005 The Isoelectric Point of Proteins

This video tutorial explains the concept of the isoelectric point of proteins, which is the pH at which a protein has no net charge. Most proteins in cells have an isoelectric point between 4.5 and 4.7. The video discusses how the pH inside cells, approximately 7.2, affects protein charge, making them negatively charged. The tutorial emphasizes the attraction between opposite charges and concludes with a reminder of the negative charge inside cells due to the isoelectric point and cell pH.

What is the isoelectric point of a protein?

• The pH at which a protein is most soluble

• The pH at which a protein has a net positive charge

• The pH at which a protein has a net charge of zero

• The pH at which a protein has a net negative charge

What is the typical isoelectric point range for most proteins in the cell?

• 4.5 to 4.7

• 6.5 to 7.0

• 5.5 to 6.0

• 3.0 to 3.5

What happens to a protein's charge when the pH is above its isoelectric point?

• The protein becomes insoluble

• The protein becomes positively charged

• The protein becomes negatively charged

• The protein remains neutral

What is the approximate pH inside a cell?

• 8.0

• 6.0

• 5.0

• 7.2

What happens when a positively charged ion is near a negatively charged protein?

• They form a covalent bond

• They neutralize each other

• They attract each other

• They repel each other