Nucleic Acids Flashcards
How is DNA adapted to its function?
- Hydrogen bonds between bases; allows DNA to seperate during replication.
- Large molecule; can carry an immense amount of information
- Complementary base pairing; allows DNA to replicate and transfer information as RNA. both strands can act as templates.
- Phosphodiester backbone; protects the genetic information from being corrupted by external physical and chemical forces.
Describe the structure of DNA
- Hydrogen bonds between bases.
- Deoxyribose pentose sugar.
- Complementary base pairing; Adenine-Thymine,Guanine-Cytosine.
- Contains a phosphate group.
- Double helix.
Describe the structure of RNA.
- Ribose pentose sugar.
- No complementary base pairing.
- Bases; Adenine, Uracil, Guanine, Cytosine
- Contains a phosphate group.
- Single, long strand.
Describe the formation of a polynucleotide.
condensation reaction between two nucleotide monomers. formation of a phosphodiester bond (strong, covalent) between the phosphate group on one monomer and the pentose sugar on another, plus the elimitation of a water molecule.
Describe the stages of DNA replication.
1- DNA present as double helix.
2- DNA helicase unwinds double helix and separates the two strands by breaking the hydrogen bonds between bases. Energy from ATP used to move the DNA helicase along the strands.
3- Free complementary nucleotides join with their complementary pair on the template strand, being activated by ATP.
4- DNA polymerase links nucleotides together aiding the formation of phosphodiester bonds between the free nucleotides to create a new phosphodiester backbone, using the pre-existing strand as a template.
Name the conditions for DNA replication
- A ‘pool’ of the four types of nucleotides (free) must be present.
- Both strands of DNA being copied.
- DNA helicase and polymerase must be present.
- A source of ATP to drive the process.
Name and define the hypothesis for the two possible DNA replication methods.
The conservative model;
- Suggested that the original DNA molecule stayed intact, and the seperate daughter DNA copy was built from new molecules of deoxyribose, phosphate and organic bases.
Semi-conservative model;
- Proposed that the original DNA molecule was split into two seperate identical strands.
Describe the structure of ATP
- contains three phosphate groups, a ribose pentose sugar and adenine base.
- contains an easily breakable bond between the phosphate groups to allow for easy release of energy.
- formed using the enzyme ATP Synthase, and broken down by the enzyme ATP hydrolase.
Give the reversible reaction involving the breaking down and reforming of ATP
Breaking down;
ATP + H2O —> ADP +Pi (+energy)
Reforming;
ADP +Pi (+energy) —> ATP + H2O
Name and explain 5 uses of ATP.
- Metabolic Processes;
provides energy needed to build up polymers from their basic units (e.g: starch from glucose) - Movement;
provides energy for muscle contraction, and for filaments of muscle to slide past one another. - Active Transport;
provides energy to change the shape of carrier proteins in plasma membranes. - Secretion;
needed to form lysosomes required for secretion of cell products. - Activation of molecules;
The Pi formed from the hydrolysis of ATP can be used to phosphorylate other compounds in order to make them more reactive, so lowering the Ea of enzyme-catalysed reactions.
How is water important in:
- metabolism
- as a solvent (e.gs?)
- in other ways (3)
Metabolism;
- water is used to break down complex molecules during hydrolysis and produced during condensation reactions.
- chemical reactions usually take place in aqueous medium.
- water is a major raw material from photosynthesis.
Solvent;
- water readily dissolves other substances such as…
- O2, CO2, NH3, Urea, inorganic ions, small hydrophilic molecules (amino acids), monosaccharides, ATP, enzymes.
Other;
- helps cool organisms by evaporation.
- provides support as difficult to compress.
- transparency allows aquatic plants to photosynthesise.
Describe the specific heat capacity of water.
(Definition, Why high in water, uses)
- The thermal energy required to raise 1kg of a substance’s temperature by 1˚C without a change of state.
- Due to hydrogen bonds between water molecules, it requires more energy to seperate them.
- Allows water to act as a buffer against sudden temp changes, making aquatic environments/organisms stable.
Describe the latent heat of vapourisation of water.
(Definition, Why that high, uses)
- the amount of energy needed to change the state of 1g of a substance without changing it’s temperature.
- a lot of energy is required to evaporate 1g of water due to its hydrogen bonding between molecules.
- allows water to be an efficient cooling system when evaporating off organisms bodies due to the body heat being used.
What is cohesion and surface tension in water? (Uses?)
- Cohesion - the tendancy of water molecules to stick together. (high in water due to hydrogen bonding).
allows water to be pulled through a tube. - Surface tension - the tendancy of water molecules to be pulled back into a body of water instead of escape from it.
allows water’s surface to act as a ‘skin’ for supporting small organisms.
Name the four most common inorganic ions in the body and their importance.
> Sodium ion;
- provides +ve charge outside of cell and co-transport of glucose and amino acids across plasma membranes due to sodium-potassium pump.
Iron ion;
- used in transport of O2 and CO2 in haemoglobin.
- is an essential component of cytochromes (e- transport chain).
Hydrogen ion;
- helps form HCl in stomach and pepsin to digest food.
- Allows pH of solutions to be determined, therefore the functioning of enzymes.
Phosphate ion;
- Produce nuclei acids (DNA/RNA) in cells, and phospholipids in cell membranes, along with ATP for cells.
