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Biochemistry > Chapter 5: Proteins: Primary Structure > Flashcards

Chapter 5: Proteins: Primary Structure Flashcards

1
Q

the composition of a polypeptide chain (sequence) is limited by the ability of the
polypeptide to fold into a what

A

functional structure

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2
Q

If the pI is greater than the pH what is the charge

A

positive

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3
Q

If the pI is less than the pH what is the charge

A

negative

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4
Q

contain subunits

A

Multisubunit proteins

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5
Q

identical and/or non-identical chains

A

subunits

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6
Q

A given protein is frequently obtained from a source chosen primarily for convenience

A

protein source

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7
Q

produces large amounts of a foreign protein often sequesters it in what

A

inclusion bodies.

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8
Q

A protein’s ionic charge, polarity, size, and ligand-binding ability influenced its

A

chromatographic behavior

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9
Q

is not necessarily to minimize the loss
of the desired protein, but to eliminate selectively the other components of the mixture so that only the required substance
remains.

A

purification technique

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10
Q

what pH do cells have to be to go from positive to neutral

A

high PH and PI

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11
Q

what pH do cells have to be to go from negative to neutral

A

low PH and PI

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12
Q

how to separate proteins by charge

A

Ion exchange chromatography
Electrophoresis
Isoelectric focusing

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13
Q

how to separate proteins by size

A

size exclusion
SDS-PAGE
Gel filtration chromatography

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14
Q

how to separate proteins by polarity

A

Hydrophobic interaction chromatography

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15
Q

how to separate proteins by binding specificity

A

Affinity chromatography

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16
Q

how to separate proteins by ligand-binding

A

affinity

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17
Q

A protein in a complex mixture can be detected by its binding to its

A

corresponding antibodies

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18
Q

Enzymes coupled to antibodies include alkaline phosphatase, and β-galactosidase. The amount of antigen is quantified by the
formation of a colored reaction product produced by the enzyme.

A

Direct Enzyme-Linked Immunosorbent Assay (ELISA)

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19
Q

this absorbance is commonly used to measure the concentration of proteins.

A

Trp

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20
Q

A protein with a what, absorbs in the
visible region of the spectrum

A

chromophore

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21
Q

to change the solubility of a protein what can you do?

A

adjust the pH to approximate the isoelectric point (pI) of the desired protein

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22
Q

charged molecules bind to oppositely charged
groups that are chemically linked to a matrix

A

ion exchange chromatography

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23
Q

Anions bind to cationic groups on

A

anion exchanger

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24
Q

most frequently used anion exchanger

A

diethylaminoethyl (DEAE) groups

25
Q

most frequently used cation exchanger

A

carboxymethyl (CM) groups

26
Q

depends on the presence of other
ions that compete with the protein for binding to the ion exchanger and on the pH of the solution

A

binding affinity of a particular protein

27
Q

As the column is washed, proteins with relatively low affinities for the ion
exchanger move through the column faster than proteins that bind with higher
affinities

A

what to know about ion exchange

28
Q

influences the net charge of the protein

A

pH of the solution

29
Q

proteins that bind tightly to the ion exchanger can be

A

eluted

30
Q

washed through the column

A

eluted

31
Q

has a higher salt concentration or a pH that reduces the affinity with which the matrix binds the protein

A

eluant

32
Q

buffer

A

eluant

33
Q

proteins are separated by their pI values.

A

ion exchange chromatography

34
Q

molecules are separated according to their size and shape.

A

gel filtration chromatography
size exclusion
molecular sieve chromatography

35
Q

The stationary phase consists of gel beads containing pores that span a
relatively narrow size range.

A

gel filtration chromatography
size exclusion
molecular sieve chromatography

36
Q

These what molecules therefore
traverse the column more rapidly than what molecules that pass through the pores

A

large
small

37
Q

In this technique, a molecule a ligand that
specifically binds to the protein of interest
is covalently attached to an inert matrix

A

affinity chromatography

38
Q

a divalent metal ion such as Zn 2+ or Ni 2+ is
attached to the chromatographic matrix so that proteins bearing metal-chelating groups can be retained.

A

metal chelate affinity chromatography

39
Q

what stains the gel for SDS-PAGE

A

coomassie blue

40
Q

Separated bands may be
visualized in the gel by soaking
the gel in a solution of a stain
(such as coomassie blue) that
binds tightly to proteins.

A

SDS-PAGE

41
Q

how does electrophoresis differs from
gel filtration

A

electrophoretic mobility of smaller molecules is greater than the mobility of larger molecules

42
Q

why is the pH of a SDS-PAGE usually high

A

so that nearly all proteins have net negative charges and move toward the positive electrode when the current is switched on

43
Q

what shape do proteins assume in the presence of SDS.

A

rodlike

44
Q

In SDS-PAGE, the relative mobility of proteins
vary approximately linearly with what?

A

the logarithm of their molecular masses

45
Q

If a mixture of proteins is electrophoresed through a solution or gel that has a stable pH gradient in which the pH increases smoothly from anode to cathode, each protein will migrate to the position in the pH gradient
corresponding to its

A

pI

46
Q

IEF can be combined with SDS-PAGE in an extremely powerful separation
technique named

A

two-dimensional (2D) gel electrophoresis

47
Q

First, a sample of
proteins is subjected to IEF in one direction, and then the separated proteins are
subjected to SDS-PAGE in what direction

A

perpendicular direction

48
Q

is a biochemical method for separating
complex mixtures of proteins into individual species.

A

2-dimensional electrophoresis (2DE)

49
Q

what is included in protein sequencing

A

2 subunits
2 different amino acids

50
Q

To be sequenced, a protein must be
separated into what

A

individual polypeptides

51
Q

a procedure for removing N-terminal
residues one at a time

A

Edman degradation

52
Q

the amino acid sequence can be
determined by what

A

Edman degradation

53
Q

a procedure that liberates amino acids one at a time from the N-terminus of a polypeptide

A

first step of Edman degradation

54
Q

evolutionarily related proteins

A

homologous proteins

55
Q

indicate which of the protein’s residues are
essential to its function, which are less significant, and which have little specific
function

A

homologous proteins

56
Q

Finding the same residue at a particular position makes it an

A

invariant residue

57
Q

Changes in other amino acids with similar side chains

A

conservatively substituted

58
Q

A particular amino acid position that tolerates many different amino acid residues, indicating that the position is

A

hypervariable

Biochemistry (17 decks)

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