Nucleic Acids

1
Nucleic Acids Structure and Function
The nucleic acids include the amazing DNA
molecule. It is the source of constancy and
variation among species, and is the foundation
for the unity and diversity of all life on Earth.
2
Nucleic Acids

• Nucleic acids store and transmit 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

• Genes
• Are the units of inheritance
• Program the amino acid sequence of polypeptides
• Are made of specific nucleotide sequences on DNA

3
The Roles of Nucleic Acids

• There are two types of nucleic acids involved in
  inheritance and protein synthesis
• Deoxyribonucleic acid (DNA)
• Ribonucleic acid (RNA)

• DNA
• Stores information for the synthesis of specific
  proteins
• Found in the nucleus of cells

• Directs RNA synthesis (transcription)
• Directs protein synthesis through RNA
  (translation)

• RNA
• Single stranded nucleic acid which carries the
  code for protein synthesis
• Found in nucleus, and outside of nucleus in
  association with ribosomes

4
The Structure of Nucleic Acids

• Nucleic acids
• Exist as polymers called polynucleotides

• Each polynucleotide
• Consists of monomers called nucleotides
• Sugar phosphate nitrogen base

• Nucleotide monomers
• Are made up of nucleosides (sugar base) and
  phosphate groups
• The portion of a nucleotide without the phosphate
  group is called a nucleoside

5
Nucleotide Monomers

• Nucleoside nitrogenous base sugar
• There are two families of nitrogenous bases
• Pyrimidines (cytosine, thymine, and uracil) have
  a single six-membered ring
• Purines (adenine and guanine) have a six-membered
  ring fused to a five-membered ring
• In DNA, the sugar is deoxyribose in RNA, the
  sugar is ribose

6
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

7
DNA Double Helix

8
DNA Structure

• Antiparallel nature
• Sometimes called complementary sugar/phosphate
  backbone runs in opposite directions

• one strand runs 5 to 3, while the other runs
  3 to 5
• One DNA molecule includes many genes

9
Scientists can use DNA and Proteins as Tape
Measures of Evolution

• Molecular comparisons
• Help biologists sort out the evolutionary
  connections among species
• How similar are the sequences of nucleotides?
• The closer the sequence, the closer the
  relationship
• Remember, all life, from the simplest prokaryote
  to the most complex eukaryote, contains the same
  four nitrogenous bases.

It is simply the sequence of base-pairs, and
amount of DNA that differs from organism to
organism!
10
ATP
Adenosine triphosphate is a common source of
activation energy for metabolic reactions. ATP is
essentially an RNA adenine (adenosine) nucleotide
with two additional phosphate groups.
The wavy lines between these two phosphate groups
indicate high energy bonds. When that last bond
is broken, and the ATP is converted to ADP
(adenosine diphosphate), energy is released, and
can be used to spur a reaction.
Conversely, a new ATP molecule can be built by
combining ADP and a phosphate through a process
known as phosphorylation using energy obtained
from glucose.