3.8 Nucleotides and nucleic acids Flashcards
What are the five elements in a nucleic acid?
oxygen
hydrogen
nitrogen
carbon
phosphorous
What are the two types of nucleic acid and what do they do?
DNA and RNA
- they both have roles in the storage and transfer of genetic information and the synthesis of polypeptides ( proteins )
- they are the basis for heredity
What is the the summarised structure of a nucleic acid?
- large polymers formed from many nucleotides ( the monomers ) linked together in a chain
What are the three components that make up an individual nucleotide?
- a pentose monosaccharide ( sugar ) containing five carbon atoms
- a nitrogenous base is a complex organic molecule containing one or two carbon rings in its structure as well as nitrogen
- a phosphate group ( PO4 2-) has a negative charge, is inorganic and is acidic
How are nucleotides linked together, what is the reverse reaction of this and what does it create?
- they are linked together by condensation reactions
- to form a polymer called a polynucleotide
- hydrolysis, releasing the individual nucleotides
How does the phosphate group and pentose sugar connect and what are the bonds called?
- the phosphate group at the fifth carbon of the pentose sugar of one nucleotide forms a covalent bond with the hydroxyl group at the third carbon of the pentose sugar of an adjacent nucleotide
- called phosphodiester bonds
What does the nucleotides being joined together create?
- a large, strong sugar phosphate ‘backbone’ with a base attached to each sugar
What does DNA stand for?
Deoxyribonucleic acid
What sugar is used in DNA and how is it different to a ribose?
- Deoxyribose
- it has one fewer oxygen atoms
What is pyrimidines and what are the bases?
- the smaller bases, which contain single carbon ring structures
- thymine (T) and cytosine (C)
What is purines and what are the bases?
- the larger bases, which contain double carbon ring structures
- adenine (A) and guanine (G)
What is DNA made out of overall?
- two strands of polynucleotides coiled into a helix, know as the double helix structure
How are the two strands of the double helix held together?
- hydrogen bonds between the bases
What does each strand that makes up the helix have?
- a phosphate group (5) at one end and a hydroxyl group (3) at the other end
How are the two strands of the double helix arranged?
- they run in opposite directions to one another
- antiparallel
What does the pairing of bases allow and what are the key properties for?
- DNA to be copied and transcribed
- molecule of heredity
What bases bind together and what do they form?
What is this known as?
- Adenine and thymine to create two hydrogen bonds
- Cytosine and Guanine to create three hydrogen bonds
- complementary base pairing
What does complementary base pairing arrange further than the bases and what does this make in the DNA structure?
- a small pyrimidine base always binds to a larger purine base
- arrangement maintains a constant distance between the DNA ‘backbones’ which results in parallel polynucleotide chains being created
What was known about the bases in DNA long before Watson and Cricks discovery in 1953?
- that DNA always has equal amounts of adenine and thymine and equal amounts of cytosine and guanine
What carries the genetic information of an organism and in what form?
- the sequence of bases along a DNA strand
- a code
What does RNA stand for?
- Ribonucleic acid
What essential role does RNA play?
- the transfer of genetic information from DNA to the proteins that make up the enzymes and tissues of the body
What is the one issue with DNA?
- the DNA of each eukaryotic chromosome is a very long molecule, comprising many hundreds of genes and is unable to leave the nucleus in order to supply the information directly to the sites of protein synthesis
How is the DNA able to be transported out of the nucleus?
- the relatively short section of the the long DNA molecule corresponding to a single gene is transcribed into a similarly short messenger RNA molecule (mRNA)
