(2) Nucleic Acids Flashcards
Compare Structure of RNA and DNA
Include Similarities
DNA:
Double Helix
Deoxyribose Sugar
Bases: AT CG
Larger Molecule
RNA:
Single Helix
Ribose Sugar
Bases: AU CG
(Uracil replaces thymine)
Similarities:
Have phosphodiester bonds
Explain why DNA is a stable molecule
Phosphodiester backbone:
Protects more chemically active bases in double helix
Many hydrogen bonds that link the organic bases
C-G have 3 hydrogen bonds
hence the more C-G Pairings the more stable the DNA molecule.
How is DNA adapted for its purpose
Very stable structure
passes from generation to generation without change. Rarely mutates
Has two separate strands held by hydrogen bonds allowing them to separate by DNA Helicase during DNA Replication and protein synthesis.
Large molecule- Carries immense amount of genetic information.
Base pairings lead to DNA being able to replicate and transfer information as mRNA
Explain the steps to Semi Conservative Replication
(1)DNA Helicase breaks down hydrogen bonds of base pairs linking the two strands together.
(2) Each exposed polynucleotide acts as a template to which complementary free nucleotides bind by specific base pairing
(3) Nucleotides join together by condensation reaction by DNA Polymerase
This question is about ATP:
Structure of ATP
Word equation for hydrolysis of ATP
Uses of ATP
Adenine (Nitrogen containing base)
Ribose (pentose sugar)
3 phosphates
ATP +H20–> ADP + Pi + E
Uses:
Metabolic processes
movement: muscle contraction
Active Transport
Mucus Secretion(ATP required to form lysosomes necessary for secretion of cell products)
Explain how the structure of water is related to its roles in organisms (6marks)
Dipolar water molecule:
H20 has no overall charge
oxygen slightly negative
hydrogen is slightly positive
Cohesion and surface Tension:
With hydrogen bonding water has large cohesive forces which allow it to be pulled up a tube, eg xylem vessel.
Water in Metabolism:
Used to hydrolyse many complex molecules
Water is also produced during condensation reactions
Water and hydrogen bonding:
Opposite charges attract.
Hydrogen of one molecule is attracted to the oxygen of a different water molecule forming hydrogen bonds.
Specific Heat Capacity:
Water has high SHC due to hydrogen bonds hence
Water acts as a buffer against sudden temperature change, making an aquatic environment temperature stable.
Latent Heat of evaporation of water.
MANY Hydrogen bonds hence requires a lot of energy for evaporation.
(Evaporation of sweat in mammals as cooldown mechanism)
Name Two Enzymes involved in replicating DNA.
- DNA Helicase
Breaks hydrogen bonds between base pairs. - DNA Polymerase
Reforms Double Helix by condensation reaction
Catalyses formation of phosphodiester bonds
