Amino Acids

Question 1

Each amino acid has at least two pKas:

Answer 1

• amino group attached to central alpha C
• carboxylic acid group attached to central alpha C
• R group/side chain

Question 2

R groups are the only…

Answer 2

difference between the 20 amino acids

Question 3

Amino acids are monomers of…

Answer 3

polypeptide/protein molecules

Question 4

Protein shape and function are determined by…

Answer 4

sequence in which amino acids are linked together and the interactions with the side chains

Question 5

Side chains and their position relative to the adjacent/nearby chain from another amino acid determine…

Answer 5

shape and function of protein

Question 6

Sequence of amino acids are also known as…

Answer 6

primary structure of proteins

Question 7

Longer side chains leads to the molecule becoming more…

Answer 7

hydrophobic

Question 8

Examples of uncharged polar side chains:

Answer 8

• Glutamine (Glu)
• Tyrosine (Tyr)
• Cysteine (Cys)
• Serine (Ser)
• Threonine (Thr)
• Asparagine (Asn)

Question 9

Examples of charged polar side chains:

Answer 9

• Lysine (Lys)
• Arginine (Arg)
• Histidine (His)
• Aspartic acid (Asp)
• Glutamic acid (Glu)

Question 10

Histidine is often used in…

Answer 10

acid/base enzyme reactions due to pKa close to neutrality

Question 11

Lysine and Arginine side chains are always…

Answer 11

positive at physiological pH

Question 12

Aspartic and Glutamic acid are the only amino acids w/…

Answer 12

negative charge at physiological pH

- often termed aspartate and glutamate due to negative charge

Question 13

Carboxylic acid (COOH) and amine group (NH3+) remains protonated at…

Answer 13

pH at or below their own pKa

Question 14

Zwitterionic molecules have…

Answer 14

net charge of 0

Question 15

Isoelectric point (pl) is the point where…

Answer 15

net charge is equal to 0

pl = [pKa1 + pKa2]/2

Question 16

If pH is above the pKa…

Answer 16

group is deprotonated

Question 17

If pH is below/equal to the pKa…

Answer 17

group is protonated

Question 18

Changes in charge on amino acids are important b/c…

Answer 18

• can make amino acid inactive
• disrupt protein structure/function
• alter E levels of protein
• keep reaction from occurring

Question 19

Fully protonated amino acid would have a _____ pH

Answer 19

low

Question 20

Fully deprotonated amino acid would have exist at pH…

Answer 20

above pKa of amino group on side chain

Question 21

T/F: amino acids are optically active

Answer 21

T

Question 22

Why are amino acids optically active?

Answer 22

• rotate the plane of polarized light
• asymmetric
• result from chiral C
• are enantiomers

Question 23

Dextrorotatory (D form) amino acids are…

Answer 23

on the right side

Question 24

Levorotatory (L form) amino acids are…

Answer 24

on the left side

Question 25

T/F: all amino acids incorporated by organisms in proteins are of the D form

Answer 25

F, they're of the L form

Question 26

Modified amino acids are...

Answer 26

amino acids that are modified after incorporation into a protein

Question 27

5-HTP (5-hydroxytryptophan):

Answer 27

- derivative of amino acids - used to treat neurological problems associated w/ PKU and depression - ex: serotonin and melatonin

Question 28

Serotonin is a:

Answer 28

neurotransmitter that doesn't cross blood brain barrier

Question 29

Serotonin is involved in regulation of:

Answer 29

- mood - sleep - vomiting - sexuality - appetite

Question 30

Serotonin is associated w/...

Answer 30

- depression - migraines - bipolar-disorder - anxiety

Question 31

Precursor of serotonin:

Answer 31

Trp and 5HTP

Question 32

Ecstasy is thought to cause...

Answer 32

a mass release of 5 HT

Question 33

Levels of serotonin are controlled by...

Answer 33

- MAO inhibitor: stops breakdown of neurotransmitters | - reuptake inhibitors

Question 34

Melatonin regulates...

Answer 34

circadian cycle

Question 35

Melatonin can prevent...

Answer 35

hyperphosphorylation of tau

Question 36

DOPA (L-dihydroxyphenylalanine) is a drug that is used to treat...

Answer 36

Parkinson's

Question 37

Examples of DOPA (L-dihydroxyphenylalanine) are...

Answer 37

- epinephrine | - norepinephrine

Question 38

Epinephrine is involved in...

Answer 38

stress action

Question 39

Action of epinephrine:

Answer 39

- binds to multiple receptors | - participates in adenylate cyclase pathway that breaks down glycogen

Question 40

Norepi is involved in...

Answer 40

- ADD/ADHD - depression - replenishing catecholamine stores

Question 41

T/F: tyrosine and cysteine carry a positive charge

Answer 41

F, they don't carry a charge

Question 42

What is the side chain of cysteine in its reduced form?

Answer 42

SH

Question 43

When cysteine participates in a disulfide bonds w/ another cysteine amino acid, the side chain turns into its...

Answer 43

oxidized form (S-S)

Question 44

Which amino acids are hydrophobic?

Answer 44

- gly - ala - val - leu - ile - pro - phe - met - trp

Question 45

Which amino acids are hydrophilic?

Answer 45

- lys - arg - his - asp - glu - ser - thr - tyr - gln

Question 46

Cysteine has a side chain that...

Answer 46

ionizes

Question 47

Amino acids that are ionizable:

Answer 47

- arg - asp - cys - glu - his - lys - tyr

Question 48

Functional group on side chain of lysine:

Answer 48

NH3+

Question 49

Functional group on side chain of arginine:

Answer 49

guanidino

Question 50

Functional group on side chain of histidine:

Answer 50

imidazole ring

Question 51

Functional group on side chain of glutamate:

Answer 51

COOH

Question 52

Functional group on side chain of aspartate:

Answer 52

COOH

Question 53

How are disulfide bonds formed?

Answer 53

oxidation between pairs of cysteine side chains

Question 54

What reduces disulfide bonds?

Answer 54

dithiotheritol (DTT)

Question 55

What oxidizes disulfide bonds?

Answer 55

cysteine