Search giant Google has come under pressure to provide a fuller picture of its mobile efforts, ahead of its quarterly results presentation later today.

According to Reuters, there is concern that the company’s planned US$12.5 billion acquisition of Motorola Mobility will see it moving into a fiercely competitive and low margin business sector, of which it has little direct experience. Despite its own experience in the sector, Motorola has struggled to make a profit from its handset business, as the industry focus shifted to smartphones from feature phones.

So far, Google has not broken-out the proportion of its revenue which comes from mobile. However, it has previously indicated that this is a US$1 billion/year business, which is “growing at an amazing blazingly pace.”  In addition, Google has mobile businesses from which it does not generate a significant direct income – such as the Android device platform – but which drive consumption of its other products and services.

Google also has its own mobile advertising proposition, built on its acquisition of AdMob.

Away from mobile, Reuters notes that there is concern about how slowness in the economy in general will affect the company, as advertisers potentially look to cut their expenditure. There are also question marks over the growth of its recently-launched Google+ social networking service, designed to be a rival for Facebook.