Which of the following is most accurate when discussing the sliding filament theory?
1. Nerve impulse (action potential) arrives at the neuromuscular
junction triggering the release of the neurotransmitter acetycholine
2. Sodium binds to the protein troponin which is located on the actin
myofilament
3. When energy (ATP) is released, troponin slides over actin and the
muscle shortens
4. Actin heads bend (cross bridge) to attached to the exposed binding
sites on the myosin myofilament

If a strand of dna has 35% thymine. what is the percentage of cytosine, adenine, guanine?

Ascientific idea becomes valid when it is what?

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.