Proteins

• Key protein information


  • Complex molecules (carbon, hydrogen, oxygen, and nitrogen, also sometimes sulphur)
  • Many form complexes with other molecules containing; phosphorus (P), iron (Fe), zinc (Zn), or copper (Cu)
  • Large Macromolecules with one or more unbranched polypeptide chains built from amino acid monomers
  • Two main groups: globular and fibrous
• Amino Acids

  • Have an Amino group (-NH_2) and a Carboxyl group (-COOM)
  • R-group differ from one to another (20 R-groups and 20 amino acids)
  • R-groups can be either: hydrophilic/polar or hydrophobic/non-polar, acidic or basic
  • General Formula: NH_2RCHCOOH
  • Key Examples:
  • Glycine (R-group = H); just a hydrogen ion, simplest amino acid
  • Cysteine (R-group = CH_2 - SH); sulphur is important for disulphide bonding
• Amino Acid Ionisation:

  • Amino group acquires a hydrogen ion
  • Now positively charged (NH_3^+) it dissolves in water
  • As carboxyl group (now negatively charged, COO^-) dissociates
  • Freeing hydrogen ion
  • Amino acids are amphoteric
  • Act as both acids and bases
  • It has positive and negative end; dipolar ion or zwitterion
  • Makes them pH buffers
  • Carboxyl ion can take up H^+ ions from solutions (prevents acidity)
  • Amino ion can readily release H^+ into solutions, neutralise OH^- ions (reduces alkalinity)
• Classification according to Function:

  A) Regulates Blood Sugar Levels

  B) Transport

  C) Amylase

  D) Albumin

  E) Antibodies (Immunoglobulin), Fibrinogen

  F) Muscle

  G) Islets of Langerhans

  H) Duodenum

  I) pH

  J) B lymphocytes

  K) blood clotting

  L) Arteries, connective tissue

  M) oxygen

  
• Amino Acid Diagram

  Label

  A) R

  B) C

  C) H

  D) C

  E) O

  F) OH

  G) N

  H) H

  I) H