Active Transport Concepts

Questions and Answers

What is the purpose of active transport?

To speed up movement across the plasma membrane by expending ATP and moving solutes against their electrochemical gradient.

What are aquaporins involved in?

The diffusion of water.

What are ion channels?

Gated channels used to diffuse ions.

How do carrier proteins diffuse substances across the plasma membrane?

They undergo a change in conformation. Signup and view all the answers

What is the difference between primary and secondary active transport? Explain.

Primary active transport uses energy directly from ATP through hydrolysis, while secondary active transport uses energy stored in concentration gradients of ions. Signup and view all the answers

Give and explain three examples of primary active transport.

<ol> <li>Sodium-potassium pump: pumps Na+ out and K+ in using ATP. 2. Calcium pump: transports Ca2+ out of muscle cells. 3. Proton pumps: secrete H+ to regulate stomach acidity.</li> </ol> Signup and view all the answers

Identify four different factors that affect the rate of diffusion across a membrane.

Distance, surface area, temperature, and concentration of solute. Signup and view all the answers

How does surface area affect the rate of diffusion across a membrane?

The more surface area available to diffuse, the higher the rate of diffusion. Signup and view all the answers

How does temperature affect the rate of diffusion across a membrane?

The higher the temperature, the higher the kinetic energy, the more molecular movement, resulting in more random collisions with the membrane. Signup and view all the answers

How does concentration affect the rate of diffusion across a membrane?

The higher the concentration, the longer the net movement will take. Signup and view all the answers

How are protein pumps specific?

They each only transport a particular substance. Signup and view all the answers

What kinds of proteins are ATPases?

ATPases are integral enzymes. Signup and view all the answers

What does ATP stand for?

Adenosine triphosphate. Signup and view all the answers

What substances can be transported by pumps that directly hydrolyze ATP?

Positively charged ions, such as Na+, K+, Ca+, or H+. Signup and view all the answers

Describe how the sodium-potassium pump works.

<ol> <li>3 Na+ ions enter the pump. 2. ATP transfers a phosphate group to the pump. 3. Conformational change releases Na+ outside. 4. 2 K+ ions bind, causing dephosphorylation. 5. Pump returns to original conformation.</li> </ol> Signup and view all the answers

What is secondary active transport?

A form of active transport that couples the movement of an ion down its gradient to the movement of another molecule against its gradient. Signup and view all the answers

Where does the energy come from in secondary active transport?

The energy is provided by the concentration gradient of a substance/ion that moves back into the cell. Signup and view all the answers

Describe glucose-sodium cotransport.

Sodium ions move down their concentration gradient, providing energy to pull glucose into the cell against its gradient. Signup and view all the answers

What is a uniport? Symport? Antiport?

A uniport transports one molecule in one direction, a symport transports two types of molecules in one direction, and an antiport transports two types of molecules in two directions. Signup and view all the answers

What is exocytosis?

Exocytosis is the secretion of a substance from inside the cell to the outside using vesicles. Signup and view all the answers

Study Notes

Purpose of Active Transport

Active transport speeds up movement across the plasma membrane by using ATP to move solutes against their electrochemical gradient.

Aquaporins

Aquaporins facilitate the diffusion of water through the plasma membrane.

Ion Channels

Ion channels are gated channels that allow the diffusion of ions across membranes.

Carrier Proteins

Carrier proteins transport substances across the plasma membrane by undergoing conformational changes.

Types of Active Transport

Primary active transport uses energy directly from ATP hydrolysis.
Secondary active transport relies on energy stored in ion concentration gradients.

Examples of Primary Active Transport

Sodium-potassium pump: Moves Na+ out and K+ into the cell by hydrolyzing ATP.
Calcium pump: Transports calcium ions out of muscle cells after contraction.
Proton pumps: Facilitate H+ secretion in the stomach and lysosomes.

Factors Affecting Diffusion Rate

Distance, surface area, temperature, and concentration of solute influence how quickly diffusion occurs.

Surface Area Impact

Increased surface area correlates with a higher rate of diffusion through membranes.

Temperature Impact

Higher temperatures increase kinetic energy, leading to more molecular movement and collisions with the membrane.

Concentration Impact

Greater solute concentrations prolong net movement as diffusion continues until equilibrium is reached.

Specificity of Protein Pumps

Protein pumps each transport a specific substance, ensuring targeted movement.

ATPases

ATPases are integral enzymes responsible for hydrolyzing ATP.

ATP Definition

ATP stands for adenosine triphosphate, a key energy carrier in cells.

Substances Transported by ATP Hydrolyzing Pumps

Positively charged ions like Na+, K+, Ca+, or H+ can be transported by these pumps.

Sodium-Potassium Pump Process

The pump binds 3 Na+ ions from inside the cell and hydrolyzes ATP for phosphorylation.
This conformational change allows Na+ release outside and the binding of 2 K+ from outside, which leads to dephosphorylation and a return to the original shape.

Secondary Active Transport

Utilizes a transporter protein to couple the movement of an ion down its gradient with another molecule/ion moving against its gradient.

Energy Source in Secondary Active Transport

Energy comes from the concentration gradient of the ion moving into the cell.

Glucose-Sodium Cotransport

Both sodium and glucose move across the membrane simultaneously, with sodium providing energy for glucose transport without direct ATP use.

Transport Types

Uniport: Transports one molecule in one direction.
Symport: Transports two molecules in the same direction.
Antiport: Transports two molecules in opposite directions.

Exocytosis

Exocytosis is the process of secreting substances from the cell, involving vesicles that fuse with the plasma membrane.

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Description

This quiz covers key concepts related to active transport and its mechanisms. Explore topics such as the role of aquaporins, ion channels, and carrier proteins in the movement of substances across the plasma membrane.