Cell Membrane Structure and Function

Mr. Poser, the AP Biology teacher, discusses membrane permeability, focusing on the phospholipid bilayer's structure and its role in selective permeability. He explains how small nonpolar molecules can pass through the membrane easily, while large polar molecules require transport proteins. The video also covers water movement through aquaporins and clarifies the difference between cell walls and cell membranes in plant cells.

What is the primary function of the plasma membrane?

• To produce proteins

• To store genetic information

• To separate the cell from its surroundings and maintain a stable internal environment

• To provide energy to the cell

What is the main component of the fluid mosaic model of the cell membrane?

• Proteins

• Phospholipid bilayer

• Nucleic acids

• Carbohydrates

What characteristic of the phospholipid bilayer makes it amphipathic?

• It has a polar head and nonpolar tails

• It is entirely hydrophobic

• It is made of proteins

• It is entirely hydrophilic

What does 'selectively permeable' mean in the context of cell membranes?

• No substances can pass through

• Only water can pass through

• All substances can pass through easily

• Some substances can pass through more easily than others

Which molecules can pass through the cell membrane without assistance?

• Large polar molecules

• Charged molecules

• Small nonpolar molecules

• Proteins

How do large polar molecules like glucose cross the cell membrane?

• Through simple diffusion

• By dissolving in the lipid bilayer

• Using channel and transport proteins

• They cannot cross the membrane

What is the role of aquaporins in the cell membrane?

• To allow water molecules to pass through

• To synthesize proteins

• To transport glucose

• To block ions

What is the function of proteins in the plasma membrane?

• To assist in the transport of molecules like glucose and sodium

• To provide energy

• To store genetic information

• To synthesize lipids

What is the main structural component of plant cell walls?

• Nucleic acids

• Proteins

• Cellulose

• Lipids

How do cell walls differ from cell membranes?

• Cell walls are made of lipids, while cell membranes are made of cellulose

• Cell walls provide structural support, while cell membranes regulate permeability

• Cell walls are found in animal cells, while cell membranes are found in plant cells

• Cell walls are permeable to all substances, while cell membranes are not