3.1.5 nucleic acids are important information carrying molecules Flashcards
What is DNA?
-stands for deoxyribonucleic acid
-an example of a nucleic acid
-DNA is a polynucleotide, made up of many nucleotides joined together
-holds the genetic information in all living cells
What is RNA?
-stands for ribonucleic acid
-a single polynucleotide strand, made up of many nucleotides joined together.
-transfers genetic information from DNA to the ribosomes
Name the 4 bases in a DNA molecule
-Adenine
-Cytosine
-Guanine
-Thymine
What does a DNA nucleotide consist of?
-phosphate group
-deoxyribose (a pentose sugar)
-a nitrogenous base
Explain how bases pair in a DNA molecule
-through complementary base pairing
-A and T bond to each other with 2 weak hydrogen bonds
-C and G bond together with 3 weak hydrogen bonds
What is a pentose sugar?
A sugar which contains 5 carbon atoms
Describe the structure of DNA
-made up of 2 polynucleotide strands
-double helix shape
-the strands are held together by weak hydrogen bonds between complementary base pairs.
-has a sugar-phosphate backbone which is held together by phosphodiester bonds
What is a phosphodiester bond?
-the bond between the pentose sugar molecule and the phosphate group
-forms the sugar-phosphate backbone in DNA and RNA
-in DNA the deoxyribose sugar is linked to the phosphate group by a phosphodiester bond
How is a phosphodiester bond formed?
-in a condensation reaction between two nucleotides
Key feature of the phosphodiester bonds
They are strong covalent bonds, so they create a strong sugar-phosphate backbone.
What is the function of the sugar-phosphate backbone?
To give the DNA molecule a stable structure, that does not easily denature
What is the function of the weak hydrogen bonds between complementary base pairs?
The two strands can split easily for transcription and replication
Why is DNA double-stranded?
So that replication can occur using each strand as a template for new nucleotides to bind to.
Why is DNA so long?
So it can store lots of genetic information
Why is DNA coiled?
To make it compact so that it fits into the nucleus
What is the function of complementary base pairing?
They can both act as templates during semi-conservative replication.
Allows identical copies to be made as new nucleotides can join the exposed bases
Why are the DNA bases in sequence?
To determine the structure of proteins during protein synthesis
Why is DNA in a double helix shape?
To protect the weak hydrogen bonds between bases
Name the 4 bases in an RNA molecule
-Adenine
-Cytosine
-Guanine
-Uracil
Name the pentose sugar in a DNA molecule
Deoxyribose
Name the pentose sugar in an RNA molecule
Ribose
Describe the structure of an RNA molecule
-made up of one polynucleotide strand (single stranded)
-the polynucleotide strands are relatively short
-the sugar-phosphate backbone of the polynucleotide chain is linked by phosphodiester bonds between the ribose sugar and the phosphate group.
What is the features and function of mRNA/messenger RNA?
-a copy of one gene in your DNA
-leaves the nucleus to carry the copy of the genetic code of one gene to a ribosome
-this occurs when a gene is copied during protein synthesis, as each 3 bases code for a specific sequence of amino acids
-mRNA is shorter in size, short lived and single stranded
What is the function of tRNA/transfer RNA?
-to transfer amino acids to the ribosomes during protein synthesis
-it is single stranded but forms a cloverleaf shape, held in place by hydrogen bonds
What is the function of rRNA/ribosomal RNA?
-to combine with a protein to make a ribosome
-ribosomal RNA makes up the bulk of ribosomes
What is the anti-sense strand?
The name given to the polynucleotide strand in a DNA molecule that codes for the protein.
What is the sense strand?
The name given to the polynucleotide strand in a DNA molecule which is simply there for support.
What is a purine?
-a base which has 2 rings of atoms in its structure and is therefore larger
-includes guanine and adenine
What is a pyrimidine?
-a base which has only one ring of atoms in its structure
-includes cytosine, thymine and uracil
Why is RNA susceptible to hydrolysis?
It has a hydroxyl group on the 2’ carbon of the ribose sugar molecule
-this means it is useful as a transport molecule with a short lifespan
