Amino Acids & Protein (midterm) Flashcards
What are amino acids involved in?
-cellular metabolism (enzymes)
-precursors of various biologically active compounds like neurotransmitters and hormones
What are zwitterions?
amphoteric electrolytes
-its a neutral molecule with a positive and negative electrical charge
-neutral amino acids with 2 charges that cancel each other out
Acids are proton _________
donors
Bases are proton __________
acceptors
What are the different major categories of R groups?
-nonpolar
-polar (neutral, acidic, or basic)
What are characteristics of nonpolar R groups (think definition)?
-do not gain or lose protons or form H bonds
-hydrophobic and neutral
-in aqueous solutions, those side chains tend to cluster in the interior (wanted to be buried in the protein)
-CH or CC bonds
What are the 3 types of polar R groups?
1) neutral (side chains are hydrophilic but have no charge at physiological pH (7/neutral, pka is 7), participates in hydrogen bonds, ex: R group with OH)
2) acidic (at physiological pH (pka < 7), the side chains are ionized with a negatively charged carboxylate group (COO-))
3) basic (side chains accept protons (H+), at physiological pH (pka > 7) the side chains are ionized and positively charged, ex: side chains with NH2)
Which AA is important for collagen production?
glycine
What is the most abundant protein in the body?
collagen (glycine is needed to make collagen, and so 1/3 of our AAs in body are glycine)
What are chiral carbons?
alpha carbons that have a D and L form, and have 4 different attachments
SO, glycine is the only achiral AA bc it does not have 4 different groups attached, and so it also does not have D and L form bc of this
What does aliphatic mean?
linear (only CH bonds)
What are the 3 different nonpolar AAs groups?
-aliphatic or branched chain AAs
-aromatic
-sulfur containing AAs
What are the 3 nonpolar aliphatic AAs?
-glycine
-alanine
-proline
What is the simplest AA?
glycine
What AA is this?
glycine/gly
What happens to alanine if the amino group is removed?
it becomes an alpha ketoacid and the NH2 will be replaced with H
What is the side chain on alanine?
methyl group (CH3)
Which AA is closely linked with pyruvate? Why?
alanine
If alanine is broken down, it will make pyruvate
note: pyruvate makes glucose
-this is called gluconeogenisis (making new glucose that is not from carbs, glycogen to glucose is NOT gluconeogenisis)
-glycogen only maintains blood glucose levels for up to 12 hours, usually overnight, after that gluconeogenisis is used
What AA is this?
alanine/ala
Is proline aromatic?
no, its cyclic
and bc its cyclic it will form a kink when it binds to other AAs in peptide chain
What AA is this?
proline/pro
What are the 3 branched chain AAs (BCAAs)?
valine, leucine, and isoleucine
What AA is this?
valine/ val
What AA is this?
leucine/ leu
What AA is this?
isoleucine/ ile
What happens to BCAAs if you remove the amino group?
it will be converted to a branched chain alpha keto acid, which is good for heart muscle and performance especially in athletes (if theres a deficiency then it can lead to heart failure)
What is maple syrup urine disease?
-enzyme deficiency that increases branched chain alpha keto acids
-causes vomiting, brain damage, and eventually death
-high conc. of branched chain alpha keto acids will make urine smell like rotten maple syrup
-treatment is to avoid BCAAs, aka high quality proteins (animal products)
-newborn screening is done to prevent brain damage and death
-this is genetic when found in children, but can also be found in adults and at this point its usually associated with a high protein diet
Are all vitamins essential?
YES
What are the 2 nonpolar neutral aromatic AAs?
phenylalanine and tryptophan
What are the 3 aromatic AAs?
1) phenylalanine (nonpolar neutral)
2) tryptophan (nonpolar neutral)
3) tyrosine (polar neutral)
Which 2 aromatic AAs are essential?
phenylalanine and tryptophan (both are nonpolar neutral as well)
What AA is this?
phenylalanine/ phe
What AA is this?
tryptophan/ trp
What is the largest AA?
tryptophan/ trp
Which AA is a precursor for niacin (vitamin B3)?
tryptophan/ trp
Which AA can be used to make serotonin?
tryptophan/ trp (so lack of trp can cause depression)
Which AA can synthesize vitamin D from sunlight?
tryptophan/ trp
What are the 2 nonpolar neutral AAs with sulfur containing side chains?
cysteine and methionine
Which AA has a thiol group attached?
cysteine (which also means its an antioxidant)
What AA is this?
