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Biochemistry > DNA Lecture 1 > Flashcards

DNA Lecture 1 Flashcards

1
Q

type of RNAs that are a component of

ribosomes

A

rRNAs

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2
Q

type of RNAs that are intermediaries,
transmitting genetic information from the site of
DNA in a cell (primarily the nucleus) to the site of
protein synthesis in the cell (ribosome).

A

mRNAs

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3
Q

Type of RNAs that are adapter molecules,
translating the information in mRNA into a
specific amino acid sequence

A

tRNAs

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4
Q

The repositories and
transmitters of genetic information for every
cell, tissue and organism

A

nucleic acids

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5
Q

nucleic acids are polymer chains with
similar monomers (called nucleotides) connected
by

A

covalent bonds

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6
Q

What are the three characteristic components of nucleotides

A

1) A phosphate group
2) A five-carbon sugar
3) A heterocyclic nitrogenous base

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7
Q

What are the five carbon sugars in RNA and DNA?

A

beta-D-ribose in RNA

beta-2’-deoxy-D-ribose in DNA

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8
Q

The molecule in RNA/DNA without the phosphate group is called the

A

nucleoside

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9
Q

The numbered carbon atoms of the ribose component in the nucleotides are given a prime (‘) designation to distinguish them from the numbered atoms of the

A

Nitrogenous base

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10
Q

In DNA nucleotides, the C-2 hydroxyl group of ribose in replaced by…(called 2-deoxy)

A

A hydrogen atom

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11
Q

refers to the stereochemical configuration of C-1 (anomeric carbon) in the cyclic form of 2-deoxy-D-ribose. Note that the OH on the C-1 is on the same side of the ring as C-5

A

β

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12
Q

Refers to the stereochemical configuration of the C-4 (penultimate carbon). It has the same configuration as D-glyceraldehyde

A

D

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13
Q

Ribose is an _____ because it has an aldehyde group

A

Aldose

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14
Q

In _______, the straight chain (aldehyde) and ring (β-furanose) forms of free ribose are in equilibrium

A

Solution

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15
Q

In _______, both types of pentoses are in their β-furanose form (closed-five membered ring)

A

Nucleotides

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16
Q

n solution, all monosaccharides with five or more carbon atomsin the backbone occur predominantly as cyclic (ring) structures in which the carbonyl group forms a ____ with the oxygen of the hydroxyl group along the chain

A

covalent bond

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17
Q

The cyclic hemiacetal form that results from intramolecular reaction of the the C-4 OH group with the C-1 aldehyde group

A

D-ribose

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18
Q

The anomeric carbon (C-1) is the

The chiral carbon that is most distant from the carbonyl carbon is the

A

Hemiacetal carbon

Penultimate carbon

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19
Q

Is the pentose ring planar?

A

No, it has puckered conformations

20
Q

The bases in nucleotides can be characterized as ___ and _____

A

purines and pyrimidines

21
Q

Bases in nucleotides that are monocyclic nitrogen heterocycles

A

Pyrimidines

22
Q

Bases in nucleotides that are bicyclic nitrogen heterocycles

A

Purines

23
Q

Both DNA and RNA contain two major ____ bases:

A

Purine, Adenine (A) and Guanine (G)

24
Q

DNA and RNA also contain two major _____ bases

For DNA, they are

A

pyrimidine

cytosine and thymine

cytosine and uracil

25
Q

Why are purines and pyrimidines referred to as bases?

A

The NH2 and or ring nitrogen atoms are weakly basic, the lone pair of electrons on the nitrogen atom can accept a proton in an acid-base equilibrium

26
Q

Another characteristic of nucleotide bases is that they can exist in other ______ forms

There reaction equilibria favors the ____ and _____ forms (they are the most stable)

A

tautomeric

amino and keto

27
Q

Tautomeric forms of nucleotide bases have different ______ characteristics

A

H-bonding

28
Q

N-1 of adenine is an H-bond _____ in the amino form, but an H-bond ____ in the imino form

A

acceptor

donor

29
Q

The keto oxygen on C-4 of thymine can as as an H-bond ______ while the nol form can act as an H bond ______

A

acceptor

donor

30
Q

Why is hydrogen bonding so important in nucleotide bases?

A

H-bonding of amino and keto forms of the bases allows a complimentary association of two strands of DNA

31
Q

What are the complimentary base pairs in DNA and RNA?

A

DNA: A-T , C-G

RNA A-U, C-G

32
Q

Since the imino form of A can’t form H-bonds with the keto form of T in the same way, spontaeneous ___ can result from the formation of abnormal base pairs

A

mutations

33
Q

The purines and pyrimidines are what kind of molecules?

A

Aromatic

34
Q

Electron delocatlization among ring atoms or purines and pyrimidines results in most of the bonds having partial…

A

double bound character

35
Q

Pyrimidines are nearly planar/planar

purines are nearly planar/planar

A

planar

nearly planar

36
Q

Are purines and pyrdimidines hydrophilic or hydrophobic?

Are they soluble or insoluble in water at the cell pH (near neutral)?

A

Hydrophobic

insolube

37
Q

Bases are covalently bonded to ribose or deoxyribose in an N-β - glycosyl bond to the ___ carbon of the pentose ring

A

1’

38
Q

The bonding of bases to ribose or deoxyribose occurs where on pyrimidines?

Where on purines?

A

N-1 of pyrdimidines

N-9 of purines

39
Q

The N-β-glycosyl bond is formed by removal of the elements of..

The resulting structure (ribose or deoxyribose with base attached) is called a

A

Water (OH from pentose and H from heterocyclic base)

Nucleoside

40
Q

When a phosphate is _______ to the 5’ carbon of the pentose ring with base attached, the resulting structure is a

A

esterified, nucleotide

41
Q

The nucleotides are linked together by ____ t0 _____ phosphodiester bonds to form a linear polmer

A

5’ to 3’ phosphodiester bonds

42
Q

The covalent backbones of nucleic acids consist of alternating phosphate and pentose residues

The nitrogenous bases may be thought of as side groups joined to the backbone at regular intervals

A

!

43
Q

The polymer chain at the terminal nucleotide at the 5’ end has a free ________ group

The terminal group at the 3’ end has a free

A

5’ phosphate group

3’ OH group

44
Q

When the phosphate group forms a diester linkage, there’s on ionizible oxygen shown in the ionized form. Why is phosphodiester in the ionized form?

A

Phosphoric acid is a tribasic acid that has 3 ionization equilibria…

The ionization of the phosphodiester group found in a nucleic acid corresponds to a pKa ~ 1.4

Based on this pKa, the unionized form of a polymer of nucleotides would be a strong acid

45
Q

The ionized form of a polymer of nucleotides with the negative charge on the phosphate oxygen will exist almost exclusively at pH =

A

7.0

Biochemistry (27 decks)

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