Which of the following describes an example of molecular movement across a membrane through active transport?
O Channel proteins bind with extracellular solutes and release them inside the cell.
O Hydrocarbons enter the cell by dissolving in the lipid bilayer of the membrane.
Proton pumps move hydrogen ions out of the cell against a concentration gradient.
O Vesicles carrying waste products fuse with the membrane during endocytosis.

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

The serengeti plains are part of the african savanna ecosystem and are home to a variety of different species of plants and animals. the serengeti plains experience a seven-month period of seasonal drought each year, during which the ecosystem receives only four inches of rain and the availability of some resources becomes very scarce. which type of limiting factors does the seasonal drought in the serengeti plains affect?

Which of these is one of the nitrogenous bases in dna? a. proline b. leucine c. glycine d. thymine