Question

1. what is the function of a cell membrane?
2. in passive transport, substances move from an area of ____ concentration to an area of ____ concentration.
3. during osmosis, which substance moves across the cell membrane?
4. is osmosis an example of active or passive transport?

Explanation:

Question 1

The cell membrane (plasma membrane) has several key functions. It acts as a selective barrier, regulating the entry and exit of substances (like nutrients, waste, and ions) into and out of the cell. It also provides structural support, helps in cell - cell communication (through receptors and signaling molecules), and maintains the cell's internal environment (homeostasis) by controlling the concentration of substances inside the cell.

In passive transport, substances move along their concentration gradient. A concentration gradient exists when there is a difference in the concentration of a substance between two areas. Substances naturally move from an area where their concentration is high (more of the substance) to an area where their concentration is low (less of the substance) without the need for energy input.

Osmosis is a specific type of passive transport that involves the movement of water molecules. It occurs across a selectively permeable membrane (like the cell membrane). Water moves to balance the concentration of solutes on either side of the membrane. So, during osmosis, water is the substance that moves across the cell membrane.

Answer:

The cell membrane functions as a selective barrier to regulate the passage of substances in and out of the cell, provides structural support, enables cell - cell communication, and maintains cellular homeostasis.

Question 2