Cystine is dimer of Cystein amino acid formed by oxidation reaction. Its main function is to provide mechanical strength to proteins and allow them to retain their 3-D structures and also serves as a substrate for the cystine-glutamate antiporter.
As shown in figure cystine has two amino groups (highlighted blue) and two carboxylic groups (highlighted green). In its original structure cystine is neutral in nature as it has equal number of basic (NH₂) and acidic (COOH) moieties along with two chiral centers (asymmetric carbons) highlighted with red spots.
When one -NH₂ group is replaced by -COOH group the cystine is converted into an acidic compound with three COOH groups and a NH₂ group. Also, one asymmetric carbon will convert into a symmetrical carbon with a loss of one chiral carbon.
In second step, when another NH₂ is replaced by COOH, the acidic strength of resulting compound will increase along with conversion of last chiral carbon into symmetric carbon.
Therefore, the final structure will be acidic in nature with zero chiral carbons as shown in figure attached below.
Answer:
Lowering the temperature typically reduces the significance of the decrease in entropy. That makes the Gibbs Free energy of the reaction more negative. As a result, the reaction becomes more favorable overall.
Explanation:
In an addition reaction there's a decrease in the number of particles. Consider the hydrogenation of ethene as an example.
.
When 
is added to 
(ethene) under heat and with the presence of a catalyst, 
(ethane) would be produced.
Note that on the left-hand side of the equation, there are two gaseous molecules. However, on the right-hand side there's only one gaseous molecule. That's a significant decrease in entropy. In other words, 
.
The equation for the change in Gibbs Free Energy for a particular reaction is:
.
For a particular reaction, the more negative 
is, the more spontaneous ("favorable") the reaction would be.
Since typically for addition reactions, the "entropy term" of it would be positive. That's not very helpful if the reaction needs to be favorable.
(absolute temperature) is always nonnegative. However, lowering the temperature could help bring the value of
Answer: Option (c) is the correct answer.
Explanation:
Ionic compounds are the compounds formed by transfer of electrons. An ionic compound contains ions which are arranged in an ordered lattice.
This lattice is repeating in nature and thus results in the formation of a compound.
For example, NaCl is an ionic compound that has an ordered crystal lattice.
Thus, we can conclude that the statement they are made up of particles that are arranged in a repeating pattern, is true.
Answer: 
represents oxidation.
Explanation:
Oxidation-reduction reaction or redox reaction is defined as the reaction in which oxidation and reduction reactions occur simultaneously.
Oxidation reaction is defined as the reaction in which a substance looses its electrons. The oxidation state of the substance increases.
Example:
Reduction reaction is defined as the reaction in which a substance gains electrons. The oxidation state of the substance gets reduced.
Example: 
represents oxidation.
