Biological molecules

• Carbohydrates: C H O

  Lipids: C H O

  Proteins: C H O N S

  Nucleic Acids: C H O N P
• Cations


  • Calcium ions (Ca2+)
  • Sodium ions (Na+)
  • Potassium ions (K+)
  • Hydrogen ions (H+)
  • Ammonium ions (NH4+)
• Calcium ions (Ca2+)


  Involved in muscle contraction and nerve impulse transmission
• Sodium ions (Na+)


  Involved in co-transport, reabsorption of water in the kidney and nerves impulse transmission
• Potassium ions (K+)


  Involved in stomatal opening and nerve impulse transmission
• Hydrogen ions (H+)


  Involved in chemiosmosis, pH determination and catalysis of reactions
• Ammonium ions (NH4+)


  Involved in nitrogen cycle, where by bacteria convert ammonium ions into nitrate ions
• Anions


  • Nitrate (NO3-)
  • Hydrogencarbonate (HCO3-)
  • Chloride (Cl-)
  • Phosphate (PO43-)
  • Hydroxide, (OH-)
• Nitrate (NO3-)


  Mineral ion absorbed by plants to provide a source of nitrogen to make amino acids
• Hydrogencarbonate (HCO3-)


  Maintains the pH of the blood
• Chloride (Cl-)


  Provide a negative charge to balance to positive sodium ion and potassium ions in cells
• Phosphate (PO43-)


  Involved in the formation of phospholipids for cell membranes, nucleic acid and ATP formation and in making bones
• Solvent


  Polar (hydrophilic), or charged, molecules dissolve readily in water due to the fact water is polar
• Water is a polar molecule that acts as a solvent
• Non polar ( hydrophobic) molecules cannot dissolve in water and are repelled by water
• The cytosol in eukaryotic and prokaryotic cells is mainly water so this ensures many solutes can dissolve within the cell and then be easily be transported
• Cohesion 


  Water molecules sticking together by hydrogen bonds
• Due to cohesion when water moves up the xylem implants due to transpiration, it is as a continuous column of water
• Water as a coolant

  Water has a high specific heat capacity due to energy required to break the hydrogen bonds between the molecules. It also has a large latent heat of vaporization due to energy required to break the hydrogen bond between water molecules to turn it into a gas
• The high specific heat capacity of water is advantageous as internal temperatures of plants and animals should remain relatively constant. This is important so the enzymes do not denature or reduce an activity with temperature fluctuations
• Water as a Habitat 


  Water buffers temperature meaning it provides a stable environment in terms of temperature for aquatic organisms.

  Cohesion provides surface tension to water which enables small invertebrates to move and live on the surface, providing them with a habitat away from predators within water.

  Ice is less dense than liquid water due to the hydrogen bonds. Therefore ice floats on top of water providing a surface habitat for animals
• Disaccharide 


  Made of two monosaccharides

  Join together by glycosidic bonds

  Formed via a condensation reaction

  Broken down by hydrolysis

  Glucose and glucose makes maltose and water

  Glucose and galactose makes lactose and water

  Glucose and fructose makes sucrose and water
• Condensation reaction


  Joining two molecules together by removing water
• Hydrolysis reaction


  Splitting apart molecules through the addition of water
• Polysaccharides


  Created by condensation reactions between many glucose monomers

  Starch is found in plants and is a store of glucose

  Cellulose is found in plants and is used for structural strength

  Glycogen is found in animals and is a store of glucose
• Starch 


  Alpha glucose

  1-4 glycosidic bonds in amylase

  1-4 and 1-6 bonds in amylopectin

  Store of glucose

  It's found in plant cells

  Made of two polymers: amylose (an unbranched helix) and amylopectin (a branched molecule)

  Helix can compact to fit a lot of glucose in a small space.

  Branch structure increases surface area for rapid hydrolysis back to glucose insoluble therefore won't affect water potential
• Cellulose 


  Beta glucose

  1-4 glycosidic bonds

  Structure strength for cell walls

  Found plant cell wall

  Polymer forms long straight chains

  Chains are held in parallel by many hydrogen bonds to form fibrils

  Microfibrils combine to form a cellulose fiber

  Many hydrogen bonds provide collective strength

  Insoluble therefore won't affect water potential
• Glycogen 


  Alpha glucose

  1-4 and 1-6 glycosidic bonds

  It is a store of glucose

  Found an animals mainly in muscle and liver cells

  It is a highly branched molecule

  The brunch structure increases surface area through rapid hydrolysis back to

  Insoluble therefore won't affect water potential
• Lipids 


  Nonpolar molecules

  In soluble in water

  Dissolve an organic solvent such as ethanol

  Hydrophobic

  Made off of two molecules, fatty acid and glycerol

  They do not form polymers
• Triglyceridestructure 


  One glycerol molecule attached to three fatty acids. Formed via condensation reaction. Contains ester bonds .
• Phospholipid


  Glycerol attached to two fatty acids with a phosphate group. Formed via a condensation reaction. Forms ester bonds
• Properties of phospholipids 


  Hydrophilic head of a phospholipid can attract with water as it is charged

  The fatty acid chain is not charged. It is known as the hydrophobic tail and it repels water but mix well with fats

  Due to the two charged regions, they are polar. In water they are position so that the heads are exposed to water and the tails are not. This forms a phospholipid bilayer membrane structure which makes up the plasma membrane around cells
• Cholesterol


  It is a sterol

  Sterols have full carbon rings and hydroxyl group at one end and they have both hydrophobic and hydrophilic regions

  Cholesterol is embedded with cell membranes to impact fluidity

  They help produce the fluidity of membranes at high temperatures and increased fluidity at low temperatures.
• Amino acid structure 


  They contain a central carbon with an amino group, a carboxyl group and a variable r group in which there are 20 options.
• Primary structure of an amino acid

  The order of the amino acid in the polypeptide chain.
• Secondary structure of an amino acid

  The sequence of amino acids causes parts of a protein molecule to bend into alpha helix or fold into beta pleated sheets

  Hydrogen bonds hold the secondary structure
• Tertiary structure of an amino acid

  3d shape of amino acid

  Held together by hydrophobic and hydrophilic interactions, hydrogen bonds, ionic bonds and disulfide bonds
• Quaternary structure of an amino acid

  A protein made up of more than one polypeptide chain
• Fibrous proteins


  Polypeptide chains from long twisted strands linked together

  Stable structure

  Insoluble in water

  Strength gives structural function

  Collagen in bones and keratin in hair
• Globular protein 


  Polypeptide chains rolled into a spherical shape

  Relatively unstable structure

  Soluble

  Metabolic functions such as all enzymes, antibodies, some hormones and hemoglobin.