Portage Biochemistry- Module 6

What is the difference between a nucleoside and nucleotide?

A nucleoside is formed from the covalent bonding of a base, purine or pyrimidine, to either ribose or 2-deoxyribose. Nucleotides are built from a nitrogen-containing organic base, a monosaccharide, and phosphate.

What characteristic makes purines and pyrimidine heterocyclic?

Each has a ring with nitrogen in the ring instead of all carbon atoms in the ring.

Is this molecule ribose or 2-deoxyribose? Briefly explain what structural information was used to determine this.

Ribose. This molecule contains an -OH on carbon 2. 2-deoxyribose has an -H atom on the second carbon.

Is the following a pyrimidine or purine? Provide the name and one-letter symbol.

Pyrimidine. It is thymine (T).

What is the difference between thymine and uracil?

These two bases differ by a methyl group. Thymine has an extra methyl group on the ring.

From the course and module information, where in a eukaryotic or prokaryotic cell, is the DNA located? How about the RNA?

DNA is located in the nucleus of a eukaryotic cell or the nucleoid of a prokaryotic cell. RNA is found in the nucleus, on the ribosome, and in other parts of the cell.

Which DNA and RNA bases contain a carbonyl group?

Guanine, cytosine, thymine, and uracil all contain C=O group attached to the rings. Adenine is the only base that does not.

What constitutes the backbone of DNA?

In DNA, this consists of the alternating deoxyribose and phosphate groups linked together through covalent bonds (Figure 6.6).

How many hydrogen bonds form between A and T?

Two hydrogen bonds are formed between these two bases. G and C form three H-bonds.

Which nucleic acid is single-stranded?

RNA. RNA forms single strands. Particularly this was noted in this module for tRNA. DNA forms a double helix.

What interactions stabilize the DNA double helix?

Hydrogen bonds stabilize the helix. Each AT pair and form two hydrogen bonds, and each GC pair forms three hydrogens that stabilize the helix, permitting it to maintain this shape.

What type of RNA has a sequence that is complementary to DNA?

mRNA is complementary so that it can transmit the information to the ribosome.

Which has the largest molecular weight chains: mRNA, tRNA, or rRNA?

rRNA. These molecules make up ribosomes.

What structural forms of DNA have a right-handed helix? Which form has a left-handed helix?

The A- and B-forms are right-handed, while the Z-form is left-handed.

What function does cAMP perform in cells?

cAMP is a communication molecule in cellular signaling. It acts as a secondary messenger.

In DNA, guanine always pairs with ________.

Thymine

Guanine

Uracil

Cytosine

Both A and B

Cytosine

The repeating units, or monomers, that are linked together to form nucleic acids are known as _________.

Nucleosides

Nucleotide

Genes

Purines

Codons

Nucleotide

The Z-form helix of DNA is stabilized mainly by __________.

Ionic bonds

Covalent bonds

Hydrogen bonds

Ion-dipole bonds

Hydrogen covalent bonds

Hydrogen bonds

Which of the following pentose sugars is a constituent of DNA?

Xylose

Ribitol

2-deoxyribose

Arabinose

Ribose

2-deoxyribose

Purines have ________ ring(s), (each) containing ______ nitrogen(s), whereas pyrimidines have ________ ring(s), (each) containing ______ nitrogen(s).

1; 1; 1; 1

1; 2; 1; 2

2; 1; 1; 2

2; 2; 1; 1

2; 2; 1; 2

2; 2; 1; 2

Identify the base uracil from among the following structures.

B

_______ enables the production of proteins from genetic information.

Codons

Ribose nucleic acid

Deoxyribonucleic acid

Ribonucleic acid

Glycerol nucleic acid

Ribonucleic acid

Identify the complementary bases from the following.

Adenine-Cytosine

Adenine- Thymine

Guanine-Thymine

Guanine-Adenine

Cytosine-Uracil

Adenine- Thymine

How many hydrogen bonds are made between T and its complementary nucleotide?

