Question

Could someone please help?

1. Which of the following best identifies base 1?

purine
pyrimidine
cytosine
nucleotide

2. Which of the following could base 2 bind with?

a purine
a guanine
an adenine
a pyrimidine

Answer 1

One easy way to remember the difference between purines and pyrimidines is that purines (the shorter word) are larger and are two-ring structures, whereas pyrimidines (a longer word) are smaller, one-ring structures.

Answer 2

Okay, let me tell you WHAT exactly each base is.

Base 1 is Adenine.

Base 2 is Guanine.

Now, you know the nucleo bases, right? Adenine, Thymine, Guanine, Cytosine.

And you know how ADENINE pairs with THYMINE?
And GUANINE pairs with CYTOSINE?

~~~~~~~~~~~

Now, there are two more things we have to remember:

1. ADENINE and GUANINE are PURINES.
2. THYMINE and CYTOSINE are PYRIMIDINES.

So, the two bases in your picture are both PURINES, because they are ADENINE and GUANINE.

~~~~~~~~~~~~~

Now, the answer to #1 is Purine, since Adenine isn't one of the choices.

Now, look at #2. It's guanine.

What does guanine pair with? Cytosine.

And what is cytosine? It's a pyrimidine.

So there, #2 would be a pyrimidine.

~~~~~~~~~~~~~~

Calliope made a good point.
Just remember that Purines bind with Pyrimidines.

And remember....

1. Adenine and Guanine are PURINES.
2. Thymine and Cytosine are PYRIMIDINES.

Answer 3

Oh yeah, I have a couple of tips for figuring out what base it is when you just see the structure:

First of all, G and A are the purines, i.e. the big two-ring structures. Just think about ATP and GTP -- two very important energy-storing molecules that you'll hear about a lot.

To remember which bases have an NH2 instead of a double bond O sticking out the top, the mnemonic I used is "CAN". Cytosine (C) and Adenine (A) have NH2.