Download Slide 12

Biochemistry notes : lec. # 12
Slide 10
* Each amino acid has two major groups ( carboxylic group and amine
group )
-COOH
-NH2
OH-
H+
+
O
H
-C-
+ -N-
>>
>> H2O ( dehydration/condensation reaction )
O H
peptide bond
-C N-
(covalent bond )
*Sequence of amino acids matters :
Example : If you have 2 amino acids you can make 2 peptides
( Ala – Cys ) and ( Cys – Ala ) are 2 different peptides
-By convention , we read the sequence of amino acids in a peptide from
free amino group toward free carboxylic group
Slide 11
* Athletes usually use supplement amino acids because they are protein
building .
* Arginine : - the major component of seminal fluid in males .
- supplement arginine is used for sexual impotence .
Slide 12
*Tyr & Trp >> special attention > because they are key precursors for
many hormones and neurotransmitters in human body .
*Tryptophan is the precursor for serotonin .
-Serotonin : a neurotransmitter found mainly in the nervous system
*Sedation : relaxation of muscles , act as drugs ‫المخدرات‬
*Tryptophan found in large amounts in milk , so milk aids to sleep
especially in children .
Slide 13
* Monoamines (catechol amines): -dopamine
-epinephrine
*Monoamines hydrolyzed in the body by monoamine oxidases ( MAOs )
enzymes which inhibit their epinephrine effects
-there are monoamine oxidase inhibitor drugs which inhibit these
enzymes , so epinephrine stays in large amounts inside the human body
and gives activity to the patient .
-depression patients  monoamine oxidase inhibitors > to increase the
level of tyrosine , dopa , dopamine and epinephrine inside human body
*Beautiful mind is a movie .
*more tyrosine  more activity (that’s why some people take tyr
supplement in the morning )
*Tyramine : – similar to tyrosine in structure
-has the same effect as epinephrine (constricition of blood
vessels and increase blood pressure )
- found in cheese and red wine .
Slide 14
*Glutamate + Na  monosodium glutamate (MSG)
*Histidine (-COO- )  histame
(decarboxylation reaction)
Decarboxylase enzyme
*Histamine : is responsible for allergic reactions inside human body .
Slide 15
*Asporatame composed of 2 amino acids :
aspartyl and phenylalanine .
slide 16
*Phenylketonuria : genetic disorder, ( defect in the enzyme
that convert phenylalanine into tyrosine ).
the level of phenylalanine increase inside the body
the metabolites of phenyalanine increases (phenylpyruvate ,
phenyllactate , and phenylacetate) causes mental retradation inside
the brain
deficient tyrosine  deficient of tyrosine metabolites (dopadopamine-epinephrine)
no activity for the patient
* Aspartame carry a warning for phenylketonuria patients
because it is containing phenylalanie .
*Alatame  phenylketonuria patients if they want to take diets they
can take it instead of aspartame .
Slide 17
*Antioxidant : reacte with free radicals
*Glutathione  has reactive thiol group (-SH) the hydrogen protons (H+)
bind to the free radicals and cancel bad effect of free radicals inside
human body .
-Sulfur binds to another sulfur forming disulfide bond of two glutathione
Slide 18
*Analgesics : medications to relieve pain ( e.g. profine , voltaren , and
revanin ) .
*Morphine  gives to the patients of cancer after operations to relieve
pain .
Slide 19
*Oxytocin and vasopressin
-Are two hormones each one composed of 9 amino acids in ( sigma-like
shape >> cyclic ring + extra 3 acids ) .
-The ring formed because number 1 amino acid and number 6 amino
acid are cysteine and they can form disulfide bond with each other .
*Oxytocin :
-Secreted from posterior pituitary gland , it's receptors found in the
uterine wall and in breasts
-receports increase during pregnancy until time of delivery when the
greater contraction of uterus muscles occurs( positive feedback)
-Breasts receptors found on smooth muscle around mammary glands in
the breasts
-in breast-feed oxytocin stimulates contraction of smooth muscles and
then milk secreted
*Reabosorption of water in kidney  to increase blood pressure
*Blood pressure : the pressure that exerted by blood on the walls of the
vessels
*Water reabsorption  increases the amount of fluid in certain volume
– blood vessels - so the pressure increased
Questions
1-which of the following amino acids are polar :
abcd-
sreine
tyrosine
arginine
all of abore
the answer is : d
2-of the amino acids( lysine, glutamic acid, tryptophan and glutamine )
which is a basic amino acid with a positive charge :
abcd-
lysine
glutamic acid
tryptophane
glutamine
the answer is : a
3-which of the following amino acids is not positively charged :
the answer is : glutamic acid
4-which of the following amino acids could form ionic interactions (
positively charged and negatively charged )
abcd-
aspartic acid + lysine
arginine + glutamine
glutaminc acid + valine
proline + glycine
the answer is : a
5-which of the following amino acids is the largest of all amino acids :
the answer is : tryptophan
6-which of the following amino acids side chains have a single methyl
group :
the answer is : alanine
7-the 3 letter abbreviation Asn correspondes to which amino acid :
the answer is : asparagine
8-identify the amino acids present in the peptide shown below
( From free amino group  carboxylic group )
9-Bradykinin, is a peptide which regulates the blood pressure inside the
human body and present kinking :
 duo to presence of proline
10-which of the following amino acids is the smallest of all amino acids :
the answer is : glycine
11-oxytocin is held in a cyclic configuration :
 due to presence of 2 cysteine #1 and #6 so they can form disulfide
bond .
12-which of the following amino acids can form a special covalent bond
called the disulfide bond :
the answer is : cysteine
13-interactions of amino acids with interior of the protein
( The pairs which make hydrophic interactions  nonpolar amino acids )
abcd-
proline + phenyalanine
lysine + serine
threonine + leucine
alanine + glycine
the answer is : a & d
14-which pairs form ionic interactions (acid + base)
abcd-
valine + leucine
glutamic acid + lysine
methionine + cysteine
aspartic acid + histidine
the answer is : b & d
15-what amino acids do the following abbreviations stand for :
Ala >> alanine
Cys >> cysteine
Asp >> aspartic acid
16-name all tripeptides that contains valine-methionine-luecine
( without repeating )
123456-
valine – methionine - luecine
valine – leucine - methionine
methionine – valine – leucine
methionine – leucine – valine
leucine – methionine – valine
leucine – valine - methionine
17- which of the following amino acids are most likely to be found in the
outside of the globular protein and which of them are more likely to be
found in the inside of the protein :
( in globular protein , the outside is hydrophilic and the inside is
hydrophobic )
Valine >> inside
Aspartate >> outside
Histidine >> outside
Alanine >> inside
** the body can only absorb either single amino acids or dipeptides .
18- at neutral pH which of these amino acids are ( basic , acidic , or
neutral )
Glutamine >> neutral / polar
Histidine >> basic
Methionine >> neutral / non-polar
Glutamic acid >> acidic
19- which of the following carbon atoms is chiral
20- which would you expect to be more soluble in water :
a- Peptide rich in alanine and leucine
b- Peptide rich in glycine and aspartic acid
The answer is : b
Best wishes
Mohammad R. Al-Dibs