All categories

3 years ago

Identify two structural features of purines and Pyrimidines

Chemistry

1 answer:

Elena L [17]3 years ago

5 0

Answer:

The answers are:

Purines:

C. contain four ring nitrogen atoms.

E. contain two heterocyclic rings.

Pyrimidines:

C. contain only two ring nitrogen atoms.

E. contain one heterocyclic ring.

Explanation:

Purines and Pyrimidines are nitrogenous bases which are the building blocks of nucleic acids (DNA and RNA).

<u>Purines</u> are composed by two fused heterocyclic rings, one of them is a 6-ring and the other is a 5-ring. Each ring contains two nitrogen atoms which form part of the ring. Thus, the nitrogen positions in purines are: 1', 3', 7' and 9'. Depending on the functional groups bonded to the two-ring structure, a purine base can be Guanidine (G) or Adenine (A).

The structure of <u>Pyrimidines</u> is a single heterocycle ring wich contains two nitrogen atoms in positions 1' and 3'. Depending of the functional groups, they can be: Cytosine (C), Thymidine (T) and Uracil (U, which is found in RNA).

You might be interested in

HZ is a weak acid. An aqueous solution of HZ is prepared by dissolving 0.020 mol of HZ in sufficient water to yield 1.0 L of sol

dlinn [17]

Answer: below is the calculation for Ka

Explanation:

Download pdf

7 0

3 years ago

How does waer evapourate? one question brainlyist

Ratling [72]

Answer:

water evaportaes from heat it then turns into a gas then can go into a solid one day and repeat the cycle

Explanation:

4 0

3 years ago

How is energy transferred during convection?

Natalija [7]

The field of energy is wide and interesting due to it can be expressed by differents way.

The thermal energy is associated like internal energy of the atoms or molecules of a substance. The transfer of thermal energy as heat can take place via convection.

Convection via is the transfer of thermal energy due to the motion of the substance that contains the thermal energy.

4 0

3 years ago

Read 2 more answers

Which of the following phases of matter has a fixed shape and volume

kodGreya [7K]

A matter in the solid phase has a fixed shape and volume.

4 0

3 years ago

Read 2 more answers

Need help asap with this chemistry if someone could help me

Burka [1]

Answer:

Structure One:

N: -2
C: 0
O: +1

Structure Two:

N: 0
C: 0
O: -1

Structure Three:

N: -1
C: 0
O: 0.

Structure Number Two would likely be the most stable structure.

All five C atoms: 0
All six H atoms to C: 0
N atom: +1.

The N atom is the one that is "likely" to be attracted to an anion. See explanation.

Explanation:

When calculating the formal charge for an atom, the assumption is that electrons in a chemical bond are shared equally between the two bonding atoms. The formula for the formal charge of an atom can be written as:

$\text{Formal Charge} \\ = \text{Number of Valence Electrons in Element} \\ \phantom{=}-\text{Number of Chemical Bonds} \\\phantom{=} - \text{Number of nonbonding Lone Pair Electrons}$ .

For example, for the N atom in structure one of the first question,

N is in IUPAC group 15. There are 15 - 10 = 5 valence electrons on N.
This N atom is connected to only 1 chemical bond.
There are three pairs, or 6 electrons that aren't in a chemical bond.

The formal charge of this N atom will be $5 - 1 - 6 = -2$ .

Apply this rule to the other atoms. Note that a double bond counts as two bonds while a triple bond counts as three.

Structure One:

N: -2
C: 0
O: +1

Structure Two:

N: 0
C: 0
O: -1

Structure Three:

N: -1
C: 0
O: 0.

In general, the formal charge on all atoms in a molecule or an ion shall be as close to zero as possible. That rules out Structure number one.

Additionally, if there is a negative charge on one of the atoms, that atom shall preferably be the most electronegative one in the entire molecule. O is more electronegative than N. Structure two will likely be favored over structure three.

Similarly,

All five C atoms: 0
All six H atoms to C: 0
N atom: +1.

Assuming that electrons in a chemical bond are shared equally (which is likely not the case,) the nitrogen atom in this molecule will carry a positive charge. By that assumption, it would attract an anion.

Note that in reality this assumption seldom holds. In this ion, the N-H bond is highly polarized such that the partial positive charge is mostly located on the H atom bonded to the N atom. This example shows how the formal charge assumption might give misleading information. However, for the sake of this particular problem, the N atom is the one that is "likely" to be attracted to an anion.

5 0

3 years ago