Plasma Membrane Structure and Function

The video explains the structure and function of the plasma membrane, focusing on the lipid bilayer. It describes how phospholipids form a bilayer with hydrophilic heads and hydrophobic tails, creating a selective barrier. The bilayer's structure allows selective permeability, enabling nonpolar molecules to diffuse freely while polar molecules require protein channels. This arrangement is crucial for maintaining cellular stability and regulating material exchange.

What is the primary function of the plasma membrane?

• To produce proteins

• To store genetic information

• To protect the cell and regulate material entry and exit

• To provide energy to the cell

Which molecules are primarily found in the plasma membrane?

• Phospholipids

• Proteins

• Nucleic acids

• Carbohydrates

What characteristic makes phospholipids unique?

• They have both hydrophilic and hydrophobic regions

• They are entirely hydrophobic

• They are nonpolar

• They are entirely hydrophilic

Why can't the plasma membrane consist of just one layer of phospholipids?

• Because the hydrophilic heads would repel each other

• Because the hydrophobic tails would have to interact with water

• Because it would be too rigid

• Because it would not allow any molecules to pass through

How does the bilayer structure contribute to the stability of the plasma membrane?

• By allowing only hydrophilic molecules to pass

• By creating a hydrophobic region between two layers of heads

• By forming a rigid structure

• By being impermeable to all molecules

How do polar molecules typically enter the cell?

• Through direct diffusion across the bilayer

• By dissolving in the hydrophobic core

• By being repelled by the membrane

• Using protein channels

Which type of molecules can freely move through the hydrophobic region of the membrane?

• Polar molecules

• Nonpolar molecules

• Ions

• Sugars

What is the role of protein channels in the plasma membrane?

• To facilitate the movement of polar molecules

• To store water

• To transport nonpolar molecules

• To provide energy to the cell

Which gases move through the membrane by free diffusion?

• Oxygen and nitrogen

• Carbon dioxide and methane

• Hydrogen and helium

• Oxygen and carbon dioxide

What is the significance of the lipid bilayer's hydrophobic core?

• It allows all molecules to pass freely

• It prevents the passage of polar molecules

• It makes the membrane impermeable

• It stores energy for the cell