3.1 Chapter 2- Nucleic Acids, Water and Inorganic Ions Flashcards
What do nucleic acids do?
Nucleic acids carry the genetic code. for the production of proteins. Information carrying molecules.
Where are nucleic acids found and what is this evidence for?
The genetic code is common to viruses and all living organisms, it is found in all living cells, providing indirect evidence for evolution.
What does DNA do?
DNA stores genetic information and passes on genetic information as it is hereditary material The variety of sequences of bases in DNA provides genetic diversity.
What does RNA do?
- RNA transfers genetic information from DNA to the ribosomes, and is read to make polypeptides in translation.
- RNA is combined with proteins to form ribosomes.
What are the similarities between RNA and DNA?
Both RNA and DNA are polynucleotides formed in a condensation reaction between a pentose sugar and a phosphate group forming phosphodiester bonds. Both have a sugar phosphate backbone formed by the nucleotide chains.
Describe the structure of RNA.
- Relatively short polynucleotide chain- made of nucleotide monomers
- Single stranded
- 3 types
- Nucleotides contain ribose pentose sugar, a phosphate group and an organic nitrogenous base of either adenine, cytocine, guanine or uracil which replaces thymine.
- Nucleotides are joined together by phosphodiester bonds between the ribose and the phosphate group forming a sugar- phosphate backbone.
Describe the structure of DNA.
Not enough space on original paper
- Long polynucleotide chain- polymer of nucleotides.
- Double helix - two strands in a spiral held together by hydrogen bonds. Double helix forms a structural backbone.
- The strands run antiparallel and in opposite directions.- the phosphate at one end and the pentose sugar at the other end.
- Each nucleotide contains a deoxyribose pentose sugar, a phosphate group and a nitrogenous organic base of either adenine, thymine, cytocine or guanine.
- The nucleotides are joined together by phosphodiester bonds between the pentose sugar and the phosphate group formed in a condensation reaction catalysed by DNA polymerase.
- Bases held together by hydrogen bonds to form the double helix: adenine and thymine have two hydrogen bonds, cytosine and guanine have three hydrogen bonds.
- The DNA is tightly coiled to store a large amount of genetic information in a small space.
What is deoxyribose made of vs ribose?
Deoxyribose- OH and H
Ribose- OH and OH
What are the 3’ and 5’ ends and what does “’” mean?
’= prime. 3’- third carbon of pentose sugar unattatched. 5’- phosphate attatched to 5th carbon.
How are phosphodiester bonds formed in DNA?
- Condensation reaction occurs
- Bonds formed between phosphate and deoxyribose
- Loss of water
- catalysed by DNA polymerase.
What type of molecules are DNA and RNA and what are they made of?
Polymers of nucleotides- polynucleotides made of nucleotide monomers.
What does DNA stand for?
Deoxyribosenuceic acid.
What does RNA stand for?
Ribosenucleic acid
What are nucleotides made of?
- A pentose sugar (5 carbons), deoxyribose or ribose.
- A nitrogenenous organic base (adenine, thymine, cytocine, guanine or uracil)
- A phosphate group
Draw a nucleotide and label it (including the carbons)
Answer on revision card.
Draw DNA.
Answer on revision card.
How are nucleotide components joined together?
By a condensation reaction
What did two mononucleotides form and how do they form it?
- Form dinucleotides in a condensation reaction
- Contain phosphodiester bonds between the pentose sugar and the phosphate group.
What happens if mononucleotides keep on joining?
A polynucleotide forms.
What was there some doubt about surrounding DNA and RNA and how was this disproved?
- There was doubt about DNA and RNA carrying the genetic code as they are very simple molecules. Some argued that protiens carried the genetic code.
- Virus and mouse experiments involving bacteria disproved this
- DNA structure was worked out by Franklin, Crick and Watson.
What are pyrmadines and describe their structure?
- One ringed structure bases
- Thymine, cytocine and uracil
What are purines and describe their structure.
- Two ringed structure bases
- Guanine and Adenine
How are two polynuclear strands joined together?
Two polynucleotide strands are joined by hydrogen bonds between specific complementary bases.
Describe the different bond structures between bases.
Guanine and Cytocine- 3 hydrogen bonds- more stable
Adenine and Thymine- 2 hydrogen bonds
There are always equal amounbts of adenine and thymine, and guanine and cytocine.
What is hugely important about nitrogenous bases?
Their sequence- determines the genetic code.
Describe how DNA suits its purpose.
- Sugar phosphate backbone- protects the bases as well as the helix structure
- Hydrogen bonds keep the molecule upright, stable and together. Easily broken which allows the strand to separate for protein synthesis and DNA replication by enzymes.
- Stability- passes from one cell to another without change, mutations rare and often repaired
- Large molecule- stores lots of genetic information
- Double helix wrapped around histones- keeps the structure compact to store large amounts of genetic information in a small space
- Complementary base pairing- accurateand easy DNA replication.
- Two strands- both can act as templates for DNA replication