2.1.2 General Biological molecules

• What is water composed of?

  Hydrogen and Oxygen (H20)
• Explain the bonding of water?


  - the whole is electrically neutral , however the sharing of the electrons is uneven between oxygen and hydrogen

  
  

  - it is like this because the oxygen atom attracts the electrons more strongly than the hydrogen atoms resulting in a weak negatively charged region on the oxygen atom(δ- )

  
  

  - weak positively charged region on the hydrogen atoms (δ +) this also results in assymmetrical shape
• Define dipole?


  separation of charge due to the electrons in the covalent bonds being unevenly shared
• What is a polar molecule?


  When a molecule has one end that is negatively charged and one end that is positevly charged.
• What bonds form between water molecules?


  Hydrogen form between water molecules

  
  

  = results of the polarity of water hydrogen bonds form between the positive and negatively charged regions of adjacent water molecules
• Why does water have such a strong structure?


  Hydrogen bonds are weak when few, so they are constantly breaking and reforming.

  
  

  - However when large numbers are present they form a strong structure
• List water's properties?

  - An excellent solvent

  
  

  - relatively high specific heat capacity

  
  

  - relatively high latent heat of vaporisation

  
  

  - water is less dense when a solid

  
  

  - water has high surface tension and cohesion

  
  

  - its acts as a reagent
• What is water's essential roles in living organisms due to its properities?


  - polarity of water molecules

  
  

  - presence and number of hydrogen bonds between water molecules
• Explain why water is a good solvent?


  - Polar molecules many ions (ionic) and covalently bonded pair substances (e.g glucose) will dissolve in it

  
  

  - allows chemical reactions to occur within cells ( as the dissolved solutes are more chemically reactive when they are free to move about)

  
  

  - Metabolites can be transported efficiently (except non-polar molecules which are hydrophobic)
• Define Heat specific capacity?


  The amount of thermal energy required to raise the temperature of 1kg of that substance by 1*c.
• What is water's specific heat capacity?


  4200J/kg°C
• Explain water's high specific heat capacity?


  Water's spec. heat capacity needs a relatively large amount of energy to raise its temperature

  
  

  - this is due to many hydrogen bonds present in water > thus takes a lot of thermal energy to break these bonds and a lot of energy to build them,

  
  

  =thus temperature of water does not fluctuate
• What is the advantage of water's high specific heat capacity


  - provides suitable habitats

  
  

  - able to maintain a constant temperature ( as water absorbs a lot of heat w/o big temp fluctuation)

  
  

  -vital in maintaining temps in enzyme activity

  
  

  -water in blood plasma is also vital in transferring heat around the body to allow fairly constant temperature ( as blood passes through more active (warmer) regions of the body, heat energy is absorbed but the temperature remains fairly constant.

  
  

  - water in tissue fluid also plays an important regulatory role in maintain a constant body temperature
• Explain latent heat of vaporisation in water?


  In order to change state of matter a large amount of thermal must be absorbed b water to break the hydrogen bonds and evaporate
• Explain how latent vaporisation is advantage in water?


  - As only a little water is required to evaporate for the organism to lose a great amount of heat

  
  

  - provides cooling effect > e.g transpiration or sweat
• Explain why cohesion happens in water? Breifly..


  Because hydrogen bonds between water molecules allows for strong cohesion between water molecules
• Explain in more detail cohesive forces in water molecules?


  This allows columns of water to move through the xylem of plants or through blood vessells in animals

  
  

  -> this enables surface tension where a body of water meets the air, these hydrogen bonds occur between the top layer of water molecules to create a sort of film on the body of water ( allows insects such as pond skaters to float)
• Explain adhesion in terms of water particules?


  -> Water is also able to hydrogen bond to other molecules such as cellulose

  
  

  - enables water to move up the xylem due to transpiration.
• List the 5 molecules required to build structures that enable organisms to functions are:

  - Carbohydrates

  - Proteins

  -Lipids

  -Nucleic Acids

  -Water
• Define monomer


  are smaller units from which larger molecules are made
• Define Polymer?


  Molecules made from large number of monomer joined together in a chain
• What are macromolecules?


  Are very large molecules

  
  

  - 1000 or more atoms and so have a high molecular mass

  
  

  - not all macromolecules are polymers as the subunits of polymers have to be the same repeating units
• Explain covalent bonds?


  The electrons can be shared equally forming a non polar covalent bond or unequally (electronegative atom) to form a polar covalent bond

  
  

  -very stable as high energies are required to break the bonds
• In covalently bonded substances when two monomers are close..


  close enough that their outer orbitals overlap this results in their electrons being shared and a covalent bond form.

  
  

  If more monomers are added then polymeristation occurs (or macromolecules )
• Explain condesation reactions?

  (dehydration syntheis)

  
  

  - occurs when 2 monomers combine by covalent bonds to form polymers (polymerisation) or macromolecules (e.g lipids) and water is removed
• Explain hydrolysis?


  In the hydrolysis of polymers, covalent bonds are broken when water is added
• Carbohydrates have what type of covalent bond?


  glycosidic

  
• Proteins have what type of covalent bond?


  Peptide

  
• Lipids have what type of covalent bonds?


  ester

  
• Nucleuic Acid have what type of covalent bonds?

  phosphodiester

  
• Why are lipids not a polymer?


  Not made from either monomers or polymers as each fatty acid joins to glycerol molecule, rather to each other

  
  

  > not held together by covalent bonds.
• What elements does carbon bond w/?


  - oyxgen, nitrogen and sulfur

  
  

  - form straight chains, branched chains or rings
• What is carbohydrates composed of


  carbon, hydrogen, oxygen

  
  

  - H and O are always in 2:1 ratio Cx(H2O)y

  
  

  -monosacchride, disacchride, polysacchride
• What are the 3 functions of Carbohydrates ?


  - Source of energy (e.g glucose is used for release for ATP)

  
  

  - Store of energy (e.g glycogen is stored in the muscles and liver of plants

  
  

  - Structurally important ( e.g cellulose in the cel walls of plants
• Define Monosaccharide?


  single sugar monomer, all are reducing sugars
• Give 3 examples of monosaccharide?


  - Glyceraldehyde (3C)

  
  

  - Ribose (5C)

  
  

  - Glucose (6C)
• Function of monosaccharides


  - source of energy in respiration

  
  

  - building blocks for polymers
• Define disaccaride?


  a sugar formed from 2 monosaccharides joined by glycosidic bonds in a condensation reation
• examples of disaccharides


  - Maltase

  - Sucrose

  -Lactose
• Maltose structure and bonding


  (A-glucose) + (A-glucose)