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11 Cards in this Set
- Front
- Back
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Define the primary structure of amine acids |
The sequence at which the amino acids are arranged |
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How are peptide bonds formed? |
The carboxylic group of the first amino acid reacts wijt the amino group of the second amino acid and this reaction produces water, so it is a condensation reaction. A peptide bond is formed between C-N and this is called a peptide unit. |
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Why do proteins have a direction. |
Because amino group of new amino acid joins onto polypeptide chain amino acids carboxyl group. So proteins have a free amino acid group at start of polypeptide and a free carboxyl group qt their end. |
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What is the eternal coherent direction that is essential to the functioning of the molecule itself in proteins |
Read from N (amino group) to C (carboxyl group) direction always |
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Why is there no free rotation around the peptide bond |
Because of the electron distribution. Also because the peptide bond has a partial double bond character which also restricts rotation. THE PEPTIDE UNJT IS RIGID AND PLANAR |
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Which bonds can a polypeptide chain use to rotate around the chain? |
C-C bond PSI N-C bond PHI THERE IS NO ROTATION AROUND PEPTIDE BOND |
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What are the degrees of rotation of phi and psi angles? |
Psi - 1.51 Phi - 1.46 C-N peptide bond for reference is 1.32 |
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What is protein conformation |
Most combinations of psi and pho angles are not allowed because or the steric collisions between the side chains and the main polypeptide chains THE SHAPE OF THE ENTIRE PROTEIN IS DETERMINED BY THE VALUES ODBTHE PSI ANS PHI ANGLES FOE EACH AMINO ACIDS Overall proteins 3d structure are affected by these angles |
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Is proetin folding not a random process and why? |
Protein folding is not a random process as it would take way too long for a protein to adopt the correct 3d shape to function properly as there are way too many different combinations Life would not exist if random - longer than age of universe for protein on avg to be right angles |
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What is the main driving force behind protein folding |
It is the most energetically stable structure the protein can make. For example water soluble proteina pack hydrophobic side chains inside interior of protein to hide them from surrounding water molecule. This forms a hydrophobic core. Qs the main polypeptide chain is hydrophilic because orbthe polar C=O and N-H groups, the protein must adopt structures which 'neutralise' these groups by hydrogen bonding. |
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Why are alpha helix and beta sheet stabilised secondary structure produced? |
These structures are formed when a number of continuous amino acid residues have the same psi and PHI angles |
