9.3

C28. What chemical group (phosphate group, hydroxyl group, or a nitrogenous base) is found at the 3ʹ end of a DNA strand? What group is found at the 5ʹ end?

A hydroxyl group is at the 3 end and a phosphate group is at the 5 end.

C4. What are the building blocks of a nucleotide? With regard to the 5ʹ and 3ʹ positions on a sugar molecule, how are nucleotides linked together to form a strand of DNA?

Answer: The building blocks of a nucleotide are a sugar (ribose or deoxyribose), a nitrogenous base, and a phosphate group. In a nucleotide, the phosphate is already linked to the 5 position on the sugar. When two nucleotides are hooked together, a phosphate on one nucleotide forms a covalent bond with the 3 hyrdroxyl group on another nucleotide

1. Which of the following could be the components of a single nucleotide found in DNA? a. Deoxyribose, adenine, and thymine b. Ribose, phosphate, and cytosine c. Deoxyribose, phosphate, and thymine d. Ribose, phosphate, and uracil

C

pyrimidines

Name of class of single-ring, nitrogen-containing bases (found in nucleotides) which includes Thymine, Cytosine, and Uracil.

3' hydroxyl

the -OH group attached to the 3ʹ carbon is important in allowing nucleotides to form covalent linkages with each other.

3. In a nucleotide, what functional groups are attached to the 5' carbon and the 3' carbon?

5'- attached to Phosphate 3' attached OH

deoxyribose

5-carbon sugar found in deoxyribonucleotides; Has a -H on the 2' carbon instead of a -OH.

ribose

5-carbon sugar present in ribonucleotides.

ATP

A nucleotide composed of ribose, adenine, and three phosphate groups is called adenosine triphosphate

ADP

adenosine diphosphate -nucleotide(not nucleoside because has phosphate) contains adenine, 2 phosphate and 1 ribose

2. Compare and contrast the structure of nucleotides found in DNA versus RNA

As shown in Figure 9.7, nucleotides vary with regard to the sugar and the nitrogenous base. The two types of sugars are deoxyribose and ribose, which are found in DNA and RNA, respectively. The five different bases are subdivided into two categories: the purines and the pyrimidines. The purine bases, adenine (A) and guanine (G), contain a double-ring structure; the pyrimidine bases, thymine (T), cytosine (C), and uracil (U), contain a single-ring structure. The sugar in DNA is always deoxyribose. In RNA, the sugar is always ribose. Also, the base thymine is not found in RNA. Rather, uracil is found in RNA instead of thymine. Adenine, guanine, and cytosine occur in both DNA and RNA.

phosphate

Chemical group found on the 5' carbon of nucleotides; participates in the dehydration synthesis reactions to form a phosphodiester bond between adjacent nucleotides.

pentose sugar

General name for a 5-carbon sugar; includes ribose and deoxyribose.

AMP

If a nucleotide contains ribose, adenine, and one phosphate, it is named adenosine monophosphate,

2. What does 1', 2', 3', etc. mean with respect to ribose and deoxyribose?

In comparison, the five carbons found in the sugars are designated with primes, such as 1ʹ, to distinguish them from the numbers found in the bases.The locations of the attachment sites of the base and phosphate to the sugar molecule are important to the nucleotide's function. In the sugar ring, carbon atoms are numbered in a clockwise direction, beginning with a carbon atom adjacent to the ring oxygen atom. The fifth carbon is outside the ring structure. In a single nucleotide, the base is always attached to the 1ʹ carbon atom, and one or more phosphate groups are attached at the 5ʹ position. As discussed later, the -OH group attached to the 3ʹ carbon is important in allowing nucleotides to form covalent linkages with each other.

nucleoside

contains only a sugar and a base. NO PHOSPHATE INVOLVED. only sugar attached to a base

purines

Name of class of double-ring, nitrogen-containing bases (found in nucleotides) which includes Adenine and Guanine.

C13. List the structural differences between DNA and RNA.

