Nucleic Acids Flashcards
What is DNA?
Deoxyribonucleic acid- a polymer that holds important genetic information.
Why is DNA described as anti parallel?
The two strands of DNA run in opposite directions, with one being 5’ and the other 3’.
What make up a nucleotide?
A phosphate, a penrose sugar and an organic nitrogenous base
Explain the significance of DNA to organisms
DNA codes for proteins, holds genetic information and passes on hereditary information.
What is the base pair ruling?
Whatever the amount of Adenine, there will be the same amount of Thymine as they pair together. This is the same for Guanine and Cytosine as they pair together.
Where are phosphodiester bonds found?
Between the phosphate of one nucleotide and the pentose sugar of another
What is the sugar phosphate backbone?
The sides of the DNA ladder, that form the structural framework of DNA.
Where are hydrogen bonds found in nucleic acid?
Between the nitrogenous bases, to join the two polynucleotide strands.
Where are glycosisic bonds found in nucleic acids?
Between the penrose sugar and base of a nucleotide.
What base pairs with Adenine?
Thymine
What base pairs with Thymine?
Adenine
What base pairs with Guanine?
Cytosine
What base pairs with Cytosine?
Guanine
Which of the organic bases are purines?
A and G
Which DNA bases are pyrimidines?
Thymine and Cytosine
Define monomer
Small molecules that bond together to form larger structures called polymers.
Define polymer
Large molecule of many small repeating units called monomers
If thymine is 34%, what % will be adenine?
34
If thymine has 34%, what % will cytosine be?
16%
Which has been proven as the way DNA replicates?
Semi Conservative replication
Describe the function of DNA helicase
Breaks the H bonds between bases in order to ‘unzip’ the two strands of DNA.
Describe the function of DNA polymerase?
Catalyses the condensation reaction to form the missing polynucleotide strand
Describe the function of DNA ligase
Joins fragments of the lagging strand together
What is a gene?
A specific sequence of DNA that codes for one protein chain.
What is a base triplet?
A sequence of 3 bases that code for a specific amino acid.
How does DNA result in a polypeptide chain?
RNA carries the genetic information from the dna in the nucleus to the ribosomes where protein is produced.
Summarise semi-conservative DNA replication
2 DNA double helix molecules are produced, each containing one old and one new strand of DNA
Summarise conservative DNA replication.
2 DNA double helix molecules are produced, with one containing only new dna strands, and the other containing only original strands.
Summarise dispersive DNA replication.
Results in 2 DNA molecules that are a hybrid of old and new DNA fragments.
Whose experiment proved semi-conservative replication was true?
Meselsohn and Stahl.
Summarise Meselsohn and Stahl’s experiment.
E.Coli bacteria was cultured in heavy nitrogen, N15, so the bacteria’s DNA began to contain heavy nitrogen and became more dense than usual. They then transferred these samples into light nitrogen and allowed it to grow.
What part of DNA was cultured in nitrogen?
The bases
What did Meselsohn and Stahl’s experiment conclusively prove?
That DNA replicates semi-conservatively.
In Meselsohn and Stahl’s experiment, why did the bands appear at different levels?
Lighter DNA collected nearer the top of the centrifuge tube, whereas heavier DNA near the bottom.
State the function of single-stranded binding proteins?
Protects DNA during replication and prevents secondary structure.
What is the biological significance of iron ions?
They are found in haemoglobin and help to transport oxygen by binding to it.
What is the biological significance of sodium ions?
Generate nerve impulses and muscle contractions
What is the biological significance of hydrogen ions?
Used in photosynthesis, and determines the pH of a solution.
What is the biological significance of phosphate ions?
A component of phospholipids and nucleotides
What is the biological significance of water having a high specific heat capacity?
Water requires lots of energy for the temperature to be raised, which means it prevents sudden temperature changes which protects organisms as they are mostly water.
What is the biological significance of water having a high specific latent heat of vaporisation?
Hydrogen bonding means water requires lots of energy in order to evaporate. This means water acts as a coolant as body heat is used up to evaporate sweat/water.
Give two functions of water in metabolic reactions.
- a reactant in photosynthesis
-used to break down many molecules by hydrolysis
Whats the biological significance of the large cohesion of water molecules?
As water is a polar molecule, this allows it to be pulled upwards like in the xylem of a plant.
What is the simple structure of ATP?
Adenine- a nitrogenous base
Ribose- a pentose sugar
Phosphates- a chain of 3 phosphate ions
Give two ways that the structure of ATP is similar to DNA
-both contain a pentose sugar
-both contain a phosphate
Describe the hydrolysis of ATP.
Water is used in the hydrolysis of ATP, where it is converted into ADP and an inorganic phosphate and energy.
What enzyme catalyses the hydrolysis of ATP?
ATP hydrolase
Why is the hydrolysis of ATP useful in cells?
Bonds are broken which release an immediate energy source.
How is ADP resynthesised?
In a condensation reaction, catalysed by ATP synthase where a phosphate ion is added.
