1. The Structure and Function of Large Biological Molecules
Chapter 5
The Structure and Function of Large Biological Molecules

2. Concept 5.5: Nucleic acids store, transmit, and help express hereditary information
The amino acid sequence of a polypeptide is programmed by a unit of inheritance called a gene
Genes are made of DNA, a nucleic acid made of monomers called nucleotides
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3. The Roles of Nucleic Acids
There are two types of nucleic acids
Deoxyribonucleic acid (DNA)
Ribonucleic acid (RNA)
DNA provides directions for its own replication
DNA directs synthesis of messenger RNA (mRNA) and, through mRNA, controls protein synthesis
Protein synthesis occurs on ribosomes
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4. DNA 1 Synthesis of mRNA mRNA NUCLEUS CYTOPLASM Figure 5.25-1
Figure 5.25 DNA → RNA → protein.

5. Movement of mRNA into cytoplasm
Figure
DNA 1
Synthesis of mRNA
mRNA
NUCLEUS
CYTOPLASM
mRNA 2
Movement of mRNA into cytoplasm
Figure 5.25 DNA → RNA → protein.

6. Movement of mRNA into cytoplasm Ribosome
Figure
DNA 1
Synthesis of mRNA
mRNA
NUCLEUS
CYTOPLASM
mRNA 2
Movement of mRNA into cytoplasm
Ribosome
Figure 5.25 DNA → RNA → protein. 3
Synthesis of protein
Amino acids
Polypeptide

7. The Components of Nucleic Acids
Nucleic acids are polymers called polynucleotides
Each polynucleotide is made of monomers called nucleotides
Each nucleotide consists of a nitrogenous base, a pentose sugar, and one or more phosphate groups
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8. Figure 5.26 Components of nucleic acids.
Sugar-phosphate backbone
5 end
Nitrogenous bases
Pyrimidines
5C
3C
Nucleoside
Nitrogenous base
Cytosine (C)
Thymine (T, in DNA)
Uracil (U, in RNA)
Purines
5C
1C
Phosphate group
3C
5C
Sugar (pentose)
Adenine (A)
Guanine (G)
3C
(b) Nucleotide
Figure 5.26 Components of nucleic acids.
Sugars
3 end
(a) Polynucleotide, or nucleic acid
Deoxyribose (in DNA)
Ribose (in RNA)
(c) Nucleoside components

9. Nitrogenous base Phosphate group Sugar (pentose)
Figure 5.26ab
Sugar-phosphate backbone
5 end
5C
3C
Nucleoside
Nitrogenous base
5C
1C
Figure 5.26 Components of nucleic acids.
Phosphate group
3C
Sugar (pentose)
5C
3C
(b) Nucleotide
3 end
(a) Polynucleotide, or nucleic acid

10. There are two families of nitrogenous bases
Pyrimidines (cytosine, thymine, and uracil)
Purines (adenine and guanine)
In DNA, the sugar is deoxyribose; in RNA, the sugar is ribose
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11. (c) Nucleoside components
Figure 5.26c
Nitrogenous bases
Pyrimidines
Cytosine (C)
Thymine (T, in DNA)
Uracil (U, in RNA)
Sugars
Purines
Figure 5.26 Components of nucleic acids.
Deoxyribose (in DNA)
Ribose (in RNA)
Adenine (A)
Guanine (G)
(c) Nucleoside components

12. Nucleotide Polymers
Nucleotide polymers are linked together to build a polynucleotide
Adjacent nucleotides are joined by covalent bonds that form between the —OH group on the 3 carbon of one nucleotide and the phosphate on the 5 carbon on the next
These links create a backbone of sugar-phosphate units with nitrogenous bases as appendages
The sequence of bases along a DNA or mRNA polymer is unique for each gene
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13. The Structures of DNA and RNA Molecules
RNA molecules usually exist as single polypeptide chains
DNA molecules have two polynucleotides spiraling around an imaginary axis, forming a double helix
One DNA molecule includes many genes
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14. Called complementary base pairing
The nitrogenous bases in DNA pair up and form hydrogen bonds: adenine (A) always with thymine (T), and guanine (G) always with cytosine (C)
Called complementary base pairing
Complementary pairing can also occur between two RNA molecules or between parts of the same molecule
In RNA, thymine is replaced by uracil (U) so A and U pair
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15. Base pair joined by hydrogen bonding
Figure 5.27 5 3
Sugar-phosphate backbones
Hydrogen bonds
Base pair joined by hydrogen bonding
Figure 5.27 The structures of DNA and tRNA molecules.
Base pair joined by hydrogen bonding 3 5
(a) DNA
(b) Transfer RNA

16. Figure 5.UN02
Figure 5.UN02 Summary table, Concepts 5.2–5.5

17. Figure 5.UN02a
Figure 5.UN02a Summary table, Concepts 5.2–5.3

18. Figure 5.UN02b
Figure 5.UN02b Summary table, Concepts 5.4–5.5