Macromolecules Part IV: Nucleic Acids Informational molecules.
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Transcript of Macromolecules Part IV: Nucleic Acids Informational molecules.
Macromolecules Part IV:
Nucleic Acids
Informational molecules
Introduction: Nucleic Acids The amino acid sequence of a polypeptide
is programmed by a gene A gene consists of regions of DNA, a
polymer of nucleic acids (100’s to 1000’s) DNA (and their genes) is passed by the
mechanisms of inheritance Only molecule that can produce identical
copies of themselves
There are two types of nucleic acids: ribonucleic acid (RNA) deoxyribonucleic acid (DNA)
DNA provides direction for its own replication
DNA also directs RNA synthesis and, through RNA, controls protein synthesis
Nucleic acids store and transmit hereditary information
Roles of DNA Protein expression (Phenotypes) Inheritance (Genotypes)
3.Evolution (Mutations)
Nucleotides Nucleic acids are
polymers of monomers called nucleotides
Each nucleotide consists of three parts: a nitrogen basea pentose sugara phosphate group
Sugar-Phosphate “Backbone”
Nucleic Acids Polynucleotides are synthesized by
connecting the sugars of one nucleotide to the phosphate of the next with a phosphodiester link
The phosphodiester links create a repeating backbone of sugar-phosphate units with the nitrogen bases as appendages
RNA
DNA
Phosphodiester link
Nucleotides The nitrogen bases, rings of carbon and
nitrogen, come in two types: Purines pyrimidines
Pyrimidines have a single six-membered ring The three different pyrimidines that differ in the
atoms attached to the ring: cytosine (C), thymine (T), and uracil (U)
Purines have a six-membered ring joined to a five-membered ring and there are two types: adenine (A) and guanine (G)
Purine BasesPurine Bases Adenine and guanine are purinesAdenine and guanine are purines Purines are the larger of the two types of bases Purines are the larger of the two types of bases
found in DNAfound in DNA
Pyrimidine BasesPyrimidine Bases
Cytosine, uracil and thymine are pyrimidinesCytosine, uracil and thymine are pyrimidines Mnemonic: Pyramids CUTMnemonic: Pyramids CUT
Because of their shapes, only some bases Because of their shapes, only some bases are compatible with each otherare compatible with each other
Purines always pair with pyramidinesPurines always pair with pyramidines Adenine (A) always pairs with thymine (T) (in Adenine (A) always pairs with thymine (T) (in
RNA, Adenine pairs with Uracil RNA, Adenine pairs with Uracil (U)(U)) ) Guanine (G) with cytosine (C)Guanine (G) with cytosine (C)
Nucleotide Bases Nucleotide Bases PairingsPairings
Counting Carbons
Nucleosides VS. NucleotidesNucleosides VS. Nucleotides A nucleoside is one of the four A nucleoside is one of the four
DNA bases covalently attached DNA bases covalently attached to a sugarto a sugar
Nucleosides differ from Nucleosides differ from nucleotides in that they lack nucleotides in that they lack phosphate groupsphosphate groups
A nucleotide is a nucleoside A nucleotide is a nucleoside with one or more phosphate with one or more phosphate groups covalently attached to groups covalently attached to the sugar groupthe sugar group
Step 1: Base
Step 2: Nucleoside
Step 3: Nucleotide
RNA RNA is made
by copying DNA and is used to make proteins
It is a SINGLE strand of nucleotides
DNA1. Take two nucleic
acid strands
2. Flip one of the strands
3. Line the strands together so that they bond
4. Twist them
5. Now you have DNA!
DNA: Double Helix Structure• DNA has a double helix structure with two strands that are antiparallel so that nucleotides can form hydrogen bonds
One Strand One Strand
H-Bonds
But why is it important that the strands are H-bonded and not covalently bonded?
Why H-bonds? In order to replicate, the strands
must separate to make new DNA strands (cannot be broken if the strands were covalently bound)
The sugar-phosphate backbones of the two polynucleotides are on the outside of the helix
Pairs of nitrogenous bases, one from each strand, connect the polynucleotide chains with hydrogen bonds
Most DNA molecules have thousands to millions of base pairs
Recap: What are the base-pair rules? Adenine (A) always pairs with thymine (T) (in
RNA, Adenine pairs with Uracil (U)) Guanine (G) with cytosine (C)
With these base-pairing rules, if we know the sequence of bases on one strand, we know the sequence on the opposite strand
The two strands are complementary
Nucleotide Bases Pairings
DNA - Base pairingDNA - Base pairing
Adenine and Thymine Adenine and Thymine always bind togetheralways bind together
Guanine and Guanine and Cytosine always bind Cytosine always bind togethertogether
Result: Double Helix Structure
An RNA molecule is single polynucleotide chain while DNA molecules have two polynucleotide strands that spiral around an imaginary axis to form a double helix
The pentose joined to the nitrogen base is ribose in nucleotides of RNA and deoxyribose in DNA
Nitrogen bases - thymine is replaced by uracil
What’s the difference between RNA and DNA?
ATP (adenosine triphosphate)
ATP is a nucleotide that is used to provide energy in cells
NAD+ and FAD These are nucleotide-containing molecules
that function as electron carriers in a variety of cellular processes.
NAD+ - nicotinamide adenine dinucleotide
FAD- flavin adenine dinucleotide
Home work
Study the table on page 30
Do Question on page 31 Questions1-12
Macromolecules Quiz Next Thursday 15th for day 1 classes and Friday 16th for day 2 classes