2. Facilitated diffusion of glycerol into E. coli: Facilitated diffusion is the

ID: 202613 • Letter: 2

Question

2. Facilitated diffusion of glycerol into E. coli: Facilitated diffusion is the assisted transport of molecules across a membrane from an area of higher concentration to an area of lower concentration. Facilitated diffusion of glycerol into E. coli involves transport through a membrane protein. Glycerol will move in either direction (in or out of the cell) depending on the concentration in the cell interior versus in the environment. Although this transport is carrier-mediated and specific, no energy is used. Extracelular luld OHOHOH 0000 042900 Cyloplasm A. What is meant by the phrase "carrier-mediated"? ursme movement of mdeculec accoss the all mm1rone ia special tran decaules acass the all memlorone awe tm he uulor memlrure B. What is meant by "specific"? C. Which functional groups on glycerol tell you if glycerol is hydrophobic or hydrophilic? How will glycerol enter the cell? Through diffusion or facilitated diffusion? 59

Explanation / Answer

Question 2

a) Carrier mediated: Carrier mediated movements across membrane are mediated by specific proteins which allows only specific molecule to pass through across from high to low concentration. Flow of the molecules will be slow as compared to channels as carriers are very specific in choosing specific molecules.

b) If carrier is meant to transport glycerol, it always allows glycerol to pass though, not any other molecule.

c) Three –OH groups in glycerol shows its hydrophilic nature. Therefore can be transported through facilitated diffusion (only hydrophobic molecules can pass freely through plasma membrane).

Question 3

A) Bacteria are single cell organisms, and may be surviving in nutrient deficient regions. Therefore mostly they have to transfer nutrients against the concentration gradient, which is not a function of facilitated diffusion or passive transport (but active transport).

B) As mentioned above bacteria have to intake nutrients from low (outer environment) to high (within call), energy will be needed in the form of ATP which is a function of active transport.

Question 4

Active transport: Active transport is the movement of molecules against the concentration gradient (from high to low concentration). It requires energy mostly in the form of ATP. Example: Movements of glucose, ions, and amino acids needed for cell survival.

Facilitated diffusion: Facilitated diffusion is the movement of molecules along the concentration gradient (from low to high concentration) with the help of carrier proteins. It does not require any energy. Examples: Passage of K+ ions through potassium transport proteins.

Diffusion: Flow of molecules from high to low concentration freely across membrane. No energy is needed. Examples: Oxygen, carbon dioxide

Question 5

Active transport

Facilitated diffusion

Diffusion

Required energy input by the cell

+ (yes)

_ (no)

_(no)

Molecule move along the concentration gradient

Molecule move against the concentration gradient

Always involves channels

Molecules pass between phospholipids

Moves ions like Na+ and K+

+ (Na+/ K+ ATPase pump)