Cystine/Cys
What 2 AAs provide 100% of the sulfur in our body?
cysteine and methionine
Is sulfur abundant in the body?
yes, 3rd most abundant (1st is calcium and 2nd is phosphate)
Which AA initiates protein synthesis?
methionine
What AA is this?
methionine/ met
Which AAs face the water?
polar AAs
Which AAs fold/try to hide away inside of the protein?
nonpolar AAs
T/F: usually AAs with OH are neutral
true
What are the 3 polar neutral AAs with OH in the side chain?
serine, threonine and tyrosine (this means phosphate can bind to any of these and make an enzyme easily)
What AA is this?
serine/ ser
What AA is this?
threonine/ thr
What AA is this?
asparagine/ asn
What AA is this?
glutamine/ gln
What is the most abundant AA in the blood?
glutamine
What is the difference between tyrosine and phenylalanine?
OH group!
phenylalanine can make tyrosine
What AA is an important precursor for catecholamines (dopamine, epi, NE)?
tyrosine
What are the 5 polar neutral AAs?
1) serine
2) threonine
3) asparagine
4) glutamine
5) tyrosine
note: they all have a side chain that contains OH bond OR CO-NH2 bond
What are the 5 polar charged AAs?
1) lysine
2) arginine
3) histidine
4) aspartate (aspartic acid)
5) glutamate (glutamic acid)
What are the 3 basic/positively charged (protonated) polar AAs?
1) lysine
2) arginine
3) histidine
Which enzyme is used to add OH to make tyrosine?
phenylalanine hydroxylase
Which AA helps with oxidative stress?
cysteine bc its an antioxidant bc of the thiol group in side chain
Which AA is this?
tyrosine/ tyr
What AA is this?
lysine/ lys
Which AA is a precursor for NO?
arginine
Which AA is a precursor for urea?
arginine
Which AA is a precursor for histamine/inflammation?
histidine
Which AA is this?
arginine, arg
Which AA is this?
histidine/ his
Histones are basic. Why?
rich in lysine and arginine
Is DNA basic or acidic?
acidic bc of the phosphate backbone
What are the 2 acidic/ negatively charged (deprotonated) polar AAs?
1) aspartate (aspartic acid)
2) glutamate (glutamic acid)
Aspartate can make asparagine. How?
add an amino group to aspartate
What AA is this?
aspartate/ asp
Glutamate can make glutamine. How?
add an amino group to glutamate
Which AA is a neurotransmitter activator/stimulatory neurotransmitter?
glutamate
What happens if glutamate is decarboxylated?
will become GABA, which is an inhibitory neurotransmitter
What AA is this?
glutamate/ glu
Which 2 AAs are ketogenic (cannot make glucose)?
lysine and leucine
ALL OTHER AAs ARE GLUCOGENIC, NOT KETOGENIC
What are the 10 essential AAs?
-phenylalanine
-valine
-threonine
-tryptophan
-isoleucine
-methionine
-histidine
-arginine
-leucine
-lysine
PVT TIM HALL
Which 8 AAs are essential all the time?
-phenylalanine
-valine
-threonine
-tryptophan
-isoleucine
-methionine
-leucine
-lysine
Which 2 AAs are conditionally essential, only during positive nitrogen balance?
histidine and arginine
Which 3 amino acids do kinase modification (addition of phosphate group)?
serine, tyrosine, and threonine
define nitrogen balance
the normal condition in which the amount of nitrogen entering the body everyday equals the amount excreted
Define negative nitrogen balance
occurs when nitrogen loss exceeds nitrogen intake (less N in, more N out) and is associated with the following:
-protein malnutrition (kwashiorkor)
-dietary deficiency of 1+ essential AA (body will breakdown existing proteins to try to find essential AAs it needs)
-starvation (maramus, no carbs, lipids, or proteins in food, body eats itself, body muscles are breaking down)
-uncontrolled diabetes (insulin is low in diabetes and the body thinks you’re not eating so it will make more glucose even if you have a bunch, so insulin injections are needed to stabilize)
-infections
define positive nitrogen balance
occurs when the amount of nitrogen intake exceeds the amount excreted (more N in, less N out) and is associated with the following:
-growth (usually in children, kids create more proteins for growth)
-pregnancy
-recovery phase of injury or surgery (regain muscles, muscles increase because the change of AAs into protein through DNA replication, transcription, and translation)
-recovery from any negative nitrogen balance
What is the cause of pellagra?
niacin (vitamin B3) or tryptophan deficiency
Who commonly has pellagra?
people who obtain most of their food energy from maize, usually in rural parts of South America
What are the 4 Ds of pellagra?
