2: Nucleic acids Flashcards
DNA
Deoxyribonucleic acid
RNA
Ribonucleic acid
Role of dna
Carries genetic information
Nucleotide structure
- a pentose sugar
- a phosphate gorup
- a nitrogen containing organic base (thymine, adenine, guanine, cytosine, uracil)
All joined by condensation reaction, polynucleotide joined by phosphodiester bond
RNA structure
A polymer made up of nucleotides. Its a single, relatively short polynucleotide chain
- the pentose sugar is always ribose
- organic bases are G, C, A, U
- transfers genetic info from dna to ribosomes
DNA structure
- the pentose sugar is deoxyribose
- organic bases G,C,A,T
- made of TWO strands of nucleotides
- extremly long strands joined by hydrogen bonds
- double helix
Is DNA a stable or unstable molecule, why?
Stable
- the phosphodiester backbone protects the more chemically reactive organic bases inside the double helix
- hydrogen bonds link bases forming bridges (3 bonds between G+C so more gc the more stable)
How is DNA adapted for its function
- v stable structure, passes from generation without signif change. most mutations are repaired
- strands only joined by hydrogen, can be seperated for dna replication and protein synthesis
- v large, carries lots of info
- bases protected from chemicals
Cell division occurs in two main stages:
- nuclear divison (nucleus divides; mitosis + meiosis)
- cytokinesis (whole cell divides)
Requirements for semi-conservative replication
- four types of nucleotide with each of their bases present
- both strands act as template for attachment of nucleotides
- the enzyme dna polymerase
- source of chemical energy
Process of semi-conservative replication
1) enzyme dna helicase breaks hydrogen bonds so double helix unseperates and unwinds
2) each polynucleotide strand is exposed and acts as template to bind complementary nucleotides
3) binded by condesation reaction by enzyme dna polymerase, makes phosphodiester bonds
4) each of new DNA molecules contains one original dna strand
Structure of ATP
Adenosine triphosphate
- adenine (nitrogen containing organic base
- ribose (pentose sugar, backbone)
- phosphates (chain of 3 phosphate groups)
How does atp store energy?
The chain of three phosphate groups are only connected by an unstable weak bond so theres low activation energy, when bonds broken lots of energy is released.
equation to have energy as a product of atp
atp + h20 = adp + Pi + energy
Synthesis of ATP
reversible reaction to convert ATP to ADP. ATP formed by an inorganic phosphate and ADP. Condensation reaction catalysed by the enzyme ATP synthase.
Is ATP an immediate or long term energy source?
- its an immediate energy source not long term bc of instable phosphate bonds
It cant be stored and so is continously made in mitochondria
Why is ATP better than glucose?
- energy released in smaller more manageable quantities
- the hydrolysis of ATP to ADP is just one single reaction
Role of ATP
- metabolic processes
- movement
- active transport
- secretion
- activation of molecules
why is a water molecule dipolar?
A hydrogen atom has a slightly positive charge and an oxygen atom has a slightly negative charge so the water molecule has both positive and negative poles
Does water have a high or low specific heat capacity?
High, as it takes more energy to heat a given mass of water.
Makes water act as a buffer against temp change
Latent heat of vaporisation in water
hydrogen bonding between water molecules means more energy needed to evaporate. means sweats effective way of cooling body bc body heats needed to evaporate
Where do inorganic ions occur
in solution in the cytoplasm and body fluids of organisms. some in high conc some in very low
Role of diff ions example
hydrogen- determining pH (enzyme)
iron ions- carry oxygen in haemoglobin
sodium ions - co transport of glucose and amino acids
phosphate ions - components of DNA and ATP