2

3

4

5

6

2

The base sequence along one strand of DNA of 5'-GCATGAGCC-3'. What is the sequence of the complementary strand of DNA?

5'-CTAGTCCGC-3'

3'-CGTACTCGG-5'

3'-CTAGTCCGC-5'

3'-CAGTCAGCT-5'

5'-CTGACTACG-3'

3'-CGTACTCGG-5'

Which of the following types of RNA functions as the molecule to bring amino acids to ribosomes?

mRNA

gRNA

rRNA

snRNA

tRNA

tRNA

The ________ is the set of three sequential nucleotides that encodes for a particular amino acid.

Anticodon

Allele

Gene

Codon

Chromosome

Codon

The type of DNA that has a left-handed helix is the __________.

A form

B Form

C form

L form

Z form

Z form

Which of the following is a second messenger in cells?

FAD

cAMP

AMP

dATP

UTP

cAMP

Which of the following acts as a coenzyme?

FAD

ATP

AMP

cAMP

GGG

FAD

rRNA makes up about _________ percent of ribosomes.

65

35

20

90

0

65

The conclusion that G and C are present in DNA in equimolar amounts is credited to ______.

James Watson

Francis Crick

Erwin Chargaff

Both A and B

None of the above

Erwin Chargaff

he primary sequence of DNA is written __________.

N to C

C to N

5' to 3'

3' to 5'

Both A and D

5' to 3'

In the Watson-Crick model for the double helix, which statement is NOT true?

The two strands run anti-parallel to one another

The base-pairing occurs on the inside of the double helix.

The double helix (B form) is right-handed.

Two equally sized grooves that run up the sides of the helix.

The two strands have complementary sequences.

Two equally sized grooves that run up the sides of the helix.

In the tRNA, below, the amino acid is attached to which position?

A (top, open end)

Besides ATP, which other nucleotide is part of energy storage in cells?

ATP

UTP

TTP

CTP

GTP

GTP

Which of the following is a nucleoside?

Both A and C

Which of the following is heterocyclic?

C (has a Nitrogen)

A major component of RNA but not DNA is:

AMP

GMP

UMP

CMP

TMP

UMP

On the following molecule, which letter (A, B, C, D, or E) indicates the nucleotide base?

A

(Short answer) One strand of a double-helical DNA has the sequence (5')GCGCAATATTCTCAAAATAT(3').

A) Write the base sequence of the complementary strand.

B) Explain what complementary means in nucleic acid chemistry.

A. (3')CGCGTTATAAGAGTTTTATA(5')

B. The nucleotide sequences of complementary strands are such that, whenever an A occurs in one strand, there is a T in the other strand with which it can form a hydrogen-bonded base pair. Whenever a C occurs in one strand, a G occurs in the other. A is the base that is complementary to T, and C is the base complementary to G.

(Short answer) DNA can form a double helix. Describe how noncovalent interactions contribute to the three-dimensional shapes and structures of the helix.

Hydrogen bonding in regions of complementarity between DNA chains results in the formation of the natural helical structure. The complementary base pairing of A-T and G-C permit H-bonds to form.

(Short answer) In one sentence, identify the most obvious similarity between the A-form of DNA and the B-form of DNA.

Both A and B form a right-handed helix.

n nucleic acid chemistry, compounds that contain an organic nitrogen-containing base and a sugar are called ____A_____.

Two pyrimidine found in DNA in are _____B____ and ____B____.

A pyrimidine found in all DNA but not in RNA is ____C_____.

In DNA, the pair ____D_____ is held together by two hydrogen bonds.

In RNA, the pentose ______E______ serves as the monosaccharides.

A) Nucleosides

B) Cytosine and Thymine

C) Thymine

D) A-T

E) Ribose

(Short answer) The monomers of DNA nucleic acids, called nucleotides, consist of three parts. What are those three parts? (Give three)

phosphoric acid, deoxyribose (a pentose sugar), and an organic base.