4. Which of the following best explains how molecules such as O, and CO, can move across the membrane of a cell?
A. The majority of the cell membrane contains protein channels that allow this type of
molecule into the cell.
B. The majority of the cell membrane is nonpolar, which allows small, nonpolar
molecules to freely cross.
C. The phospholipids of the membrane are tightly packed, so only small molecules and
ions can fit between phospholipids

Match the pollutants. 1. a chlorofluorocarbon smoke 2. a biodegradable organophosphate insecticide freon 3. particle pollution paint 4. hazardous waste monoxide 5. carbon is completely burned malathion 6. carbon is incompletely burned dioxide

Based on the observation that only male crickets produce a song, you hypothesize that a male's song is a form of communication to potential mates. you set up a simple experiment to test this hypothesis. in the laboratory, you place a male snowy tree cricket in enclosure a, which is adjacent to enclosureb. in enclosure b, you place other insects, one at a time, and observe their responses to the male's song. the enclosures are designed so that the two insects being tested cannot see or smell each other, but sound is transmitted from enclosure a to enclosureb.

Which type of transport is responsible for oxygen entering into blood cells? a. vesicle b.passive c. facilitated d.active b.passive