More biological molecules (Topic 1B)

• Nucleotide structure 


  DNA and RNA are polymers of nucleotides and nucleotides are their monomer.

  nucleotide molecule contains phosphate bone a pentose sugar(5 carbon sugar) and a nitrogen containng prganic base.

  
• Polynucleotide structure 


  many nucleotides form a polynucleotide strand/chains via condensation reaction between the phosphate group of one and sugar of the other forming a ester bond .This forms a phosphodiester bond.

  • The chain oof phosphates and sugars are known as the sugar -phosphate backbone.

  
• DNA Structure +DNA nucleotides structure

  Deoxyribonucleic acid

  • double helix structure

  2 seperate polynucleotides strand that wind together forming a spiral.

  • really long+coiled tightly so genetic material can fit in small spaces in cell nnucleus.

  DNA nucleoides contains phosphate group. a nitrogen containing organic base and a deoxyribose sugar.

  • There are 4 bases

  (A)denine-(T)hymine

  (C)ytosine-(G)uanine

   

  
• Complementary based paring


  2 DNA polynucleotide strands are joined together by hydrogen bonds between the two bases (A-T &C-G)

  • the two polynucleotide strands are antiparallel these two strands twist forming a double helix.

  
• RNA Structure


  RNA contains a phosphate group a ribose sugar(still a pentose sugar)and 4 bases but thymine is replaced by URACIL (U)

  • it form a single polynucleotide strand
  • RNA strands are much shorter than DNA

  
• DNA &RNA Comparision


  comparison table

  
• DNA as the carrier of the gentic code


  DNA was first observedin the 1800s but lots of scientist at the time doubtedthta it could carry the gentic code because it has a relatively simple chemical compostion. Some argued that genetic informationmust be carried by proteins which are much more chemically varied

  By 1953 experiments had shown that DNA was the carrier of the genetic code. This was also the year in which the double helix structure which helps DNA to carry out it's function was determined by scientist James Watson and Francis Crick
• Why does DNA Replicate 


  DNA copies itself before cell division so each cell has the full amount of DNA. the method is called semi conservative replication due to half of the new strand that come from new DNA molecule comes from the orginal DNA strand. This means there is gentic coninuity and cells produced by cell division inherit their genes from parent cells
• Step 1 of how DNA is replicated

  The enzyme DNA helicase breaks the hydrogen bonds between bases on the two polynucleotide DNA strands. This makes the helix unwind to form two single strands.

  
• Step 2 on how DNA is replicated


  Each original single strand acts as a template for a new strand

  Complementary base pairing means that free floating DNA nucleotides are attracted to their complementary exposed baseson each original template strand- A with T and C with G.

  
• Step 3 on how DNA is replicated

  Condensation reactions join the nucleotides of the new strand together -catalysed by the enzyme DNA polymerase. Hydrogen bonds form between the bases on the original a new strands.

  • Each new DNA molecule contains one strand from the original DNA molecule and one new strand.

  
• The action of DNA polymerase


  Each end of a DNA strand is slightly different in it's structure .One end is called 3 prime end and one end is called 5 prime end.

  • During DNA replication the active site of DNA polymerase is only complementary to the 3p end of the newly forming DNA strand-so the enzyme can only add nucleotides to the new strand at the 3p end. This means that the new strand is made in 5p to 3p direction and that DNA polymerase move down the template strand in a 3p to 5p direction

  
• The action of DNA polymerase


  Since the strands are antiparrallel the DNA polymerase working on one of the template strands moves in the opposite direction to the DNA polymerase working on the other template strand

  
• Evidence for semi conservative replication

  +Meselson and stahl's expeiment


  hiiii

  
• Step 2 and 3 of meselson and stahl's experiment


  hiiiii

  
• Step 4,5,and 6 of meselson and stahl's experiment


  hiii

  
• Energy is important for biological processes to occur e.g

  • active transport
  • cell division
  • protein synthesis
  • DNA replication in both animals and plants
• Energy is released through respiration but cells cab't get it's energy directly from glucose so in respiration energy released from glucose is used to make ATP.
• ATP(Adenosine triphosphate) Structure


  contains and adenine base(nucleotide base) ribose sugar and 3 phosphates

  • Known as a nucleotide derivative due to it being a modified form of a nucleotide
  • made from a condensation reaction
  • cells gain energy from ATP by hydrolysis reaction

