Answer:
An ion channel, more specifically a calcium channel.
Explanation:
The electrical activity of the cells is regulated by ion channels. Calcium channels, also referred as the voltage-gated calcium channels constitute one group of a superfamily of ion channels. A change in voltage across the membrane or small molecules triggers calcium channels to open, allowing calcium to flow into the cell. Inside the cell, calcium acts as a second messenger, it binds to calcium sensitive proteins to induce different responses and support several functions such as muscle contraction, hormone and neurotransmitter secretion, gene regulation, activation of other ion channels, control of action potentials, cell survival, etc.
Answer:
B: Carbon Dioxide emissions from fossil fuels
<span>They keep the same form no matter what tense is used.
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