Biospherics Inc., a Rockville-based firm, reported a 5 percent increase in profits and a 39 percent increase in revenues for 1979.

Net income for the firm increased from $290,536 (20 cents a share) in 1978 to $305,491 (21 cents) last year. Revenues rose from $3.7 million to $5.1 million.

About $250,000 in investments as part of an expansion program constrained the company's earnings last year, according to Willard M. Hillegeist, vice president for finance. The company, however, expects the investment will result in more growth and greater profits this year, Hillegeist said.

"The company starts 1980 with a sales backlog of $7.3 million, of which $4.2 million is expected to be delivered in the current year," Hillegeist said.

Scope Inc., one of the area's largest electronic technology companies, reported a 38 percent decrease in earnings for 1979 from $3.7 million ($3.08 a share) to $2.3 million ($1.89). Sales rose 11 percent, however, from $59.2 million in 1978 to $65.4 million.

Fourth-quarter profits decreased 86 percent from $1.2 million (97 cents) last year to $168,000 (14 cents.) Fourth quarter sales also dropped, from $18.2 million to $16.7 million.

The lower 1979 profits were attributed to expenses associated with expanding one of Scope's subsidiaries and with high debt service expenses, according to William C. Schaub, chairman and chief executive officer.

MCD Holdings Inc., a Seabrook firm specializing in development of communities, reported 1979 earnings of $764,587 (18 cents a share), up from $489,587 (12 cents) for 1978. Revenues rose from $30.5 million to $38.9 million.

Commonwealth Natural Resources of Richmond reported earnings increased last year to $5.5 million ($4.70 a share) from $3.8 million ($3.23) in 1978.

The natural gas and propane producer said revenues for the year increased 30 percent to $154.3 million from $118.2 million. Most of the increases in both sales and profits were due to higher natural gas prices, the company said.