What type of feedback occurs when a neuron is stimulated to open a membrane channel, which causes other channels to open? 1. Negative feedback, because the message is being depressed

2. Negative feedback, because the message is increasing the effect

3. Positive feedback, because the message is being amplified

4. Positive feedback, because the message is weakening the signal

frogs. the lower the ph the higher the acid content. frogs have the highest tolerance in this scenario.

many other transport proteins, often called pumps, move materials against a concentration gradient. active transport drives molecules across a membrane from a region of lower concentration to a region of higher concentration. this process, shown in figure 5.1, uses transport proteins powered by chemi- cal energy.

a metamorphic rock would be formed.