BIOL 115 - Chapter 7 Notes

Chapter 7: Inside the Cell

Introduction to Cells

  • The structure and function of cells serve as the basis for understanding biology.

What is a Theory?

  • In Science:

    • Broader in scope than a hypothesis, leading to generalizations.

    • Can generate new, testable hypotheses.

    • Based on a substantial body of evidence, becoming less tentative.

  • Components of Theories:

    • Pattern: A recurring observation in the natural world.

    • Process: A mechanism or explanation for creating that pattern.

  • A theory is not just a guess or belief.

Theories in Biology

The Cell Theory

  • Core Concepts of Cell Theory:

    • All organisms are made of cells (Pattern).

    • All cells arise from preexisting cells (Process).

    • Proposed by Robert Hooke, noted for using a microscope for cell observation.

Attributes of Life

  • Cells represent one of the five key attributes of life:

    1. Energy

    2. Cells

    3. Information

    4. Replication

    5. Evolution

  • These attributes unify concepts in Biology 115.

Common Features of Cells

Chemistry (Biomolecules)

  • Lipids: Function as a selectively permeable membrane barrier.

  • Nucleic Acids: Store and transmit genetic information.

  • Proteins: Execute most cell functions.

  • Carbohydrates: Provide chemical energy, carbon, structural support, and cell identity.

Structural Components

  • Plasma Membrane: Delimits the interior of the cell from its environment.

  • Chromosomes: Carry genetic information.

  • Ribosomes: Sites of protein synthesis.

Functions of Cells

  1. Survival: Ability to maintain homeostasis.

  2. Function: Perform metabolic processes.

  3. Reproduction: Cell proliferation and genetic information transfer.

Common Threads:

  • The roles of biomolecules, bonding, and membranes.

  • Mechanisms for transport and movement within the cell.

Differences Between Cells

Structural Component Differences:

  • Chromosomes:

    • Prokaryotic: Circular, usually 1 chromosome.

    • Eukaryotic: Linear, more than one chromosome.

  • Presence of Nucleus:

    • Eukaryotic cells: Membrane-bound nucleus.

    • Prokaryotic cells: No nucleus.

Cell Classification

  • Based on morphology:

    • Eukaryotic Cells: Include a membrane-bound nucleus.

    • Prokaryotic Cells: Lack a nucleus.

Cell Walls in Prokaryotes

  • Functions: Provide protection and shape to the cell.

  • Composition: Varied according to the type of prokaryote (e.g., Gram-positive vs. Gram-negative).

Gram Staining

  • Gram-positive bacteria: Characterized by thick peptidoglycan layer, retains crystal violet stain.

  • Gram-negative bacteria: Contains less peptidoglycan and an outer membrane that may be toxic, reveals red safranin stain.

Cell Walls in Eukaryotes

  • Plants: Composed of cellulose fibers, providing structure and water barriers.

Extracellular Matrix in Eukaryotic Cells

  • Functions: Protection, and communication between cells.

  • Composition: Primarily glycoproteins.

Cellular Differences: Eukaryotic Cells

  • Organelles for Functionality:

    • Includes Golgi apparatus, endoplasmic reticulum, lysosomes, and vacuoles.

  • Compartmentalization: Enhances efficiency of chemical reactions, separates incompatible reactions.

The Endomembrane System

  • Network of membranes within eukaryotic cells:

    • Nuclear Envelope: Controls traffic in and out of the nucleus.

    • Endoplasmic Reticulum: Serves as a biosynthetic factory (both rough and smooth ER).

    • Golgi Apparatus: Modifies and sorts proteins and lipids for transport.

    • Lysosomes & Vesicles: Function for digestion, storage, and transfer of materials.

Importance of Compartmentalization

  • Organelles facilitate specific functions:

    • Smooth ER synthesizes lipids and detoxifies substances.

    • Rough ER synthesizes proteins for export.

    • Golgi apparatus modifies products from ER, packages them into vesicles for transport.