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Biochem - 1-3 > Amino Acids and Peptides > Flashcards

Amino Acids and Peptides Flashcards

1
Q

What is the 21st amino acid?

A

Selenocysteine

(that include certain peroxidases and reductases, selenoprotein P1, and the iodothyronine deiodinase responsible for converting the prohormone thyroxine(t4) and t3.

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2
Q

The alpha carbon of every amino acid is chiral except

A

GLYCINE

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3
Q

All protein amino acids all share the absolute configuration of L- glyceraldehyde and thus are defined as L- amino acids. TRUE OR FALSE

A

True

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4
Q

Provide monomer units for formation of long polypeptide chains of proteins

A

L-amino acids and their derivatives

Cellular fxns:
Nerve transmission
Biosynthesis of porphyrins, purines, pyrimidines, urea

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5
Q

Cellular fxns of L amino acid

A

Nerve transmissions

Biosynthesis of porphyrins, purines, pyrimidines, urea

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6
Q

Short polymers of amino acids

A

Peptides

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7
Q

Perform roles in neuroendocrine system

A

Peptides

.. Such as hormones, hormone-releasing factors, neuromedulators, neurotransmitters

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8
Q

Only L-amino acids occur in Proteins. TRUE OR FALSE

A

TRUE

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9
Q

Amino acids may have positive or negative charge. TRUE OR FALSE

A

TRUE

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10
Q

pKa values express the strengths of strong acids. TRUE OR FALSE.

A

FALSE. Weak acids.

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11
Q

pKa values do not vary w/ the environment. TRUE OR FALSE.

A

False. Do vary.

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12
Q

At its isoelectric pH (pI), an amino acid bears no net charge. TRUE OR FALSE

A

True

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13
Q

The solubility of Amino Acids reflects their ionic character. TRUE OR FALSE.

A

TRUE

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14
Q

A given amino acid having more than one triplet coding for it.

A

Redundancy. (Limits the available codons to the 20 amino acids)

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15
Q

Humans cannot synthesize 10 of the 20 common L-amino acids. TRUE OR FALSE

A

TRUE. Thus, human diet must contain adequate quantities of these essential amino acids

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16
Q

Nutritionally essential Amino Acids

A

HILLAMPTTV

Histidine
Isoleucine
Leucine
Lysine
Arginine
Methionine
Phenylalanine
Threonine
Tryptophan
Valine
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17
Q

Found in peroxidases and reductase where it participates in the catalysis of electron transfer reactions.

A

Selenocysteine

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18
Q

Not specified by a simple three letter codon unlike the others

A

Selenocysteine

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19
Q

A selenium ion replaces ______ of its structural analog, cysteine.

A

Sulfur

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20
Q

All proteins/amino acids all share the L-glyceraldehyde configuration. TRUE OR FALSE

A

TRUE. thus are L-amino acids.

Some proteins/amino acids are dextrorotatory/ levorotatory.

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21
Q

Amino acids that fulfill roles in metabolic processes

A

OCA - urea synthesis

Ornithine
Citrulline
Argininosuccinate

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22
Q

Other metabolic processes

A

Tyrosine in thyroid hormone
Glutamate in neurotransmitter
Biosynthesis

23
Q

Both -COOH and R-NH3 are strong acids. True or false

A

False. Weak acids.

24
Q

Molecules that contain an equal number of ionizable groups of opposite charge and therefore bear NO NET CHARGE (electrically neutral)

A

Zwitterions

25
Q

At its isoelectric ph (pI), an amino acid bears no net charge. TRUE OR FALSE

A

True

26
Q

Isoelectric pH

A

pI

  • the pH midway between pKa values on either side of the isoelectric species
  • zwitterions are examples of isoelectric species
27
Q

Net charge depends upon

A

1) pKa values of its functional groups

2) pH of its surrounding medium

28
Q

Characteristic pH at which the net electric charge is zero is called

A

Isoelectric point or “pI”

29
Q

Amino acid at the isoelectric pI is called

A

Zwitter ion - electrically neutral ( not migrating in an electrical field)

30
Q

Polar environment favors _____ form.

A

Charged form.

Polar- charged form
(Non polar - uncharged form)

31
Q

Non polar environment:
A) raises the PKa of a _____ group.
B) lowers pKa of ____ group.

A

A) carboxyl group (making it weaker acid)

B) amino group (making it a stronger acid)

32
Q

Charged functional groups of AA ensure that they are:

________ in polar solvents (ex. ___ and ____)
________ in nonpolar solvents (___, ____, ____)

A

Soluble ( water and ethanol)

Insoluble (benzene, ether, hexane) BEH

33
Q

Can reinforce/counteract solvent effects

A

Adjacent charged groups

34
Q

Amino acids do not absorb light and thus are colorless. True or false.

A

True

35
Q

Ten times more efficient in absorbing light than phenylalanin and tyrosine.

Major contributor of protins to absorb light

A

TRYPTOPHAN (250-290nm)

36
Q

Hydrophobic R groups of alanine, valine, leucine and isoleucine occur primarily in the + AROMATIC R groups of phenylalaninr , tyrosine and tryptophan

A

Interior of cytosolic proteins

37
Q

Smallest amino acid, often occurs where peptides bend sharply

A

Glycine

38
Q

Stabilize specific protein conformations via ionic interactions or salt bridges

A

Charged R groups of basic and acidic amino acids

39
Q

Histidine

A

Plays unique roles in enzymatic catalysis

40
Q

Plays a role in ezymatic catalysis

A

Histidine

Pka of its imidazole proton permits it to fxn at neutral ph as either a base or acid

41
Q

Most important reaction of amino acids

A

Formation of peptide bond

42
Q

Chemical reactions exhibit all of its characteristic chemical rxns

A
  • carboxylic acid group (formation of esters, amides, acid anhydrides)
  • amino groups: acylation, amidation, esterification
43
Q

Alcohol group of SERINE and the primary thioalcohol group of cysteine are excellent

A

NUCLEOPHILES

44
Q

Amino acid sequence determines primary structure. True or False

A

TRUE

45
Q

Peptide bond has

A

Partial Double bond character

46
Q

Peptides are

A

Polyelectrolytes

47
Q

Noncovalent forces constrain

A

Peptide conformations

48
Q

Amino acids present in peptides are called

A

Aminoacyl residues

49
Q

Peptide hormones typically contain ONLY the a-amino acids of proteins. TRUE OR FALSE

A

True.

Other peptides contain non protein amino acids or amino acids linked by ATYPICAL PEPTIDE BOND ex. Glutathione

50
Q

Formation of peptides from amino acid is therefore accompanied by a net loss of one positive and one negative charge per peptide bond formed.

A

TRUE

51
Q

The physiologically active conformation reflects the collective contributions of the

A

Amino acid sequence
Steric hindrance
Non covalent interactions

52
Q

Widely used for detecting amino acids, forms a purple product w/ amino acids and a yellow adduct with imine groups of proline and hydroxyproline

A

NINHYDRIN

53
Q

Some proteins contain additional amino acids that arise by

A

Post- translational modification of an amino acid present in the peptide

Biochem - 1-3 (2 decks)

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