Question

active transport
extracellular fluid
cytoplasm

1. using the diagram above, label a) sodium - potassium pump, b) proton pump, and c) cotransport.
2. define active transport.
3. why is atp required for active transport?
4. what would happen to the flow of molecules across a membrane if atp was broken down?
5. how do proton pumps contribute to membrane potential?
6. using the figure above, how is cotransport used to move sucrose across the membrane?
7. sodium - potassium pumps are vital to neurons because they create a change in membrane potential. how do they accomplish this?

Explanation:

1. In the diagram, the sodium - potassium pump is the structure that pumps sodium (Na⁺) out and potassium (K⁺) in. The proton pump is the structure that pumps protons (H⁺) out. Cotransport is the process where the movement of one molecule (like sucrose) is coupled with the movement of another (like H⁺).
2. Active transport is the movement of molecules or ions across a cell membrane from an area of lower concentration to an area of higher concentration, requiring energy (usually ATP).
3. ATP is required for active transport because it provides the energy needed to move molecules against their concentration gradient.
4. If ATP was broken down, the energy - dependent active transport would stop. Molecules that rely on active transport for movement across the membrane would no longer be able to move against their concentration gradient, and their flow would be disrupted.
5. Proton pumps contribute to membrane potential by pumping protons (H⁺) out of the cell, creating an electrochemical gradient. This gradient consists of a charge difference (more positive outside) and a concentration difference of protons.
6. In the figure, cotransport is used to move sucrose across the membrane by coupling the movement of sucrose with the movement of protons (H⁺) down their electrochemical gradient. The energy from the proton movement is used to drive the uptake of sucrose into the cell.
7. Sodium - potassium pumps are vital to neurons because they create a change in membrane potential. They pump 3 sodium ions out of the neuron and 2 potassium ions in for each ATP molecule used. This creates a negative resting membrane potential inside the neuron, which is essential for generating and propagating action potentials.

Answer:

1. a) Sodium - potassium pump: Structure pumping Na⁺ out and K⁺ in. b) Proton pump: Structure pumping H⁺ out. c) Cotransport: Coupled movement of molecules (e.g., sucrose and H⁺).
2. Movement of molecules/ions against concentration gradient using energy (ATP).
3. Provides energy for movement against concentration gradient.
4. Flow of molecules relying on active transport would stop.
5. Create an electrochemical gradient by pumping H⁺ out.
6. Coupled with H⁺ movement down its electrochemical gradient.
7. Pump 3 Na⁺ out and 2 K⁺ in per ATP, creating negative resting potential.