C13. Answer: The sugar in DNA is deoxyribose; in RNA it is ribose. DNA contains the base thymine, while RNA has uracil. DNA is a double helical structure. RNA is single stranded, although parts of it may form doublestranded regions.

C5. Draw the structure of guanine, guanosine, and deoxyguanosine triphosphate.( just explain and don't draw them

C5. Answer: The structures can be deduced from Figures 9.7 and 9.9. Guanine is the base by itself. Guanosine is the base attached to a ribose sugar. Deoxyguanosine triphosphate is a base attached to a deoxyribose sugar with three phosphates.

2. A key difference between the nucleotides found in DNA versus RNA is that a. DNA has phosphate, but RNA does not. b. DNA has deoxyribose, but RNA has ribose. c. DNA has thymine, but RNA has uracil. d. both b and c are correct. .

D

1. Chemically, how does ribose differ from deoxyribose?

DNA contains deoxyribose as its sugar and the bases A, T, G, and C. RNA contains ribose as its sugar and the bases A, U, G, and C. In a DNA or RNA strand, the oxygen on the 3ʹ carbon is linked to the phosphorus atom of phosphate in the adjacent nucleotide. The Ribose contains on the 2'd carbon of Sugar an OH, deoxyribose contains H

6. Distinguish between AMP, ADP, and ATP.

If a nucleotide contains ribose, adenine, and one phosphate, it is named adenosine monophosphate, abbreviated AMP. A nucleotide composed of ribose, adenine, and three phosphate groups is called adenosine triphosphate, or ATP. By comparison, a nucleotide made of deoxyribose, adenine, and three phosphate groups is referred to as deoxyadenosine triphosphate (dATP). the difference between the three is how many phosphate groups added mono-1 di-2 tri-3

3. Use the terms listed below to correctly explain concepts, assigned figures, and specified end-of-chapter questions. Phosphate Nitrogenous/Nitrogen-containing base Pentose sugar Deoxyribose Ribose 3' hydroxyl 5' phosphate Purines Pyrimidines Adenine (A) Guanine (G) Thymine (T) Cytosine (C) Uracil (U) Nucleoside AMP ADP ATP

Nucleotide is composed of a phosphate a sugar and a nitrogenous base. Phosphate is attached at 5' carbon of sugar, outside the ring. Sugar is also called pentose sugar because contains 5 Carbons. If the sugar has H' at 2' C is called deoxyribose, if has OH' at 2' C is called ribose. The 3' hydroxyl contains OH at the 3' end and forms covalent linkage with the next phosphate. The nitrogenous base is attached at the 1' Carbon. There are two types of nitrogenous bases: purines and pyrimidines. Purines have short name long structure-double rings A and G, pyrimidines form single ring C,T,U. C is found only in Deoxyribose, U only in Ribose. If a chemical structure contains a nitrogenous base and a sugar with no phosphate is called nucleoside. Adenosine plus ribose sugar plus one phosphate group is called AMP. Adenosine plus ribose sugar plus two phosphate groups is called ADP and if same thing with three phosphates is called ATP.

5. Is uracil associated with DNA and/or RNA nucleotides? It is classified as a pyrimidine or purine base?

RNA, pyrimidine

5' phosphate

The fifth carbon is outside the ring structure. In a single nucleotide, the base is always attached to the 1ʹ carbon atom, and one or more phosphate groups are attached at the 5ʹ position.

1. Describe the structure of a nucleotide.

The nucleotide is the repeating structural unit of both DNA and RNA. A nucleotide has three components: at least one phosphate group, a pentose sugar, and a nitrogenous base.

guanine G

purine double ring, contains NH2 and C=O

4. Which type of base (purines or pyrimidines) is a double ring structure?

purines

adenine A

purines double ring, contains an NH2

cytosine C

pyrimidine single ring contains NH2

Thymine T

pyrimidine single ring only DNA, contains two C=O bonds, and 1 CH3

Uracil U

pyrimidine single ring only RNA contains only two C=O bonds