05_Lecture_Presentation

Introduction to Cell Function

• The plasma membrane is crucial for cell survival and function.

• This chapter explores the roles of membranes, energy, and enzymes in working cells.

Membrane Structure and Function

Fluid Mosaic Model

• Describes cell membranes as diverse protein molecules suspended in a fluid phospholipid bilayer.

• Membranes exhibit selective permeability, with proteins performing various functions.

Functions of Membrane Proteins

• Transport Proteins: Facilitate the movement of ions or molecules in and out of the cell.

• Enzymatic Proteins: Some membrane proteins act as enzymes to speed up reactions.

• Attachment Proteins: Connect cells to the extracellular matrix and help support the membrane.

• Receptor Proteins: Bind signaling molecules and relay messages inside the cell.

• Junction Proteins: Form connections between adjacent cells.

• Glycoproteins: Serve as ID tags for cell recognition.

Transport Mechanisms

Passive Transport

• Diffusion: Movement of particles from high to low concentration without energy investment.

• Osmosis: Diffusion of water across a selectively permeable membrane.

• Tonicity: Describes the ability of a solution to cause a cell to lose or gain water.

  • Hypertonic: Cells shrink.

  • Hypotonic: Cells swell.

  • Isotonic: Cells remain normal.

Active Transport

• Requires energy (ATP) to move substances against their concentration gradient.

• Transport proteins facilitate this process.

Energy and Cellular Function

Energy Transformations

• Kinetic Energy: Energy of motion.

• Potential Energy: Stored energy, including chemical energy.

• Laws of Thermodynamics:

  • Energy cannot be created or destroyed.

  • Energy transformations increase disorder (entropy).

ATP Functionality

• ATP is the primary energy carrier in cells, powering various cellular processes.

Enzymatic Function

Enzymes as Catalysts

• Enzymes lower activation energy to speed up reactions.

• Each specific enzyme corresponds to a specific chemical reaction.

• Enzyme inhibition can regulate activity:

  • Competitive Inhibitors: Compete for the active site.

  • Noncompetitive Inhibitors: Alter the enzyme's function by changing its shape.

Summary of Learning Objectives

• Understand the fluid mosaic structure of membranes.

• Describe membrane protein functions and their importance.

• Explain diffusion, osmosis, and transport mechanisms.

• Relate energy concepts and ATP function to cellular activities.

• Discuss enzyme roles and inhibition in cellular reactions.