Class Four Flashcards
3 basic components of an AA
carboxyl group
amino group
R group
all AAs are chiral except for..
glycine
*alpha carbon is bonded to 2 Hs
what makes each amino acid unique
their variable R group
all animal amino acids are of __ configuration
L
all naturally occurring carbohydrates have __ configuration
D
L and D amino acids are..
enantiomeric stereoisomers
what are enantiomeric stereoisomers
molecules with the same connectivity but different spatial orientation
non superimposable mirror images
simplest/smallest carbohydrate
glyceraldehyde
animal amino acids are derived from..
L-glyceraldehyde
animal carbohydrates are derived from..
D-glyceraldehyde
(+) and (-) describe..
optical activity
is L - or +
-
is D - or +
+
what do R and S describe
actual structure or absolute configuration
what do D and L tell us
tells us the basic precursor of a molecule
four categories of AAs
acidic basic non polar & polar
acidic AAs have..
carboxylic acid functional groups
pka of acidic AAs
4
acidic AAs
aspartic acid: asp (D)
glutamic acid: glu (E)
basic AAs
lysine
arginine
histidine
lysine
lys: K
basic AA
pka = 10
arginine
arg: R
basic AA
pka = 12
histidine
his: H
basic (but can act as an acid as well)
pka = 6.5
nonpolar AAs (7)
glycine
alanine
valine
leucine
isoleucine
phenylalanine
tryptophan
glycine
non polar
gly: G
glycine
non polar
gly: G
alanine
non polar
ala: A
valine
non polar
val: V
leucine
leu: L
non polar
isoleucine
ile: I
non polar
phenylalanine
phe: F
non polar
tryptophan
trp: W
non polar
aromatic AAs (3)
phenylalanine
tryptophan
tyrosine
serine
ser: S
polar
threonine
thr: T
polar
tyrosine
tyr: Y
polar
asparagine
asn: N
polar
glutamine
gln: Q
polar
cysteine
contains a thiol - polar
cys: C
methionine
contains a thioether
non polar
met: M
proline
non polar
pro: P
has a secondary amino group
Strecker synthesis
using ammonium & cyanide salts to transform aldehydes → amino acids
Strecker amino acids are..
racemic (naturally occurring ones are pure L-enantiomers)
Gabriel-Malonic ester synthesis
transform primary alkyl halides into primary amines
way of making AAs
are AAs amphoteric
has acidic and basic activity
acids are proton ___
donors
bases are proton ____
acceptors
if pH is higher than pKa..
the site if mostly deprotonated
if pH is lower than pKa..
the site is mostly protonated
zwitterion
balancing of positive and negative charges
average of the pKas
what happens in gel electrophoresis
technique to separate amino acids based on their charge
gel electrophoresis.. if the pH is greater than pI..
AA will be negative charged
will move towards the positive electrode
gel electrophoresis.. if the pH is lower than pI..
AA will be positively charged
will move towards the negative electrode
gel electrophoresis.. if the pH = pI
AA will be a zwitterion = no migration
2 types of covalent bonds between AAs in proteins
peptide bonds: link the AAs together
disulphide bridges: between cysteine R-groups
peptide bond is between..
carboxyl group of one AA and amino group of another
is a peptide bond between 2 AA thermodynamically favourable
no
what is DCC coupling used for
to synthesize peptides artificially
why are peptide bonds planar & rigid
because the resonance delocalization of the N’s electrons to the carboxyl oxygen gibes double bond character to the bond between C and N
2 ways to increase rate of peptide bond hydrolysis
strong acids
proteolytic enzymes
disulphide bond forms in-between..
thiols of 2 cysteines
denaturation
disruption of a protein’s shape without breaking peptide bonds
bond for primary structure
peptide bonds
bond for secondary structure
H bonds between backbone NH and CO groups
bonds for tertiary and quaternary structures
van der Waals, disulphide, H bonds etc etc
molecular formula for carbohydrates
CnH2nOn
how can carbohydrates be broken down to CO2
oxidation
single carbohydrate molecule
monosaccharide
two monosaccharides bonded together
disaccharide
two part name system of monosaccharides
first part: aldo or keto (depending on whats present)
second part: the number of C atoms in a chain
sugar in our bodies have the __ configuration
D
we only have _ amino acids and _ sugars
L and D
pyranoses
6 membered ring (monosaccharides)
furanoses
5 membered ring (monosaccharides)
Benedict’s test distinguishes between..
hemiacetals and acetals
reducing sugar
a carbohydrate that can be oxidized by Benedict’s reagent
reduces the Cu2+ to Cu+ while itself being oxidized
what gives a positive result in Benedict’s test
monosaccharides
aldehydes/ketones/hemiacetals
what gives a negative result Benedict’s test
acetals (they do not react with Cu2+)
synonym for hydrophobic
lipophilic
synonym for hydrophilic
lipophobic
fatty acid structure
long unsubstituted alkanes that end with a CA
saturated FA
has no C-C double bonds
unsatured FA
has at least one or more double bond in the tail
storage form of fatty acids
triglycerides
triglyceride structure
3 FAs esterified to a glycerol molecule
why is it important to store fatty acids as triglycerides
fatty acids are reactive
why do fat molecules store more energy than carbohydrates
fats are more reduced - can oxidize more to release energy
importance of squalene
used in the manufacture of steroids
terpenoids
bulit from an isoprene skeleton and functionalized with other elements
how do steroid hormones cause effects
no receptors - diffuse through the lipid bilayer membrane into the cytoplasm
