond can happen naturally

A

false, needs enzymes

53
Q

what is the convention to write the chain of proteins

A

n on the left and c on the right

54
Q

T or F : the peptide bond can rotate

A

false.

55
Q

What is the reason of the secondary structure?

A

the peptide bond can’t rotate (charality) and creates an angle of 6˚ and causes stearic hindrance

56
Q

Where are the hydrogen bonds in the a-helix

A

between the nitrogen of one amino acid and the carboxylic of 4th amino acids after

57
Q

Complete : The helical structure is stabilized by _______ due to the repetitive proximity of the peptide carbonyl oxygen (electron-rich) and the hydrogen from the peptide nitrogen four residues away.

A

hydrogen bonding

58
Q

What is the sequence that is responsible for the helical structure of the amino acid chain

A

P-N-P-P-N-N-P-

59
Q

What are the two amino acid that doesn’t participitate in the helical structure

A

proline and hydroxyproline

60
Q

What is the sequence of the ß-sheets

A

-N-P-N-P-N- (alterning polar and non-polar amino acids)

61
Q

How many amino acids is there in the ß-strands?

A

5-15 amino acids

62
Q

What are the three secondary structures configurations

A
  1. alpha-helix
  2. ß-sheets
  3. suprahelix
63
Q

What is the difference in configuration of the anti-parallale and parallel beta-sheets ?

A

in the parralel ß-sheets, the R groups are pointing in the same direction.

64
Q

What are the three amino acids that are in the suprahelix 2˚ structure

A

proline, hydroxyproline and glycine.

65
Q

complete : structures that alternate the polar and non polar amino acids have the propensity to form ____

A

ß-sheets

66
Q

What bonds are responsible for the secondary structre

A

hydrogen bonding

67
Q

what bonds are responsible for the tertiary structure

A
  1. electrostatic bonds (ionic bonds between the r chains that are positive and negative)
  2. hydrogen bonds
  3. disufide bonds (covalent)
    4 hydrophobic interactions and van der waals interactions
68
Q

What is the amino acid responsible for the disulfide linkages?

A

cystein

69
Q

T or F : the tertiary structure give the enzyme its functionality

A

true

70
Q

T or F : the 4˚ contains S-S bonds

A

false

71
Q

What are the bonds/forces in the 4˚ structure

A
  1. electrostatic bonds (ionic bonds between the r chains that are positive and negative)
  2. hydrogen bonds
  3. hydrophobic interactions
  4. van der waals
72
Q
A

FDSC251 (22 decks)

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