Nucleic Acids Flashcards
what does DNA consist of
Deoxyribose sugar, a phosphate group and a nitrogen containing base (adenine, cytosine, guanine or thymine)
What does RNA consist of
Nucleotides containing ribose sugar, a phosphate group and a nitrogen containing base- adenine, uracil, cytosine and guanine
The purpose phosphodiester bond and how one forms
Forms: condensation reaction between adjacent nucleotides
Forms the sugar-phosphate backbone of the nucleic acid
What does DNA code for
Codes for the primary sequence of amino acids
3 bases=triplet=one amino acid
Describe the antiparallel nucleotide structure
To remain parallel the complementary base pairs pair together with the two strands of DNA running in opposite directions.
Each end of the molecule has a 5’ and 3’ end
DNA polymerase is only complementary to the 5’ end of the molecule.
How does the structure of DNA allow it to carry out its function
- Sugar phosphate backbone and double helix structure- provides strength and stability- protects bases and protects the hydrogen bonds between bases
- Long large molecule- so stores a lot of information
3.helical so compact
4.base sequence allows information to be stored/codes for amino acids and therefore proteins - Double stranded so replication can occur semi conservatively, because each strand acts as a template
6.complementary base pairs- allows accurate replication, identical copies are made - Hydrogen bonds between bases are weak, allows for easy strand separation for semi-conservative replication
- Many weak hydrogen bonds so DNA is strong
Describe the role of DNA polymerase
- catalyses the condensation reactions between DNA nucleotides to form the sugar-phosphate backbone of the new strand
Describe the role of DNA helicase
Breaks the hydrogen bonds between complementary base pairs so each strand can act as a template
Describe the process of DNA replication
- DNA helicase breaks weak hydrogen bonds between complementary base pairs
- both strands act as a template
- adjacent nucleotides bind to complementary base pairs, adenine, thymine, cytosine and guanine
- DNA polymerase joins adjacent nucleotides together to form phosphodiester bond
- consists of one old and one new strand
Describe how DNA polymerase works
DNA polymerase has a specific active site to the 5’ end of the incoming free DNA nucleotide and the 3’ end of the developing strand.
What would a conservative model be
An entirely new molecule is synthesised from a DNA template
What would a semi-conservative model look like
Each new molecule consists of one newly synthesised strand and one template strand
Explain what a dispersive model would look like
New molecules are made of segments of new and old DNA
What is ATP
Adenosine triphosphate consists of nitrogenous organic base, ribose sugar and three phosphate groups
2 uses of ATP
- Provides energy for active transport, muscle contraction, protein synthesis
- Phosphorylation of molecules with lower activation energy- makes substrates more reactive by altering tertiary structure
Describe how ATP formed
The condensation reaction between ADP and Pi catalysed by condensation reaction, it requires energy to add phosphate group to ADP to form ATP creating a high energy bond
How is ATP broken down
Breaks back down into ADP and Pi catalysed by ATP hydrolase
Pi can be used to phosphorylate other compounds and make them more reactive
Why is ATP useful
- Releases relatively small amounts of energy
- Releases energy instantaneously
- Phosphorylates other compounds,making them more reactive
- Can be rapidly re-synthesised
- It is not lost from the cells
Contrast the structures of ATP and a nucleotide found in DNA
- ATP has ribose and DNA nucleotide has deoxyribose
- ATP has 3 phosphate and DNA nucleotide has one phosphate
- ATP base always has adenine and in DNA nucleotide base can be different
What are the properties of water important in Biology
- Polar (molecules);
- Dissolves charged particles/acts as a (universal) solvent;
OR - A metabolite;
- Involved in metabolic/cell reaction/condensation/hydrolysis;
OR - Water molecules stick together/cohesion between water
molecules; - Provides surface tension/prevents columns of water
breaking;
OR - High specific heat capacity;
- Reduces fluctuations in temperature (of water bodies);
OR - High latent heat of evaporation;
- Evaporation of small amount of water cools organisms;
Suggest why water becomes lighter as it expands and explain an advantage
- Density=mass/volume
- Ice has same mass of water but greater volume
Advantage: ice is colder than water, ice floats on water, reduces freezing of water
Explain why water is considered so important for life to occur
- Life has evolved in water
- Water provides support for bodies of organisms
- Water is a major component of the cytoplasm
- Water is a universal solvent so metabolic reactions occur
- Water is a metabolite
- Water stabilises external temperature
