Draw and label the plasma membrane of a cell that is placed in a solution with concentrations of calcium ions and lactose that are greater than those on the inside of the cell. Use arrows to show the relevant gradients and the activity of the following membrane proteins: (1) a pump that exports protons; (2) a calcium channel; and (3) a lactose carrier.

Verified step by step guidance

1. Draw a bilayer to represent the plasma membrane, with hydrophilic heads facing outward and hydrophobic tails facing inward.
2. Label the extracellular space and intracellular space on either side of the membrane.
3. Draw and label a proton pump, indicating it moves protons (H+) from the inside to the outside of the cell against their concentration gradient.
4. Draw and label a calcium channel, showing calcium ions (Ca2+) moving from the outside to the inside of the cell down their concentration gradient.
5. Draw and label a lactose carrier, indicating lactose moving from the outside to the inside of the cell, possibly using facilitated diffusion or active transport.

Key Concepts

Plasma Membrane Structure

The plasma membrane is a phospholipid bilayer that surrounds the cell, providing structural support and regulating the movement of substances in and out of the cell. It contains various proteins, including channels and carriers, that facilitate transport processes. Understanding its structure is crucial for analyzing how ions and molecules, like calcium and lactose, interact with the membrane.

Concentration Gradient

A concentration gradient occurs when there is a difference in the concentration of a substance across a space, such as the inside and outside of a cell. In this scenario, the higher concentration of calcium ions and lactose outside the cell creates a gradient that drives the movement of these substances into the cell. Recognizing how gradients influence transport mechanisms is essential for understanding cellular processes.

Membrane Transport Proteins

Membrane transport proteins, including pumps, channels, and carriers, are integral to the movement of substances across the plasma membrane. For example, a proton pump exports protons against their gradient, while calcium channels allow calcium ions to flow into the cell. Lactose carriers facilitate the transport of lactose into the cell, often utilizing the energy from the sodium gradient. Understanding these proteins is vital for analyzing how cells maintain homeostasis.