BRAINCAKEIonic Bonds
Some amino acids have R groups that carry an electric charge in the conditions inside cells. An ionic bond in a protein is the attraction between a positively charged R group and a negatively charged R group. It is sometimes called a salt bridge.
• Amino acids such as lysine and arginine have an extra amino group in their R group. At normal pH it gains an H+ and becomes –NH3+.
• Amino acids such as aspartic acid and glutamic acid have an extra carboxyl group in their R group. At normal pH it loses an H+ and becomes –COO−.
–NH3+ ··· −OOC–
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Key terms in this lesson
- tertiary structure
- The overall three-dimensional shape formed by further folding of a polypeptide chain, held by bonds between R groups.
- quaternary structure
- The structure formed when two or more polypeptide chains are held together to make one functional protein.
More in Biological Molecules
- Test for Lipids
- Amino-acids
- Hydrogen Bonding
- Disulfide Bridges
- Protein Structure
- Globular Proteins
- Fibrous Proteins
- Collagen
All 25 lessons in Biological Molecules · All Edexcel AS-level Biology topics