Chapter 7: Lecture Notes

Overview of Cellular Processes

• Analogy of Scantron and Cell Components

  • Scantron: Comparable to RNA in the role it plays in information processing and synthesis in cells.

  • Scantron Machine: Represents the ribosome, which crucially translates RNA into proteins.

  • Protein Synthesis: Occurs in the rough endoplasmic reticulum.

Protein Synthesis and Transport

• Ribosomes Function in Protein Synthesis

  • Ribosomes translate RNA into proteins by stringing together amino acids.

  • As protein synthesis continues, ribosomes move toward the Golgi apparatus.

• Golgi Apparatus

  • Proteins are processed and packaged for transport after synthesis.

  • Key for sorting proteins and sending them to their appropriate destinations.

• Transport Vesicles

  • Formed directly off the Golgi apparatus to ferry proteins.

  • Transport vesicles are vital for transporting materials to the plasma membrane for exocytosis (release from the cell).

Importance of ATP in Cellular Functions

• ATP Production

  • Most ATP is produced in the mitochondria, essential for cellular energy.

  • Understanding ATP's production is vital as it may be a focal point in exam questions.

• Role of Lysosomes

  • Lysosomes contain enzymes that digest cellular waste and help in fighting off infections by destroying pathogens.

  • Critical function of lysosomes in white blood cells to break down harmful microorganisms.

Phagocytosis

• Definition

  • Phagocytosis refers to the process by which cells engulf large particles or cells (often referred to as "cell eating").

  • Plays a significant role in immune response and the maintenance of tissue homeostasis.

• Endocytosis vs. Exocytosis

  • Endocytosis: Process of bringing substances into the cell.

  • Exocytosis: Process of sending materials out of the cell (i.e., transport vesicles fusing with the plasma membrane).

Membrane Structure and Function

• Passive Transport

  • Movement of molecules across the cell membrane without the use of energy.

  • Often involves transport proteins that assist but do not expend energy.

• Active Transport

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

  • Includes mechanisms like the sodium-potassium pump which is essential for maintaining cell potential.

• Membrane Composition

  • Composed primarily of phospholipids, forming a bilayer where hydrophobic tails face inward and hydrophilic heads face outward.

  • Proteins play various roles, including transport and signaling.

  • Membranes exhibit selective permeability, allowing some molecules to pass while restricting others.

Fluid Mosaic Model

• Describes how the cell membrane is flexible, not rigid, allowing for lateral movement of components to maintain function.

• Membrane fluidity is affected by temperature and the types of lipids present (unsaturated vs. saturated).

• Cholesterol plays a role in maintaining membrane stability.

Transport Proteins

• Channel Proteins: Create tunnels for the passage of ions and small molecules.

• Carrier Proteins: Bind to specific molecules to transport them across the membrane, often requiring conformational changes.

Diffusion & Osmosis

• Diffusion: Movement of molecules from high to low concentration; does not require energy.

• Osmosis: Specific diffusion of water across a selectively permeable membrane.

• Tonicity Types

  • Hypotonic: Lower concentration of solutes outside the cell leading to cell swelling.

  • Hypertonic: Higher concentration of solutes outside the cell leading to cell shrinkage.

  • Isotonic: Equal solute concentration inside and outside the cell, resulting in no net movement of water.

Membrane Potential and Ion Transport

• Membrane potential is established by differences in ion distribution, critical for nerve signal transmission.

• Cotransport mechanism allows the simultaneous transport of one solute down its gradient while transporting another solute against its gradient, relevant in the uptake of nutrients.

Summary of Key Points

• Understanding the interaction between cellular components helps in grasping how cells maintain function and homeostasis. Study of structures such as the Golgi apparatus, lysosomes, and membrane proteins are essential for comprehension of cellular processes.