Question

Chapter 5 1. Compare and contrast simple diffusion with facilitated diffusion being sure to mention direction of movement, source of energy, and how movement across the membrane occurs. 2. Compare and contrast the terms active transport with facilitated diffusion addressing the same issues as above. 3. Draw a diagram of a membrane receptor and include the following details. Include a depiction of the plasma membrane with which it is associated; label the locations of the extracellular space, the cytoplasm, and the ligand-binding domain. 4. Compare and contrast the terms ligand (signal molecule) and second messenger. 5. What is an enzymatic receptor, how does ligand binding affect its activity? Include how an enzymatic receptor functions differently from a chemically-gated ion channel.

Answer 1

1. Simple diffusion-movement of molecules from high concentration to low concentration,for tensport,protein is not required, direction from high concentration to low concentration, never seturates ,energy required is potential energy.

FACILITATATED TRANSPORT-movement from high concentration to low, for transport, carrier protein is requaired,direction from high concentration to low, saturates because carrier protein have its own transport capacity, potential energy is required.

2.ACTIVE TRANSPORTAT-transport from low concentration to high concentration, always requires carrier protein ,energy required is from ATP,saturates due to protein capicjty

FACILITATATED DIFFUSION-transport from high concentration to low.,always requires carrier protein, energy required is POTENTIAL ENERGY,saturates due to protein capicity.

3.4 .LIGAND is the signal molecule which is specific for special receptore.It is found outside the cell.It may be harmones and ither substance.

Ligand-receptor complex extrocelular intracelular "Luck and Key" Intracellular Response

SECOND MESSENGER-It is the intracellular molecule developed due to work of PRIMARY MASSENGER.It involves in physiological responses.

Example-cAMP,Ca etc.

5.ENZYMATIC RECEPTOR are those receptors which when bind with ligand ,starts catalytic /enzymatic function due at intracellular site.when receptor bind with ligand,its shape changes at cytosolic side ,resulting in wnzymatic activity .This leads to cascade of reaction.

IN chemically gated channel protein ligand is litself the transporting molecule, due to which configuration of channel protein changes resulting in opening of channel protein.