It will be 5 different updates inside the same transaction.
This is not a problem if you execute the 5 updates in one server side function, it is very slow if you do it from the client side.
It could actually be even more than 5 sql commands if you update more than one field per row. Here are two ways to do the same, the first does it in 3 commands, the second in 1:
row['col1'] = 1
row['col2'] = 2
row['col3'] = 3
row.update(col1=1, col2=2, col3=3)
The second is equivalent to:
row.update(**{'col1':1, 'col2':2, 'col3':3})