C2 Nucleic Acids Flashcards
Nucleotides
Made up of
- Deoxyribose sugar (if RNA; ribose sugar)
- phosphate group
- organic base
Compare DNA with RNA
BOTH:
- have polynucleotides
- have A, C, G bases
DIFFERENCE:
- RNA is single-stranded, whereas DNA is double-stranded
- RNA contains ribose sugar, whereas DNA contains deoxyribose sugar
- RNA contains uracil, whereas DNA contains thymine
- RNA is a relatively short polynucleotide, whereas DNA is a long nucleotide
-DNA has base pairings (H-bond) between specific complementary bases whereas RNA doesn’t
-DNA has introns (non-coding sequence), whereas RNA does not
Base Structures
- Adenine and Thymine are DOUBLE ring structures; PURINES (A=T)
- Guanine and Cytosine are single-ring structures; PYRIMIDINE ∴ are complementary due to needing three H-bonds (G≡C)
Functions of the DNA Structure
- Double helix that protects weak hydrogen bonds and makes molecule stable
- Sugar-phosphate backbone provides strength, ensuring DNA is a stable information carrier
- Individually weak Hydrogen bonds between complementary bases: allow strands to separate for replication
- Many hydrogen bonds formed between complementary base pairs give molecule stability
- Complementary base pairing: enables information to be accurately replicated
- Two strands: both act as a template in DNA replication
- DNA molecules are tightly coiled around histone proteins resulting in a compact shape so that the full genome can fit into every individual cell
- Long molecule: stores a large amount of information
Phosphodiester bond
The bond between the deoxyribose sugar and phosphate group in a di-nucleotide
Mononucleotide
Formed via condensation reaction between Deoxyribose sugar, phosphate group, and organic base
Polynucleotide
More than 2 nucleotides linked with phosphodiester bonds between them(,via condensation reaction)
2 main differences between Watson and Crick and Pauling and Corey’s proposed structures for DNA
- P+C
- 3 intertwined chains
- bases on the outsides
- W+C
- 2 intertwined chains
- bases on the inside
Features of DNA to allow for replication
- Weak H bonds between bases allow strands to separate.
- 2 strands, so both can act as a template
STEPS OF DNA REPLICATION
1- Starts at a specific sequence on the DNA molecule
2- DNA helicase unwinds and unzips DNA
3- This breaks the hydrogen bonds that join on the specific complementary base pairs
4- 2 seperate strands are formed
5- Nucleotides with complementary bases line up against each original strand; act as a template
infernal strand - act as a template
6- Eg Cytosine with Guanine, Adenine with Thymine
7- Hydrogen bonds from between the complementary bases
8- DNA polymerase joins the new nucleotides with phosphodiester bonds
9- This is a condensation reaction
10- the two new strands wind up to form double helices
11- The two new molecules are identical to the old molecule
12- Each has one original strand and one new strand (semi conservative replication.)
ATP
- Adenosine Tri-phosphate
- Nucleic acid - nucleotide derivative ie;
1. Adenine base
2. Ribose sugar
3. Three phosphate groups
Properties of ATP
- Releases a small amount of energy when hydrolysed (approx. 28-24 kJ/mol) which is a more managebale quantity than what is released by glucose
- Third phosphate bonds are easily broken (simple and easy reaction)
- Can be reformed rapidly
- Immediate energy source,unlike glucose, which requires a long series of reactions and therefore takes a longer amount of time to relase energy
- Phosphorylates (adds a phosphate) to molecules to make them more reactive
- Cannot leave the cell
ATP hydrolase
Catalyst used in the hydrolysis of ATP to produce ADP
ATP synthase
Catalyst used in the condensation reaction of producing ATP from ADP
How ATP stores energy
Bonds between the phosphate groups are unstable ∴ have a low activation energy ∴ easily broken. When they do break, they release energy.
3 WAYS of SYNTHESIS of ATP
Reversible reaction ∴ energy can be used to RE-ADD the phosphate group to ADP
1. In chlorophyll-containing plant cells during photosynthesis(photophosphorylation)
2. plant and animal cells during respiration(oxidative phosphorylation)
3. plant and animal cells when phosphate group are transferred from donor molecules to ADP ( substrate-level phosphorylation)
Structure of water
- Dipolar: has 𝛿+ dipole H and 𝛿− dipole O.
- The positive pole of one water molecule will be attraced to the negative pole of another one via H bonding ∴ forms forces that allow water to stick together
Properties of Water
- High boiling point
- High heat capacity
- High latent heat of vaporisation
- Cohesion
- Metabolism
- Solvent
High boiling point of water
Water molecules tend to stick together ∴ to seperate them takes more energy than expected
High heat capacity of water
Meaning it acts as a buffer against dramatic temperature changes ∴ making aquatic environments’ temperature stable
High Latent Heat of Vapourisation of Water
- H bonds between the water molecules result in needing a lot of energy to evaporate 1 gram of water.
- Therefore the evaporation of water (eg; sweat in mammals), is very effective for cooling the body as heat energy evaporates with it.
Cohesion of Water
- Cohesion - tendency of molecules to stick together
- Hydrogen bodning causes strong cohesive forces between the moecules
- Enables it to be pulled up through a tube i.e. xylem vessels in plants
- Also where water molecules meet air they tend to be pulled back to the body of water (surface tension), can act as a floor to support small organisms
Metabolite (water)
- Produced in condensation reactions
- Used to break down molecules
- Water is a major raw material in photosynthesis
Solvent as a Property of Water
- Dissolves gases (O2, CO2)
- Wastes(ammonia)
- Inorganic ions and small hydrophilic molecules (amino acids, monosaccharides, ATP)
- Enzymes
