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Lab > Analysis and Denaturation of Proteins > Flashcards

Analysis and Denaturation of Proteins Flashcards

1
Q

function as biological catalysts or enzymes, transporter of oxygen and hormone

A

proteins

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2
Q

repeating unit of protein

A

amino acid

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3
Q

4 levels of protein structure

A
  1. Primary structure
  2. Secondary structure
  3. Tertiary structure
  4. Quaternary structure
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4
Q

composed of single covalently bonded amino acid

A

primary structure

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5
Q

two types of secondary structure

A

alpha helix structure
beta-sheet structure

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6
Q

contains one strand of amino acid chain that is bonded by intramolecular hydrogen bond

A

alpha helix structure

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7
Q

two chains that are linked by hydrogen bonds

A

beta-sheet structure

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8
Q

combination of pure helix or pure beta, or a combination of both

A

tertiary structure

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9
Q

stabilizing interactions in tertiary level

A
  1. salt linkages
  2. hydrophobic interactions
  3. disulfide linkages
  4. hydrogen bonds
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10
Q

interaction of two or more folded polypeptides

A

quaternary structure

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11
Q

is the unfolding of complex secondary, tertiary, and quaternary structure of protein

A

denaturation

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12
Q

what can denature proteins?

A
  1. heat
  2. strong acid
  3. organic solvents/acids
  4. heavy metals
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13
Q

it causes the atom within the protein molecule to vibrate more rapidly, causing the hydrogen bonds and hydrophobic interactions to break.

A

heat

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14
Q

they split salt linkages by ionizing the caboxylic group

A

strong acids

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15
Q

it denatures the protein by disrupting the hydrogen bonds

A

alcohol

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16
Q

they denature proteins by combining the carboxylate anions of the acidic amino acid with the metal, causing precipitation

A

heavy metal ions (silver, lead, mercury)

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17
Q

are used to precipitate alkaloids, giving “alkaloidal reagents”

A

organic acids like picric acid and tannic acid

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18
Q

the anion of these acids will react to the protonated amino acid group of protein, causing the disruption of salt linkages

A

organic acids ( picric acid and tannic acid)

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19
Q

Color Tests of Protein

A
  1. Biuret Test (2 mL 10% NaOH + 5 drops CuSO4)
  2. Ninhydrin Test
  3. Xanthoproteic Test
  4. Millon’s Test
  5. Hopkin’s Cole Test
  6. Sakaguchi Test
  7. Lead Acetate Test (Test for Sulfur)
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20
Q

Positive result for compounds that contain two or more peptide linkages

A

Biuret Test

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21
Q

Color of biuret test

A

purple (due to complex by cupric ions)

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22
Q

dipeptides and amino acids that do not give positive result to BT

A

serine, threonine

23
Q

when amino acids are sprayed w/ ninhydrin, it will give

A

blue to violet

24
Q

the presence of amino group including amine and ammonia will give positive result in NT except

A

proline & hydroxyproline (yellow)

25
Q

in XT, nitration of amino acids that contain benzene ring will yield the product of ____ that will give color

A

nitrobenze, yellow to orange

26
Q

in XT, they will produce nitrobenzene when treated w/ concentrated nitric acid

A
  1. tryptophan
  2. phenylalanine
  3. tyrosine
27
Q

in XT, what do not give a positive reaction

A

collagen and gelatin

28
Q

in MT, the phenol group in amino acid like tyrosine is nitrated by a solution of ___ in concentrated nitric acid

A

mercuric and mercurous nitrates

29
Q

what will be formed in millon’s test

A

white precipitate, turning brick red (due to mercury complex)

30
Q

in MT, addition of ____ will turn the precipitate to

A

NaNO2, darker pink or red

31
Q

color of precipitate in MT

A

white - brick red (due to mercury complex - darker pink/red (upon addition of NaNO2

32
Q

BT is for

A

two or more peptide linkages

33
Q

XT is for

A

amino acids that contain benzene ring

34
Q

Ninhydrin is for

A

amino group

35
Q

MT is for

A

phenol group (ex. tyrosine)

36
Q

HT is for

A

aldehyde

37
Q

in HT, the aldehyde present in reagent will cause the formation of a

A

blue or violet colored ring (due to formation of a complex bet. reagent and indole ring

38
Q

ST is to identify the presence of

A

arginine

39
Q

in ST, sodium hypobromite or hypochlorite react with guanido group giving a

A

red-orange colored complex

40
Q

This is a test for sulfur-containing amino acids like cysteine and methionine

A

Lead Acetate Test

41
Q

The sulfahydryl or disulfide group are converted to

A

Na2S (inorganic sulfide)

42
Q

Na2S reacts with lead acetate to form

A

brownish-black precipitate of lead sulfide (Pbs)

43
Q

Xanthoproteic Procedure

A

reagents: HNO3, NH4OH
albumin - yellow, richer yellow
gelatin - no reaction
casein - pale yellow, richer yellow

44
Q

Millon’s Procedure

A

reagents: millon’s reagent, 0.1% NaOH
albumin - red, yellow-orange
gelatin - no reaction
casein - red, yellow-orange

45
Q

HCT Procedure

A

reagents: HCT reagent, sulfuric acid
albumin - blue ring below the albumin
gelatin - no reaction
casein - blue ring below the milk

46
Q

Lead Acetate Procedure

A

reagents: 5 drops 10% NaOH, 3 drops 5% Lead acetate
albumin - black precipitate (Pbs)
gelatin - no precipitate

47
Q

NT Procedure

A

reagents: Ninhydrin
albumin - dark violet top, white bottom
gelatin - no reaction
casein - violet

48
Q

Biuret Procedure

A

reagents: 10% NaOH, 5 drops CuSO4
albumin - slightly cloudy, dark purple
gelatin - orange to red
casein - purple

49
Q

Heat

A

albumin + 3 mL water + boiling water bath:
after cooling = cloudy
color: purple/violet (peptide bond)

50
Q

Heat

A

albumin + 3 mL water
- violet

51
Q

Inorganic Acids

A

3 mL 5% albumin + HCL = precipitate at 8th drop
3 mL 5% albumin + H2SO4 = precipitate at 8th drop, increased 2 drops

52
Q

Alcohol

A

reagents: 5 mL 95% ethanol
albumin - no precipitate, albumin became opaque
gelatin - no precipitate formed
casein - white precipitate

53
Q

Heavy Metals

A

reagents: egg albumin
lead acetate - black precipitate
silver nitrate - white precipitate mercuric chloride - cloudy or white

54
Q
A

Lab (4 decks)

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