Name: coupled solute movement across membranes
Uploaded: 2025-05-22T09:05:54.000Z
Duration: 1 min 32 s
Channel: JoVE

K12 Standards

Texas Essential Knowledge and Skills

High School

Biology

BIO.5

BIO.5.C

Secondary Active Transport

Unlike primary transport, secondary active transport utilizes energy stored in ions&#39; electrochemical gradients, to transport solutes against their concentration gradients.
One protein that exemplifies secondary active transport is the sodium-glucose-linked transporter or SGLT1. Initially, this transporter is positioned so that the cytosol facing side is closed, but the extracellular end is open. This exposes two negatively charged sodium-binding sites to the environment, which are then bound by positively charged sodium ions.
Since more sodium ions populate the extracellular space than the cytoplasm, the transporter-bound sodium ions move down their electrochemical gradient.
The sodium-bound transporter has a high affinity for glucose, present at a low-level outside but a high concentration inside the cell.
A glucose molecule then attaches to the transporter against its concentration gradient, and this simultaneous binding of sodium and glucose causes the protein to close its extracellular region and open the cytoplasm facing side.
The sodium ions then detach and enter the cytoplasm. This decreases the protein&#39;s affinity for glucose, releasing it into the cytoplasm. Once empty, the transporter returns to its initial orientation.

secondary active transport

One example of how cells use the energy contained in electrochemical gradients is demonstrated by glucose transport into cells. The ion vital to this process is sodium (Na+), which is typically present in higher concentrations extracellularly than in the cytosol. Such a concentration difference is due, in part, to the action of an enzyme &#34;pump&#34; embedded in the cellular membrane that actively expels Na+ from a cell. Importantly, as this pump contributes to the high concentration of positively-charged Na+ outside a cell, it also helps to make this environment &#34;more positive&#34; than the intracellular region. As a result, both the chemical and electrical gradients of Na+ point towards the inside of a cell, and the electrochemical gradient is similarly directed inwards.
Sodium-glucose linked transporters
Sodium-glucose linked transporters (SGLTs) exploit the energy stored in this electrochemical gradient. These proteins, primarily located in the membranes of intestinal or kidney cells, help in the absorption of glucose from the lumen of these organs into the bloodstream. In order to function, both an extracellular glucose molecule and two Na+ must bind to the SGLT. As Na+ migrates into a cell through the transporter, it travels with its electrochemical gradient, expelling energy that the protein uses to move glucose inside a cell&#8212;against its chemical gradient, since this sugar tends to be at a higher concentration within a cell. As a result, glucose travels uphill against its concentration gradient simultaneously with Na+ that travels down its electrochemical gradient. This is an example of secondary active transport, so-named because the energy source used is electrochemical in nature, rather than the primary form of ATP.
Therapies Targeting SGLTs
Given the role of glucose in certain diseases, scientists have begun to look at ways of interfering with glucose transport into cells. For example, diabetes is characterized by excess glucose in the bloodstream, which can lead to nerve damage and other complications. As a result, some researchers are assessing how SGLT expression differs between diabetics and non-diabetics, and whether inhibiting different SGLTs can help treat the disease. Alternatively, since cancer cells have been demonstrated to require more glucose compared to their normal counterparts, other investigators are examining whether glucose transporters can be a new target of anti-cancer therapies.

One example of how cells use the energy contained in electrochemical gradients is demonstrated by glucose transport into cells. The ion vital to this ...

Education

JoVE Core

Anatomy and Physiology

Unit 1

Cell Membrane Structure and Functions

KEY TERMS AND CONCEPTS

coupled solute movement across membranes

Secondary active transport moves solutes across a membrane by using the energy stored in an ion gradient. The transporter itself does not use ATP directly. Instead, it links the movement of one solute to the movement of another.

This process depends on a gradient that was built earlier by primary active transport. As ions move down their gradient, they provide the energy that drives another substance in the opposite direction or along with them, depending on the carrier. This coupling lets cells move materials that would not move on their own.

Secondary active transport is an important way cells manage nutrient uptake and ion balance. It shows how membrane transport systems can work together to move substances efficiently across the cell membrane.

Coupled Solute Movement Across Membranes

what are membranes?

Membrane Layers in Cells and Tissues

Membranes are thin layers that help define cells and tissues. They act as boundaries and support important biological roles in the body. In cells, membranes help separate the inside of a cell from its surroundings. They also help control what moves in and out of the cell. In tissues, membranes can form covering layers that protect and support body structures. The video focuses on membranes as key parts of cell biology. It shows how these layers are organized and why they matter in living...

membrane proteins

Membrane Proteins and Cell Transport

Membrane proteins help cells move materials across the cell membrane. They are part of the membrane structure and are closely linked to how cells function. Some membrane proteins act as channels or carriers. These proteins help selected substances pass through the membrane when direct movement through the lipid layer is not possible or is limited. Other membrane proteins help cells respond to signals. They can bind to molecules outside the cell and pass information inward. Membrane proteins...

membrane lipids

Membrane Lipids and Cell Membranes

Membrane lipids are the main building blocks of cell membranes. They help form the thin barrier that surrounds cells and many cell parts. This barrier controls what can enter and leave the cell. The most common membrane lipids are phospholipids. These molecules have a water-loving head and water-fearing tails. In a membrane, they arrange themselves into a bilayer, with the heads facing water and the tails tucked away inside. Other membrane lipids also play important roles. Some lipids help...

