4.1 Plasma Membrane Structure and Function

• The plasma membrane regulates the passage of molecules into and out of the cell.
• The membrane contains lipids and proteins. Each protein has a specific function.

1. Why is the term "fluid-mosaic" used to describe the plasma membrane?
   Answer

2. What is the glycocalyx?
   Answer
   

Essential Study Partner
    Membrane Structure
    Cell Interactions

Explorations
    Cell-Cell Interactions

Labeling Exercises
Fluid-Mosaic Model of Membrane Structure 1 (50.0K)
Fluid-Mosaic Model of Membrane Structure 2 (49.0K)
Membrane Protein Diversity (33.0K)

4.2 The Permeability of the Plasma Membrane

• Some substances, particularly small, noncharged molecules, pass freely across the plasma membrane.
• The plasma membrane is differentially permeable. Therefore, some ions and polar molecules need assistance to cross the membrane.

1. What is meant by "differentially permeable?"
   Answer
   
   
2. How does passive transport differ from active transport?
   Answer
   

Essential Study Partner
    Movement Through Cell Membranes

Explorations
    Cystic Fibrosis

4.3 Diffusion and Osmosis

• Molecules spontaneously diffuse (move from an area of higher concentration to an area of lower concentration), and some can diffuse across a plasma membrane.
• Water diffuses across the plasma membrane, and this can affect cell size and shape.

1. Why does oxygen diffuse from the lungs into the blood and not in the opposite direction?
   Answer
   
   
2. If a cell is placed into a hypotonic solution, in what direction will there be movement of water?
   Answer
   

Essential Study Partner
    Diffusion
    Osmosis

Art Quizzes
    Diffusion
    Osmotic Pressure

Animation Quizzes
    Diffusion
    Osmosis

4.4 Transport by Carrier Proteins

• Carrier proteins assist the transport of some ions and molecules unable to diffuse across the plasma membrane.

1. What does it mean when membrane carrier proteins are "specific?"
   Answer
   
   
2. What is the sodium-potassium pump?
   Answer
   

Essential Study Partner
    Facilitated Diffusion
    Active Transport

Art Quizzes
    Functions of Plasma Membrane Proteins
    Facilitated Diffusion
    Sodium-Potassium Pump

Animation Quiz
    Active Transport

Explorations
    Active Transport

4.5 Exocytosis and Endocytosis

• Vesicle formation takes other substances into the cell, and vesicle fusion with the plasma membrane discharges substances from the cell.

1. Pinocytosis differs from phagocytosis in what way?
   Answer
   

Essential Study Partner
    Exo/Endocytosis

Animation Quiz
    Exocytosis/Endocytosis