1.3: Membrane Transport

By being selectively permeable, the cell membrane plays a crucial role in regulating the concentrations of materials within the cell, including ions, nutrients, and waste products. Smaller nonpolar substances, like oxygen, carbon dioxide, and steroid hormones, can easily traverse the lipid bilayer due to the nonpolar nature of the lipid tails in the membrane. Conversely, water-soluble materials such as glucose, amino acids, and electrolytes necessitate transporter molecules like carrier proteins to cross the membrane, as the hydrophobic tails of the phospholipid bilayer repel them. Several mechanisms facilitate substance transport across the cell membrane. Passive transport involves the movement of substances without expending energy. In contrast, active transport utilizes energy from ATP to move substances across the membrane. We will examine membrane proteins more closely before delving into the specifics of transport mechanisms.

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