Biomolecules 3

• Structure of follicle stimulating hormone (FSH):


  Quaternary protein

  2 non-identical subunits (alpha & beta)

  beta unit is unique so is specific to FSH's function (every sub unit has a different gene to create it)
• Insulin structure:

  Alpha & beta chain connected by peptide.

  Has positions where you can make disulphide bonds (extracellular protein)
• Where is insulin secreted from?


  Beta cells in islets of Langerhans in pancreas.
• Structure of trypsin enzyme:


  Alpha-helix & beta-pleated sheet mixture
• How is the tertiary structure of a protein formed?


  Folding of polypeptide chain upon itself- forms spontaneously (creates stable structures).
• What 2 structures do most proteins form?


  Compact globular structures or extended fibrous structures.
• What role do extended fibrous structures have?


  Structural
• How is the conformation of globular proteins stabilised?


  Ionic bonds, hydrophobic interactions, hydrogen bonds & van der waals.
• What are motifs?


  Folding patterns which involve 2 or more elements of secondary structure.

  E.g, beta-alpha-beta loop
• What are domains/binding pocket?


  Tend to be larger regions of a single polypeptide chain, which fold stably & independently.

  E.g, the 2 separate calcium binding domains in troponin C (muscle).
• Binding pocket in receptors/enzymes example:


  Active site (lysozyme)

  Binding sites: bind & orient substrate(s)

  Catalytic site: Reduce chemical activation energy
• What can proteins be classified on the basis of?


  Complexity (simple chains or conjugated), structure (fibrous or globular), location (cytosol, membrane-bound, extracellular) & function (enzymes, support, defence, transport, signalling, hormone, receptor).
• Structure of haemoglobin:

  2 alpha & 2 beta subunits

  Tetramer held together by interactions between subunits (ionic bonds)
• What are nucleic acids polymers of?


  Nucleotides.
• Genome:


  All of an organism's genetic info (DNA)
• Gene:


  Basic unit of inheritance.

  A segment of DNA encoding a protein.
• Sugar-phosphate backbone links...


  nucleotides with phosphodiester bonds
• Nucleotide structure:


  Sugar

  Nitrogenous base

  Phosphate
• Complementary base pairing:


  GCAT

  Makes stable DNA double helix (antiparallel strands)

  Helix turns every 10 residues
• How many H bonds between G & C?


  3
• How many H bonds between A & T?


  2
• What type of structure do nucleic acids have?


  alpha helical
• How is a hybridised molecule formed?


  Single stranded DNA will hybridise with single stranded RNA.
• DNA 3D structure has what kind of grooves?


  Narrow minor grooves & wider major grooves in which proteins can bind.
• Semi-conservative DNA replication:


  Parent strands separate at forks & complementary daughter strands formed by DNA polymerase.

  New DNA contains 1 parent & 1 daughter strand

  Sequence of bases on parent strand act as template for daughter strand
• 3 main RNA classes:

  mRNA carries transcript of gene from nucleus to ribosome

  tRNA reads codon on mRNA & brings specific amino acids to ribosome

  Ribosomal RNA (rRNA) are constituents of ribosomes
• What do microRNA do?


  Regulate & inhibit translation & gene expression
• Similarity between RNA & DNA?


  Backbone structure
• Differences between DNA & RNA?


  RNA has uracil instead of thymine

  RNA has ribose sugar instead of deoxyribose
• Which enzyme is A?

  DNA helicase

  
• Which enzyme is B?


  DNA polymerase

  
• Which enzyme is C?


  RNA polymerase

  
• Compare nuclear & mitochondrial DNA:

  
• Which component of DNA double helix is located along the central core of the molecule?

  Nucleobase pairs