  
• Making and Using ATP


  When energy is needed ATP is broken down into ADP(Adenosine diphosphate) and Pi(inorganic phosphate)This is a hydrolysis reaction- a phosphate bond is broken releasing energy. The reaction is catalysed by the enzyme ATP hydrolase

  
• Making and Using ATP Part2


  ATP hydrolysis can be 'coupled' by other energy required reactions in cells. This enables energy that's released to be used straight to make coupled reactions occur rather than being lost as heat

  • The released inorganic phosphate can be added to another compound known as phosphorylation which often makes compounds more reactive
• Making and using ATP PART 3


  ATP can be resynthesised by condensation reaction between ADATP can be resynthesised by condensation reaction between ADP and Pi. Ths occurs during both respiration and photosynthesis and it is catalysed by the enyme ATP synthase

  
• Importance of water

  • Is a metabolite in loads of important metabolic reactions
  • A solvent which means some substances dissolve in it
  • Help with temperature control due to it's high latent heat of vapourisation and high specific heat capacity
  • very cohesive (stick together)this helps water transport in plants as well as other organisms.
• Structure of water + Polarity of water


  one atom of O2 is joined to 2 atoms of H2 covalently(by shared electrons)

  • because the shared negative hydrogen electrons are pulled towards the oxygen atom the other side of each hydrogen atom is left with a slight positive charge.The unshared negative electrons on the oxygen atom give it a slight negative charge. This makes water a polar moleule -it has a slightly (partial)negative charge on one side and a slight(partial) positive charge on the other

  
• Hydrogen bonding


  very weak bonds

  • hydrogen bonds formed as slightly negative O2 atoms of water attract slightly positive charged hydrogen atoms of other water molecules. This hydrogen bond gives water some useful properties

  
• Properties of water

  • Important metabolite
  • Good solvent
  • High latent heat of vapourisation
  • Can buffer (resist) changes in temperature
  • Very cohesive
• Important metabolite


  For hydrolysis reactions(energy release from ATP) and condensation reactions(amino acids are joined together to make polypeptides)
• Good solvent


  Waters polarity makes it a useful solvent as the slightly negative charged attract slightly positive charged and vice verca

  • This enables organisms useful substance (miineral ions that is dissolved in water and this can betransported around the body

  
• High latent heat of vaporisation


  alot of energy needed to break hydrogen bonds in water

  • organisms can cool down without losing too much water
• Can buffer(resist) changes in temperature


  Alot of energy to change temperature of a substance

  • This means water can't experience rapid temperature change which enable it to be a good habitat as the water temperature under water is mostly stble than on land
  • In organism also remains stable temperature helping to maintain a constant internal body temperature
• Very cohesive (due to them being polar)


  • High surface tension when in contact with air

  This is the reason why sweat tension when sweat forms dropletswhich evaporates from the skin to cool an organism down.It's also the reason that pond skaters and some other insects can walk on the surface of a pond

  • great for transporting substances e.g xylem
• Inorganic ions


  most doesn't contain carbon

  found in

  • solution
  • in the cytoplasm of cells
  • body fluids of organisms

  ions role determines whether it is found in high or low concentration
• Iron ions in haemoglobin


  Haemoglobi is a large protein which carries blood around the body.It is made of 4 polypetide chains each with Fe2+ in it's centre .Fe2+ bind to the oxygen in the haemoglobin. When O2 is bound the Fe2+ temperarily becomes Fe3+ ion until O2 is released
• Hydrogen ion


  pH is calculated based on the concentration of H+ ions in the environment. More H+ present lower pH and more acidic environment. Enzyme controlld reactions are all affected by pH
• Sodium ion


  Glucose and amino acids can be transported into a cell (across the cell surface membrane) alongside sodium ions. This is known as co transport
• Phosphate ions


  Phosphate ions attaches to another molecule it's known as a phosphate group.

  • It's the bonds between phosphate groups that store energy in ATP
  • phosphate group in DNA & RNA allow nucleotides to join up to form polynucleotides .