Which of the following is (are) characteristic of the (na+–k+)–atpase?
i. it binds na+ and k+ simultaneously prior to binding atp
ii. it is covalently modified by phosphorylation at an asp residue when na+ is present.
iii. transport of na+ and k+ occur in a 1: 1 ratio, thus maintaining a balanced gradient until opening of the gated portion of the channel.
iv. it is essential for excitation of nerve cells.

Patricia is told by her physician that her body and brain chemistry have physically adapted to the drug and that she has become dependent on the tranquilizers prescribed for her by another doctor.

Which events are likely to be catastrophic to an ecosystem? select the three correct answers.a-hurricane.b-steady population growth.c-seasonal flooding.d-introducing of an aggressive invasive species.e-tsunami.

Researchers randomly divide participants into groups. each group takes a different amount of omega-3 fatty acid supplements daily for a month. one group receives a placebo. the researchers measure the impact on cholesterol levels in the blood. what is the purpose of random assignment in this experiment? a, to produce treatment groups with similar characteristics b, to ensure that all people with high cholesterol have an equal chance of being selected for the study c, to increase the accuracy of the research results and prevent skewness in the data