AP Bio Insta-Review Topic 1.6*: Nucleic Acids

What are the three components that make up a nucleotide?

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Answer explanation

› Pentose sugar

› Nitrogenous Base

› Phosphate

How are all of the components of a nucleotide oriented? 

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Answer explanation

The pentose sugar has three sites that are important to binding:

1'- nitrogenous base

3'- hydroxyl (but this is a functional group on the pentose sugar not an additional component)

5'- phosphate

How does the pentose sugar differ between DNA and RNA?

• DNA= deoxyribose,

  RNA= ribose

• DNA= dextrose, RNA= ribose

• DNA= deoxyribose,

  RNA= ribozyme

• DNA= dextrose, RNA= ribozyme

Answer explanation

DNA is deoxyribonucleic acid while RNA is ribonucleic acid. DNA has deoxyribose and RNA has ribose. The deoxyribose is missing an oxygen on the 2nd carbon of the sugar.

How does the nitrogenous base differ between DNA and RNA?

• DNA - cytosine, RNA - guanine

• DNA - uracil,

  RNA - thymine

• DNA - guanine, RNA - cytosine

• DNA - thymine, RNA - uracil

Answer explanation

DNA has adenine, thymine, cytosine, & guanine. RNA has adenine, uracil, cytosine, & guanine.

Adenine will pair with either thymine or uracil depending whether its DNA or RNA.

Test Tip: If you are asked for DNA and there are “U”s in the answer, you can cross those options out.

How does the phosphate differ between DNA and RNA?

• DNA- 1 phosphate,

  RNA- 2 phosphate

• DNA- phosphate acts as acid,

  RNA- phosphate acts as base

• There is no difference

Answer explanation

All nucleotides have:

› pentose sugar (deoxyribose or ribose)

› nitrogenous base (adenine, thymine, uracil, cytosine, or guanine)

› phosphate

Traditionally, how is the strands different?

• DNA - single,

  RNA - double

• DNA - single,

  RNA - triple

• DNA - double,

  RNA - single

• DNA - triple,

  RNA - single

Answer explanation

DNA is a double stranded molecule with strands running antiparallel and bound by hydrogen bonds

mRNA is a single stranded molecule formed from base pairing with a split DNA strand.

Which nitrogenous base is not found in DNA?

• Adenine

• Cytosine

• Thymine

• Uracil

Answer explanation

DNA has adenine, thymine, cytosine and guanine.

There is no uracil. This is only found in RNA molecules.

What is the pentose sugar found in DNA?

• Deoxyribose

• Dextrose

• Ribose

• Rubisco

Answer explanation

DNA stands for deoxyribonucleic acid and has the sugar deoxyribose. This is the same as the ribose, except it is missing an oxygen on the 2nd carbon in the pentose sugar.

What is the pentose sugar found in RNA?

• Deoxyribose

• Dextrose

• Ribose

• Rubisco

Answer explanation

RNA stands for ribonucleic acid and has the sugar ribose. This is the same as the deoxyribose, except it has an oxygen (specifically a hydroxyl group) on the 2nd carbon in the pentose sugar.

Which nitrogenous base is not found in RNA?

• Adenine

• Cytosine

• Thymine

• Uracil

Answer explanation

RNA has adenine, uracil, cytosine and guanine.

There is no thymine. This is only found in DNA molecules.