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Biology 1107 Exam 1 > Chapter 4 - Nucleic Acids and the RNA World > Flashcards

Chapter 4 - Nucleic Acids and the RNA World Flashcards

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1
Q

what are nucleic acids made of?

A

nucleotides (monomers)

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2
Q

what are the 3 components of a nucleotide?

A

1) phosphate group
2) a five-carbon sugar
3) a nitrogenous base (contains nitrogen)

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3
Q

what are two types of nucleotides?

A

1) ribonucleotides –> ribonucleic acid (RNA)

2) deoxyribonucleotides –> deoxyribonucleic acid (DNA)

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4
Q

what is the sugar component of ribonucleotides?

A

ribose

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5
Q

what is the sugar component of deoxyribonucleotides?

A

deoxyribose (deoxy means “lacking oxygen)

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6
Q

purines

A

type of nitrogenous base

  • adenine
  • guanine
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7
Q

pyrimidines

A

type of nitrogenous base

  • cytosine
  • uracil (RNA)
  • thymine (DNA)
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8
Q

what type of nitrogenous base does RNA use?

A

pyrimidine (uracil)

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9
Q

what type of nitrogenous base does DNA use?

A

pyrimidine (thymine)

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10
Q

DNA primary structure

A

the sequence of deoxyribonucleotides

-bases are A,T,G,C

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11
Q

DNA secondary structure

A

2 DNA strands running in opposite directions held together by complementary base pairing, twisted into a double helix

  • stabilized by hydrogen bonding between nitrogenous bases and hydrophobic interactions
  • A = T
  • G = C
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12
Q

RNA primary structure

A

sequence of ribonucleotides

-bases are A,U,G,C

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13
Q

RNA secondary structure

A

short regions of double helices and structures called “hairpins”

  • -stabilized by hydrogen bonding between nitrogenous bases (complementary base pairing)
  • RNA bases fold over and make hydrogen bond base pairings with bases on the SAME strand
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14
Q

what is more easily made, sugars/purines or pyrimidines/ribose?

A

sugars and purines are easily made. pyrimidines and ribose are not

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15
Q

what reaction occurs when nucleotides polymerize to form nucleic acids?

A

a condensation reaction

  • this forms a phosphodiester bond
  • between 5’ carbon and 3’ carbon of two different nucleotides
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16
Q

qualities of the sugar-phosphate backbone of nucleic acid

A

-they are directional (one end has an unlinked 5’ carbon/one end has unlinked 3’ carbon)

17
Q

primary structure of nucleic acid

A
  • the directional nucleotide sequence of the growing molecule
  • goes from 5’ –> 3’ (only added to the 3’ end)
18
Q

qualities of the polymerization of nucleotides

A
  • endergonic (requires energy input, not spontaneous)
  • catalyzed by enzymes
  • energy used in this process comes from the “phosphorylation” of nucleotides
19
Q

phosphorylation

A
  • transfer of one or more phosphate groups to a substrate molecule
  • raises the potential energy of the substrate
  • enables endergonic reactions
20
Q

why can polymerization take place in cells?

A

the potential energy of the nucleotide monomers is raised by reactions that add two phosphate groups to either ribonucleotides or deoxyribonucleotides

  • this creates nucleoside triphosphates (3 phosphate groups)

** the addition of one or more phosphate groups raises the potential energy of substrate molecules enough to make the reaction possible)

21
Q

ATP

A

adenosine triphosphate (“activated” nucleotide) with 3 phosphate groups

22
Q

2 empirical rules of DNA

A
  • total number of purines and pyrimidines are the same
  • the number of A’s = T’s
  • the number of G’s = C’s
23
Q

describe the secondary structure of DNA

A
  • antiparallel configuration, double helix
  • hydrophilic sugar-phosphate backbone (exterior facing)
  • nitrogenous base pairs (interior facing, A-T and G-C)
  • two different sized grooves (major and minor)
24
Q

what nitrogenous base pairings exist in DNA?

A

purines always pair with pyrimidines

-complementary base pairs include A-T and G-C

25
Q

how many hydrogen bonds do A-T pairings have?

A

2

26
Q

how many hydrogen bonds do G-C pairings have?

A

3

27
Q

how is DNA stabilized?

A
  • hydrophobic interactions in its interior

- hydrogen bonding between complementary base pairs

28
Q

how does DNA contain biological information?

A
  • language of nucleic acids is contained in the sequence of the bases
  • DNA carries info for growth and reproduction of all cells
29
Q

what makes DNA replication possible?

A

complementary base pairing (A-T and G-C)

-each strand serves as a template for the formation of a new complementary strand

30
Q

steps of DNA replication

A

1) double helix separates
2) each existing strand of DNA serves as the template for a new strand to form. free nucleotides attach to existing 3’ ends according to complementary base pairing
3) polymerization - new strands come together/forms a sugar-phosphate backbone (secondary structure is restored)

31
Q

is DNA stable? reliable? is it a good catalyst?

A

-DNA is extremely stable and reliable for storing information
-HOWEVER is it not a good catalyst because it is so stable
(because DNA is not a good catalyst, they think RNA composed the first life form, not DNA)

32
Q

what are the two functions that the first living molecule would have needed to carry out?

A

1) carry information

2) catalyze reactions that promoted its own reproduction

33
Q

how are DNA and RNA similar?

A

-both have same primary structure (phosphodiester linkages –> sugar-phosphate backbone + sequence of 4 nitrogenous bases extending from the backbone)

34
Q

what are the two main differences between DNA and RNA?

A

1) RNA sugar = ribose
DNA sugar = deoxyribose

2) RNA = pyrimidine base is uracil
DNA = pyrimidine base is thymine

35
Q

is RNA more or less stable than DNA?

A

less stable!

-OH makes ribose much more reactive and less stable than DNA

36
Q

can RNA have tertiary and quaternary structures? if so, what are they?

A

tertiary- folds that form distinct 3 dimensional shapes

quaternary- associations between several RNA molecules

37
Q

what are some capabilities of RNA?

A
  • intermediate between DNA and proteins
  • capable of storing information, self-replicating
  • can function as catalytic molecule
38
Q

ribozymes

A

enzyme-like RNA’s

39
Q

RNA replicase

A

a type of ribozyme

-can catalyze the addition of ribonucleotides to a complementary RNA strand

Biology 1107 Exam 1 (6 decks)

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