The 4-year old Apture focuses on providing instant access to information with in-page search technology.
Katango, on the other hand, was founded a little over a year ago and builds algorithms for automatically sorting friends that improves online social interaction.
However, financial terms of the deals were not disclosed.
Google buyout of Apture is expected to bolster the firm's Chrome browser.
"We have been acquired by Google and will be joining the Chrome team to continue driving innovation and creating a better user experience on the web," Apture said on its site.
The acquisition of Katango will help over 40 million users of internet search giant's social networking platform Google Plus to organise their circles. Katango's technology is similar to the circles feature on Google Plus, which helps users to group their contacts easily.
"We are excited to join the Google Plus team and carry on fulfilling that mission. Google Plus is seeing tremendous momentum, so it's a perfect time to join and make Circles smarter for millions of people," Katango said.
In the first nine month this year, Google had completed the acquisition of 57 companies for total of USD 502 million. This exceeds Google's previous annual record of 44 purchases completed last year. The company had spent cash worth USD 669 million for its all acquisitions in 2010.
Google is estimated to have acquired over 100 firms in the last decade, translating into purchase of 10 companies a year on average.
