Lecture 9 Review

These proteins embedded within cell membranes control the movement of molecules in and out of the cell, providing cells with the power to regulate their internal composition.

While both are membrane transport proteins, channels act as tunnels that allow molecules to quickly pass through based on size and charge. Transporters, on the other hand, bind to specific molecules and move them across the membrane through a conformational change.

This is the combined force of both electrical and chemical gradients driving the movement of molecules across a membrane. It influences the direction of passive transport.

This type of transport doesn't require energy as molecules move down their electrochemical gradient, from an area of high concentration to low concentration.

This transport method requires energy, typically ATP, to move molecules against their electrochemical gradient, from a low concentration area to a high concentration area.

Transporters bind to specific molecules and change shape to shuttle them across the membrane. Channels act as tunnels through the membrane, allowing molecules to pass through quickly based on size and charge.

The force that drives the movement of charged molecules across a membrane. It combines the electrical gradient (charge difference) and the concentration gradient.

Passive transport doesn't require energy. Molecules move from an area of high concentration to low concentration, following their electrochemical gradient.

Active transport requires energy (usually ATP) to move molecules against their electrochemical gradient, from an area of low concentration to high concentration.

ATP provides the energy needed to move molecules against their electrochemical gradient, which is required for active transport.

The Na+-K+ pump actively transports sodium ions (Na+) out of the cell and potassium ions (K+) into the cell, using energy from ATP hydrolysis.

The pump moves three Na+ ions out of the cell for every two K+ ions it moves into the cell.

The hydrolysis of one ATP molecule provides the energy needed to transport three Na+ ions out of the cell and two K+ ions into the cell.

The Na+-K+ pump is used to create a Na+ concentration gradient across the vesicle membrane.

Condition B sets up the necessary conditions for the Na+-K+ pump to function correctly, creating a Na+ gradient by pumping Na+ out of the vesicle.

Condition A lacks ATP, the energy source required for the pump to function, so no Na+ gradient can be generated.

Condition D has randomly oriented pumps, meaning some are facing the wrong direction, hindering the formation of a directed Na+ gradient.

Conditions C & E provide the pump with ATP, the energy source, and the appropriate ion concentrations, allowing the pump to create a Na+ concentration gradient.

The Na+/K+ pump is embedded in the cell membrane, with its active site facing the cytoplasm.

The pump actively transports three sodium ions (Na+) out of the cell and two potassium ions (K+) into the cell, utilizing ATP for energy.

The Na+/K+ pump is crucial for maintaining cell volume, generating nerve impulses, and transporting nutrients into the cell.

A type of transport that utilizes the energy stored in an electrochemical gradient to move molecules across a membrane.

These are types of gradient-driven transport where two molecules move across a membrane together. Symport moves both molecules in the same direction, while antiport moves them in opposite directions.

Channels are membrane proteins that allow specific molecules to move passively across the cell membrane, following their electrochemical gradient. They act like tunnels, allowing molecules to diffuse freely down the concentration gradient.

Transporters are membrane proteins that bind specific molecules and move them across the membrane. They can mediate both passive and active transport. Passive transport occurs when molecules move down their electrochemical gradient, while active transport requires energy and moves molecules against their gradient.

Active transport uses energy (usually ATP) to move molecules against their electrochemical gradient, from an area of low concentration to high concentration. This is like pushing a ball uphill, requiring energy to move it against gravity.

The sodium-potassium pump is an active transporter that uses ATP to pump sodium ions out of the cell and potassium ions into the cell. This process is crucial for maintaining cell volume, nerve impulse transmission, and muscle contraction.

Passive transport is the movement of molecules across a cell membrane without requiring energy. Molecules move down their electrochemical gradient, from an area of high concentration to low concentration. This is like a ball rolling downhill; no energy is needed for its movement.

Channels and transporters are both membrane proteins that facilitate the movement of molecules across the membrane. However, channels allow passive movement by providing a simple tunnel, while transporters can actively move molecules against their gradient by undergoing conformational changes.

By understanding the principles of passive and active transport, we can explain how molecules are transported across cell membranes, enabling cells to maintain their internal environment and carry out essential functions. Both channels and transporters play vital roles in this process.

Symport is a type of membrane transport where two different molecules move across the cell membrane in the same direction using a single transport protein. Both molecules bind to the protein simultaneously, and their movement is coupled.

Antiport is a type of membrane transport where two different molecules move across the cell membrane in opposite directions using a single transport protein. One molecule moves into the cell while the other moves out. Their movement is coupled.

Uniport is a type of membrane transport where a single molecule moves across the cell membrane using a dedicated transport protein. The movement is not coupled to other molecules.

Symport and antiport can be involved in either active or passive transport. If at least one molecule is moving against its concentration gradient, it requires energy and is considered active transport. If both molecules move down their concentration gradient, it's passive transport.

The Na+-K+ pump actively moves sodium ions (Na+) out of the cell and potassium ions (K+) into the cell, creating a concentration gradient. This gradient is then used by the glucose-Na+ symporter to bring glucose into the cell alongside sodium ions.

The symporter protein binds to both glucose and sodium ions simultaneously. The movement of sodium ions down their concentration gradient provides the energy for glucose to move against its concentration gradient, bringing glucose into the cell.

1. Glucose-Na+ symporter: Active transport, utilizing Na+ gradient. 2. Glucose uniporter: Passive transport, moving glucose down its concentration gradient. 3. Na+-K+ pump: Active transport, establishes the Na+ gradient.

The electrochemical gradient is the combined force driving the movement of molecules across a membrane. It results from both the concentration difference and the electrical potential difference. It determines the direction and rate of transport.