Exp 2.2: Protein Denaturation, Hydrolysis, and Separation Flashcards

1
Q

a loss of three-dimensional structure sufficient to cause loss of function

A

protein denaturation

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2
Q

Protein denaturation involves disruption of what levels of structures?

A

secondary and tertiary
(primary remains intact)

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3
Q

Identify the type of denaturation:
biological function/ activity cannot be regained

A

irreversible denaturation

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4
Q

Identify the type of denaturation:
biological function/ activity can be regained

A

reversible denaturation

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5
Q

Determine the denaturing agents:
disrupts ionic interactions

A

strong acids and bases
heavy metals

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6
Q

Determine the denaturing agents:
disrupts hydrophobic interactions

A

organic solvents
detergents
temperature

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7
Q

Determine the denaturing agents:
disrupts disulfide bonds

A

reducing agents

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8
Q

Determine the denaturing agents:
strip off essential layer of water molecule from the protein surface

A

salts

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9
Q

2 methods for salting

A
  1. salting in
  2. salting out
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10
Q

Identify the method of salting:
low salt concentration: increase solubility of solute
(increasing ionic strength)

A

salting in

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11
Q

Identify the method of salting:
high salt concentration: decrease solubility of solute
(non-electrolyte could be less soluble)

A

salting out

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12
Q

Determine the denaturing agents:
disrupts
1. hydrogen bonds
2. hydrophobic interactions

A

temperature

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13
Q

Complete Hydrolysis:
components used
product/s
types

A

components used: strong acid/base and high temp
product/s: amino acids
types: acid and alkaline

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14
Q

Acid Hydrolysis:
reagent
disadvantages

A

reagent: 6N HCl
disadvantages:
1. Cys & Tyr: partial destruction
2. Trp: complete destruction
3. Val & Ile: incomplete destruction
4. Ser & Thr: racemization & destruction
5. Asn+Gln: converted to Asp+Glu

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15
Q

Alkaline Hydrolysis:
reagent
advantage
disadvantage

A

reagent: NaOH or KOH
advantage: Trp - not destroyed
disadvantage: Arg, Asn, Gln, Ser - destroyed

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16
Q

Incomplete/ Partial Hydrolysis:
components used
product/s
types

A

components used: enzymes (protease)
product/s: amino acids + oligopeptides
type: enzymatic

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17
Q

Identify the type of hydrolysis:
presence of proteolytic enzymes results to partial or selective hydrolysis of polypeptide to yield a mixture of peptide fragments

A

enzymatic hydrolysis

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18
Q

enzymes that hydrolyze peptide bonds at specific sites

A

proteases/ peptidases

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19
Q

Enzymatic Hydrolysis:
reagent
advantages

A

reagent: protease
advantage: amino acids - not affected;
it requires certain temp & pH conditions for optimum activity of enzymes

20
Q

Enzymatic Hydrolysis:
2 types of enzymes

A
  1. exopeptidases
  2. endopeptidases
21
Q

Identify the enzyme:
cleavages at the terminal peptide

A

exopeptidases

22
Q

Identify the enzyme:
cleavages at the non-terminal peptide

A

endopeptidases

23
Q

3 types of exopeptidases

A
  1. Carboxypeptidase A
  2. Carboxypeptidase B
  3. Aminopeptidase
24
Q

3 types of endopeptidases

A
  1. Trypsin
  2. Chymotrypsin
  3. Papain
25
Q

Identify the specificity:
Carboxypeptidase A

A

C-terminal residues except R, K, and P

26
Q

Identify the specificity:
Carboxypeptidase B

A

R or K at C-terminus

27
Q

Identify the enzyme:
Aminopeptidase

A

most N-terminal except when P is the next residue

28
Q

Identify the specificity:
Trypsin

A

C-side R and K

29
Q

Identify the specificity:
Chymotrypsin

A

C side of F, Y, and W

30
Q

Identify the specificity:
Papain

A

C side of hydrophobic groups/ aromatic-R groups

31
Q

6 properties of proteins being considered in separation or purification

A
  1. charge
  2. molecular size
  3. shape
  4. solubility
  5. affinity to a ligand
  6. pI/ IpH
32
Q

a procedure in which the pH of the protein mixture is adjusted to the pI of the protein to be isolated to selectively minimize its solubility

A

isoelectric precipitation

33
Q

Enumerate proteins in cow milk

A
  1. Casein
    a. alpha-s1
    b. alpha-s2
    c. beta
    d. kappa
  2. Whey proteins
    a. alpha-lactalbumin
    b. beta-lactoglobulin
    c. serum albumin
    d. immunoglobulins
    e. other proteins
34
Q

Identify the protein:
present as micelles in milk and acts as a storage for amino acids

A

casein

35
Q

Identify the protein:
major protein component of cow’s milk

A

casein

36
Q

Casein:
function
source
isolation method
composition
shape
isoelectric point

A

function: storage of amino acids
source: skimmed milk
isolation method: isoelectric precipitation
composition: conjugated (Ca & Ph)
shape: globular
isoelectric point: pH 4.6

37
Q

Identify the protein:
globular proteins that are soluble in water and diluted salt salutions

A

albumin

38
Q

Identify the protein:
second major protein in bovine milk

A

albumin

39
Q

Albumin:
function
source
isolation method
composition
shape
isoelectric point

A

function: regulating lactose biosynthesis
source: skimmed milk
isolation method: denaturation and coagulation by heat
composition: conjugated (metalloprotein)
shape: globular
isoelectric point: pH 4.3

40
Q

Myoglobin:
function
source
isolation method
principle
composition
shape

A

function: storage of oxygen in muscle and tissues
source: beef muscle
isolation method: salt-induced precipitation
principle: salting in, salting out
composition: conjugated (iron & oxygen)
shape: globular

41
Q

Identify the protein:
small, bright red protein common in muscle cells

A

myoglobin

42
Q

Identify the protein:
a hemoprotein containing a heme group at its center

A

myoglobin

43
Q

Isolated myoglobin:
precipitate color

A

white

44
Q

gluten:
function
source
isolation method
composition
shape
principle in isolation
test

A

function: dough’s strength and elasticity (structure)
source: wheat flour (wheat, rye, barley)
isolation method: solubility difference
composition: simple
shape: fibrous and globular (glutenin & gliadin)
principle in isolation:
- starch: partially soluble in H2O
-gluten: insoluble in H2O
test: iodine test

45
Q

Gluten:
2 major classes of storage proteins (composites)

A
  1. prolamin
  2. glutelin
46
Q

Gluten:
2 major proteins

A
  1. gliadin
  2. glutenin
47
Q

Test for isolated gluten free of starch

A

iodine test
result: negative (-)