Nucleotide Structure & the Phosphodiester Bond

Question 1

Both DNA and RNA are polymers that are made up of

Answer 1

many repeating units called nucleotides

Question 2

Each nucleotide is formed from:

Answer 2

A pentose sugar (a sugar with 5 carbon atoms)

A nitrogen-containing organic base

A phosphate group

Question 3

The components of a DNA nucleotide are:

Answer 3

A deoxyribose sugar with hydrogen at the 2’ position

A phosphate group

One of four nitrogenous bases - adenine (A), cytosine(C), guanine(G) or thymine(T)

Question 4

The components of an RNA nucleotide are

Answer 4

A ribose sugar with a hydroxyl (OH) group at the 2’ position

A phosphate group

One of four nitrogenous bases - adenine (A), cytosine(C), guanine(G) or uracil (U)

Question 5

The presence of the …………..makes RNA more susceptible to hydrolysis

which means DNA is the ……… molecule and RNA the what molecule

Answer 5

2’ hydroxyl group

This is why DNA is the storage molecule and RNA is the transport molecule with a shorter molecular lifespan

Question 6

Purines & Pyrimidines
The nitrogenous base molecules that are found in the nucleotides of DNA ..,…,….,.)
and RNA (.,..,..,..,)

Answer 6

A, T, C, G

A, U, C, G

Question 7

The nitrogenous base molecules that are found in the nucleotides of DNA (A, T, C, G) and RNA (A, U, C, G) occur in two structural forms: purines and pyrimidines

The bases adenine and guanine are ……… with a what structure

Answer 7

are purines – they have a double ring structure

Question 8

The nitrogenous base molecules that are found in the nucleotides of DNA (A, T, C, G) and RNA (A, U, C, G) occur in two structural forms: purines and pyrimidines

The bases cytosine, thymine and uracil are …………. with a what structure

Answer 8

are pyrimidines – they have a single ring structure

Question 9

Separate nucleotides are joined via …………. and where do these reaction take place

Answer 9

condensation reactions

These condensation reactions occur between the phosphate group of one nucleotide and the pentose sugar of the next nucleotide

Question 10

A condensation reaction between two nucleotides forms a …………… and why is it called that

Answer 10

phosphodiester bond

It is called a phosphodiester bond because it consists of a phosphate group and two ester bonds (phosphate with double bond oxygen attached - oxygen - carbon)

Question 11

The chain of alternating phosphate groups and pentose sugars produced as a result of many phosphodiester bonds is known as the ……….

Answer 11

sugar-phosphate backbone (of the DNA or RNA molecule)