Biological Molecules

• Carbohydrates can be classified into three main types: monosaccharides, disaccharides, and polysaccharides.
• The key biological molecules are...

  Carbohydrates, proteins, lipids, and nucleic acids
• Metabolism


  The sum total of all the biochemical reactions taking place in the cells of an organism
• Catabolic reactions


  Breaking larger molecules into smaller ones
• Anabolic reactions


  Joining smaller molecules into larger ones
• Monomers


  Single small molecules
• Polymers


  large molecules made up of many similar monomers, covalently bonded together
• What are the monomers and polymers of carbohydrates?

  monomers - monosaccharides

  Polymers - polysaccharides
• What are the monomers and polymers of proteins?

  monomers - amino acids

  Polymers - polypeptides and proteins
• What are the monomers and polymers of nucleic acids?

  monomers - nucleotides

  Polymers -DNA and RNA
• What is a condensation reaction?


  The chemical reaction that combines biological monomers
• What happens during a condensation reaction?


  a new covalent bond is formed, a water molecule is released, a larger molecule is formed by joining smaller molecules
• What is a hydrolysis reaction?

  Splitting larger molecules into smaller ones
• What happens during the hydrolysis reaction?

  A covalent bond is broken, a molecule of water is used, smaller molecules are formed
• What are the properties of water?

  water is a very small dipolar molecule, made up of two slightly positive hydrogen, atoms covalently bonded to one slightly negative oxygen atom
• What is the biological importance of water?

  metabolite

  High latent heat of vaporisation

  Liquid with relatively high boiling point

  Low density of ice

  High specific heat capacity - thermostability

  Cohesion and adhesion

  Solvent

  Transport medium

  Transparent
• Why is water a metabolite?

  Many metabolic reactions require water, such as photosynthesis, or splitting disaccharides to monosaccharides by hydrolysis reactions
• Why does water have a high latent heat of vaporisation?

  The evaporation of water requires a lot of energy to break the hydrogen bonds. When water evaporates from the surface it 'removes' the heat and has a cooling effect e.g. sweating and transpiration.
• why does water as a liquid have a relatively high boiling point?

  The continue making and breaking of hydrogen bonds in water means that it is a liquid not a gas and it is difficult for water molecules to escape the liquid which means that the boiling point is much higher than that of other similar sized molecules
• Why does water have a low density of ice?

  As the water is cooled, and the molecules slow down, more hydrogen bonds form, holding the water molecules to form a crystalline structure, which is less dense than liquid water. This means that ice floats on water and insulates the organisms that live beneath it.
• Why does water have a high specific heat capacity?

  The hydrogen bonds in water prevent the movement of the water molecules, so relatively large amounts of energy required to increase the temperature of the water. Water therefore has a high specific heat capacity. This means that large bodies of water or thermostable, even when there are large external fluctuations of temperature.
• Why is water cohesive?

  hydrogen bonds cause water molecules to stick together, this results in surface tension of the surface of the water. This can allow some organisms to ' Walk on water' e.g. Pond skaters. Water can be transported up the xylem in the transpiration stream as cohesion between water molecules makes long thin, columns of water difficult to break.
• what is adhesion in regards to water?

  when water molecules stick to other surfaces, for example, the wall of the xylem
• How is water a good solvent?

  The polarity of water allows it to be a really good solvent. Any polar molecules like ions dissolve well in water, the negative ions will be attracted to the positive end of the water molecule and be positive ions to the negative end. Water molecules tend to cluster around any charge parts of solute molecules, disallows metabolic reactions, such as photosynthesis and respiration to take place in solution in the cytoplasm.
• How is water a good transport medium?

  Since water is a good solvent and remains liquid over a wide range of temperatures means that water is a good transport, medium E.G.plasma in blood minerals ions in the xylem.
• What is good about water being transparent?

  as water is transparent, aquatic organisms, such as algae and seaweed are able to photosynthesise as the Sun light passes through the water
• Ions


  Atoms which have an electrical charge
• Cations


  positively charged ions
• Anions


  negatively charged ions
• The more hydrogen ions...


  The more acidic the solution
• Iron ion is in haemoglobin


  Haemoglobin is a lot of protein molecules for subunits found in red blood cells. Each subunits has a polypeptide chain and a non-protein Haem group which contains a single iron atom in the form of FE2+. The iron ion can attract and bind with an oxygen molecule. The Haem group has a high affinity for oxygen as each haem group can hold one oxygen molecule, each haemoglobin country for oxygen molecules and transport them from the gas exchange system to repairing tissue
• What is the equation for oxyhaemoglobin?

  Hb + 4O2 -> Hb08
• Sodium ions and co-transporters


  sodium ions are used to co-transport glucose / amino acids into cells. Who transporters are specialised intrinsic proteins, which span the phospholipid bilayer. They transfer sodium ions linked with either glucose amino acid molecules in the same direction across the membrane.
• Phosphate ion

  DNA, RNA and ATP all contain phosphate groups:

  - The phosphate bonds in ATP store energy

  - The phosphate groups in DNA and RNA allowed phosphodiester bonds to form between nucleotides forming polynucleotides
• Monosaccharides

  simple sugars like glucose, fructose and ribose
• Properties of monosaccharides

  soluble in water

  Sweet tasting

  Form crystals
• alpha glucose is...

  Easily transported and readily used in respiration
• Beta glucose is...

  Found in cellulose
• Molecular formula of alpha and beta glucose

  C6H12O6
• Disaccharides


  two Monosaccharides sugars can join together to form a disaccharide, by condensation reaction as a water molecule is removed and a covalent bond called a glycosidic bond is formed.