Ch 1: Amino Acids, Peptides, Proteins Flashcards

1
Q

amino acids have 4 groups attached to the central alpha carbon

A

amino group
carboxylic acid group
hydrogen atom
R group

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2
Q

___ amino acids appear in the proteins of eukaryotic organisms

A

20

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3
Q

stereochemistry of alpha carbon for all aa in euk is

A

L

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4
Q

D-amino acids exist in

A

prokaryotes

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5
Q

all aa except ___ have (S) configuration

A

cysteine

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6
Q

all aa except ___ are chiral

A

glycine

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7
Q

nonpolar, nonaromatic

A
glycine
alanine
valine
leucine
isoleucine
methionine
proline

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8
Q

Aromatic aa

A

Phenylalanine
Tyrosine
Tryptophan
Flap Your Wings

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9
Q

Polar aa

A
Serine
Glutamine
Threonine
Asparagine
Cysteine

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10
Q

Positively Charged - basic aa

A

Lysine
Arginine
Histidine

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11
Q

Negatively Charged - acidic aa

A

Aspartate
Glutamate

DE

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12
Q

pKa of a group is the pH at which half of the species is ____ ; HA = A-

A

deprotonated

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13
Q

aa exist in different forms at diff pH

low acidic pH, aa ___
pH near pI of aa ___
high alkaline pH, aa __

A

fully protonated

neutral zwitterion

fully deprotonated

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14
Q

isoelectric point (pI) of an aa w/o charged group can be calculated by

A

averaging the 2 pKa values

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15
Q

aa can be titrated:

titration curve nearly flat ____

nearly vertical when at the ____

A

at pKa values of the aa

pI of the aa

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16
Q

aa with charged side group can find pI by calculating

A

the average of two pKas of protonation/deprotonation of zwitterion

17
Q

aa w/o charged sides have pI around

A

6

18
Q

aa acidic have pI around

A

well below 6

19
Q

aa basic have pI

A

well above 6

20
Q

dipeptides have __ aa residues
tripeptides have __
oligopeptides ___
polypeptides __

A

2
3
less than 20
more than 20

21
Q

forming a peptide bond is a

A

condensation or dehydration reaction

releasing one molecule of water

22
Q

amide bonds are rigid due to

A

resonance

23
Q

breaking a peptide bond is a

A

hydrolysis reaction

24
Q

primary structure

A

linear seq of aa in a peptide and is stabilized by peptide bonds

25
Q

secondary structure

A

local structure of neighboring aa, and is stabilized by h bonding between amino groups and nonadjacent carboxyl groups

26
Q

2nd struc: alpha helices

A

clockwise coils around a central axis

27
Q

2nd struc: beta pleated sheets

A

rippled strands that can be parallel or anti-parallel

28
Q

proline can interrupt ___ because of rigid ___

A

2nd structure

cyclic structure

29
Q

tertiary structure

A

3D shape of a single polypeptide chain and is stabilized by hydrophobic interactions, acid-base interactions (salt bridges), hydrogen bonding, and disulfide bonds

30
Q

(3) hydrophobic interactions push hydrophobic R group to interior of protein which

A

inc entropy of the surrounding water molecules and creates a neg gibbs free energy

31
Q

disulfide bonds (3)

A

occur when 2 cysteine molecules are oxidized and create a covalent bond to form cystine

32
Q

quaternary structure is the interaction

A

between peptides in proteins that contain multiple subunits

33
Q

can lead to denaturation of 3-D protein structure

A

heat and increasing solute conc

34
Q

proteins w covalently attached molecules are ___ and the attached molecule is a ____ that may be _______

A

conjugated proteins
prosthetic group

metal ion, vitamin, lipid, carbohydrate, nucleic acid