membrane carbohydrates

Cell Surface Carbohydrates

Cell surface carbohydrates are sugar molecules found on the outside of cell membranes. They are attached to lipids and proteins, and they help give cells their outer identity. These carbohydrates are often part of glycolipids and glycoproteins. They sit at the membrane surface, where they can affect how cells interact with their surroundings. In many cells, they also play a role in cell recognition. Membrane carbohydrates are an important part of membrane structure and function. They help...

glycocalyx and its functions

Glycocalyx in Cell Recognition

The glycocalyx is a carbohydrate-rich layer on the outside of the cell membrane. It has a fuzzy appearance and is highly hydrophilic, which means it attracts water. That helps the cell interact with its watery environment and helps it obtain substances dissolved in that water. The glycocalyx is also important for how cells identify one another. It supports self and non-self recognition, and it helps in embryonic development. Cells also use it for cell-to-cell attachment, which helps tissues...

the significance of membrane transport

How Membrane Transport Supports Cells

Membrane transport helps cells move materials across the cell membrane. This process is essential for cell function and survival. Cell membranes are selective barriers. They control what enters and leaves the cell. Some materials move passively, while others require active transport. Passive transport does not use cellular energy. It includes movement down a concentration gradient, from an area of higher concentration to an area of lower concentration. Active transport uses energy to move...

diffusion

Diffusion Rates and Concentration Gradients

Diffusion is a passive transport process that moves substances from an area of high concentration to an area of low concentration. The movement continues until the concentration becomes equal across the space. In cells and in the air, this spread happens without added energy. A familiar example is perfume in a room. The perfume is most concentrated in the bottle and least concentrated at the edges of the room. As the vapor diffuses outward, more people can smell it over time. The same kind of...

facilitated transport

Transport Across Cell Membranes

Transport across cell membranes helps cells move needed substances in and out. Facilitated transport is one way this happens. It uses membrane proteins to move materials that cannot pass easily through the lipid bilayer on their own. This process still follows the concentration gradient, so it moves from higher concentration to lower concentration. Because of that, it does not require cellular energy. The membrane proteins provide a path that helps the substance cross the membrane more...

non-gated ion channels

Ion Flow Through Open Channels

Non-gated ion channels let ions move across the cell membrane without a trigger. They are open channels, so ions can pass through them directly. These channels are part of the membrane’s electrical properties. Their steady ion movement helps shape how the membrane behaves. Non-gated ion channels are different from gated channels. Gated channels open or close in response to a signal, while non-gated channels remain available for ion flow.

osmosis

Osmosis and Water Balance

Osmosis is the movement of free water molecules through a semipermeable membrane. In this process, water moves from a region with a high concentration of free water molecules to a region with a lower concentration of free water molecules. The membrane allows water to pass, but it limits the diffusion of solutes dissolved in the water. Osmosis is a special case of diffusion. Diffusion moves material across membranes and within cells when molecules can spread out evenly. In a beaker with a...

tonicity in animals

How Cells Respond to Tonicity

Tonicity describes how solute levels in a solution affect cells. The amount of solute dissolved in a given amount of solution is called osmolarity. Cells and the fluid around them can then be compared as hypotonic, isotonic, or hypertonic. In a hypotonic solution, the extracellular fluid has a lower solute concentration than the fluid inside the cell. Tap water is one example. The water concentration outside the cell is higher, so water moves into the cell along its concentration gradient. In...

primary active transport

ATP-Powered Membrane Transport

Primary active transport uses ATP to move substances across a membrane against their concentration gradient. This process helps cells move molecules and ions from a lower concentration to a higher concentration when energy is needed. ATP hydrolysis supplies the energy for this movement. In primary active transport, the transport protein uses the energy released from ATP to change shape and move the substance across the membrane. This mechanism is important in many cell processes that depend...

Secondary active transport moves solutes across a membrane by using the energy stored in an ion gradient. The transporter itself does not use ATP directly. Instead, it links the movement of one solute to the movement of another. This process depends on a gradient that was built earlier by primary active transport. As ions move down their gradient, they provide the energy that drives another substance in the opposite direction or along with them, depending on the carrier. This coupling lets...

introduction to membrane traffic

Membrane Traffic in Cells

Membrane traffic in cells moves materials between organelles and the cell surface. It helps cells sort, package, and deliver cargo to the right place. This process is essential for normal cell function. Cells use membrane-bound compartments to handle this movement. Vesicles are small membrane sacs that carry cargo from one location to another. They bud from one membrane and fuse with another membrane to release their contents. Membrane traffic also helps maintain the balance of membranes...

receptor-mediated endocytosis

Ligand Binding in Endocytosis

Receptor-mediated endocytosis is a selective way cells take in material from outside the cell. It begins when a ligand, or binding molecule, attaches to a receptor on the cell membrane. This interaction helps the cell capture specific substances instead of taking in everything around it. After the ligand binds, the membrane folds inward and forms a small pocket. That pocket pinches off and brings the bound material into the cell. This process shows how receptor binding directs endocytosis and...

key terms and concepts

Learn how secondary active transport uses an ion gradient to move solutes across membranes without direct ATP use. Clear, high school-friendly biology content.

Coupled Solute Movement Across Membranes | JoVE K12

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Coupled Solute Movement Across Membranes

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