Cell Membrane

What is the main function of the cell membrane?

It separates the cell from its surroundings and controls the exchange of materials between the cell and the extracellular environment.

What model describes the structure of the cell membrane?

The fluid mosaic model.

Describe the fluid mosaic model.

The membrane is a phospholipid bilayer where phospholipids, proteins and cholesterol can move within the membrane, while different proteins are embedded throughout it.

What are the two main parts of a phospholipid?

A hydrophilic head and hydrophobic tails.

What does hydrophilic mean?

Water-loving or attracted to water.

What does hydrophobic mean?

Water-hating or repelled by water.

How are phospholipids arranged in the cell membrane?

The hydrophilic heads face the watery environments inside and outside the cell, while the hydrophobic tails face inward toward each other.

Why do phospholipids form a bilayer?

The hydrophilic heads are attracted to water, while the hydrophobic tails avoid water and face inward.

What does selectively permeable mean?

The membrane allows some substances to pass through more easily than others.

How does the membrane's structure contribute to selective permeability?

Small molecules may cross the phospholipid bilayer, while ions and larger molecules such as glucose require membrane proteins.

What are integral proteins?

Proteins embedded within the phospholipid bilayer that remain permanently attached to the membrane.

What are peripheral proteins?

Proteins temporarily associated with one side of the membrane.

What is the function of channel proteins?

They form pathways that allow specific ions such as Na+, K+ and Cl- to move across the membrane.

What is the function of carrier proteins?

They bind to and transport specific molecules such as glucose and amino acids across the membrane.

What is the function of protein pumps?

They move substances across the membrane during active transport.

What is the function of cholesterol?

It helps regulate the fluidity of the cell membrane.

What are glycoproteins?

Proteins with attached carbohydrate chains.

What are glycolipids?

Lipids with attached carbohydrate chains.

What is the main function of membrane carbohydrates?

They help with cell recognition and cell adhesion.

Where are carbohydrate chains located in the membrane?

On the extracellular side of the membrane.

What does extracellular mean?

Outside the cell.

What does intracellular mean?

Inside the cell.

What should you be able to label on a membrane diagram?

Phospholipid bilayer, hydrophilic heads, hydrophobic tails, integral proteins, peripheral proteins, channel proteins, cholesterol, glycoproteins, extracellular side and intracellular side.