Download This syllabus was adapted from Introduction to Biochemistry I taught

BIOC 371
Second Exam
Read the following sentences carefully and put (T) for the true sentence
or (F) for the false sentence and correct the false one:
1. In Bohr effect, the release of oxygen from hemoglobin is enhanced
when the pH is lowered or when the hemoglobin is in the
presence of a decreased of a pCO2. (F)
Increased
2. Allosterism is a type of interaction that occurs at the site other
than the active site but eventually affects the active site. ( T)
3. Alanine, valine and serine are nonpolar amino acids. ( F )
Serine is a polar
4. Collagen is rich in proline and cysteine, both of which are
important in the formation of the triple stranded helix. ( F )
Proline & Glysin
5. Most organic compound are dissociate in water and in organic
liquids. ( F )
Inorganic
6. Primary structure of proteins contains disulfide bond. ( F )
Peptide bond
7. The central dogma of biology is going from DNA to RNA to
proteins. ( T )
8. Feedback control is an enzyme regulation process in which
formation of a product inhibits an earlier reaction in the sequence.
( T)
Read the following sentences and choose the right choice:
1. Type of regulation of enzyme activity occurs when the same
enzyme appears in different forms in different tissues
(a) Proenzyme (b) allosteric enzyme (c) Isoenzyme (d) Zymogens
2. Binding of 2,3-bisposphoglycerate to deoxyhemoglobin will
(a)
(b)
(c)
(d)
Increase the oxygen affinity of deoxyhemoglobin
Decreases the oxygen affinity of deoxyhemoglbin
No effects
Both (a) & (b)
3. All the following statement are true except:
(a)
(b)
(c)
(d)
Protein conformations are very sensitive to temperature
change.
If the optimal temperature is reached, any further increase
in temperature alters the enzyme conformation.
After a high temperature increase above the optimum, the
decreased rate could be increased again by lowering the
temperature because change in conformation is reversible.
Temperature affects enzyme activity because it changes the
conformation of the enzyme.
4. A protein is the three-dimensional arrangement of every atom in
the molecule.
(a) Primary structure
(b) Secondary structure
(c) Tertiary structure
(d) Quaternary structure
5. Examples of inorganic compounds are
(a) CO2
(b) protein
(c) H2O (d) Both (a)&(c)
(e) Both (a)&(b)
6. Tryptophan and proline are
(a) Polar amino acid
(c) Basic amino acid
(b) Nonpolar amino acids
(d) Acidic amino acids
7. Isoelectric point is the pH at which the number of positive charges
(a)
(b)
(c)
(d)
(e)
Less than the number of negative charges
Higher than the number of negative charges
Equals to the number of negative charges
Both (a) &(b)
Both (a)&(c)
8. Collagen contain of some of posttranslation modification amino
acids and they are
(a) Hydroxylysin
(b) hydroxyproline
(c) Hydroxyglycine
(d) Both (a)&(b)
(e) Both (a)&(c)
Answer two of the following questions: (choose two)
1. Enzyme and substrate concentration can effect enzyme activity,
Draw the graph of the effect of substrate concentration on the rate
of enzyme-catalyzed reaction and explain why? (Note that enzyme
concentration, temperature and pH are constant)
In this case, the rate does not increase continuously. Instead, a point is reached after
which the rate stays the same even if we increase the substrate concentration further.
This happens because, at the saturation point, substrate molecules are bound to all
available active sites of the enzymes. Because the reactions take place at the active
sites, once they are all occupied, the reaction is proceeding at its maximum rate.
Increasing the substrate concentration can no longer increase the rate because the
excess substrate cannot find any active sites to which to bind.
2. Draw the structure of valine at pH 1 and at pH 12?
NH3+------CH--------COOH
I
R
R= CH-----CH3
I
CH3
In PH 1 the NH3+ and COOH groups are still protonated (have H)
because the PH lower than both pKa for both groups (NH3+ = 10 and
COOH =2)
NH2-------CH---------COOI
R
In PH 12 NH2 and COO- group are deprotanated (remove the H)
because the PH is higher than the pKa for both groups (NH3+ = 10
and COOH =2)
3. What the difference between coenzyme and cofactor, then give an
examples for both of them?
Cofactor is a non-protein portion and it is inorganic compound .
ex: Mg, metal ions.
Coenzyme is a non-protein portion and it is organic compound. ex
: B-vitamin