Define passive and active in terms of energy requirement. Describe the following types of transport and identify if each type requires energy and in what form. Simple diffusion Facilitated diffusion Osmosis Primary active transport Secondary active transport Solution Active transportneeds energy, and it help to move ions against their concentration gradients. The concentration of some of the ions is more inside the cell and some is more outside the cell. For example, the concentration of sodium ions is more outside the cell. Still, the sodium ions move from the inside of cell to outside through ion channels, by means of active transport. Passive transport of molecules is independent of energy requirement, and the transport or diffusion of molecule across the channel is facilitated by the concentration gradient. Means, the molecules move down their concentration gradients. 1). Simple diffusion: Simple diffusion is a process of passive transport in which molecules diffuse down their concentration gradient. Diffusion of molecules mainly depends on the lipid solubility and their size and polarity. It does not require the carrier molecules as in case of facilitated diffusion. Small molecules such as water, gases such as oxygen, carbon dioxide, ions such as hydrogen ions, etc. can pass through the cell membranes and membranes of cellular organelles by means of simple diffusion. 2). Facilitated diffusion involves the transport of transport of molecules using the membrane bound proteins. For example, ion channels allow the transport of ions into and out of the cell, which are otherwise, cannot pass through cell membrane. Glucose binds to the carrier molecule present on the cell membrane, and enter into the cell; this process is facilitated by insulin. 3). In the primary active transport, the ATP is directly used for the transport of the molecule. For example, The Na+/K+ ATPase pump transports sodium and potassium ions against their concentration gradients. For every three sodium ions pumped out of the cell, two potassium ions enter into the cell. Thus, the membrane potential is maintained. 4). The secondary active transport is an active transport in which the downhill movement of an ion (either sodium or hydrogen) is coupled with the uphill movement of another molecule (against its concentration) by the transporter protein. Thus, the electrochemical gradient of an ion drives uphill transport of another molecule. Eg: Glucose absorption along with the sodium is an example of secondary active transport..

1. Define passive and active in terms of energy requirement. Describe the following types of
transport and identify if each type requires energy and in what form. Simple diffusion Facilitated
diffusion Osmosis Primary active transport Secondary active transport
Solution
Active transportneeds energy, and it help to move ions against their concentration gradients. The
concentration of some of the ions is more inside the cell and some is more outside the cell. For
example, the concentration of sodium ions is more outside the cell. Still, the sodium ions move
from the inside of cell to outside through ion channels, by means of active transport.
Passive transport of molecules is independent of energy requirement, and the transport or
diffusion of molecule across the channel is facilitated by the concentration gradient. Means, the
molecules move down their concentration gradients.
1). Simple diffusion:
Simple diffusion is a process of passive transport in which molecules diffuse down their
concentration gradient. Diffusion of molecules mainly depends on the lipid solubility and their
size and polarity. It does not require the carrier molecules as in case of facilitated diffusion.
Small molecules such as water, gases such as oxygen, carbon dioxide, ions such as hydrogen
ions, etc. can pass through the cell membranes and membranes of cellular organelles by means of
simple diffusion.
2). Facilitated diffusion involves the transport of transport of molecules using the membrane
bound proteins. For example, ion channels allow the transport of ions into and out of the cell,
which are otherwise, cannot pass through cell membrane. Glucose binds to the carrier molecule
present on the cell membrane, and enter into the cell; this process is facilitated by insulin.
3). In the primary active transport, the ATP is directly used for the transport of the molecule. For
example, The Na+/K+ ATPase pump transports sodium and potassium ions against their
concentration gradients. For every three sodium ions pumped out of the cell, two potassium ions
enter into the cell. Thus, the membrane potential is maintained.
4). The secondary active transport is an active transport in which the downhill movement of an
ion (either sodium or hydrogen) is coupled with the uphill movement of another molecule
(against its concentration) by the transporter protein. Thus, the electrochemical gradient of an ion
drives uphill transport of another molecule.
Eg: Glucose absorption along with the sodium is an example of secondary active transport.