The process that provides the energy required to transport substances against a concentration gradient is called active transport. Active transport is the movement of molecules across a cell membrane against their concentration gradient, requiring the use of energy. The energy required to drive this process is obtained from the hydrolysis of adenosine triphosphate (ATP). This process is called primary active transport, the energy required is used to pump molecules across the membrane and against their concentration gradient.
Secondary active transport, on the other hand, uses the energy stored in the electrochemical gradient across the membrane, which is the difference in electrical potential and chemical concentration, to move molecules across the membrane. This is done by coupling the movement of one molecule across the membrane (typically a solute) with the downhill flow of another (the electrochemical gradient). This is called symport and antiport.
Examples of active transport in cells include the Na+/K+ ATPase pump, which pumps sodium ions out of the cell and potassium ions into the cell, and the proton pump in the mitochondria, which pumps protons out of the inner membrane space to create a proton gradient.
What is a molecule?
A molecule is a group of atoms that are chemically bonded together. Molecules can be composed of a single type of atom, such as the oxygen molecule (O2), which is made up of two oxygen atoms bonded together. Or they can be composed of multiple types of atoms, such as water (H2O), which is made up of two hydrogen atoms and one oxygen atom.
The properties of a molecule are determined by the arrangement of atoms within it and the chemical bonds that hold them together. For example, water is a liquid at room temperature, while oxygen is a gas, and these properties are a result of the chemical bonds between the atoms.
Molecules are the building blocks of all matter, including gases, liquids, and solids. They play a crucial role in many physical and chemical processes, such as chemical reactions, the transport of substances across cell membranes, and the storage and transfer of energy. Understanding the behavior of molecules is essential in fields such as chemistry, biology, and physics.
Types of active transport
Active transport is the movement of molecules across a cell membrane against their concentration gradient, requiring the use of energy. There are two main types of active transport:
- Primary active transport: This type of active transport uses the energy from the hydrolysis of adenosine triphosphate (ATP) to pump molecules across the membrane and against their concentration gradient. The ATPase family of enzymes, such as the Na+/K+ ATPase and the H+-ATPase, use this mechanism. This process is also called direct active transport.
- Secondary active transport: This type of active transport uses the energy stored in the electrochemical gradient across the membrane, which is the difference in electrical potential and chemical concentration, to move molecules across the membrane. This is done by coupling the movement of one molecule across the membrane (typically a solute) with the downhill flow of another (the electrochemical gradient). This is called symport and antiport. The energy of the electrochemical gradient can be used in two different ways:
- Cotransport (Symport): molecules move in the same direction, this can be seen in the Glucose/Sodium symporter.
- Counter transport (Antiport): molecules move in opposite directions, this can be seen in the Sodium/Hydrogen antiporter.
Examples of secondary active transport in cells include the Sodium-Potassium pump, which pumps sodium ions out of the cell and potassium ions into the cell, and the proton pump in the mitochondria, which pumps protons out of the inner membrane space to create a proton gradient.
Active transport is essential for cells to maintain the balance of different ions and molecules inside and outside the cell, as well as maintain the right pH.
What is passive transport?
Passive transport is the movement of molecules or ions across a biological membrane without the use of cellular energy. Instead, passive transport relies on the natural tendency of molecules to move from an area of higher concentration to an area of lower concentration, a process known as diffusion. Other forms of passive transport include osmosis and facilitated diffusion.