Fill in the blanks. Molecules cross cell membranes.
1. Passive transport may be (_____) of polar molecules and ions.
2. Active transport requires ATP, and uses (____)
(Note, the first blank, whatever it is, also uses the second blank along with active transport.)
1. Passive transport may be facilitated by transport proteins of polar molecules and ions.
When it comes to the transport of polar molecules and ions across cell membranes, passive transport refers to the movement of these substances down their concentration gradient (from an area of higher concentration to an area of lower concentration) without the need for energy. This type of transport can occur through various mechanisms, including diffusion and facilitated diffusion.
In the case of polar molecules and ions, diffusion alone is often not sufficient due to the hydrophobic nature of the cell membrane. Therefore, transport proteins known as carrier proteins or channel proteins are necessary to facilitate the passage of these substances. Carrier proteins bind to the specific molecule they transport and undergo conformational changes to transport them across the membrane. Channel proteins, on the other hand, form channels or pores within the membrane, allowing polar molecules and ions to pass through. This means that passive transport of polar molecules and ions is facilitated by these transport proteins.
2. Active transport requires ATP, and uses transport proteins.
Unlike passive transport, active transport involves the movement of substances against their concentration gradient (from an area of lower concentration to an area of higher concentration) and requires energy, usually in the form of adenosine triphosphate (ATP). Active transport is necessary for the uptake of essential molecules, removal of waste products, and maintenance of concentration gradients essential for cell function.
To carry out active transport, cells utilize specific transport proteins known as pumps. These pumps actively pump substances across the cell membrane, consuming ATP energy in the process. One well-known example is the sodium-potassium pump, which actively transports sodium ions out of the cell and potassium ions into the cell. By doing so, the pump maintains a higher concentration of sodium ions outside the cell and a higher concentration of potassium ions inside the cell, crucial for various cellular processes.
So, the first blank of the statement "Passive transport may be ________ of polar molecules and ions." can be filled with "facilitated" since passive transport of polar molecules and ions often involves transport proteins. The second blank of the statement "Active transport requires ATP, and uses ________." can also be filled with "transport proteins" because active transport relies on transport proteins or pumps to move substances across the cell membrane.