L1 - biological elements

• An element is a substance made from one type of atom
• Atoms are the basis of biochemistry. They contain neutrons and protons in the nucleus and electrons around the nucleus on electron shells
• Protons and neutrons form the atomic nucleus
• Electrons are in the electron shells surrounding the atomic nucleus
• The first shell holds a maximum of two electrons; the second and third shells can hold maximum eight
• Two types of bonding: ionic and covalent
• Ionic bonding:

  -when a metal and non metal bond

  -transfer of electrons from the metal to the non metal
• Covalent bonding:

  -when non metals bond to each other

  -the sharing of outer electrons to make a full outer shell

  -bonding is very strong
• The number of bonds an element can make is known as the valency:

  -hydrogen has a valency of 1

  -oxygen 2

  -nitrogen 3

  -carbon 4
• Compounds are molecules made from two or more different elements that are chemically bonded together
• Covalent bonding in carbon:

  -carbon forms the backbone of most biological molecules. Therefore, life on earth is known as ’carbon based’

  -valency of 4

  -can form single or double bonds

  -can bond together in rings or long chains
• Ions:

  -formed when number of electrons is not equal to number of protons in an atom

  -if there’s an electron loss, atom will become positively charged (a cation)

  -electron gain leads to a negatively charged anion

  -ionic bonding involves one atom giving electrons to another so both have full outer shells

  -resulting cations and anion are attracted forming an ionic bond
• Groups of ions with more than one atom are called polyatomic ions
• Calcium ion: Ca2+

  Function: muscle contraction
• Sodium ion: Na+

  Function: nerve impulse transmission
• Potassium ion: K+

  Function: stomatal opening
• Hydrogen ion: H+

  Function: pH determination
• Ammonium ion: NH4+

  Function: production of nitrate ions
• Nitrate ion: NO3-

  Function: nitrogen supply for plants
• Hydrogen carbonate ion: HCO3-

  Function: to maintain blood pH
• Chloride ion: Cl-

  Function: balance sodium and potassium positive charges
• Phosphate ion: (PO4)3-

  Function: cell membrane formation
• Hydroxide ion: OH-

  Function: pH determination
• Polar molecule: a molecule with an uneven distribution of electron, resulting in positive and negative poles
• Hydrogen bonding:

  -form where a slightly positively charged part of a molecule and slightly negatively charged part of another molecule meet

  -one hydrogen bond is weak but may can stabilise a large molecule (eg. water)
• Biological molecules:

  -proteins

  -carbohydrates

  -lipids

  these are essential for life and health
• Proteins function:

  -used for transport and structure

  -basic components of all enzymes, hormones, antibodies, haemoglobin, ribosomes etc.
• Carbohydrates function:

  -used to store and supply energy

  -can be structural
• Lipids function:

  -part of cell membrane

  -used for insulation and protection

  -also a minor energy supply
• Protein: carbon, hydrogen, oxygen, nitrogen, sulfur
• Carbohydrates: carbon, hydrogen, oxygen
• Lipid: carbon, hydrogen, oxygen
• Biological molecules are often made from many smaller molecules joined together to make large molecules (macromolecules)
• -single small molecules are called monomers

  -many monomers are bonded together to form a polymer
• The chemical reaction that links monomers together is called condensation
• Condensation reactions:

  -involve the release of a water molecule

  -form a new covalent bond

  -form a larger molecule when the smaller molecules bond together
• Hydrolysis is the reverse of condensation - it involves splitting polymers to make monomers
• Hydrolysis involves:

  -the use of a water molecule

  -the breaking of a covalent bond

  -the formation of smaller molecules by the splitting of larger molecules