Question

1. How can you tell if a solution is a good buffer or not?

2. What would happen if you messed up the 1^st level of protein organization? What would the effects be?

3. Using the abbreviated periodic table, how can you quickly figure out how many electrons, valence electrons, and energy levels an element has?

4. How does the number of valence electrons impact covalent bonding? Use an example. (hint: octet/duet rule)

Answer 1

1. A buffer is defined as a solution that resists small changes in pH when supplemented by small amounts of acid or base. It is formed by a mixture of a weak acid and its conjugate base, or a weak base and its conjugate acid. For the buffer to be considered good. it must have the following characteristics:

- The pKa(dissociation constant ) must be between 6-8, generally, to maintain an optimum pH of 6-8.

-It must be soluble in the solution you wish to regulate the pH.

-It must not be affected by slight variations in temperature.

- It must not react with the ions present in your solution, as it may hinder the reaction.

-It should be stable and easy to use.

2. The first level of protein organisation involves the primary sequence of the protein. It is simply arranging the amino acid residues in order and forming a polypeptide chain. If the first level of organisation is messed up, it could affect the overall structure and function of the protein itself. All proteins undergo folding that is facilitated by covalent, disulphide and hydrogen bonding of the amino acids or the protein. If any of the amino acids are missing, extra or replaced with another amino acid, then it affects the folding pattern and 3D structure of the protein. 3D structure of proteins also plays a very important role in its function.

A typical example of how messing up with the primary sequence can lead to malfunctioning of the protein can be explained using the case of sickle cell anaemia. In this condition, one of the polypeptide chains that form haemoglobin (an oxygen-carrying protein) is slightly changed. The glutamic acid that is normally the sixth amino acid of the haemoglobin β chain is replaced by a valine. This causes the RBCs to form a sickle-like shape, instead of the usual disk-like shape of the RBCs. This hinders oxygen transport of the RBC and leads to the condition of sickle cell anaemia.

3.

The periodic table gives us information regarding the Atomic number, Group number and the row number of the atoms.

Using the abbreviated periodic table, we can determine the :

1). Number of Electrons: The number of electrons is equal to the atomic number of the element. The atomic number is usually given on the top left corner of the box as represented in the diagram for H( hydrogen). Hydrogen has an atomic number of 1 and the number of electrons it contains is also 1.

2.) Valence Electrons: Valence electrons are the electrons present in the outer shell of the atom. It denotes the number of electrons an atom can readily receive or give away to obtain stability.

The number of valence electrons can be determined for an element based on its group number, excluding groups 3-12 since they contain transition elements whose valence electrons may be in the inner shells.

The number of valence electrons, based on the Groups the belong to are shown in the figure below:

3) The number of energy levels: The no. of energy levels in an atom is equal to the row number of the atom.on the periodic table. For example, Hydrogen and helium, both in the first row or period and they have 1 energy level(n=1).

4.  The valence electrons present in the atom impact the number of covalent bonds an atom can have, and also if a covalent bond is possible. As the octet/ duet rule states, all atoms prefer to have a stable electronic configuration, with a filled outer shell( 8 electrons for octet rule, and 2 electrons for duet ).

  For example in Methane( CH₄), carbon has four valence electrons and to obtain stability covalently bonds to 4 Hydrogen atoms, and completes its octet structure. Similarly, Hydrogen has 1 electron in its valence shell, and form 1 bond with a carbon atom to obtain duet configuration.