Nucleic Acids

Structure of RNA and DNA
1. Nucleotide Structure
  1. made up of 3 components
    1. a pentose sugar
    2. a phosphate group
    3. a nitrogen containing organic base
      1. A/T/C/G/U
        A is complementary to T and C is complementary to G
  2. the pentose sugar, organic base and phosphate group are joined by a condensation reaction
    1. forms a mononucleotide
    2. bond between two mononucleotides is a phosphodiester bond
      1. dinucleotide
2. RNA - ribonucleic acid
  1. polymer made up of nucleotides
  2. single relatively short polynucleotide chain
  3. pentose sugar is always ribose. Organic bases are A,G,C,U.
  4. one type of RNA transfers genetic info. Another is involved in protein synthesis. Ribosomes are made of another type
3. DNA structure
  1. pentose sugar is deoxyribose. Organic bases are A,T,C,G
  2. DNA is made of 2 strands of nucleotides
    1. they are both very long and joined by hydrogen bonds.
  3. double helix forms a structural backbone
4. DNA stability
  1. the phosphodiester backbone protects the more chemically reactive bases
  2. hydrogen bonds link the bases
    1. C-G = 3 A-T = 2
5. DNA function
  1. hereditary material responsible for passing genetic information from cell to cell and generation to generation
  2. almost infinite variety of sequences of bases
    1. leading to increased genetic variation
  3. rarely mutates and very stable
  4. two strands joined by hydrogen bonds meaning it can separate during replication
  5. large molecule and carries lots of genetic information
  6. genetic information is protected from chemical and physical forces becuause it is located within the phosphodiester backbone
DNA replication
1. cell division occurs in two ways
  1. nuclear division = nucleus divides (mitosis/meiosis)
  2. cytokinesis = follows nuclear division and the whole cell divides
2. semi-conservative replication
  1. needs... the nucleotide bases, both strands of DNA to act as a template, DNA polymerase, source of chemical energy
  2. 1. DNA helicase breaks the hydrogen bonds
    1. 2. helix unwinds and separates into two strands
      1. 3. each exposed polynucleotide chain acts as a template
        4. nucleotides are joined together in condensation reactions by DNA polymerse
        5. each new DNA molecule has one original strand and one new one
Energy and ATP
1. Structure = adenine, ribose and phosphates
2. ATP has 3 phosphate groups
  1. the bonds between them are unstable and lave low activation energy
    1. they are easily broken and release lots of energy when they do
      1. usually only the terminal phosphate is removed
        ATP + H2O -> ADP + Pi + E
        water is used to convert AP to ADP, this is known as hydrolysis. The reaction is catalysed by ATP hydrolase
        this is a reversible reaction. That is a condensation reaction and is catalysed by ATP synthatse
        this can occur in three ways
        photophosphorylation
        oxidative phosphorylation
        substrate-level phosphorylation
3. ATP is a good immediate energy source because it is instable
  1. ATP is a better immediate energy source than glucose because the amount of energy released is more manageable and the hydrolysis of ADP to ATP is a single reaction
4. ATP is involved in energy-requiring processes in cells
  1. metabolic processes - provides the energy needed to build up macromolecules from their basic sub-units
  2. movement - provides energy for muscle contraction and the energy for filaments to slide past one another
  3. active transport - energy to change the shape of carrier proteins
  4. secretion - needed to form lysosomes
  5. activation of molecules - Pi released during hydrolysis can be used to phosphorylate other compounds to make them more reactive
Water
1. Dipolar
  1. oxygen atoms are slightly negative and hydrogen slightly positive, so the molecule has positive and negative poles
2. Hydrogen bonding
  1. opposite poles attract and the attractive forces between them is a hydrogen bond
  2. individually the bonds are weak
3. SHC
  1. water molecules bond together meaning it takes more energy to break the bonds
4. latent heat of vaporisation
  1. hydrogen bonding between water molecules means that it requires a lot of energy to evaporate 1 gram of water
5. cohesion and surface tension
  1. the tendency of molecules to stick together is known as cohesion.
  2. with its hydrogen bonding, water has large cohesive forces and these allow it to be pulled through a tube, such as a xylem vessel
6. water in metabolism
  1. used to break down complex molecules by hydrolysis
  2. produced in condensation reactions
  3. chemical reactions take place in aqueous medium
  4. major raw material in photosynthesis
7. solvent
  1. water readily dissolves other substances such as gases, wastes, inorganic ions and enzymes
8. important features
  1. evaporation cools organisms
    1. not easily compressed so provides support
      1. transparent so aquatic plants can photosynthesise
  2. inorganic ions (iron, phosphate ions, hydrogen ions, sodium ions)

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Nucleotide (binary/octet-stream)

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	Created by Orlagh Bonser about 6 years ago