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3-4 Notes
4. NUCLEIC ACIDS

Polymers of nucleotides that carry hereditary information, instructions for life, and
conduct chemical experiments

Protein conformation is determined by primary structure. Primary structure is determined
by genes – hereditary units that consist of DNA, a type of nucleic acid

Two types:
1)
DeoxyriboNucleic Acid (DNA)

Coded information that programs all cell activity

Directs its own replication

Is passed from one generation of cells to another

Is found in the nucleus (of eukaryotic cells)

Makes up genes
2) RiboNucleic Acid (RNA)

Sites of protein synthesis are ribosomes

Messenger RNA (mRNA) = a temporary copy of the gene from DNA that
will be used at the ribosome to build the protein
mRNA
Nucleus
Cytoplasm
Genetic message is transcribed
moves into
from DNA onto mRNA
genetic message translated into
a protein

Nucleic Acid = polymer of nucleotides

Nucleotide = building block molecule of nucleic acid

Each is composed of:
1) Pentose (5-C sugar)

In RNA = Ribose

In DNA = Deoxyribose
2) Phosphate - attached to carbon #5 of the sugar
3) Nitrogenous Base – attached to carbon #1 of the sugar

Two Families:

Pyrimidines = 6-membered ring
o Includes: cytosine (C), thymine (T), and uracil (U)

Purines = 6-membered ring fused to a 5-membered ring
o Includes: adenine (A) and guanine (G)

Nucleic Acids are made of nucleotides bonded together

Phosphodiester Linkages = covalent bonds between the phosphate of one nucleotide and
the sugar of the next

DNA is double-stranded and in the shape of a double helix
o Consists of:

2 nucleotide chains wound into a double helix

Sugar-phosphate backbones on the outside of the helix

Strands of DNA are held together by H-bonds between the paired
nitrogenous bases and by van der Waals attractions between the stacked
bases


(A) always pairs with (T)

(C) always pairs with (G)
the two strands are complementary and can therefore serve as templates to
make new complementary strands


the strands are antiparallel
Closely related species have more similar sequences of DNA and amino acids than more
distantly related species

Nucleotide functions:
o Monomers for nucleic acids
o Electron transfer in enzyme-controlled redox reactions of the cell
o Transfer of chemical energy

ATP (Adenosine Triphsphate) = adenine (N-base) + ribose + 3 phosphates

The last two phosphate bonds are high energy, unstable, and easily
broken

By hydrolyzing the last phosphate  ADP is formed

The free energy released by this reaction can be used to drive many
cellular processes