The Cell Membrane

Chapter 2Section 2.1- The Components of CellsTopics: Structure, Function, Diseases

Why is the cell membrane so important?

• Controls what molecules enter and leave

• Selectively permeable• O2, CO2, and water can

pass straight through membrane

• Charged or larger molecules need channel or carrier proteins to enter.

What are the parts of a cell membrane?

• Phospholipids– Create a bilayer– Phosphate head

• Hydrophilic- loves water so exposed to watery internal & external cell environment

– 2 lipid tails• Hydrophobic- hate water

so are found in the middle of the membrane

What are the parts of a cell membrane?

• Glycoproteins- carbohydrate chains attached to proteins embedded in CM

• Glycolipids- carbohydrate chains attached to phospholipids embedded in CM

• Both of these help other cells recognize each other

What are the parts of a cell membrane?

• Receptor Proteins– Have indentations or shapes

that fit and hold molecules outside the cell.

– Ligand- molecule that binds to the active site of a receptor

– After ligand binds to receptor a cascade of chemical reactions occur inside cell

– EX: Ligand might send a message inside the cell to tell cell to make more mucous, hormone, etc.

What are the parts of a cell membrane?

• Selective channel protein- allows certain ions into/out of cell; like a tube for passive movement of larger or charged ions

• Adhesion proteins- connect two bilayers to each other

• Enzymes- speed up chemical reactions

• Carrier protein- open and close to dump molecules in/out

Carrier protein clip

What are the parts of a cell membrane?

• Cholesterol– gives cell membrane

some structure so it is not “mushy”

– Keeps cell membrane from freezing in cold weather

Why is the cell membrane called a fluid mosaic model?

• Mosaic- b/c it is studded with so many different proteins, carbohydrates, enzymes, etc.

• Fluid- b/c the molecules are not rigidly joined. They are moveable around each other

• Fluid Mosaic Video Clip

Cell Membrane Rap!

• https://www.youtube.com/watch?v=Pfu1DE9PK2w

What types of diseases are associated with proteins in the cell membrane?

• Congenital Insensitivity to Pain (CIP)- – sodium channel proteins

are mutated and block sodium ions which leads to decreased or absent nerve impulses

– No nerve impulses= can’t feel pain

Normal Sodium Channel Video Clip

What types of diseases are associated with proteins in the cell membrane?

• Paroxysmal extreme pain disorder (PE or PEPD)– Sodium channel proteins

are mutated and left open too long causing a prolonged and intense pain response

What types of diseases are associated with proteins in the cell membrane?

• Cystic Fibrosis (CF)– Abnormal sodium and

chloride channel proteins– Sodium chloride trapped

inside cell draws water out of mucous lining lungs/pancreas which causes mucous to be very thick.

– CF patients have difficulty breathing due to thick mucous secretions in pancreas and lungs, & frequent lung infections