What is the purpose of heat shock in transformation?

What is the purpose of heat shock in transformation?

• A. To facilitate plasmid entry into E. coli.
• B. To kill off non-competent cells.
• C. To inactivate enzymes.
• D. To denature proteins.

Answer: (A)

Heat shock in transformation serves to temporarily increase the cell’s membrane permeability so the plasmid DNA can enter the bacteria. After the DNA is added to competent cells, a brief, rapid temperature rise (around 42°C for a short time) causes the lipid bilayer to become more fluid and form transient pores. This makes it possible for the plasmid to cross the membrane and get into the cell’s interior. Immediately returning the cells to cold helps stabilize the membrane, and then the cells recover so the plasmid’s genes, such as the antibiotic resistance marker, can be expressed for selective growth. It isn’t primarily about killing non-competent cells, inactivating enzymes, or denaturing proteins—the step is about creating a temporary opening in the membrane to allow plasmid entry.

Heat shock in transformation serves to temporarily increase the cell’s membrane permeability so the plasmid DNA can enter the bacteria. After the DNA is added to competent cells, a brief, rapid temperature rise (around 42°C for a short time) causes the lipid bilayer to become more fluid and form transient pores. This makes it possible for the plasmid to cross the membrane and get into the cell’s interior. Immediately returning the cells to cold helps stabilize the membrane, and then the cells recover so the plasmid’s genes, such as the antibiotic resistance marker, can be expressed for selective growth.

It isn’t primarily about killing non-competent cells, inactivating enzymes, or denaturing proteins—the step is about creating a temporary opening in the membrane to allow plasmid entry.