II.1 Proteins + II.2 Protein structure

11 important questions on II.1 Proteins + II.2 Protein structure

What are the structural properties of amino acids?

Amino acids contain four different functional groups, bound to a central αC atom:
  • Amino group (NH4+)
  • Carboxyl group (COO-)
  • Sidechain R
  • Proton (H+)

What is meant by an L and D form?

When a carbon has 4 different groups bound, it is asymmetric. This means that there are stereo isomers, an L and a D form. Amino acids are only found in the L form.

What are the chemical classes of amino acids?

  • Acidic amino acids
  • Alkaline amino acids
  • Polar amino acids
  • Non-polar amino acids
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What are acidic amino acids? Give two amino acids that are acidic amino acids.

Acidic amino acids are polar amino acids with a negatively charged sidechain.
Amino acids:
  • Aspartic amino acid
  • Glutamic amino acid 

What are alkaline amino acids? Give three amino acids that are alkaline amino acids.

Alkaline amino acids are polar amino acids with a positively charged sidechain.
Amino acids:
  • Lysine
  • Arginine
  • Histidine  

What is a peptide bond?

A peptide bond is the bond between a carboxyl group and an amino group. Water is extracted when this bond is formed.

How is a peptide bond formed, how is it split?

A peptide bond is formed by condensation and split by hydrolysis.

What is an α helix?

In an α helix the sidechains are faced outside the helix. It is stabilized by hydrogen bonds.

What is a β sheet?

A β sheet is formed when hydrogen bonds between β strands are formed. There are parallel and antiparallel β sheets.

What is a β turn?

A β turn connects two antiparallel β sheets. When a large distance is bridged, it is called a β loop.

What is a motif? Give two motifs.

A motif is a structure that also appears in other proteins.
Two motifs:
  • Zinc fingers
  • Helix-turn-helix 

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