-diarrhea
-dermatitis
-dementia
-death
Is pellagra easy to treat?
yes
What is the treatment for pellagra?
-tryptophan rich foods like meat, fish, and eggs
-take nicotinamide (a type of vitamin B3)
Wheat and rice are low in which AAs?
lysine and isoleucine
Maize is low in which AAs?
tryptophan and lysine
Vegetables, pulses, and legumes are low in which AAs?
methionine and tryptophan
What are the 2 types of protein?
high quality protein
-contains all/is an abudnance of all essential AAs
-animal proteins like eggs, meat, fish
low quality protein
-lacking some essential AAs
-plant based proteins
Grains are low in which AAs?
lysine and isoleucine
T/F: Peanuts are considered legumes, so a PB&J sandwich will give you all the essential AAs
true!
legumes are low in met and trp
grains are low in lys and ile
so together, you get the essentials you need
Nuts are low in which AAs?
lysine and isoleucine
Do fruits have AAs?
no
Does maize/corn have AAs?
no
Which AA is toxic to PKU patients?
phenylalanine
Which AA is non-essential but becomes essential for PKU patients?
tyrosine
What causes phenylketonuria (PKU)? What is it?
-genetic mutation that causes a deficiency in phenylalanine hydroxylase (PAH), which is the enzyme that converts phenylalanine to tyrosine
-phenylalanine builds up in the brain which causes mental retardation, seizures, and death
-newborn screening is done to avoid death
What should PKU patients avoid?
artificial sweetener like aspartame bc it contains phe+asp
so PKU patients should avoid anything sugar free
What is the tx for PKU?
low phe diet with some tyr intake
Which AA is a precursor for thyroid hormones T3 and T4?
tyrosine
Which AA is a precursor for melanin?
tyrosine
What is kwashiorkor? What is it caused by?
-due to negative nitrogen balance
-pt eats lots of carbs and lipids, but none, or not enough protein
-common in developing countries
-will result in low albumin (which is a protein in blood that keeps osmotic pressure), and causes big belly because of fluid in abdominal cavity (fluid will go to all the tissues and cause edema because of lack of albumin)
-will also result in low lipoprotein which causes fatty liver
What is thyroxine?
thyroid hormone T4
T/F: thyroid hormones are protein hormones
true, bc they’re made from AAs
The thyroid gland produces thyroxine (T4). How?
by attaching iodine atoms to the ring structure of tyrosine molecules
thyroxine contains 4 iodine atoms (note: triodothyronine T3 is identical to thyroxine but has only 3 iodine atoms per molecule)
What foods have high iodine?
seafood and salt
Glutathione (GSH) is an important antioxidant created by the body. What does it do?
GSH is a tripeptide that is biosynthesized in the body from cysteine, L-glutamic acid, and glycine
the sulfhydroyl group SH of cysteine serves as a proton donor and is responsible for it biological activity
2 GSH molecules will react with hydrogen peroxide and make water and GSSG which is the antioxidant
GSSG is made when S-S bond forms called a disulfide bond between 2 cysteines, which is now called a cystine
GSSG prevents damage to important cellular components caused by reactive oxygen species such as free radicals, hydrogen peroxide, lipid peroxides, or heavy metals
All AAs in animals are ____ form
L
What is taurine? Where is it found?
-nonstandard AA
-found in bile salts
What is hydroxyproline? Where is it found?
-nonstandard AA
-hydroxylated proline
-found in collagen
What is desmosine? Where is it found?
-nonstandard AA
-lysine crosslinked polypeptide (4 lysines linked together)
-found in elastin
What is the structure of an AA?
an amino group, carboxyl group, hydrogen atom, and an R group
AAs are linked together to form peptides with which types of bonds?
peptide bonds
The amino acids leucine, valine, and phenylalanine would best be described as….
A) polar and uncharged
B) polar and positively charged
C) nonpolar AAs
D) polar and negatively charged
C) nonpolar AAs
AAs can be described as
A) polar
B) hydrophobic
C) charged
D) uncharged
E) all of the above
E) all of the above
Of the common AAs, how many as considered essential?
A) 4
B) 8
C) 12
D) 20
B) 8
A polypeptide chain is polymerized in which direction?
amino to carboxyl (N to C terminal)
