Cell Membrane Structure and Function Quiz

Course Requirements

• Recitation is part of the course.
• There are mini quizzes and a long quiz.
• There is a final exam.
• Take-home lab experiments are part of the performance tasks.

Review: Structure and Function of the Cell Membrane

• This review focuses on the cell membrane.

Learning Competencies

• Students should be able to describe the components of a cell membrane.
• Students should be able to relate the structure and composition of the cell membrane to its function.

Structural Components of Plasma Membrane

• The cell membrane is made up of a phospholipid bilayer.
• Phospholipids have hydrophilic heads and hydrophobic tails.
• Globular proteins, glycoproteins, and glycolipids are embedded in the membrane
• Peripheral proteins are loosely bound to the membrane.
• Integral proteins are tightly bound to the membrane.
• Cholesterol is embedded in the membrane to increase fluidity at lower temperatures and prevent high temperatures.
• Carbohydrate chains are only on the outside of the membrane and sometimes bound to proteins.

Phospholipid Bilayer

• The phospholipid bilayer is a fluid structure.
• It creates a barrier between the inside and outside of the cell.
• The fluid nature of the membrane helps maintain fluidity at both high and low temperatures
• The aqueous environment energetically favors the formation of this structure.

Molecules Embedded in the Membrane

• Membrane proteins are embedded in the membrane.
• Cholesterol is a type of molecule embedded in the membrane.
• Carbohydrate chains are molecules embedded in the membrane.

Membrane Proteins

• Transport proteins help move substances across the membrane.
• Adhesion proteins help hold cells together.
• Recognition proteins help cells identify each other.
• Receptor proteins receive signals from other cells.

Carbohydrate Chains

• Carbohydrate chains are found on the exterior surface of the cell membrane.
• They aid in cell-to-cell recognition.

Plasma Membrane (Diagram)

• The plasma membrane's detailed structure with its components are illustrated.
• Extracellular fluid, cytoplasm, glycoproteins, globular proteins, and phospholipid layers are labeled in the diagram.

How does the plasma membrane permit certain molecules to enter selectively into the cell?

• This question is posed to students.

Cell Transport Mechanisms: Active and Passive Transport

• This section explores the mechanisms for moving molecules across the cell membrane.

Learning Competency

• Explain passive and active transport in cells.
• Differentiate diffusion and osmosis.
• Differentiate hypotonic, isotonic, and hypertonic solutions.
• Explain transport across membranes through facilitated transport.
• Explain how active transport works.
• Compare active transport to osmosis and diffusion.

Transport Processes

• Passive transport (diffusion and osmosis) doesn't require energy.
• Active transport requires energy to move substances across membranes.
• Vesicles are used in bulk transport.
• Endocytosis and exocytosis are used in bulk transport.

Simple Diffusion

• Molecules move from high concentration to low concentration.
• This process eventually reaches dynamic equilibrium.

Facilitated Diffusion

• Molecules move from high concentration to low concentration using proteins to assist.

Glucose Transporters and Ion Channels

• Glucose transporters help facilitate glucose transport.
• Ion channels move ions through the membrane.

Cell's Transport Mechanism II

• Ion channels are usually gated which means they can change conformation to open or close.
• They open under certain conditions.

How does osmosis play an important role in different cellular processes?

• This question is posed to students.

Osmosis

• Movement of water from high water concentration to a lower water concentration across a semi-permeable membrane.

Tonicity

• The ability of a surrounding solution to cause a cell to gain or lose water.
• Isotonic: equal solute concentration inside and outside the cell
• Hypotonic: lower solute concentration outside the cell than inside the cell
• Hypertonic: higher solute concentration outside the cell than inside the cell

Isotonic, Hypotonic, Hypertonic (Illustrations)

• Illustrations showing the effects of isotonic, hypotonic, and hypertonic solutions on animal and plant cells.

Active Transport

• Molecules move from lower concentration to higher concentration
• Active transport requires energy for transport.
• Transport proteins are involved for movement.
• Cells involved in active transport have more mitochondria.
• Mitochondria produce energy for active transport.

Sodium-Potassium Pump and Calcium Pump (Examples of Active Transport)

• Pumps that use energy to move ions across the cell membrane.

Check Your Understanding

• Questions to test understanding of different types of transport.

Bulk or Vesicular Transport

• Transport of large molecules into or out of the cell using vesicles.

Vesicles

• Structures used for transport within or outside the cell.
• Formed during secretion, uptake, and transport.

How are the types of vesicular transport different from one another?

• Question about the differences between the types of vesicular transport.

General Mechanism of Bulk Transport

• Diagram showing the categories and examples of vesicular transport.

Types of Vesicular Transport

• Diagram of the different types of vesicular transport: endocytosis, exocytosis, pinocytosis, receptor-mediated endocytosis, and phagocytosis.

Summary of Types of Vesicular Transport

• Descriptions and diagrams depicting the various types.