Question

Diagram and describe the structure of the plasma membranes of animal cells. How is membrane structure related to permeability? Explain the various ways that different substances cross cell membranes. Give an example of something that crosses membranes each way, and explain why this substance must cross membranes by that particular route, and not some other way. [Hint: Your answer should include all the things that are attached to the membrane, the interactions that hold membranes together, what controls membrane fluidity, and the concepts of the different kinds of gradients across membranes.]

Answer 1

Plasma membrane act as a barrier between external environment and cellular inside. Along with protection it also play an important role in transport of molecules and transmission of signal . Structure of plasma membrane is attached below

Decipheral protein DOC L-oligosacaride Sy glycoprotein I phospholipid hydrophobic 'tail bilayer/ 1000 hydrophilic Integral Protein cytoplasm

Main components of the plasma membrane are

1)lipids (phospholipids and cholesterol)

2l proteins

3) carbohydrate groups that are attached to some of the lipids and proteins.

• membranes usually involve two layers of phospholipids with hydrophobic part means their tails pointing inward, while hydrophilic part that us head us projecting outside thus arranged as bilayer and called phospholipid bilayer.

• Cholesterol, another lipid is found alongside phospholipids in the core of the membrane. This played an important role in fluidity of membrane

• Membrane proteins may be transmembrane which cross the membrane entirely, or be loosely attached to its inside or outside face as extracellular and intracellular proteins.

• Carbohydrate groups are present only on the outer surface of the plasma membrane and are attached to proteins, forming glycoproteins, or lipids, forming glycolipids. They act as recognition part of membrane

Different type of membrane has different proportions of proteins, lipids, and carbohydrates.For a typical human cell, contains

proteins about 50 percent

Lipids about 40 percent,

10 percent comes from carbohydrates.

Please each part separately