Nucleic Acids PowerPoint PDF

Nucleic Acids Nucleotides
Nucleotides are the monomers of nucleic acids
They are energy rich compounds
They provide energy for metabolic processes
They are a part of enzyme cofactors e.g. NAD - nicotinamide adenine dinucleotide, FAD – flavin adenine dinucleotide
They act as seco...

Nucleic Acids Nucleotides
Nucleotides are the monomers of nucleic acids
They are energy rich compounds
They provide energy for metabolic processes
They are a part of enzyme cofactors e.g. NAD - nicotinamide adenine dinucleotide, FAD – flavin adenine dinucleotide
They act as secondary chemical messengers in response to hormones Nucleotides
A nucleotide consist of three portions (a) a nitrogenous bases – purine and pyrimidine common purine bases – adenine and guanine common pyrimidine bases – cytosine, uracil, thymine http://www.uic.edu/classes/bios/bios100/lecturesf04am/nucleotides.jpg Uracil Nucleotides (b) A sugar – deoxyribose or ribose http://www.mun.ca/biology/scarr/Deoxyribose_vs_Ribose.gif Nucleotides
(c) One or more phosphate groups Nucleotides
Some common nucleotides includeATP – adenosine triphosphate ADP – adenosine diphosphate AMP – adenosine monophosphate GTP – guanosine triphosphate UTP – uridine triphosphate CTP – cytidine triphosphate Nucleotides - AMP http://www.madsci.org/posts/archives/2001-02/982619379.Bc.1.gif Nucleotides - ADP Nucleotides - ATP http://upload.wikimedia.org/wikipedia/commons/thumb/1/10/ATP_chemical_structure.png/800pxATP_chemical_structure.png Nucleic Acids
There are two types of nucleic acids (a) DNA – deoxyribonucleic acid (b) RNA – ribonucleic acid
They provide genetic information
Both nucleic acids are found in plants and animals
Viruses contain either RNA or DNA but not both Nucleic Acids - DNA
It is found in the chromatin of the cell nucleolus
It is also found outside the nucleus i.e. in the mitochondria and chloroplast
It contains genetic information in a segment called the genes
It contains information (blue print) that is used to construct other cell components
The DNA structure consist of two strands that are entwined
It is made up of nucleotide monomers
The structure is described as a double helix (proposed by Watson and Crick)
The helix is formed through the pairing of the nitrogenous bases in the nucleotide http://ghr.nlm.nih.gov/handbook/illustrations/dnastructure.jpg Nucleic Acids - DNA
The double helix is also called the B-form DNA or B-DNA
This form is very stable
There also exists different variations in DNA helix structure i.e. A-DNA and ZDNA
Both forms are converted into the B-DNA at normal physiological conditions Main Differences in Variations A-DNA B-DNA Z-DNA Right handed helix Right handed helix Left handed helix Helix has a hollow core Helix has a solid core Helix has a solid core – more tightly packed Appears when the DNA is dehydrated Occurs at normal physiological conditions Occurs when there is very high salt concentration Nucleic Acids – DNA Structure
The backbone of the DNA is comprised of a deoxyribose sugar linked by phosphodiester bridges
The 3' hydroxyl group of the sugar is linked to the 5' hydroxyl group of another sugar by a phosphodiester bond
The linking of the sugars maintains the structure of the DNA http://fig.cox.miami.edu/~cmallery/150/gene/16x3DNA.jpg Nucleic Acids – DNA Structure
The strands run antiparallel to each other, i.e. one strands run in the 3' → 5' direction and the other strand runs in the 5' → 3' direction
The nitrogenous bases found in DNA are adenine (A), thymine (T), cytosine (C) and guanine (G)
They carry the genetic information
Adenine is paired with thymine and vice versa by 2 hydrogen bonds A =T
Guanine is paired with cytosine by 3 hydrogen bonds (G ≡ C) Nucleic Acids – DNA Structure
The pairing of the bases is referred to as complementary base pairing
The two helices are complementary to each other. They are not identical
There must exist equal amounts of complementary bases http://upload.wikimedia.org/wikipedia/commons/thumb/e/e4/DNA_chemical _structure.svg/350px-DNA_chemical_structure.svg.png Nucleic Acids – DNA Structure
The DNA helix can be bent or super coiled
This flexibility allows DNA to be wrapped around proteins
Allows the DNA to be compact into smaller volumes Nucleic Acids - RNA
RNA is present in the cytosol of the cell and in the nucleolus
It is formed from DNA by a process called Transcription
The molecule consist of (a) a phosphate group (b) a nitrogenous base – adenine (A), uracil (U), cytosine (C) and guanine (G) (c) sugar – ribose Nucleic Acids - RNA
Similar to DNA, the nitrogenous bases in RNA carries the genetic information and sugar-phosphate serves to maintain the structure of the molecule Nucleic Acids – RNA Structure
The structure is single stranded and runs in the 5' → 3' direction
However because base pairing can occur, the molecule can fold on itself in the form of a hairpin
During base pairing adenine pairs with uracil and guanine with cytosine A =U
G≡C The hairpin formation does not require the molecule to have equal amounts of complementary base pairs http://www.makingthemodernworld.org.uk/learning_modules/biology/01.TU.03/illustration s/01.IL.09.gif http://en.wikipedia.org/wiki/Image:Ciliate_telomerase_RNA.JPG Differences Between DNA and RNA DNA RNA Found in the chromatin of the nucleus Found mainly in the cytoplasm and to a lesser extent in the nucleolus Helix is B form; Protected in the nucleus and is tightly packed Helix is A form; They are continually made, broken down and reuse Sugar – 2 deoxyribose (more stable sugar) Sugar – ribose Nitrogenous bases are A, T, C and G Nitrogenous bases are A, U, C and G Double stranded Normally single stranded The A/T and G/C ratio is 1 Complementary base pairs ratio not necessary Base pairing occurs throughout the molecule Base pairing occurs at specific locations Stores genetic information Transfer of genetic information needed for protein synthesis Self replicating Must be synthesized from DNA molecule Can be damaged by UV rays More resistant to damage by UV rays Types of RNA
There exist three RNA forms ribosomal RNA – rRNA transfer RNA – tRNA messenger RNA – mRNA
They differ from each other by size, function and stability Types of RNA - rRNA
It is the most abundant and makes up 80% of the RNA in the cells
It is also the most stable form
The molecule has a higher GC content than AU content
In the cytoplasm rRNA combines with proteins to form ribosomes Ribosome http://img.sparknotes.com/figures/F/f88cd44dc6a50ffa6b94cdb9d213894e/ribosome.gif Types of RNA - tRNA
It occupies 15% of the total RNA in the cell
It is the smallest polymeric form
It functions as a carrier of activated amino acids to a growing polypeptide chain (protein synthesis)
It binds to specific amino acids
All tRNA molecules have a three fold clover leaf configuration
The 3' end contains the CCA sequence. Amino acids bind to this end via esterification
The anticodon region base pairs to the corresponding codon region on the mRNA molecule
Each tRNA molecule contains a specific anticodon triplet http://universe-review.ca/I11-21-tRNA1.jpg Types of RNA - mRNA
Otherwise called template RNA
Comprises 5% of RNA in the cell
It is synthesized on the surface of the DNA template
It carries genetic information from the nuclear DNA to the cytosol
It is used as a template for protein synthesis
If the mRNA carries the code for a simple protein it is called monocistronic
If it carries the code for more than one kind of protein it is polycistronic