Answer:
A. Define boundaries
C. Deny access
D. Delay access
Explanation:
A barrier is a material or structure used to prevent or block access. Barriers can either be natural or structural and are used for many purposes usually for security reasons. The following are functions of barriers either natural or structural:
- Define areas of boundaries
- Delay or slow access. Example is the use of speed bumps to slow down vehicles.
- Provide access to entrances such as the use of gates
- Deny access to unauthorized personnel and allowing authorized personnel.
Explanation:
To move substances against a concentration or electrochemical gradient, the cell must utilize energy in the form of ATP during active transport. Primary active transport, which is directly dependent on ATP, moves ions across a membrane and creates a difference in charge across that membrane.
