Lecture Notes: Chapter 2 - The Self

Introduction to Biology

• Hierarchy of structural organization in biology starts at the chemical level.
• Cell is the basic unit of life, below which nothing is considered living.

History of Cell Discovery

• Robert Hooke (late 1600s):
  • Father of microscopy, developed the microscope.
  • Discovered cells by observing a cork.
  • Coined the term "cell" from monk's cells.
• 1830s: Matthias Schleiden and Theodor Schwann:
  • All living things are composed of one or more cells.

Hierarchy of Biological Organization

• From atoms to ecosystems:
  • Atoms > Molecules > Cells > Tissues > Organs > Organ Systems > Organisms > Populations > Communities > Ecosystems.

Diversity and Function of Cells

• Cells have different structures and functions.
• Examples:
  • Bacteria (unicellular), Archaebacteria (live in extreme conditions), Human blood cells (red and white blood cells).
• Structure determines function.

Cell Theory

• All organisms are composed of cells and cell products.
• All cells come from pre-existing cells.

Types of Cells

• Prokaryotic Cells:
  • No nucleus, simple organisms like bacteria and archaea.
• Eukaryotic Cells:
  • Have a nucleus, more complex organisms.
  • Unicellular and multicellular (e.g., humans have 210 distinct cell types).

Cell Origin and Development

• Human life starts as a single cell (zygote) through fertilization.
• Zygote undergoes cell division, forming structures like morula and blastocyst.
• Embryonic stem cells differentiate into various tissues and organs.

Cell Structure

• Generalized Cell Components:
  • Plasma membrane, cytoplasm, and nucleus.
• Plasma Membrane:
  • Composed of a phospholipid bilayer.
  • Acts as a selectively permeable barrier.

Plasma Membrane Components

• Phospholipid Bilayer:
  • Hydrophilic heads and hydrophobic tails.
• Proteins:
  • Integral and peripheral proteins, can drift within the bilayer.
  • Functions in cell signaling, transport, and recognition.

Diffusion and Osmosis

• Diffusion:
  • Movement from high to low concentration.
  • Passive process, no energy required.
• Osmosis:
  • Diffusion of water across a selectively permeable membrane.
  • Essential for maintaining cell environment.

Tonicity

• Isotonic Solution:
  • Equal solute concentration inside and outside.
  • Cells maintain their shape.
• Hypertonic Solution:
  • Higher solute concentration outside.
  • Cells shrink.
• Hypotonic Solution:
  • Lower solute concentration outside.
  • Cells swell and may burst.

Membrane Transport Mechanisms

• Vesicular Transport:
  • Endocytosis: Bringing substances into the cell.
    • Phagocytosis (cellular eating), Pinocytosis (cellular drinking), Receptor-mediated endocytosis.
  • Exocytosis: Removing substances from the cell.

Summary

• Cells are the fundamental unit of life, differing in structure and function.
• Their study involves understanding both historical discoveries and modern cellular biology concepts.
• Understanding cell structure and function is crucial for comprehending larger biological systems and processes.